Surge & die 90 GPSE

1st thing is I want to thank all of you for a great forum. The info and help that is shared here is awesome .Thanks again
I have a 1990 GP SE 3.1 with 180k . In the last 6 months its had new plugs & wires ,alt,IAC , fuel filter, fuel pump & oxy sensor. It also passed Ca. smog check a month ago with flying colors.A few days ago when i got to work it died , I started it back up and it would idle to 1200 or so and down to 300 or 400 like 2 or 3 times and die . The only time it will run on its own is 1st thing in morning and even then the surging is present .I have to do the ole nuetral rev and brake to get to work last few days .at around 1500 rpm it will stay running other than that it dies
Any advice will be greatly appreciated .....Thanx in advance
Peace

I have had this same problem. It was an engine idle problem for me. I have a 1993 GPSE 3.4. I had to do the same thing you did to get around in it.

To reset the idle try this:

Block off the tires and set the parking brake.
Press in the brake and start the car.
Immediately after starting the car, put the car in gear.
Let the car sit for 8-10 min in gear while the computer resets the idle.

I didn't think this would work for me but to my suprise it did. Give it a try and let me know.

thanks for the advice. I have tried this , thing is it wont idle for that long,when cold i can get it to idle for 3 or 4 minutes thats all .If its warm as soon as i put it in gear it dies.I got a code 45 out of it .I wonder if it could be a coil pack out ? thanks again for the advice
peace

code 45 is rich exhaust. I believe your problem is related to the IAC motor in the throttle body. When you installed the new one, did you clean the throttle body passage that it rides in? The other thing you need to check is fuel pressure. You may have a fuel pressure regulator going bad (or a broken vacuum line to it). Since it only dies when it warms up, check for spark also, as it could be a ignition module or crank sensor breaking down when they get hot. Since it stays running above 1500 rpm, I doubt it's ignition related, but I figured I'd throw that in just in case.

Thanks again richtazz , I did try a bit of propane in and around upper intake.It seemed to smooth outnear backside of plenum near map sensor also under the plenum. I had a friend keep it running and i pulled the vacuum junction (on top of throttle body ) off and it has alot of fuel coming out of the front line wich i believe goes to fuel regulator.When I plugged the holes in throttle body with my fingers it ran smooth as silk ,idled right .
Could that be a faulty regulator or vacuum leak ? I have the day off today so I am going to take off upper plenum and check it out .
I appreciate the help
peace

Sounds like a leaking fuel pressure regulator diaphragm. Some late model GM cars suffer from this also. There should never be fuel in the vacuum hose going to the pressure regulator.

Thanks raffican, I will try replacing regulator .I appreciate the info I'll let you know how it goes . thanks again
peace

yep, I agree with Gravity, there should be no fuel in the vacuum lines, so the regulator is shot.

Thank you gentlemen for all the help. I appreciate it very much.
I just finished installing new fuel pressure regulator .It runs great ! I still need to idle learn it and I might have a small vacuum leak( I broke one of the hard lines at throttle body) I will do a better splice tommorow.I got kinda freaked out after 5 minutes of running, it started billowing smoke out the tailpipes . It had to be all the unburnt fuel in the pipes and catylitic convertor finally getting heated up enough to burn out cause it pretty much stopped after another 5 min of running . I'm of to the gas station (good gas) for a test drive .
Thanx again richtazz,jsober61 & raffiican I owe yall one or two :)
Great forum , great people
Peace