Hi all, wondering if anyone has any ideas about what might be wrong with my car. Car starts fine and idles great, but when put in drive the car will barely accelerate. And the RPMs barely creep over 1.5. I have changed the ATF, and checked the gear selector. Cleaned the MAF with MAF cleaner. All these didn't help. I am thinking maybe its the MAF because when i unhook it from the air filter, the car accelerates much better (but will not shift). I also unhooked just the electric plug from it and car stalled immediately when in drive. So maybe the MAF is broken and not just dirty? I also cleaned the throttle body yesterday but haven't put it back on. I have not checked for vacuum leaks yet, which is a possibility. Could the timing be bad? I originally thought it was transmission problems, but now I'm thinking its something else. Any help would be greatly appreciated.

thanks,
matt

 

That sounds more like a clogged catalytic converter or a slipped timing belt than a MAF problem to me. In neutral, how does the engine respond?

 

In neutral, it responds great, revs up like normal. Would that be consistent with a clogged cat converter?

 

I overlooked this before, but when you say you remove the air filter are you simply removing it from the airbox or unplugging the intake hose from the airbox? How is your air filter? Have you checked for leaves, mice, etc. in your airbox and its intakes (heat riser and behind-grill tube)?

Assuming your air filter is in good condition and your airbox and is free from debris:

Usually a bad cat causes a hesitation and stumbling when revved in neutral. How does your exhaust smell? A "rotten egg" type smell is common when a catalytic converter is failing. If all of these symptoms point to the cat, try removing the oxygen sensor from the exhaust pipe, if you see an increase in performance, your cat is done. If none of these symptoms are present, make sure your brakes are not dragging and check your timing belt. Also, have you recently changed your timing belt?

 

I removed the maf, not air filter. I unplugged the MAF from the airbox, and car would rev okay in drive, but not shift pass first (limp mode?) The air filter is fine, and cleaned out airbox days ago, no change in symptoms. No hesitation in nuetral at all or a rotten egg smell. Going to go check the timing belt right now, it has not been changed since i've had car, give or take four years. Thank you so much for your help!

matt

 

Ok, I guess I misread that. I'm still not inclined to believe your MAF is bad due to the fact that your car starts and idles fine but the fact that it runs better with the MAF removed indicates there is a problem.

I mention the timing belt because a good rule of thumb for the timing belt is: if you don't know when it was last changed, do it now. If it breaks you will be dead on the road whether it is slipping and has anything to do with this problem or not. Sometimes a DIY timing belt change leaves the cam misaligned as mentioned before and leaves your car hesitating badly, I've done it myself.

Have you checked your spark plugs? They can tell you if your car is running rich, your experiment removing the MAF indicates that it likely is. That being said, how is your gas mileage? Is your check engine light on? Is the computer indicating any error codes?

As for the transmission not shifting past first with the MAF removed, someone else will have to weigh in on that, I'm not familiar with the behavior of the transmissions inthese cars in various modes of failure.

 

Well...it was the throttle body. After I cleaned it and hooked everything back up it ran just fine. Well, not perfect, but as good as it had been running. i did check the timing belt and it looked good but I may replace it as the next thing on my agenda. Check engine light is not on. And I'm not sure how to pull the codes, don't I need an instrument for that?
Now I just need to figure out why the car won't shift unless I completely let off the gas at the RPMs it should be shifting...

Thanks again for your help and your quiuck replies, Varg.

matt

 

No thanks necessary, we all try to help each other out here.

A sticky throttle body then eh? I guess I got ahead of myself in diagnosing that one.

The only thing I can think of for your transmission problem is the kick down cable, it could be binding or just out of adjustment. That could cause your car to stay in a low gear under partial throttle until you let off. Try spraying some WD-40 on the cable and in the sheathing at the top where it meets the throttle linkage and at the linkage on the transmission.