06 TB 4.2 stalling while braking..
- Thread starter jeffrobinson
- Start date
Thinking your advice to "Drive it" may be a winner. I couldn't leave well enough alone. I just went out and hammered on it, did my very best to stall it. Unsuccessfully. 
Another day of pounding on it and cant get it to stall. Looks like if this over, the moral of the story was.. If you change a bunch of sensors, go take it for a long highway drive. Thank you Texan, for that jem. For now that may have saved me a premature $2400 + $1500 install. Now how do I get the dealership to hand back some of that B.S. $225? And a round of beers for everyone who helped, on me!! 
Could be the best outcome of any advice thread I've read in nine years! Dealer diagnostic fail (unless they proved it with pics...)
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Monday and Tuesday were buisness as usual for my family. 60 miles on the TB per day. 30 of which are Austin TX rush hours, 8a and 5p. Austin has ranked in the top 10 worst traffic cities (climbing every year)in the country for the last 5+ years. I have not had one stall since taking this truck on the 100 mile journey to Gatesville Saturday morning. As I reflect back over the timeline of the whole ordeal, I think I have narrowed down the problems. The oil pressure problem was seperate, caused by the wrong oil or a defective oil filter. Or is it possible the oil filter was so over-tightened that it caused the passages to deflect? But the stalling problem, I'm having a harder time finding closure with. I have had the variable valve timing sensor replaced before, and didnt have this problem after. I replaced the cam position sensor next, but didnt go on any long drives. But I did follow the recommended steps for allowing hours of battery disconnected time (even with key in on position) for computer settings to reset. I then did the crank sensor and tried manual and dealer flashed crank relearns and updates, to no avail. Only after the long drive did the problem finally resolve. Cam or Crank sensor...will I ever know?
Since my last post post I've had two incidents. First was a sputter then stall under braking in morning rush hour, foot off gas pedal. The second was a no sputter, instant stall as I was coasting around a traffic circle. Starts with a quick right, then a long left bend around. The reason I give this detail is that is where this all began. That traffic circle i go around every morning has been home to more of the sudden death stalls than could be coincidence, I think. Does this trick sound familiar to anybody?
Texan
Member
- Jan 14, 2014
- 622
Hello Jeff, I have been out of town for the past two weeks. That traffic circle leads me to think about
what could be causing the problem when turning. I can not think of a possible cause for the stalling,
If the cause was the main bearing thrust issue, would turning a corner cause the crank to move?
I do not have a good answer. Keep us informed.
what could be causing the problem when turning. I can not think of a possible cause for the stalling,
If the cause was the main bearing thrust issue, would turning a corner cause the crank to move?
I do not have a good answer. Keep us informed.
I would check wiring to fuel pump, I recently saw a thread where the wire was pinched by the body and caused the fuel pump to stop... or possibly ignition switch?jeffrobinson said:
Texan
Member
- Jan 14, 2014
- 622
"Sputter and then stall under breaking". Just a thought, but if you could block off the vacuum to the brake booster, and
just use manual brakes, this would eliminate the booster having a leak. But, be careful and do not let anyone else
drive it like this. Have you checked for other vacuum leaks? Some owners have noted loose intake manifold bolts.
I have experienced a corroded "weather pack" wiring connector on the wiring to the fuel pump on another GM vehicle.
Contact cleaner and dialectric grease solved that problem. The connector was under the body where the wiring harness
came out of the body, under the drivers seat. I do not know if the TB has a similar connector. Just thinking out loud.
just use manual brakes, this would eliminate the booster having a leak. But, be careful and do not let anyone else
drive it like this. Have you checked for other vacuum leaks? Some owners have noted loose intake manifold bolts.
I have experienced a corroded "weather pack" wiring connector on the wiring to the fuel pump on another GM vehicle.
Contact cleaner and dialectric grease solved that problem. The connector was under the body where the wiring harness
came out of the body, under the drivers seat. I do not know if the TB has a similar connector. Just thinking out loud.
Howdy all, I'm back. I had a string a couple months back on the truck stalling while braking. Well, after changing a bunch of sensors the problem persisted. "Texan" said "drive it". So I did. Got on the toll road and cruised 100 miles. Magically the problem went away. For two weeks. Then slowly the stalling came back, every time I stopped. So out of desperation, I changed the oil again and jumped back on the toll road repeating the process that that temporarily solved my problem. Guess what? It worked again! What on earth could cause my truck to forget how to run every couple weeks, then correct after a long drive? The truck is 06' 4.2 automatic, and I did both times disconnect the battery overnight before the drive. I did both times change the oil the night before. I did notice both times that my simulated "oil pressure gauge" was dropping to 0 before the long drive fix, and never drops below 40 after. I don't know if any of those things make a difference, but I throw them out there in case it does. What do yall think?
PS My throttle body is spotless, and I have no codes.
PS My throttle body is spotless, and I have no codes.
LOL, sorry man. Just edited my question to add the answers I knew would be asked. Throttle body is spotless, and I have no codes.
Howdy Texan!! Glad to see ur still here for us green horns! As to KNBlazer, no codes, and I went to the dealership and had the updates done, as well as a crank relearn after replacing the crank position sensor. Didn't help at all.
I'm a bit hesitant to ask a leading question but...a friend suggested a failing catalytic convertor may be my problem. He said the 100 mile run is blowing out crud, then it recollects after a couple weeks. What say you guys?
I'm a bit hesitant to ask a leading question but...a friend suggested a failing catalytic convertor may be my problem. He said the 100 mile run is blowing out crud, then it recollects after a couple weeks. What say you guys?
Well it started getting more frequent, even just when coasting down, no brakes involved, now that you mention it. But always while the rpm is coming down. May or may not coincide with the trannys downshift to 1st at about 800 rpm or below.
I have tried really hard to find a pattern to this and I cannot. The only consistent thing is that it never happens during the first 10-15 min of driving. Cold start. Well, as cold a start you get in Texas. Even if the "cold start" occurs during a 92 degree afternoon, like today.
The trans was rebuilt at 160k miles, about a year ago, and I'm at 185k now. Had no problems between then and now. Thought did cross my mind. Wondered if the long drives were pushing tranny fluid to where it belongs, but the city driving dosent spin it long enough to get there.
I did replace the oil pressure sender, Texan. Didn't fix the stalling or the low reading. Only after the long drive did the bottomed gauge correct. When the stalling came back, so did the 0 readings.
I did replace the oil pressure sender, Texan. Didn't fix the stalling or the low reading. Only after the long drive did the bottomed gauge correct. When the stalling came back, so did the 0 readings.
IllogicTC
Member
- Dec 30, 2013
- 3,452
The 0 readings may be coming from an idle coming down so much that the pressure temporarily goes below the switch's threshold. How low does the tach drop when it's in stall/stumble? It may be worth having a mechanic or if you're feeling generous with your wallet a dealership tech actually take the thing for a spin, as it may be something which isn't really showing up on scanning but would present obvious signs and evidence on the road.
RayGumm
Member
- Apr 16, 2014
- 630
I concur. Sometimes an old school trained ear and eye can spot stuff even the best DIYer might miss. I have a mechanic who owns the Midas in Winchester VA and he/his team is phenomenal. They are always fair and would only try to rip you off a little IF you obviously had no idea what you were talking about. But other than that, go in there knowing what you're talking about in general, tip the actual tech doin the job/free 'estimate', and they treat you like gold. Taken every car I've owned in VA there and will still take the TB there if I need a mechanic. They also generally will let you bring your own part with no complaint. I've had them cut out and swap in a junkyard upper control arm on an old Aerostar for like 180 labor. Not bad considering it actually took 2 dudes like 4 hours to cut the beast out w/a torch without damaging the frame. The best DIYer will know when they are in over their head. It's a learning opportunity, anyway. They usually let me watch'em.IllogicTC said:
Good luck!
Howdy illogicTC. I did go to the dealership and gave them the truck for two days. They found nothing, but they did tell me with a crowbar they could pull my crank forward a 1/4 inch, which meant my endplay was so great that while braking the crank was sliding so far forward that it lost signal with the crank position sensor. The guys on this site called BS on that diagnosis for several reasons. And it was a few days after that diagnosis that I fixed it for 2 weeks after an oil change and a 100 mile drive.
IllogicTC
Member
- Dec 30, 2013
- 3,452
I forgot about that, I remember reading it too. A proper play measurement would be to do the proper procedure and use the actual tool, which being a dealership I would have thought they would have on-hand with so may I6 units floating around out there. I'm not sure how much, if any, teardown is needed to measure it, it could be cheap (relatively speaking) or it could be a real money hose.jeffrobinson said:
Lets go back to the catalytic convertor for a sec, were you implying that it was eliminated by the brakes being involved? Now that I have seen the stalling occurring without the brakes in play, is that a possibility? What does a failing convertor do? The exhaust is still original, 185k miles.
IllogicTC
Member
- Dec 30, 2013
- 3,452
A clogged converter would be a lack of power in general. Some people say they can't even get over a certain speed, like 40 MPH for example. Think like trying to breathe out through your mouth, except you have a tiny straw in your mouth you're trying to vent through. A backpressure test would help greatly in confirming if it's an issue. If there were some issue where the cat's getting clogged and the gunk is being "blown out," then that would indicate another issue which is causing rapid gunking in the first place.
And I looked up crankshaft end play measurement... wow, that looks easy. The tool's probably expensive, but it looks very easy. I don't see why the guy decided a crowbar was necessary.
And I looked up crankshaft end play measurement... wow, that looks easy. The tool's probably expensive, but it looks very easy. I don't see why the guy decided a crowbar was necessary.
Texan
Member
- Jan 14, 2014
- 622
Jeff, if you go back to the diagram that Hypnotoad provided in number 27, it shows that the thrust bearing #120 is
on both top and bottom of that main. If you look at main bearings sets on Rock Auto, the pictures show that
the thrust bearing is only on one side of that main. I have a gut feeling that the main caps are made out of steel.
The thrust may be taken on only one half of that main, and if it is only on the main cap, it would simplify the replacement.
But this would still be a major project, that I have never done on this vehicle. Just thinking out loud again.
on both top and bottom of that main. If you look at main bearings sets on Rock Auto, the pictures show that
the thrust bearing is only on one side of that main. I have a gut feeling that the main caps are made out of steel.
The thrust may be taken on only one half of that main, and if it is only on the main cap, it would simplify the replacement.
But this would still be a major project, that I have never done on this vehicle. Just thinking out loud again.
I just cant make sense out of the fact that the prob can fixed temporarily with a long drive. Makes me think the PCM is bad, but NOBODY has brought that up. No one is talking about the throttle body either. I read a thead by CaptainXL here that had some similarities, but it trailed off...
http://gmtnation.com/forums/topic/3733-envoy-stalled-at-stop-light-3rd-incidence-in-1-year/?hl=stalling
and this one too.
http://gmtnation.com/forums/topic/1005-2002-trailblazer-stalling-stumped-on-why/?hl=stalling
http://gmtnation.com/forums/topic/3733-envoy-stalled-at-stop-light-3rd-incidence-in-1-year/?hl=stalling
and this one too.
http://gmtnation.com/forums/topic/1005-2002-trailblazer-stalling-stumped-on-why/?hl=stalling
Still here, no stalling for going on two weeks now. Waiting for it. The guy who had the bad O2 sensor wiring has not responded. Trying to determine if it was up or downstream. He said it was the wiring between the sensor and the pcm. Was that the included 12 in pigtail, or part of the harness that had to be spliced?
Texan
Member
- Jan 14, 2014
- 622
Wish you could hook up a good scanner and catch a freeze frame when it stalls. You say it never happens before
10 - 15 minutes after a cold start. A cold start is in "open loop" until it reaches a certain operating temperature and then
goes "closed loop". I think that it would be in "closed loop" before 10 - 15 minutes. I hate to throw parts at a problem,
but if your front O2 sensor (on exhaust manifold) has not been changed, I would be inclined to install a ACDelco
replacement. Normally, if this is a problem, it should throw a code and turn on the SES light, but?
10 - 15 minutes after a cold start. A cold start is in "open loop" until it reaches a certain operating temperature and then
goes "closed loop". I think that it would be in "closed loop" before 10 - 15 minutes. I hate to throw parts at a problem,
but if your front O2 sensor (on exhaust manifold) has not been changed, I would be inclined to install a ACDelco
replacement. Normally, if this is a problem, it should throw a code and turn on the SES light, but?
Still not stalling, but I'm not giving up on it to do so. And yes, both the O2 sensors are factory. At this point, I'm waiting for trouble before I proceed. I have read on this blog that sometimes pcms need more time to learn than one cycle. This is the second long drive correction I'm currently enjoying. I promise to update here as things develop.
Still no stalling, but.... I have had strange behavior during 6:30 am morning start up. Rough, and quickly rising and falling rpm (up and down 300-400 rpm) during first 10-20 seconds of run time. Last 3 days in a row. If I hit the gas and rev it up to 2K rpm once or twice and let it fall, it will settle back to around 1200 to1400 for a minute or two and complete the warm up. What's going on here? Why this overnight change in warm up 3 days ago?
Does the strange idle coincide with the SAIS turbine pump operation? Can you disable the pump by pulling its fuse for the next couple of cold start attempts?
Hey Texan! Thanks for checkin up on me. Wish I could say it was all just a bad dream, but no. Same drama. Every month or two she starts idleing poorly, then the oil pressure bottoms out. I unhook the battery, change the oil and filter (getting expensive) and take her out for a hundred mile drive . Problem fixed for another month or two. Didnt wait long enough to see if the stalling was gonna start the last couple times.
I know this is a serious risk to my man card privileges, but I think it's time for a confession. I drove this truck 1-2 quarts down for a long, long time. Well past oil change mileages. Many times. Totally irresponsible on my part. I've learned my lesson. Knowing this, is there likely sludge blocking passages that could be causing these issues?
I know this is a serious risk to my man card privileges, but I think it's time for a confession. I drove this truck 1-2 quarts down for a long, long time. Well past oil change mileages. Many times. Totally irresponsible on my part. I've learned my lesson. Knowing this, is there likely sludge blocking passages that could be causing these issues?
Texan
Member
- Jan 14, 2014
- 622
Here is my confession, I can talk a lot easier than I can type. When I was growing up, I watched my dad not
do any maintenance to his vehicles until something happened. I tend to be just the opposite. But, I have yet
to flush my brake fluid, although I know I should. I wonder if running a oil flush (KW) would help clean out
the oil passages. Some other threads have used this idea for noisy lifters, with limited success. In the mean
time, keep on trucking.
do any maintenance to his vehicles until something happened. I tend to be just the opposite. But, I have yet
to flush my brake fluid, although I know I should. I wonder if running a oil flush (KW) would help clean out
the oil passages. Some other threads have used this idea for noisy lifters, with limited success. In the mean
time, keep on trucking.
I think this may be the thread you mention:
http://gmtnation.com/forums/topic/10390-dreaded-knock-sound-is-starting/page-2?hl=flush
Sounds interesting, and as often as I'm changing the oil..easy. I'll give it a try and update. They also mention a product called "MMO". What is that?
http://gmtnation.com/forums/topic/10390-dreaded-knock-sound-is-starting/page-2?hl=flush
Sounds interesting, and as often as I'm changing the oil..easy. I'll give it a try and update. They also mention a product called "MMO". What is that?