I just had my neighboorhood mechanic buddy replace the timing belt and timing belt tensioner pulley in a 2001 S40 1.9t that I just bought from my buddy. I bought it after the belt had jumped. I lucked out and no mechanical damage was caused by the belt jumping. Anyways now the car starts a little hard, then when it starts it send to run fine until it warns up a little, then the idle jumps up to about 2,000 rpm's for about ten seconds then drops to 1,000 rpm's for about ten seconds, then back up to 2,000 , and so on....send to have a steady idle when in gear but maybe a little high. I an looking for some advice on this issue and possible causes and/or remedies. Thank you in advance! In really in need of an answer to this problem before I lose my mind and girlfriend.lol! Anyways....please help!

 

How do you know there was no mechanical damage when the belt jumped? Did the car have the unsteady idle problem before the belt jumped? Is the car setting any codes?

 

Compression check showed 150 in all for cylinders. And it runs smooth and quiet now. But other than that, I really don't know, I guess. Didn't hanger idler issue until after belt replacement. It did throw throttle body sensor but noted, after being cleared, its not throwing any codes...? I need help! Thanks!

 

What's a throttle body sensor? Do you mean throttle position sensor? Did you clean the throttle body at the same time you changed the timing belt?

I suspect you already have the answer to your own question. A defective throttle position sensor will cause exactly the problems you are having. Nothing to do with the timing belt.

Also, good compression readings don't mean there was no valve damage. The valves will still seal even if the stems are slightly bent. After you replace the throttle position sensor you should give serious consideration to rebuilding the cylinder head. If you leave it alone you may be lucky but you may also drop a valve and trash your motor in 10,000 miles.

 

So, should I try cleaning throttle body first, see if that does anything, then if that does not work, I should replaced the throttle body position sensor? Someone said after replacing timing belt, that the computer needs to be reprogrammed....its that true? Also, if the belt is off by one tooth would that cause the high idle?

 

Thanks, for any and all help in this matter!!!

 

If you don't answer my questions I'm not going to answer yours.

 

I'm sorry, what questions did I not answer? I didn't mean to offend you at all. So, I friendly will answer any and all questions, anything to help me fix my problem. Thanks again!