The first 3000 miles or so after my rebuild, (2.8 to 3.1) the car performed flawlessly. Suddently it started a hesitation when I accelerate from a closed throttle. It can happen from a traffic light start or just coasting a while with the throttle closed and then give it gas. It will stumble a seccond or two then catch and go. When the ECM is in open loop all works as it should. If the car sits at a long traffic light and idles in drive, it will set a 45 code.It will go away after the engine revs a couple of times. I have replaced the O2 sensor. No help. I have checked the TPS with an ohm meter and all appears normal. The MAP is new as are all 4 temp senders and the thermostat. (Checked the thermostat in a pot of hot water on the stove) The distributor module is also new. I have checked the EGR valve with a vacuum pump and it opens and closes as it should. I disconnected and plugged the vacuum line to the EGR and test drove the car. Didn't change a thing. This is an intermittant problem. There are periods that all works as normal. The fuel pressure is good. The gas mileage has dropped from 20 - 21 to 17 or less. This would confirm the 45 code. I've checked for vacuum leaks and found none. I don't know what else to look at. It would seem that an electrical connection might be loose and causing the ECM to richen but I can't for the life of me create a scenerio thet would fit.

Would appreciate any input.

Dave

did you rebuild the fuel pressure regulator? is it old /torn, or not reassembled correctly? when did you last replace the fuel filter? is the Distributor cap loose? the plugs to the cap are they secure? edit: (plugs to the ICM)

[This message has been edited by 1FST2M6 (edited 03-13-2002).]

What about the IAC?

You need to clean your throttle plate with a cleaning chemical and tooth brush, at the same time remove and clean IAC pintle and bore.

The fuel rail, injectors and regulator were replaced during my rebuild. Not with new stuff but a used unit. I checked it all out before installation. Fuel pressure is 42#. Shouldn't be a problem there. IAC was also replaced. Throttle body was also cleaned before reassembly. Fuel filter was new 3500 miles ago. I wouldn't suspect it anyway as long as pressure is where it should be. The ignition control module/distributor module was new 200 miles ago. It was one of the first items I suspected.

I still feel the problem is electrical but I'm running out of things to check.

Keep the ideas comming.

Dave

Want to thank all that tried to help. Problem turned out to be a broken vacuum line from the MAP sensor to the fuel regulator. I really feel stupid cause I was so sure there wasn't a vacuum leak. I didn't check as throughly as I probably should have. When I re-assembled the engine, I spent hours grooming those vacuum lines. I knew they were hard to access and delicate so I took care to route and position them properly. I replaced everything that even looked suspect. Oh well, ya live and learn!

Sooooo happy though that my Fiero Toy is A+++ again

Dave

Hey, none of us will admit that a problem was something we SWORE we checked.

Glad you found it!

Terry