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Tool Hut
Tool Hut, ASE Certified Technician
Category: Buick
Satisfied Customers: 494
Experience:  Owner of a mobile diagnostics company assisting auto technicians with difficult vehicles
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I have a 2005 Buick Rendevous with an acceleration issue, if

Customer Question

Hi I have a 2005 Buick Rendevous with an acceleration issue, if I accelerate smoothly I can get up to hi way speed and run there for a long time , only issue is if I step heavier on the pedal the vehicle goes into a limp mode, if I let my foot off the pedal for 3 sec I can smoothly accelerate again, this happens at most speeds, at some times I cam accelerate and go from 0 to speed without an issue. This have been going on for 6 months change fuel filter. No codes are coming up and when it kicks into limp mode if I keep the pedal pushed the rpm can reach 4000 and the speed barely climb, thought maybe fuel pump but figured it would have died by not and couldn't do hi way speed like it does have tried to rev it to cause code be no luck
Submitted: 1 year ago.
Category: Buick
Expert:  Tool Hut replied 1 year ago.

I would suspect a TAC (Throttle actuator control) problem. GM Had a lot of problems with this generation of electronic throttle body. GM has recently came out with a replacement cover for the throttle body in lieu of replacing entire throttle body. Sometimes the harness needs to be replaced as well. My recommendation would be replace the cover and the harness. make sure harness is soldered in.

Expert:  Tool Hut replied 1 year ago.

Did you figure anything out?

Customer: replied 1 year ago.
Been trying to get to the GM dealer but parts been closed before I get off work will get on weekend for sure? Question Ben reading about TAC does it usually not give.a code, notice it usually has a. Code on the forums that the TAC comes up in
Expert:  Tool Hut replied 1 year ago.

The fact that it is going into limp mode is suspect enough. It is very likely it has a code. It just cant be read with a code reader and since it is not emissions related would not cause the service engine soon light to come on.

Customer: replied 1 year ago.
Samuel was into a GM dealership today to grab the cover and harness, they say you can do it for the 3.6L engine but it is the whole throttle control for the 3.4L and the closest one is 4 days away which surprised me
Expert:  Tool Hut replied 1 year ago.
You nay try some aftermarket parts stores.