QuestionGreetings:
I have had a problem with my Cierra (3.1 F.I.) for quite some time now. Usually if I start the car cold and just go, there is some pretty bad hesitation, almost like the car has being governed. The car will eventually accelerate to where it needs to be but not without some time. After it has warmed up, the car will act better. It will only hesitate if I push the accelerator quickly, and only hesitate a little bit.
One of the most noticeable problems is I have power problems if I'm driving the car and attempt to accelerate onto the highway…basically if I attempt to use high RPM. This happens even if the car is warmed up.
The final symptom is sometimes when I've driven the car for 10 – 20 minutes and then stop at, say, a store for about 15 minutes and then try to start the car again, the engine will start for about 10 seconds and then stall. After this I can't start it unless I let it sit for hours.
I've changed the plugs and wires in the last year, I changed the O2 sensor and have taken it to two mechanics who have changed both crank sensors. I took the electric EGR valve off and cleaned off the valves. I have also had my catalytic converter checked and the pressure is fine.
Any thoughts?
AnswerMost hesitation problems are caused by a vacuum leak somewhere on the engine such as the intake manifold gasket and or vacuum leaks at one or more of the numerous vacuum lines on the engine.
It is also highly probable in that there is a heavy BLACKISH RESIDUE BUILDUP within the throttle bore and on the throttle plate area as well as in the IDLE AIR BY=PASS circuit of which can be cleaned by using an aerosol spary cleaning agent and spraying this buildup off of the above said areas. This can also cause your vehicle to stall as per your question.
There have also been many cases whereas the THROTTLE POSITIONING SENSOR is not operating correctlt due to an intermittent failure and in many cases the CHECK ENGINE LIGHT on the dash will NOT illuminate.
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