QuestionQUESTION: car would only start if i floored it and had been revving funny for couple days. would want to stall at stop ive replaced the idle air control after cleaning the throttle body and it starts right up now but when accelerating (in park) the idle revs then goes way up i dont know how high it revs because about two months ago the rpm dial spun the other way and now doesnt work at all. Am i correct to assume the rev problem is from tps? took back apart and re-cleaned throttle body and still same effect. is there a way also to repair the tach? Thank you for your time
ANSWER: Hi Tom,
Have you tried to get a diagnostic fault code readout via the socket that is under the dash next to the steering column? That is the most direct way to determine what might be wrong. A nationwide auto parts store, such as Autoxone, will often do that readout for free, or an independent shop might charge around $40. Or you could buy an OBD-II reader for about $60. Get the 4-digit fault code numbers and let me know what they are and we'll go from there.
On the tachometer, try doing this: press and hold the trip reset button then turn the ignition switch to the run position, then release the button and see if the cluster does any self-testing that might cause the needle to revert to the other side of the pin.
Roland
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QUESTION: Thank you for your quick response! i took it to Autozone yesterday when i picked up replacement idle air valve because engine light was on and the fella said it was a coolant switch,no other codes. Also tried the reset on dash when the tach first started to go awry. it gave all the necessary info but did not take the needle to the proper position and as ive said it no longer works at all pegged in totally opposite direction
ANSWER: I would be interested to know what the fault code number was of that "cooling switch" code.
I would suggest that you examine all the vacuum hoses that are involved with the engine because a crack or leak at the attachment point at the intake manifold or the device at either end can allow unaccounted air to enter the manifold and lean out the mixture which then plays havoc with the idle/rev/accelerate behavior of the engine. With no obvious codes that is about the only other possibility. Use the vacuum hose diagram on the underside of the hood as a map.
On the tach about all one can do is to remove the cluster and see if you can flip the needle over to the other side of the pin by hand. It might work.
Roland
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QUESTION: i did go ahead and run the obd as requested although nothing happened the last time i did this and sure enough it did work thank you. So im still having a problem because the obd gave me no flashing lights just went thru the 47 checks. i replaced the idle air control valve and when tightening the bolts found they werent tightening and when i pulled the valve back out i noticed shavings on the bolts and thread marks on the part so was thinking this was causing a vacuum leak so i ended up re-tapping the holes and oversizing the holes on part which allowed tightening cleaned everything up and she started right up with just minor over revving (went to about 1800 rpm) and came down to about 900 rpm(was still cold) then turned it off and tried to restart and it will not start until i floor it and you shouldnt have to give gas to fuel injection. Im stuck since no codes coming up
AnswerHi Tom,
Absent fault codes about the only suggestions I have would be to look for a vacuum leak as described in my previous answer. I assume that since you have worked on the tps and iac that you have also cleaned the iac passageway and the throat of the throttle body as well as both sides of the butterfly plate of lt. If not then do those as well.
I don't believe that there is an exhaust gas recirculation valve which when it doesn't close well behaves like a vacuum leak, and that would be the only other possibility. But the manual doesn't show there to be an egr in the '04 2.7L. So check out the passageways and vacuum hoses using the diagram on the hood as your roadmap.
You may just have to keep checking for fault codes until a new one comes up.
Roland
