Power choking

[PProph]

Hey all, I've done some searching and come up with some ideas but I want to throw my own thread out there as well.

'03 TB LTZ, 218,000km on it.
Oil level is fine, change due in a few months.
Transmission fluid has not been changed for awhile but the level is good and it still looks pretty clean.
TC fluid was changed 2 years ago, level still good.
Front and Rear Dif fluid recently changed (during fixes at each)

I'm getting some ridiculous power choking, started being noticeable this winter at about 25-2800 rpm while accelerating steadily toward highway speed. More prominent on cold days or when the engine is working hard. A week ago or so I was accelerating hard to get up to highway speed on a busy road and when I hit 4000 rpms in second gear my throttle choked and I couldn't continue speeding up in the 2nd nor would it shift to 3rd until I let off the gas. This is not a new problem for me when "flooring it" (so perhaps I should have started looking into this awhile ago) but it usually occurs at a higher rpm and shifts easier. I repeated the attempt on a couple different occasions since, same result.

A couple of days ago I made a day trip out of town and had to bite a cold wind the whole way. My engine gave me nothing but grief, couldn't keep my speed in 4th gear, kept having to shift down to keep highway speed (the wind was up but it wasn't gale forced or anything). On the way back the wind wasn't quite as bad but I still had a few times (hour and a half trip) where I had to shift down. On the way back at some point my service engine light also came on. It stayed on for a day or so and is now off. Since returning though I'm having power choking issues while accelerating at all speeds in all gears. On "steady" acceleration I feel power being choked every couple hundred rpms for half a second before it pushes through until it ultimately caps and then I have to let off the gas a bit for it to switch gears. It's becoming very frustrating to drive this way and I'm pretty much ruling out any busy high speed roads (luckily I work nights and avoid traffic for the most part).

I will be contacting my car guy today, he has the tools and knowledge to go through the motions of hunting this problem down. We changed the plugs in December as a first attempt at a simple fix as they hadn't been done since I bought it 3 years ago. Also cleaned the throttle body at that time (though we didn't take it off, I just watched May03's video on that now). As said I have the professional help so I'm not going in blind here but the knowledge base on this site is vast and I thought I would get some ideas to take with me whenever he can look at it (I'm assuming in the next few days but sometimes I'm not that lucky).

A little more history and/or general question that may or may not be related, since I've owned this thing (3 years + 1 month, had 150000 km on when I bought) I've noticed that I have trouble with wind during highway travel as well as inclines on the same. I hesitate to use cruise control because it's always shifting down whenever I have slight changes in wind or incline requiring more power. I've also noticed that using cruise a lot of the time I'll be rolling along and it will get to the point where it should shift down to third, which it will do for a half second and then shift down ANOTHER gear. Not only is this highly irritating it is also borderline dangerous (though I'm not stupid and only use cruise control in ideal conditions). I chalked it up to a quirk of the vehicle but I'm starting to wonder if it's something that I should be looking into. I assume that being a big square vehicle with a 6 in it it's not exactly the best prairie highway traveler since we have wind 95% of the time, but again I'm thinking that this might actually be something I can fix.

Anyways sorry for the wall of text, any ideas will help as usual (the list of things you guys have helped me fix is starting to grow and the money you've helped me save is easily in the thousands by now), I'll be monitoring the thread constantly because I don't really have much of a life

Thanks in advance!

 

[The_Roadie]

Great post! Would much rather have too much detail than too little.

You haven't mentioned air filter. That new?

Wish you had snagged the code right after the CEL came on.

Could be deteriorating CPAS or clogged cat. CPAS might as well just change it. Cat requires an exhaust backpressure check.

Normally the upstream O2 sensor gets changed about the time that plugs do. Has that ever been changed or the sensor raw output reading checked to see if it's wiggling fast enough? Sluggish sensors can give you bad air/fuel ratio.

Finally, have your mechanic check long and short term fuel trims on the computer and vacuum on a test port on the intake manifold or the brake booster hose.

 

[PProph]

i will mention all of these things. air filter i did in the fall. i had him scan it early winter before we did the plugs (the service light had come on) and the only info it gave him was a historical misfire. I'm seeing mention of this torque app for the first time and pretty sure I'm gonna get that so I can pick these things up myself as opposed to relying on someone else's scanner that i have to wait for.

i also worry about the cat as I had a bad cat in the sunfire I used to drive that took the nuts right out of it. I worried at that problem for 2 years (and several thousand dollars) before my car guy figured it out. Temporarily cut the cat out and put a straight pipe into it to see if it was the problem, sure enough it did the trick. (by the by temporarily became permanent... it WAS a sunfire though ).

one other thing I'm wondering about is fuel filter. I don't know if I've replaced this one or not, it's a cheap fix that I know hasn't been done recently so we'll probably do it anyways.

Any other ideas please throw them my way, I will keep this thread updated and also (hopefully) close it with what ends up being the solution.

 

[PProph]

Hey all, the only update I can give at this moment is in symptoms. Unfortunately I haven't been able to get a hold of my car guy due to me working nights and he not yet returning my message.

In the meantime, this problem has stuck, it is no longer intermittent. Subtle things of note, the harder I try to accelerate the harder it pushes back if that makes sense. If I'm getting up to speed say on a road that's max 70 (kmph) I will fight it but get there, but as soon as I slowly let off due to reaching my near desired speed it almost feels like there's less pressure against the gas pedal if I'm getting my point across right.

Anyways I'm going to try and get a hold of my guy again as I'm off for a couple of days, and I'm also finally going to get my summer Buick up and running so I'm not bound to this annoyance.

If I'm unable to get a hold of my car guy, I plan to attempt to tackle the fuel filter first followed by the CPAS. I figure it can't hurt to change the Fuel Filter anyways and MAY03 has a good how to video on it. Voymom's CPAS Cleaning how to thread will guide me in that regard.

I've had the MAF sensor suggested to me as well, I wonder if I should change that?

And can anyone recommend a decent bluetooth odb tool for the torque app?

Thanks again!

 

[jimmyjam]

testing for a clogged cat is easy, just remove the o2 sensor on the exhaust manifold and go for a ride. if it feels like your power is back, time for a cat. fuel filter is easy enough to change. if you do these two things and symptoms persist then test fuel pressure to see if the pump is causing issues.

I don't believe the 03 I6 has a MAF

 

[MAY03LT]

In the meantime, this problem has stuck, it is no longer intermittent. Subtle things of note, the harder I try to accelerate the harder it pushes back if that makes sense. If I'm getting up to speed say on a road that's max 70 (kmph) I will fight it but get there, but as soon as I slowly let off due to reaching my near desired speed it almost feels like there's less pressure against the gas pedal if I'm getting my point across right.

First of all, way to go with your attention to detail.

The symptom matches a clogged cat. A clogged cat won't set a code. Instead of banging on a new pipe, your guy could install a backpressure tester where the front o2 sensor is mounted, or you can remove the front o2 sensor and go for a quick ride to see if your symptoms go away. (note: running the engine without the front o2 sensor will likely throw some codes and the truck will be kinda loud).

If I'm unable to get a hold of my car guy, I plan to attempt to tackle the fuel filter first followed by the CPAS. I figure it can't hurt to change the Fuel Filter anyways and MAY03 has a good how to video on it.

Thanks for the shout out. I'm with you, I don't think the filter will fix the symptoms, but it is part of maintenance (every 30k per manual, once a year per me) so it won't hurt to change it.

I've had the MAF sensor suggested to me as well, I wonder if I should change that?

Our 03s don't have a MAF.

And can anyone recommend a decent bluetooth odb tool for the torque app?

I use the bafx elm327 w/torque. It does the job well.

edit:ninja'd

 

[The_Roadie]

I have nothing to add to that excellent advice except that our platform is a drive-by-wire system. The accel pedal is like a volume control - electronic potentiometer. Not a cable that pushes on something physical under the hood that can push back. Just wires connect the pedal sensors (there are two that get compared for consistency by the PCM) to the computer.

 

[PProph]

thanks for the quick replies, yeah i thought i saw mention somewhere of not having a maf. thanks for that answer.

also thanks for the tip on the fuel filter, i will still change it but it will probably wait until summer now. i will check the cat first by pulling the O2 sensor as suggested, I agree as mentioned above the symptoms are very similar to when the cat in my sunfire went.

also thanks for the info roadie, i didn't really mean something physical pushing back, more like the engine resisting my direction to make go fast better... but i never turn away information.

oh and thanks may03 for the odb recommend. i will search it.

as usual, i will post back with my results solved or no!

 

[PProph]

Going to run some tests tomorrow, finally got a hold of my mechanic. Hopefully we pick up something before I start ripping things apart.

 

[PProph]

So had the scanner on it tonight. The historical codes that are related that came up were:

P0172 Fuel system too rich bank 1
P0300 Random cylinder misfire
and
U1194 Undocumented.

He also went through things and said my Fuel Filter should be fine, though I will probably do that sometime anyways. We did not do a backpressure test yet. When he was running diagnostics he showed how the pre-cat O2 sensor fluctuates a lot and the post-cat O2 sensor is a lot more stable which he said is what it should be doing. I mentioned the CPAS and he thought that as a possibility, but he also told me they're an expensive part. I'll price it out.

The thing I'm not sure about was his suggestion to clean it. He suggested I put a bottle of transmission oil into my crankcase, as there are more detergents in that and it should clean the CPAS. I'm not thrilled with the idea of a)putting anything into anywhere that it doesn't belong and b)mixing oils. I was curious to see the reaction to that suggestion.

He also suggested Seafoam treatments to clean the injectors. Two tanks in a row. That one doesn't bother me so much. I think the whole idea was to cheaply figure out where the problem lies rather than going and throwing parts at it.

He did run diagnostics on it but we never took it out on the road during that, which is more where the problem occurs, it generally runs fine at idle.

Anyways I'll see what you folk have to say but I think I might just end up cleaning/changing the cpas and pulling the O2 sensor as suggested.

Perhaps the codes above might give any other tips?

 

[Mark20]

I think we discussed the cleaning effects of tranny fluid and it didn't score that high. It doesn't have to face the combustion products engine oil has to, so just naturally runs cleaner in a tranny giving the illusion it has great detergent powers.

There is an article here on cleaning the CPAS. Its not too difficult. Something I will probably be doing before long.

 

[jimmyjam]

P0172 Fuel system too rich bank 1

P0172 and P0420 diagnosis help [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

this guy had a rich code, it was a clogged cat.........

 

[MAY03LT]

Plugging in a scan tool and looking at numbers isn't diagnostics. I don't know why he didn't just take it for a spin to duplicate the condition and start forming a plan on what to test.

 

[The_Roadie]

Plugging in a scan tool and looking at numbers isn't diagnostics.

As everybody who's read my "How to Troubleshoot Anything" manifesto knows.

I don't know why he didn't just take it for a spin to duplicate the condition and start forming a plan on what to test.

Because that person isn't a diagnostician. They're just playing one on TV.

 

[PProph]

I'm just gonna go ahead and say that this guy is an excellent mechanic and a family friend, without him I'm sure I'd have sunk a lot more money into cars by this point in my life. He has a great depth of knowledge and experience and I can't believe what little amounts I've paid him in the past for the jobs he's done for me. While in this instance I'm not exactly enamored with the process and route taken/suggested, I appreciate his help all the same. Not just anybody is going to let me bother them after supper on a 10 hour work day and use their expensive scan tool on my ride free of charge. I know that his fuel/oil treatment suggestions are the cheapest fix he can think of and he's trying to save me money. I know he's busy right now and probably can't spare the time to help me work on any of these things either, and probably hoping one of these fixes will work.

That said, I know that the user base here has a ton of experience and more importantly a ton of experience with this platform, hence why I come back here time and time again and have for the 3 years I've owned my TB. I also can't fight my gut feeling on the CAT, though I don't have the means to change that out myself (or rather I've never worked on exhaust and am not sure of my abilities in that area).

Question, would a backpressure test give me conclusive results if my problem occurs only working up to speed under load? If I'm clear about the test I would assume one would be stationary while performing such a thing.

 

[jimmyjam]

just pull the o2 sensor and go for a ride..........................................

 

[MAY03LT]

When I read your post I was picturing that you went to a shop and paid a diagnostic charge, which, as a vehicle owner advocate, really boiled my blood that there was no road test to duplicate the problem. I can be harsh on other technicians mainly because I've seen people get taken to the cleaners numerous times throughout my career. In fact, I could write a book on it. So when I read something like your case where you've given a very detailed description of a problem, I expect another shop/technician who has the truck in front of him to do the same thing that I would. Sure, there are quirks about our I6 engines that don't fit the norm that could very well throw technicians who aren't familiar with them through some loops, but for the most part they're the same same as every other vehicle out there.

Question, would a backpressure test give me conclusive results if my problem occurs only working up to speed under load? If I'm clear about the test I would assume one would be stationary while performing such a thing.

Yep. You can load the engine down without the truck moving. But since you've gotta pull the upstream o2 out anyway, might as well just go for a quick ride.

 

[PProph]

I've seen a few of your vids may, so I'm not surprised about the blood boil lol. Yeah I've been to shops before (the aforementioned Sunfire issue) and pis$ed away money on "diagnostics". I was younger then and have gained experience since, now I tend to find all manners of advice before throwing money at things, this obviously extends beyond car repairs into every walk of life.

Anyways I digress, so yeah I'll pick up the tool and pull the O2 sensor when I get a chance.

Assuming the CAT is what the problem is, i've been perusing other threads here and elsewhere and seen that there are other things that can cause the CAT to go bad, should I be checking other parts in the meantime and replacing them as well so as not to ruin a new CAT?

 

[MAY03LT]

I've seen a few of your vids may, so I'm not surprised about the blood boil lol.

Oh then you definitely know the deal.

Personally I wouldn't buy the tool for a one time use. Removing the front o2 will do the job just fine.

Assuming the CAT is what the problem is, i've been perusing other threads here and elsewhere and seen that there are other things that can cause the CAT to go bad, should I be checking other parts in the meantime and replacing them as well so as not to ruin a new CAT?

Running rich is the number one offender. Stuck t-stats can cause it (but not set rich code) and I've had a few cases where the MAP sensor caused it (set p0172) as well.

Edit - Also misfires which are bad enough to flash the SES light.

 

[PProph]

The O2 socket is like 8 bucks and probably something I should own. Also I love Amazon, my bluetooth ODB came today, I ordered it like Wednesday I think? Unfortunately I have a pretty busy weekend so I don't know if I'll get around to testing these things yet, luckily my Buick is running like a dream for the first time in years so I'm not stuck driving my out of sorts TB. I only hope I can get on it soon, but I know I'm going to be busy for a little while.

I priced out after market CATs and CPASs, the pricing is not as bad as I feared. And with all the useful info on gmt changing those things looks pretty doable as well.

Of course I will keep updated as usual!

 

[PProph]

Finally getting back to this. The TB sat for awhile as I got running my old buick regular. Unfortunately I now have a toasted AC Compressor clutch in that which is causing me major issues on the pulley, so now I need to fix that and focus on getting the tb back on the road. The problem is getting much worse, after sitting a month or so I drove it last week and couldn't even accelarate slowly up an incline. So I'm trying to get the O2 Sensor off tonight. What a PITA. I soaked it in PB Blaster last night before work and will try it again today. I have the O2 Sensor socket on a 3/8's drive, but it doesn't seem to snug up on the nut real well which is a recipe for rounding off the nut. As per other posts on the matter I'm going to try warming up the engine (though I don't want to burn myself and I see this as a possible and likely scenario). Any other tips on getting this puppy out?

 

[MAY03LT]

I wear welding gloves when working with hot parts. Also, a little slop in o2 sockets is normal. I have several versions for different applications and none of them are a precise fit.

 

[PProph]

I have no welding gloves, but I will definitely wear something to give me at least a little protection. Burnt my finger trying to solder a speaker wire a week ago, and I'm tired today lol so I'm sure I will be prone to some mishaps.

 

[PProph]

no mishaps but i still can't get that sensor out. too much play in the socket. i'm at a standstill for now, anyone have any ideas on what to try next? I can't get a tight enough fit and it wants to round off the nut on the sensor, which would be bad news bears.


i see a suggestion of putting a couple strips of electrical tape inside the socket. i'll try that tomorrow. maybe my socket is too cheap and a higher quality one would fit better? i don't know, it's getting a touch on the frustrating side.

 

[MAY03LT]

I'd try a different socket. I think the slop you're seeing is way more then mine. I don't know if you guys have places that rent tools up there but that's worth a shot. Or borrowing your buddies.

One time I burned a metric thread pitch into one of my fingers when I goofed and touched a hot bolt. Several days later I referenced the burn to figure out what bolt pitch I needed when one snapped. Probably the only time in history that a burn benefited someone.

 

[PProph]

i'll try and rent one, at this point i've ordered a new O2 sensor as I see there is a common suggestion of replacing it as often as plugs anyways, simply to prevent the problems I'm having. Locally the cost is almost double what I can get it for on Amazon, though there is a wait there. RockAuto is also cheaper but not as cheap as Amazon, if they don't ship right away I'll probable order from Rock Auto. It's kind of sick that locally they want $83-$100 for the same part that costs $40 online. Good thing I don't need this today. If the new one shows up before I get the old one off, I'll probably just clip the wires and use a deep/open ended socket that I can get to fit tighter.

I also started calling around for quotes on a backpressure test, the first place I called doesn't do them, they do heat sensor tests before and after the cat to determine a bad cat, the second place said it depends on if they fix the problem or not, if not it's $30-40, if I get them to do the work afterward it's free. Though I've had some sub-par experiences with that place recently. It's annoying to not have a good shop I can trust at the moment. And I don't want to take it to my car guy because I haven't tried the additives he suggested and I don't want to offend him by basically saying I didn't agree with his prior methods/diagnosis lol. Anyways, as usual I'll keep updating.

 

[MAY03LT]

Yeah it's crazy how the prices vary between stores and online. I just went through the same thing, ended up waiting for rockauto for a $20 part but saved about $30 for the same thing locally.

Oh no, not the temp gun test. I tried it on a car that definitely had a clogged cat, the difference in the in/out was marginal. Not enough to be accurate. $40 is reasonable, but I like your idea about snipping the wires and using a big socket.

Yeah it's hard finding a place that you can trust. I see peeps get screwed regularly. That's what motivates me to do my thing here.

 

[Ed H]

I had a very similar issue recently. It was the CPAS. If you are low on funds, pull that bad boy and clean the hell out of it. I bet your screens are plugged and you have oil in the connector. I pulled mine, cleaned it with brake cleaner and an old toothbrush, and put it back it. I noticed a difference immediately. The codes went away after 1 day, and the driveability / power got better everyday. It was completely healed after ~1 week. Cheap, fast, and free.

 

[PProph]

not so much a funds issue as it is a "i can't be bothered to pay $100 for a $40 part" issue lol. but i will hopefully check into cleaning that as well when i get the chance. I'm focused on the buick at the moment, gotta get something running properly.

 

[PProph]

Cleaned the CPAS today, it looked to be in pretty good shape, the o-ring is good, the screens aren't damaged, there was a bit of oil in the harness, everything's all cleaned out and back together. Did not fix my problem but at least I know that's clean.

Ordered a new O2 Sensor from RockAuto today (along with a harmonic balancer for my buick, this saved me a total of $150 compared to local), I still suspect the CAT but just can't seem to get that O2 sensor off. After road testing today I also had it in the driveway idling and stepped on the gas, it sputtered before revving up. This happened consistently so I got video of it, which I will upload later. Foot to the floor in park at idle, it immediately sputters as if it's going to die, then revs up as it should (for the most part). Perhaps that will help in further diagnosis, perhaps not but I thought I would share.

 

[PProph]

Oy I've had a bad year for vehicles. Nothing but trouble with my Buick, I drove my TB out of town to my semi-inlaws to borrow a working vehicle. It's been here for a month and a half now, finally got down here today to look at it some more.

We could not for the life of us get that O2 sensor out, I did not clip the wire yet. However what we decided to do was just disconnect the exhaust pipe at the manifold, that should recreate the same conditions as pulling the upstream O2 sensor no? Those nuts came off way easier. I drove it around and conditions did improve. I still have a bit of shifting hesitation, but I think that might be another issue. I had plenty of power with the exhaust disconnected, recently I hadn't been able to push my throttle past 4000 rpms and today I could. I was testing it on gravel which isn't an ideal surface to test smooth acceleration, but I got a pretty good idea that things had improved somewhat. Sidenote I didn't actually throw any codes even with the exhaust loosed off like that. I suppose some exhaust is still pushing into the pipe because it's only backed off an inch or two but I expected a code of some sort.

Anyways, should I conclude here that my CAT needs to be replaced? I don't think it ran perfect but it definitely seemed improved. Also I noticed that the procedure is to just unhook it from the manifold and then from the muffler end and remove/replace (I had planned on the direct fit full pipe piece). When I crawled under I noticed that the hangers near the muffler connection are welded on to the pipe. If I have to get welding involved am I almost just better off to replace only the converter (cut out and weld in)?

I have it sitting out here, gonna reconnect the pipe after it cools down awhile and it will remain parked. I also was thinking to replace the thermostat in case it might be the culprit that caused the converter to go (assuming the converter is toast). I don't have anything to indicate what the problem might have been but I read that it is a common culprit and it seems a cheap enough replace. Also the TPS was suggested to me, I see ours is built in and I would have to change the whole throttle body though.

Please advise based on new information! I'm not as certain about the CAT as I was, but i hope that's just me second guessing myself. I guess I thought maybe I'd have seen a perfect running vehicle once the exhaust had a better escape, but to be fair it's not like the pipe is right removed, it's just spaced. What do you think?

 

[PProph]

Okay double post, I tried learning the torque app a little bit (hadn't done much with it yet, I'm new to scanning of any sort), maybe some more info here will help. The exhaust is still disconnected/loosed off.

I've got some data. First of all engine coolant temp got up to a max of 206.6. It was hovering around one seventy something until I got driving then picked up. It's cool out tonight and I didn't drive far. Not sure what this might indicate for my t-stat. Let me know if there's a good way for me to test.

I ran up the road again and accelerated evenly on the pedal. Every shift hesitated up to highway speed, but I had no choke. I think this might indicate a combination of problems for me. I think the cat does need to be replaced, but that perhaps the problem was compounded/magnified by a shifting problem. In the torque app there are shift error values for each shift, 6.22 seconds in 1-2, .25 seconds in 2-3, 6.07 seconds in 3-4. This is adding to suspicions I've previously had, such as my cruise control two gear drop that drives me nuts and has since I got the vehicle. I would assume this to be transmission related?

Finally are there any other readings I should be checking on Torque to help me try and diagnose any of this stuff. Now that I'm finally figuring out how to use the thing I'd like to run more tests.

 

[The_Roadie]

I think you're on track so far. Bad cat. Thermostat OK if that's what you read on Torque. I also like to examine long and short term fuel trims, which can contain a clue if you have a problem keeping mixture controlled such as caused by a vacuum leak.

 

[PProph]

I can do that, what's the best way to monitor them? Do I watch it over time or just get data after it's been running or driving or? I noticed it in your first post here you mentioned it and I found the gauges on torque, just need to know what I'm looking for and how I'm looking for it.

Also I was thinking would the fact that my exhaust was disconnected affect the temperature in the engine (and coolant temp as a result) and therefore skew my results?

I'm heading back to the city without it today, I think I'm gonna take out the cluster before I go though, it's just sitting here it's a good time for me to do my stepper motors.

 

[MAY03LT]

I've never tried running this (or any) motor with the manifold off, so I don't know what side effects (like excessive heat in the engine bay) could happen. But, with power restored after disconnecting the exhaust I think replacing the cat might be the next best step. Of course I'm a stickler for evidence so until there is a backpressure test or o2-removed-road-test it's a gamble in my book.

I wouldn't rule out the stat based off of the one test. I've seen the p0128 code have passed/failed history more then a few times. If the history is unknown, it might be best to do it anyway.

 

[BlazingTrails]

no mishaps but i still can't get that sensor out. too much play in the socket. i'm at a standstill for now, anyone have any ideas on what to try next? I can't get a tight enough fit and it wants to round off the nut on the sensor, which would be bad news bears.


i see a suggestion of putting a couple strips of electrical tape inside the socket. i'll try that tomorrow. maybe my socket is too cheap and a higher quality one would fit better? i don't know, it's getting a touch on the frustrating side.

I removed mine with a six point 7/8 wrench and an extension. It was very hard to remove. Do not use the more common 12 point wrench it will not work.

 

[PProph]

I've never tried running this (or any) motor with the manifold off, so I don't know what side effects (like excessive heat in the engine bay) could happen. But, with power restored after disconnecting the exhaust I think replacing the cat might be the next best step. Of course I'm a stickler for evidence so until there is a backpressure test or o2-removed-road-test it's a gamble in my book.

I wouldn't rule out the stat based off of the one test. I've seen the p0128 code have passed/failed history more then a few times. If the history is unknown, it might be best to do it anyway.

Would the O2 removed road test create different conditions than my pipe removed road test? I thought the goal in the O2 removed test was basically to give the exhaust an escape that isn't through a potentially plugged CAT. Obviously the proper backpressure test would be the right way to go. I will be taking my new information back to my car guy as well to see what he recommends or can do for me. I'm pretty sure he can do the backpressure test, and I'm pretty sure he'll find a way to get that O2 sensor out. We'll see what comes I guess.

Hopefully I do need to replace my CAT (there's an uncommon statement), but I do have a feeling I will be starting a new thread soon about possible shifting issues.

for what it's worth I'll probably change the tstat (and as per thread recommendation the temp sensor), and I do have a fuel filter that i'll change for kicks.

I took the cluster out today to replace my stepper motors this week and I think I will also order a new 4wd switch (mine has had intermittent problems in the past, $20 can't hurt to change).

That's all for now, thanks again for continued comments and suggestions!

 

[KNBlazer]

On removing o2 sensor

The way I did it was, I sprayed some WD40, that's all I had, let it sit a few minutes...truck was cold, so I fired her up for one minute... then using o2 sensor socket, a 3/8 ratchet, and my floor jack handle for leverage, I very carefully and slowly broke it lose, I then tightened a little, loosened it more, then tightened it, back and forth until there was no resistance, or a crunchy type sensation...

 

[PProph]

Can't find my replacement stepper motors. grrr... car guy would like me to do a backpressure test before I go out and buy the CAT, which I suppose is the sensible thing to do. He said he'll get that O2 sensor out for me. The pain is now that I can't find my steppers I have to go put my cluster back in before I try bringing the ride back into town.

I love being horribly unorganized and a terrible procrastinator...

 

[The_Roadie]

The vehicle drives just fine without a cluster.