Alaxgoaly8
TYF Newbie
- Joined
- Feb 11, 2023
- Posts
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Here's my scenario. 2004 GMC Yukon Denali 6.0 AWD... I bought this back in February with 177k miles and noticed it had some issues (no big deal. Knew that when I bought it). Had a troublesome P0300 but we seemed to have calmed that down to the point where the CEL hasn't come back on and the misfires are minor.
So far, these things have been done:
1. spark plugs and wires
2. cleaned the maf sensor
3. replaced the pcv valve
4. replaced the hydroboost
5. BG Induction service
6. Replaced Intake manfold gaskets
7. Smoke tested it but there were no leaks
8. Compression is good
9. Fuel data was where it should be
HERE'S THE PROBLEM THAT WON'T GO AWAY
If I'm driving slightly uphill at 35 to 45 mph and pressing lightly on the accelerator to keep my speed, the engine will rev up and down between about 1300 to 1500 rpms. Like "RRR...RRR...RRR...RRR". I can accelerate out of it or remove my foot from the accelerator and the action will stop. It doesn't happen when accelerating up to speed (like accelerating 0-30 or passing 50-70 on the highway)... It just seems to do it holding speed with light accelerator pressure. I took it to a transmission shop and they didn't see anything in the computer saying it was the torque converter or transmission acting up but said they saw misfires but not a lot of them... I took it to my mechanic to do the same test drive. Both felt the sensation I did, but my mechanic said he thinks its the transmission starting to go because that's what it feels like and he didn't see any data telling him it was anything else. The transmission only has about 50k miles on it since it was replaced by the previous owner.
The original mechanic that did all the work basically threw his hands up...
From the videos on youtube I've seen, here are some things it could be...
1. Bad ground wire from the pcm, or one of the others in the engine bay or under the drivers side door (those seem to cause all sorts of issues)
2. Torque converter lockup issue?
3. Coil pack arcing (although both mechanics said nothing in the scan tool data showed an issue with the coil packs).
4. Maybe the trans is shot? But the trans shifts through the gears pretty smooth. It doesn't shift hard at all. It's just that very specific issue at those specific speeds.
It's about $3500 to put in a new trans and torque converter, and I don't want to spend money to throw parts at it and still have the issue.
Coil packs would be about $170 for all 8 plus I'm going to guess its 2 labor hours per book... so maybe a $400 job ($120/hr labor rate around here)?
Having the ground wires refreshed... I'm guessing 3 labor hours and cost of wire... so maybe another $400?
My question is, has anyone had this specific problem and been able to figure it out? And if so, please share what fixed it for you. Thank you in advance.
So far, these things have been done:
1. spark plugs and wires
2. cleaned the maf sensor
3. replaced the pcv valve
4. replaced the hydroboost
5. BG Induction service
6. Replaced Intake manfold gaskets
7. Smoke tested it but there were no leaks
8. Compression is good
9. Fuel data was where it should be
HERE'S THE PROBLEM THAT WON'T GO AWAY
If I'm driving slightly uphill at 35 to 45 mph and pressing lightly on the accelerator to keep my speed, the engine will rev up and down between about 1300 to 1500 rpms. Like "RRR...RRR...RRR...RRR". I can accelerate out of it or remove my foot from the accelerator and the action will stop. It doesn't happen when accelerating up to speed (like accelerating 0-30 or passing 50-70 on the highway)... It just seems to do it holding speed with light accelerator pressure. I took it to a transmission shop and they didn't see anything in the computer saying it was the torque converter or transmission acting up but said they saw misfires but not a lot of them... I took it to my mechanic to do the same test drive. Both felt the sensation I did, but my mechanic said he thinks its the transmission starting to go because that's what it feels like and he didn't see any data telling him it was anything else. The transmission only has about 50k miles on it since it was replaced by the previous owner.
The original mechanic that did all the work basically threw his hands up...
From the videos on youtube I've seen, here are some things it could be...
1. Bad ground wire from the pcm, or one of the others in the engine bay or under the drivers side door (those seem to cause all sorts of issues)
2. Torque converter lockup issue?
3. Coil pack arcing (although both mechanics said nothing in the scan tool data showed an issue with the coil packs).
4. Maybe the trans is shot? But the trans shifts through the gears pretty smooth. It doesn't shift hard at all. It's just that very specific issue at those specific speeds.
It's about $3500 to put in a new trans and torque converter, and I don't want to spend money to throw parts at it and still have the issue.
Coil packs would be about $170 for all 8 plus I'm going to guess its 2 labor hours per book... so maybe a $400 job ($120/hr labor rate around here)?
Having the ground wires refreshed... I'm guessing 3 labor hours and cost of wire... so maybe another $400?
My question is, has anyone had this specific problem and been able to figure it out? And if so, please share what fixed it for you. Thank you in advance.