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08 Yukon Denali mysterious problem?

Hello! I have an 08’ Yukon Denal XL and I have been experiencing an issue ONLY while the car is in drive and ONLY from a cold start and while outside temperatures are very cold as well, like freezing temps. When I start my car and drive it immediately, the first couple times I come to a complete stop and it has a vibration that reminds me of the feeling you get in a car that is a stickshift and you don’t push the clutch in, the car does not stop as it normally does, it will come to a stop but rolls a little past where it should and as the car stops, the idle gets super rough and usually the car will completely stall out. It re-starts right after. The car will do this 3-4 times and then won’t do it again until the next time I drive it from a cold start again and in cold temps outside. We were told this was a bad solenoid that was inside the transmission. We got 2 other opinions and were told this was a bad throttle body-also had a code suggesting this I believe. After having the part replaced, the car seemed fixed for approximately 4-5 weeks. Now the car is doing the exact thing again. I have also noticed lately, that sometimes when I go to accelerate after already driving on the road, coasting and then press on the gas petal again…the car doesn’t immediately accelerate, it bogs down, almost like a choking sensation and then it will accelerate. I’m not sure if this has anything to do with my big problem, but it never used to do this. I just started noticing this right after having a new throttle body put on. ??? Please help!!!

Please tell us the codes that are present.

No codes present now. The only code was for the throttle positioning sensor. It went away after the repair.

Try doing a throttle body relearn procedure to see if that helps.

https://www.bing.com/videos/search?q=08+yukon+denali+throttle+body+relearn&pc=cosp&ptag=G6C999A005A2B4283&conlogo=CT3210127&ru=%2Fsearch%3Fq%3D08%20yukon%20denali%20throttle%20body%20relearn%26pc%3Dcosp%26ptag%3DG6C999A005A2B4283%26form%3DCONBDF%26conlogo%3DCT3210127&view=detail&mmscn=vwrc&mid=214FD10F9DD67974F023214FD10F9DD67974F023&FORM=WRVORC

Tester

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The engine management may not be correctly adjusting the idle speed for engine load. Try a few experiments

  • When the engine seems bogged down, stopped, foot on the brake, and in D, does it unbog when putting the transmission in N?

  • Same thing, but instead of N, try putting it in other gears (R, 1, 2, 3 etc).

  • With the engine bogged down in D as before, what happens when you turn on the headlights to bright?

  • As above, what happens when you turn on the AC to max cold?

  • As above, what happens when you turn on the rear window electrical defroster?

  • As above, what happens when you turn the steering wheel slowly left and right?

I will have to try these and update!

Kept up on trans fluid changes? in 2wd or auto?

I don’t believe we have ever changed the fluids since we have owned the car. Its AWD.

I have been able to try this several times now…when car is bodding down, it does stop doing it or will not do it when in neutral…only drive. Not sure what this means??

UPDATE: Took the car back to the mechanic…he went through the entire electrical system and found bare wires and misc things that needed buttoned up. Just checked it this morning…NOT FIXED. I’m beginning to wonder if we should just get rid of the car. At this point we have put a decent amount of money into it and I just don’t know what to do. The mechanic told us that at this point, if it was not fixed we will just have to start replacing things, starting with crank shaft positioning sensor.

If the car otherwise meets your needs and is paid for… suddenly getting rid of it is like putting on a full body cast for a paper cut.

You said earlier you didn’t think the “fluids” had been changed since you owned this vehicle. I’d zero in on the transmission fluid, myself. It’s good, relatively cheap first step that solves a lot of problems like this.

Good point. Yes, the car is paid for. It has just been frustrating giving it up multiple times trying to figure this out not having an extra car and having 3 kids to take to school daily.
Trans fluids May be the next stop! Thanks for your input!

I guess there’s some sort of problem with the idle rpm management. Before going down that path though the engine should get a tune-up, new plugs, air filter, fuel filter, ignition timing check, fuel pressure check, intake manifold vacuum check, fuel trims, and a test for possible vacuum leaks. Once that’s all been done and everything tests ok, next measure the engine rpm in the various situations posted above. If any are below spec, check the throttle-body for indications of the throttle plate sticking, and the sensors associated with the idle rpm management, for example the engine coolant temp sensor, the transmission gear selector sensor, throttle position sensor, alternator load sensor, AC compressor load sensor, power steering load sensor, etc. The throttle body re-learn idea posted above seems worth a try also, might get lucky.