Z3 with idle jumping to 4500 rpm

[BigMike23]

My name is Mike and I work in a shop in Los Angeles, CA. Recently we had a 97 Z3 with a 1.9l and a five speed come in. The origional complaint was that the car was surging. What happens is that when the car is being driven it runs fine, no hunting or surging at idle, but when you go to make a stop and the cluth is depressed the RPMs will start to drop like they are suppossed to but then all of a sudden they will make a sharp rise to around 4500 RPM. We replaced the Mass Air Meter(the signal was bad and there was a code), and also the cluth(it was toasted and slipping badly). We are thinking that it might be a computer related ploblem because when either the Idle Air Bypass Motor or5 the Throttle Position Sensor are disconnected the problem does not occur. The problem is that we can not find a way to test the DME and since it has to be coded to fit the car exactly, we can not just pull another from a different Z3 and try it. Any help would be appreciated.

Thanks, Mike

 

[Big Daddy]

I would also check and make sure the cruise control cable recall has been done on the vehicle. The problem was that the crusie control cables were sticking and not allowing the car to decellerate.

 

[BigMike23]

WE did check to make sure that the cable was releasing properly. We also used the Snap-On scanner to make sure that the TPS was regestering that the throttle was closing all the way, and it shows the throttle dropping to 0%. The thing that we did notice was happening was that the MAF sensor is showing air flowing when the throttle is closed. In response top that the computer is increasing the injector pulses, which would cause the enging to rev up, but with the throttle closed how is the air bypassing the throttle? WE even clamped off the Idle Air Bypass hose to insure that the IAC motor isn't opening too much. THis had no effect on the prob.

 

[Big Daddy]

Wow, I am totally at a loss. I have no idea how the air is getting around the MAF when the throttle is in the off position. I am sorry I cannot be any help, anybody else?

 

[grc]

my check engine light came on one day on my way to work. i took a quick look see at lunch and the rubber intake bellows was showing some cracking but didn't really appear compromised. i stopped at the dealer on the way home and picked up a new one, put it on when i got home and the light went off as i started the engine. just a suggestion, check it out. could be a bad intake/TB gasket?