I just rebuilt (stock) my 1985 5.7. The problem is it runs and revs up fine until it gets about 185 degrees. Then the engine starts to surge to the point it will die. It will start right back up but it continues to surge. As I said this problem is only after its warm. The Chevrolet dealer here is no help.

 

Welcome to the forum! My first guess would be that you need a new ignition coil and or module. Both of these are in the distributor. If its heat related, then I would think it would be either of those. Replace both at the same time. The coil is in the cap and the module is underneath on the base of the distributor. Make sure to use the dielectric grease on the bottom of the ignition module for heat dissipation. Also, check the harness in the distributor for wear. I would also check for codes. You can do this with a gem clip if you don't have a scan tool. Under the dash on the driver side, there is a plug. With the ignition off, place a gem clip between the top right 2 terminals. Turn the ignition on, but don't crank. You should hear the fan running. Now the service engine soon light should blink. First, it will blink code 12 (flash-pause-flash-flash), three times. Then it will blink any trouble codes (example: code 32: flash-flash-flash-pause-flash-flash). then code 12 will blink again after all trouble codes are displayed. If there are no trouble codes, then only code 12 will appear. Check these things out and let us know what you find. :auto:

 

All the above are new. Also I failed to mention there are no codes. Fuel pressure good. I have checked everything I can think of. I've done a-lot of motors but this is the first computor controled one :banghead:

 

How new is the O2 sensor?

 

Have you checked out the egr? When the engine is cold, try pulling and plugging the vacuum line to the egr just to eliminate the possibility of it opening and causing a problem. It should not open at idle.


[Modified by Siveck, 6:38 PM 1/28/2003]

 

O2 sensor is new as the EGR but I'll try that tonight. I put everything on new because it take forever to get back to them once you button it up. Who knows I've seen several bad new parts.

 

A few things come to mind. You may have an injector(s) shorting out when warm. Ohm them out (when the trouble starts) ..they should be within 1 ohm of each other. Pull the vac. hose off the FPR and check for gas in the vac line. You may have a bad FPR. Be sure your ignition voltage at the spark plugs is good and "hot" when the engine dies off. A long shot is to check the canister purge solenoid (and related hoses) for leaks. Good luck.

 

Ok. I tried everything suggested last night. It still surges after warm up like it has a 671 blower on it. :banghead: :banghead:

 

It sounds like an IAC issue to me. The throttle counts at warm idle should read between 25-30 (you'll need DiaCom+ or a similar scanning tool to see this).

If you didn't change anything on the throttlebody (including making no changes to the screw under the cap) try doing this. Turn the ignition on (don't start the car). Press the throttle to the floor and release it. Turn the key off. This resets the IAC. Then start the car and see what effect it had.

If you returned everything back to stock when you rebuilt it, this is the most likely cause. The idle circuit is one of the most finicky ones to tune on a TPI car. Any performance changes and it will hunt for a smooth idle. If it doesn't smooth out, then find someone who has a scantool to see what the throttle counts are. If they are off, you'll need to remove the cap on the top left back corner (as seen from the drivers seat) and use a torx to adjust the throttle blades a touch. If the counts are high, back it out. Then you'll have to do the ignition on, full throttle and release, key off procedure to reset and start the car again and see what the counts are at again.

I just had to do this last week to mine, so it is still fresh in my mind.

Good luck...

 

I can't believe it was that easy. Last night I went out turned the key on pushed the pedal all the way down then up key off then started it. Smooth idle all the way up to 205 degrees. NO SURGE. Thanks a-lot Joe 90 :party: :party: :cheers:

 

No problem...glad it worked for you.

Many people forget to do this when working on the intake systems on these things.

I'm guilty of it myself :bb