hesitation/bucking in my 99 Tahoe

[Stripermike]

Just talked to my tranny guy - supposedly they had the distributor installed and set up at a GM dealership and he's saying the cam retard checks out right. Now I'm wondering if I should go somewhere else and get the work checked - I'm smelling BS...

 

[rockenthebowtie]

Hmm well the only thing that I can say about that is ask him what dealer they took it to and call the dealership to see if they have any records of your truck being there they should be able to pull up your info with a license plate# and vin # if so they should be able to see if they had it there for that

 

[Stripermike]

Thanks - I have already talked to someone else and I'm going to have them look at the cam/crank correlation issue to see where things are at. New guy is pretty insistent that until the 1345 code issue is resolved there can't be any real assessment of the transmission. I just need to know whether I've been dealing with someone who's not going the distance on this but acting as though they are - the truck WAS at their shop for 3 months - in hindsight I probably shouldn't have picked it up at all until it was right, but I needed to have the truck back.

 

[lesterl]

Check the crank sensor and timing set for wear incluidng cam shaft.....

 

[Stripermike]

@ Tex, Rock, Slammed, lester and all who've tried to help with info and ideas - Thanks, it has been appreciated. Now an update and a request for input.
I'm at the end of my rope with this situation. We hooked up the scanner yesterday and after clearing the 1345 & 0340 codes last week they have not come back. Symptoms with the transmission are the same, if not worse. I've been back to my tranny shop 3 times now since picking up the truck - "keep driving it, come back in a week and we'll pull the codes, something is going to happen - a breakdown or something that will enable us to diagnose the problem."
Bottom line - I was sold an overhaul as the remedy for my transmission issue. The transmission issue is the same as when I brought the truck in. My feeling is that something went wrong with the overhaul, or something was missed. I'm thinking that it's time to bring the truck back to the shop and tell them "pull the tranny, figure out why the overhaul didn't cure the issue (that's why they sold me the overhaul in the 1st place) and make it right. Whatever's going on, the symptom is that the transmission isn't functioning properly - fix it.
Am I right to take this position?

 

[Tex99Tahoe]

Absolutely! This has gone on long enough! They're stalling you! In my situation years ago, I returned to the shop IMMEDIATELY when the symptoms occurred. There are time limits, you'll be slowly nudged outside the warranty period!

Even though the truck is swarmed with computer controls and diagnostics, it is still a mechanical thing, capable of things beyond the diagnostics. What codes would be logged if you get a flat, break a lugnut, scratch a door, break the glovebox latch, tear a seat, ...etc? These guys are either incompetent, pirates, fly-by-nights, or afraid of your truck (maybe they know something they don't want you to know, it's happened before).

"No, I won't do your diagnostics, that's why I brought it to you!" "I won't risk my life and time doing your job!" "Why won't you honor your warranty/guarantee?" "Can I get a refund?"

If you meet resistance, there's a sequence of steps to elevate the complaint. Look up the shop in the BBB, follow their procedure. Know that there are steps beyond BBB to elevate the issue.

There's still the AAmco free diagnostic...

 

[Slammed]

I guess but what ever happened to resetting the timing via the distributor

 

[lesterl]

I would take it back ASAP....

 

[Stripermike]

Tranny shop swears the distributor timing is correct & codes haven't come back. I don't think I should have to spend more $$ somewhere else to re-check what they've already done - again my position is make it right. You sold me an overhaul as the fix & it ain't fixed, it's the same as it ever was....

 

[Slammed]

Well hit them hard and don't back down

 

[Stripermike]

Well, here I am again. Transmission shop doesn't want to pull the tranny back out of the truck until/unless something definitive warrants doing it. So I've chosen to reserve the part where I go off like a bomb on them and start making demands until I'm 100% confident that it is in fact warranted.
I'm going to have the other shop I talked to render an opinion on the situation, but while I'm waiting to get the truck looked at by them I've been trying to rule out a few things myself, along with hunting down the source of the thunking noise.
On that topic - I've discovered that the limited slip seems to be gone - one thought is that the noise is coming from a broken axle on the right side.

Also, it was suggested to me that the "bucking" could be caused by the egr valve since the condition seems to occur regularly when I let up on the accelerator. I have removed the egr valve and inspected it then reinstalled. It did not appear stuck or gummed up, etc. I also cleaned the connector and plug (along with most of the other connectors as tex had suggested). This didn't change things. I drove the truck with the egr unplugged just to see if the truck behaved differently and noticed no change. Does anyone have any thoughts on this?

I have also experimented with driving the truck in different gears. I cannot recreate the symptom in 1st, although it is difficult to drive any real distance. In 2nd I am able to drive quite a while, and I can get a slight "pull" if I get some speed going and let up on the pedal a little - it's not nearly as pronounced as if I am driving in 3rd or D.

I had the truck plugged in and the 1345 code has still not re-appeared.

You've all been helpful with info - anything additional would be greatly appreciated.

 

[Stripermike]

New developments with my 99 Tahoe troubles

So today I drove the truck to work (have to do that sometimes) about 15 miles. Parked on the street and after about 45 minutes wanted to move the truck into the driveway at the house I'm working on. Went out and tried to start it and no luck. Engine turned over fine, sort of wanted to run, but as soon as I released the key, no go. I tried a few times - same result. Just for the hell of it I tried starting it with the remote starter (aftermarket, installed by previous owner). Lights flashed like usual but the engine didn't even crank over. Tried a couple more times and nothing. Series of clicks from the unit under the dash, along with some fluttering gauges and 3 or 4 dings of the bell but no engine turn over.
I started thinking maybe it was out of gas - I have the gas gauge "flutter" on start up and since I bought the truck haven't been certain of the reliability of the gauge. Was just about to dump a can of gas in, decided to try a few more times with the remote, which still didn't turn the engine over, then got in and hit the key. Fired right up.
WTF! Now I'm wondering how this relates to my bucking/hesitation issue, or if it does at all?!
Has anyone had similar experiences with remote starters? I really couldn't care less about the thing - do you all think I would be just as well off disabling it?

 

[Tex99Tahoe]

Wow, Mike, you're having a good week.

NOW is a good time to get codes, since that's a bona-fide engine problem!

However, it may not be related to the original issue. The fact that the syndrome only occurs in 3rd and overdrive is significant, to me still points to the tranny...

 

[lesterl]

Check the ignition switch....

 

[Stripermike]

OK. I've learned quite a bit about transmissions through this whole experience - probably more than I really wanted to know.

I did get the codes read yesterday. Nothing but the minor evap code that we pulled at the tranny shop last week and an egr fault that I probably threw when I unplugged the egr valve and drove the truck a little. Nothing of any consequence or help.

But I started thinking about the TCC lockup, as I have most days that I've driven the truck and had it buck and bang down the road. Since I can't ever create the symptom when the truck is cold 1st thing in the morning, until the temp gauge gets up to the normal operating level, I wondered what would happen if I unplugged the coolant temp sensor to do a little test. Presto - no symptoms for 25 or so miles of driving, even when I REALLY tried to create the conditions when I would usually have them.

Not being an optimist at this point, especially with this truck, I wasn't holding my breath on a $20 coolant temp sensor being the answer to my woes, but I bought one anyway and this morning I installed it and plugged the connector back in. No luck. Once again, as soon as the truck warmed up, it started it's usual tantrums.

So I have once again unplugged the connector, sacrificing about 30% of my gas mileage I suspect, and am driving the truck around - symptom free, for the most part. A couple times today I noticed a slight hesitation, very minor compared to what I've been experiencing, and the truck definitely starts a little harder. If I don't let the starter crank the engine over quite a few times it doesn't want to stay running, and when it does it takes a few seconds to smooth out. After that it runs fine, plenty of power, etc. I'm sure the sensor being unplugged is confusing more than just the transmission.

Here's my question - by taking the TCC lockup offline I can eliminate the symptom. That kind of makes me feel like the problem is all about the functioning, or proper functioning of the TCC, and it should be chased down starting at the TCC - is that sound logic?

 

[lesterl]

This may be stupid, but have you checked the brake light switch?

 

[Stripermike]

Another day and hopefully 1 step closer to a solution. I had a lot of driving to do today, both highway and back roads. I made a point of using the Tahoe instead of the wife's car so I could really put some miles on under many different driving conditions and see how things went - with coolant temp sensor unplugged.

This morning before we started out I did 1 thing I've been meaning to do, especially with the "finicky" starting of late. I pulled the MAF and gave it a good cleaning. I wouldn't say it was all that dirty, but there was some carbon on the screen and a little crud around the elements and tube. Whether coincidence or not the truck had no starting issues today.

The truck also had no driving issues today. In fact it ran great. Plenty of power on the highway, nice and even, no bucks, no hesitation or lurching, basically ran just like my old 95 used to. Gas mileage is definitely down without the lockup in play.

At this point I'm confident that I have 100% cause to DEMAND that the tranny gets pulled again and they find out whatever is causing the TCC to malfunction - it certainly doesn't seem to be anything that affects the engine performance in any way, so I think it's more than reasonable to assume something with the transmission components - solenoid, sensor, something. Whatever the case may be, I'm not going to drive the truck around without a working TCC after a $2500 transmission job.

I'll post an update after I give my tranny shop the "bad news".

 

[Slammed]

Good luck don't give up and if you need to threaten with better business Bureau or your local dmv's dealer's and repairs division

 

[Tex99Tahoe]

Wow, coolant temp sensor. I'm gonna think out loud here, hope lester, samo and rockin can jump in.

With the temp sensor unplugged, the computer thinks that the truck isn't warmed up, and stays in open loop mode. In this mode, the computer will not perform egr, TCC, and will run rich using a default fuel delivery table, rather than the 'learned' table. So, expect starting problems running in this 'limp' mode.

But, this is a good test, got a positive response. It tells me that the jerk/bucking happens when the computer is allowed to activate the TCC.

Can't think of another sensor plug to pull to get more info, unless you could interrupt the TCC solenoid line...

 

[Stripermike]

Well.... the head honcho at the tranny shop was off today - I've been dealing directly with him on this issue so there was no movement on that front today. But....

Being the obsessive thinker and being unable to avoid trying to figure this out I decided to try something that's probably not recommended - I pulled the plug on the TPS and drove the truck around. Since my symptoms have seemed to appear most often when I am starting to lighten up on the accelerator pedal it somehow made sense.

The results were interesting. The truck wasn't always happy - it stalled a few times backing out of parking spaces and idled erratically at times. Once I got it rolling down the road however, it didn't exhibit the same symptoms. Some of the shifts were rough, as would be expected I guess, but the TCC seemed to function without the usual bucking. I drove quite a distance in 3rd because it's pretty easy to tell when the converter locks up and things seemed better.

I took a shot and threw down the $35 for a new TPS. No change once I installed it and plugged back in.

Am I chasing my tail on this? None of it is making sense at this point, so Tex you were right on that score.