06 TB 4.2 stalling while braking..

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Howdy Gents, migrating from Trailvoy. I have been chasing run probs with TB. Have cleaned throttlebody spotless (idles like a new truck now between stalls), replaced cam position sensor, variable valve timing solenoid, oil pressure sensor, crankshaft position sensor, and a seafoam treatment. Truck is at stealership for crank relearn tonight, but I noticed last week during seafoam treatment that the vacuum line between manifold and brake booster was missing clamp and not really tight at booster. Just read online that this causes stalling and surging on other makes and models. Could this really be causing my stalling while braking problem? Didn't think that hose could be super important based on the cheapo clamp the factory used. I have no prob with brakes, just infuriating stalling problem. Thoughts?
 

IllogicTC

Member
Dec 30, 2013
3,452
It could be. It'd be worth having the clamp on there either way, and if it fixes your issue, great! If I remember right it's just one of those clamps your squeeze with a pair of pliers to get off, it's dark out so I'm not going out to look :rotfl: It may be a cheap-o but it may make all the difference if there's a vacuum leak. Generally though a vacuum leak would cause higher idle... it may also have something to do with the required CASE relearn but I wouldn't think that would come up only when braking... When you get the vehicle back from the dealership maybe we can get some more light shed on the issue?

And welcome to the new fountain of knowledge! :thumbsup:

Mandatory link I have to provide, it's not necessary for you to read but it provides the backstory on why the founding group here splintered off in the first place: http://gmtnation.com/forums/topic/218-welcome-to-gmtnationcom-heres-the-story/

If you don't already have service manuals, here's a thread with a ton of them: http://gmtnation.com/f23/need-service-manuals-get-them-here-371/
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Thanks for your quick response! It is the squeeze clamp, stay inside man, the junebugs are swarming! LOL. I txtd the svc manager about my findings at 9pm. Hope he relays the msg to the techs tomorrow morning. And I will update, cause the interwebbings have lots of folks with these symptoms, but nobody with the (SOLVED) headline. Another problem, but I doubt related, I have always had great oil pressure, but the day after having a quicklube oil change last week, my pressure gauge drops to near redline when warm. Figured they used the wrong oil so I changed it, but not the filter cause the goons over tightened and I cant get it off. The pressure now bounces between 5 and 40psi when warm at idle. Bad filter?
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
I have noticed just before stalling a small rpm surge from 600 up to 800 just before falling out the bottom like I turned the key off...
ps.. a very cool bro a trailvoy tipped me to yall, but his response to my introduction that mentioned yall was deleted after a couple days. NSA? LOL
 

IllogicTC

Member
Dec 30, 2013
3,452
The 4.2's oil gauge is a lie. To simplify it, it's a highly-glorified dummy light. The 5.3 V8 has an ACTUAL WORKING gauge, but the 4.2 has a simulated one. Meaning, if the oil pressure switch (not sender, SWITCH) has enough pressure hitting it (>=12PSI when warn) the PCM makes up a bogus number and displays it. Generally it will sit at 40 at idle, while running from 50 to 60 depending on driving conditions. The number is a fabrication of some software inside the PCM. So all in all, it's either you have at least the minimum acceptable pressure or you don't.

Could be a bad filter. Did they use a PF61 GM filter, or a good equivalent such as a Purolater PureOne(?) or a Bosch? The filter alone can hold something upwards of a pint, which means a bit over 5% of the oil circulating is still the potentially wrong stuff. Who knows what else the clown did, too, especially since they decided the oil filter is a lower control arm bolt. Did they make sure to put in a solid 7 quarts (including the filter), or just do the 5-and-drive?

And a rise before a stall condition, could very well be something related to the vacuum, or the bad diaphragm as mentioned above.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Cant see brand on filter, but it is banana yellow. I have a Bosch 3423 ready to go in. It did have seven quarts, but they really pissed me off. Told him "give me your cheapest oil change, I'll be back in one week before I change my variable valve timing sensor". After 30 min he calls me to the register and says "that'll be $82". I say "WTF, I asked for cheap?" He says "uh, I guess he saw you had synthetic last time".
 

Robbabob

Member
Dec 10, 2012
1,096
jeffrobinson said:
ps.. a very cool bro a trailvoy tipped me to yall, but his response to my introduction that mentioned yall was deleted after a couple days. NSA? LOL

Welcome to the Nation!

LOL NSA :lipsrsealed:... it's their version of stopping us from helping fellow owners find/get the help they need! Your name looks familiar, but I can't be certain how long ago I was banned and got ALL my posts deleted. The point is, you're here now.

Relax and enjoy the ride!
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
Welcome aboard!

Banana yellow oil filter - I'll guess it's pennzoil.

Just out of curiosity, who made the cam sensor that you used?
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
The cam sensor is AC Delco. Variable valve timing sensor was Delphi. ("Oil pressure" sensor Duralast, Crank Position sensor Duralast---I know ,I know. I just was growing impatient and didnt want to wait another week on RockAuto) . Which brings me to todays update. The stealership called at 10am to say they did the crank relearn and did some updates it needed. Said it didnt fix my stall problem, and the brake booster end of that vacuum line wasnt supposed to have a clamp. Anybody got a minute to peek at theirs for me to verify that? Anyway, he says for $129.99 we can run diagnostics on it for you. I told him to go for it. Well time ticks by till 5pm and I'm leaving work so I call them back. Jesse says "Well, right now he's tracing wiring looking for problems and we just need a little more time. I'll give you a call before I leave work". 8:30pm now here in central Texas, guess Jesse works late....LOL Glad my 96 Tahoe still runs....
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
jeffrobinson said:
The cam sensor is AC Delco. Variable valve timing sensor was Delphi. ("Oil pressure" sensor Duralast, Crank Position sensor Duralast---I know ,I know. I just was growing impatient and didnt want to wait another week on RockAuto).

Thanks for the info. My work uses a particular brand of parts and said brand has a very bad rep for cam sensors on these trucks.

I can't knock duralast, I've used enough of their stuff over the years for the need-it-now repairs and they've done well.:cool:
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Well, the stealership called back. Said my crank is sliding forward out of range of the sensor. Said 1/4 in of endplay. Seems strange that it runs perfectly for first 10 min of driving then starts acting up. Yeah, I can see how..Oil warms up, bearings warm up, crank slides. When I replaced the crank position sensor I looked at the buisness end and there was a a circular-ish clean spot in the dead center about 1/4 in across. Would this confirm or deny crank slide? Any other thoughts? Looks like rebuilts around Austin, TX are running $2K. Will it run with sensor disconnected? LOL ...seriously..will it?:worried:
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
:undecided:
jeffrobinson said:
Well, the stealership called back. Said my crank is sliding forward out of range of the sensor. Said 1/4 in of endplay. Seems strange that it runs perfectly for first 10 min of driving then starts acting up. Yeah, I can see how..Oil warms up, bearings warm up, crank slides. When I replaced the crank position sensor I looked at the buisness end and there was a a circular-ish clean spot in the dead center about 1/4 in across. Would this confirm or deny crank slide? Any other thoughts? Looks like rebuilts around Austin, TX are running $2K. Will it run with sensor disconnected? LOL ...seriously..will it?:worried:
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Such an outrageous claim is unique in my experience. I honestly can't see how it's true, but I'm not an engines internal sort of mechanic. Sure sounds worth a second opinion. Wicked sorry you didn't get more folks to chime in. This group is almost never wowed into silence, but you succeeded.

A crankshaft that has 1/4" fore/aft play might be a huge whopper or it might be a new failure mode we need to know about.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
I'm curious how the crank "walks" far enough away but doesn't set a loss of crank code. I'm also curious how tracing wiring went to measuring endplay.:undecided:

edit:

jeffrobinson said:
First code in a long time pops up P0017.

I didn't know there was a crank code.
 

Texan

Member
Jan 14, 2014
622
jeffrobinson said:
Well, the stealership called back. Said my crank is sliding forward out of range of the sensor. Said 1/4 in of endplay. Seems strange that it runs perfectly for first 10 min of driving then starts acting up. Yeah, I can see how..Oil warms up, bearings warm up, crank slides. When I replaced the crank position sensor I looked at the buisness end and there was a a circular-ish clean spot in the dead center about 1/4 in across. Would this confirm or deny crank slide? Any other thoughts? Looks like rebuilts around Austin, TX are running $2K. Will it run with sensor disconnected? LOL ...seriously..will it?:worried:

I do have sympathy for your problem. It is hard to believe a 1/4" of end play. Could you check
this with a broom handle at the harmonic damper or crow bar at flywheel? I believe the thrust is
taken on one of the main bearings, but don't know which one. Is this a 4x4 vehicle. What is the history
of this vehicle and how many miles? Did you read codes when you started having problems? Can you share
them? My 03 does have a clamp on both ends of the PB hose. I am confused about the cheap oil change
because of the CPSA change "next week". A fellow Texan who would like to help.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Started out running like crap. It then threw a code for the cam pos sensor. Found trailvoy and some how to's. Got oil change and oil pressure started acting strangely. Cleaned throttle body and changed the variable valve timing sensor (remembered it being a problem in the past). Ran like a brand new truck. Changed oil, got a little pressure back. Three days later it started stalling while braking. Did some more reading and swapped cam sensor. Still stalling. More reading, swapped crank position sensor and attempted manual crank relearn. First code in a long time pops up P0017. Still stalling, so I took it in to the dealership for crank relearn and update. The truck accepted that, but still stalled for the tech on test drive. They offered the $129 diagnostic check and I accepted. They had it for a total of 24hrs before calling me with that diagnosis. Said w crowbar tech could show me the crank slide forward 1/4 inch. I declined, cause f that wasnt the real problem, I sure didnt want him making a new problem yanking on my crank pulley. Sorry Texan, its a two wheel drive. And I wanted the grunge in the pan out before the variable valve timing sensor change. Hence the quick cheap change, I knew was gonna do another change in 7 days just before the new sensor. Didnt want to trash 7 day old synthetic.
 

Texan

Member
Jan 14, 2014
622
If what they say is true, you might get away with pulling the oil pan and replacing the main
bearing that takes the thrust. If it is 2 wheel drive, that simplifies the process.
Just a suggestion.
 

IllogicTC

Member
Dec 30, 2013
3,452
On the oil pressure, it could very well be something involving the crank (oil pump runs off it, you know) or maybe the seafoam busted out some nasty crap that's stuck somewhere now like in the oil pickup. Or maybe both.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Thank you, Gentleman. Both of those options sound a little less painful than the full rebuild. I could combine both options, right? Change the oil pump and front main with one drop of the pan..? It does have 180K on the motor.
 

Texan

Member
Jan 14, 2014
622
jeffrobinson said:
Thank you, Gentleman. Both of those options sound a little less painful than the full rebuild. I could combine both options, right? Change the oil pump and front main with one drop of the pan..? It does have 180K on the motor.

Somewhere in another thread the is a exploded view of the engine. I will try to find a link to it.
I think that the oil pump is a part of the front cover, but am not positive.
 

Hypnotoad

Member
Dec 5, 2011
1,584
Are you sure it's the crank itself or just the pulley? I find it hard to believe the crank could be moved like that. Every main bearing would have to be F'd up pretty bad.
 

Texan

Member
Jan 14, 2014
622
Hypnotoad said:
Are you sure it's the crank itself or just the pulley? I find it hard to believe the crank could be moved like that. Every main bearing would have to be F'd up pretty bad.

Normally one main bearing is picked to take the thrust load. In the old days it was the rear main.
Not so today. I bought the $120 shop manuals for my TB when I bought it, but gave them to my
nephew who lives 250 miles south and has a 2004 TB. Can somebody confirm which main bearing
takes the thrust on I6? Thanks.
 

Hypnotoad

Member
Dec 5, 2011
1,584
Texan said:
Normally one main bearing is picked to take the thrust load. In the old days it was the rear main.
Not so today. I bought the $120 shop manuals for my TB when I bought it, but gave them to my
nephew who lives 250 miles south and has a 2004 TB. Can somebody confirm which main bearing
takes the thrust on I6? Thanks.

You're right, I remember now that on a SBC its number 5.
e3ahudy2.jpg
 

Texan

Member
Jan 14, 2014
622
After sleeping on what I said last night, I must try to clarify my thoughts.
This is not a DIY or amateur type project. It would require a knowledgeable and skilled
machinist who has the tools and can fit insert/shell type bearings. If you believe what
the dealer says, and with 180k miles, a rebuilt engine may be best bet. Good luck.

Thanks Hypnotoad for the diagram. #120 is the main thrust bearings.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
I was thinking you were saying I could just pull that lower main cap from below the truck in the driveway , and swap the lower half of that bearing. Hoping that would band aid the prob for long enough to trade it back to CarMax in a couple months after hoarding up a few bucks. Sounds like that's not the case. Things sure have changed under the hood since the late 80's. Just when I was beginning to think it was actually easier after comparing the throttle body cleaning to a quadrajunk rebuild...anywho, I'll be back to let yall know what happens. As far as believing the dealership, I'd love not to, but what else could be causing this prob? Should I have more diagnostic testing done? How do I find somebody better than dealerships?
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Seems like most of yall were skeptical of that dealer diagnosis of death. Lets just look at the current situation. My truck purrs like a kitten for the first 10 min of driving, then starts stalling at low idle or braking. What would yall suggest?
 

Texan

Member
Jan 14, 2014
622
My real problem is I have not been inside one of these I6's. So I do not want to mislead anyone.
I think that if you found somebody familiar with this engine, you could probably do as we discuss above.
Anyhow best of luck and let us know the outcome. I will say my 2003 TB has been the best vehicle that I
have owned, and I would buy a new one if I could.

PS: keep driving it and we will think about the issue.

PS2: see if it throws any codes.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Texan said:
My real problem is I have not been inside one of these I6's. So I do not want to mislead anyone.
I think that if you found somebody familiar with this engine, you could probably do as we discuss above.
Anyhow best of luck and let us know the outcome. I will say my 2003 TB has been the best vehicle that I
have owned, and I would buy a new one if I could.

PS: keep driving it and we will think about the issue.

PS2: see if it throws any codes.

Will do. Think I should keep swapping cheaper sensors? Read the most about folks having purge valve issues and fan clutch, Still have not changed:

MAP Sensor- Delphi $34 AC Delco $57
Vapor Canister Purge Valve -Airtex $28
Mass Airflow Sensor-$54
Air Pump check Valve -more
O2 sensors- more
Fan Clutch- a lot more and a real pain

I have changed:
Cam position sensor
Variable Valve timing Sensor
Crankshaft Position Sensor
 

Texan

Member
Jan 14, 2014
622
Just thinking out loud. Do you have a scanner that you can use to monitor the various
outputs, such as O2's, and fuel trims when it acts up? Have you checked for vacuum leaks?
There is a small vacuum nozzle on the intake manifold at the front side next to the resonator.
The SWB model has a rubber cover, the LWB has a hose to rear HVAC. Loose intake manifold
bolts seem to be a common issue. Clamp on brake booster hose.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
Texan said:
Just thinking out loud. Do you have a scanner that you can use to monitor the various
outputs, such as O2's, and fuel trims when it acts up? Have you checked for vacuum leaks?
There is a small vacuum nozzle on the intake manifold at the front side next to the resonator.
The SWB model has a rubber cover, the LWB has a hose to rear HVAC. Loose intake manifold
bolts seem to be a common issue. Clamp on brake booster hose.

I do not have a scanner, but I have checked for vacuum leak, but I only know of two possible leak locations. The brake booster hose (which I haven't added a second clamp yet, but intend to. Drove the Tahoe to work today) And the short hose at the front left side of the Plastic box w the VORTEC name over the center of the motor to the manifold by the variable valve timing solenoid. #1 in picture.View attachment 33933 Are there any more vacuum lines? It is a short wheel base.
 

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jeffrobinson

Original poster
Member
Mar 31, 2014
40
Was thinking if there was anything I was forgetting to mention that could be relevant, and I remembered that when it isnt an instant stall, that it blubbers wildly at idle unless I hit the throttle. It revs fine then, then falls back down into the blubber or stall. If I let the blubbering continue for 5-10 sec the P0017 code pops up. If I turn it off instead of catching the throttle, and restart the truck, it starts with a high and smooth (about 900rpm), and settles in to smooth 600rpm idle, blubber free and no codes. It will then accelerate fine, runs highway speeds fine, untill next stop, then stall or blubber starts all over again. Again, this is only after warm up. Runs perfect, with or without AC, for around 15 min or miles after a cold start (75-85 degrees outside). When the P0017 code does come up, it disappears the following morning, or after the autozone guy pulls the code, when I go back to the truck and start it to leave Autozone.
 

IllogicTC

Member
Dec 30, 2013
3,452
I'm wondering if there isn't faulty wiring or a need for a PCM update or something. Or maybe the thrust bearing indeed.

Here's a random idea - the next time you go to stop, first shift to Neutral before braking. Keep it neutral for the duration of your stop then go back into gear when you're ready to go. See if the issue stays even when stopping in neutral rather than drive.
 

Texan

Member
Jan 14, 2014
622
jeffrobinson said:
Will do. Think I should keep swapping cheaper sensors? Read the most about folks having purge valve issues and fan clutch, Still have not changed:

MAP Sensor- Delphi $34 AC Delco $57
Vapor Canister Purge Valve -Airtex $28
Mass Airflow Sensor-$54
Air Pump check Valve -more
O2 sensors- more
Fan Clutch- a lot more and a real pain

I have changed:
Cam position sensor
Variable Valve timing Sensor
Crankshaft Position Sensor

I would not recommend throwing parts at it. Borrow a scanner (Harbor Freight has one for $90), we need to know
what the brain (PCM) is thinking. You may or may not have a air pump (SAIS). Here is a link that a picture of the
nozzle on the intake manifold in #10.

http://gmtnation.com/f25/clean-throttle-body-now-high-fluctuating-idle-10306/

If you have a android phone, check out the Torque app and a Bluetooth adaptor for the OBD2 connector.
 

Texan

Member
Jan 14, 2014
622
jeffrobinson said:
I do not have a scanner, but I have checked for vacuum leak, but I only know of two possible leak locations. The brake booster hose (which I haven't added a second clamp yet, but intend to. Drove the Tahoe to work today) And the short hose at the front left side of the Plastic box w the VORTEC name over the center of the motor to the manifold by the variable valve timing solenoid. #1 in picture.View attachment 21546 Are there any more vacuum lines? It is a short wheel base.

FYI: That hose is for the PCV system, although the engine does not have a PCV valve. I know that
this can be confusing, but you can find threads that discuss this issue.
 

jeffrobinson

Original poster
Member
Mar 31, 2014
40
So, I went back to quickie lube this morning and soft-talked the manager with the "I know mistakes happen" approach. Left with a free oil change, and they installed my Bosch filter. I then piled into TB and made the 120 mile journey to the in-laws in Gatesville. It starts with a 70 mile run of 85mph toll road which I never run more 75mph on cause I have the family on board. While making that stretch I did several of the coast down cycles mentioned in the manual crank relearn process. When we hit our exit it was time for the real test. Did not stall. Pulled in to gas up and yet again it did not stall, nor blubber. Stoplight time..again, no stall no blubbering. Now another 30 mile run of 55mph country road. Unexpectedly rolled up on an ugly wreck, cops stopped me while the loading an unlucky individual into ambulance. That was 5 min in drive, foot on brake. No stall no blubber. Proceeded on to destination. Not one incident the entire trip. And the oil pressure indicator never fell below 40. Today is a cooler day than it has been, so there's that..I don't expect everything is golden now, but today thus far, has been a better day.:shhh:
 

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