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Trailblazer SS Acceleration is unpredictable

516 views 3 replies 2 participants last post by  Ravalli Surfer 
#1 ·
Ive been the owner of a 06 AWD TBSS for a few months with what has been said to be rebuilt transmission and some light mods (CAI, Coilovers, Etc) and when turning it will not accelerate in 2nd gear, it hesitates and will not accelerate or rev. It has recently gotten a new MAF sensor and will be getting a new MAP sensor in a few days. Only engine code its ever given me was p0171 and I believe I've fixed that code. It almost stalls it seems until it finally decides it wants to accelerate. Giving it gas, it will usually downshift and accelerate hard, and if i give it too much gas it will rev high and wont accelerate at all. I am at a complete loss.
 
#2 · (Edited)
Any transmission that 'blows out' and won't hook up is talking to you. It needs internal attention.
Run a pressure test to affirm the line pressure is OK.​
Watch for shift-changes in pressure as the factory designed it to do.​
Make sure that manula Low and Reverse get the proper pressure spike and then make sure that the spike drops to normal in OD or 4 or any gear but Manual Low or Reverse.​

The front pump might have a badly scored internal machined surface and the pump is making maximum pressure because it's partially seized or stuck until it gets moving and a couple of shifts under belt in the AM.

QUESTION: Does the transmission "slam" into either Reverse or Drive at first start up in the morning?

SIDEBAR: This transmission is easy to screw up on the bench with mismatched parts or just bad bench work so saying it's a "rebuilt" carries no pondus at all. I just don't trust anyone but ME when it comes to working on my transmissions.​

The "B" solenoid might be failing - but I don't think I'd go there yet. It CAN make the vehicle feel sluggish in Low gear until it hits 2nd. You didn't say this was in the symptoms - but you kinda hinted around in that area - just a bit.

To eliminate that "B solenoid" as a possible culprit - manually put the quadrant into 2nd gear and accelerate (some calibrations will start in 2nd and stay there --- and some will start from a stop in 1st and then shift up to 2nd and just stay there) ... either way - the transmission will ceae feeling like it's holding back if it accelerates the way it should.

Not accelerating in a certain gear MIGHT be the TCC isn't releasing at the appropriate throttle pressure. That could be a bad sensor in the trans - the TCM, the TPS or maybe the MAF - but that last one isn't likely because it's gonna manifest itself in other ways that you didn't mention - so I'll sign off on that for now.

It's NOT a screwed up adaptive value - so don't go there yet. DON'T do the famous "disconnect the battery" test or attempt to "reset" the adaptives in the transmission. That will only cloud the issue at hand.

IIWY - I'd be looking into the PWM to make sure that it's working correctly. I'm pretty sure that your vintage vehicle has a PWM - but I might be wrong. I personally have locked mine down so it doesn't operate at all because I don't like heat generating, partial apply/release TCC.


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#3 ·
To quickly answer your question, it shifts smoother when it’s been freshly started. I did a bunch of testing and I’m more leaning towards it’s engine related. I found it doesn’t fire a majority of its cylinders when it “hesitates” and was able to track it down to original spark plugs, replaced the plugs and wires and the hesitation has almost entirely disappeared. Seems something else is having a minor impact though, which I now need to track down. So far the spark plugs have had a major impact on the problem, I’m sure that with a combination of a dirty maf and throttle body is why the last guy sold it. It’s gotten a new MAF, MAP plus spark plugs and wires and a thorough cleaning of the throttle body. Going to check fuel pressure tomorrow and see what it gives me, I think that might be the last piece of the puzzle. I still need to determine the condition of this transmission, it seems to shift hard when the car is being worked hard.
 
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