Background:

Car is a 1992 Pontiac Firebird with an L03 (305 TBI)

The headgasket's had been leaking for a while, but was always drivable until recently so I replaced them. Back when I did my T5 swap I bought a chip from Tuned Performance for the manual tranny, but also had him program in VATS and EGR delete. When we did the headgaskets we removed all the EGR.

Once everything was done, went to start the car and it now has a surging idle and the fans run constantly. The car runs good when cold at a constant 900RPM, once it warms up it surges up and down and eventually dies soon.

This video is NOT of me or my car, but pretty much exactly what it is doing, if it helps describe the issue.
The car has a 6 month old fuel pump and fuel filter.
Just replaced the coolant temp sensor.

Help please!

 

The fan running constantly check that you didn't swap the gauge and fan sender side to side. If the grey wire on the passengers side gets grounded the fan will be commanded on.
I didn't watch your video but are you positive you lashed the valves correctly. you can adjust the real quickly with the engine running.

 

When you unplug the fan switch, the fans shut off.

Pretty sure the valves were lashed correctly it runs good when it's cold and they aren't making any noises or anything.

 

The fan switch is defective if you unplug it and the fan goes off. the switch closes at around 226-228f. The almost dying when warm I'm not sure during cl the engine will lean out from cold start. When the rpm drops it maybe the throttle is set to low the iac may not be able to compensate.

 

On used lifter I don't go more than 1/2 over zero lash

 

Yeah we did 180deg over zero lash with a snap-on digital torque wrench so I think we're good there. Like I said, it runs good when cold, so I'm pretty sure it's something else.

EDIT: I just don't understand how anything could have gone bad because we didn't mess with anything and everything worked on the car prior to the head gasket repair.

 

The egr block I'm sure covers the vacuum and exhaust post real well ? base timing at tdc with the est disconnected ? Not sure what else to check of the top of my head unless the idle stop screw is moved out.

 

We made a plate to cover the egr valve holes and once it starting surging, we took it off and put the valve back on and it still did it. We haven't been able to get an accurate timing setting because the car surges when it warms up. But it should be within 2 degrees

 

Any progress ? Did by chance you leave the ecm grounds disconnected from the back of the pass cylinder head .

 

Re-checked the grounds today and they were all solid. The exhaust had to be re-welded today (long story) so no updates as of yet. Car is still running very poor. Still am not sure of my next move?

In my above post I mentioned that we made a plate to cover the egr valve and bolted a plate on top of it, the car still surged when the plate was on, so we took it off and put the egr valve back on to see if that would do anything. It didn't do anything, but should I put the plate back on?

Only other things I can think of are IAC, but the idle is changing so I think it is working...and fuel pump, but it pretty much has a brand new one on it. And a brand new filter. About 6mos old or so...

 

Has me stumped, I wish I knew what to tell you to do next. This is all new symptoms after the head gasket swap ? Iirc the prom I burned has been fine for quite awhile ?

 

Yes all new symptoms. The car is throwing code 42 from the CEL. Will see where that leads me

And yes I haven't had any issues with the prom

 

That's a start, look close at the 4 pin connecter at your distributor for corrosion or damaged terminal. Sounds like it might be a bad icm or pickup coil.

 

I bought a new ICM, a new cap and rotor, and all new plugs and wires. Will update soon

 

I also bought a new pickup coil for the distributor, but didn't put it on because I didn't know you had to take the distributor out to get the gear looking thing off the top to have access to the pickup coil. So tonight I just did, the new ICM, cap and rotor, and the new plug wires. Well it fixed it!!! Car is running great!!! Had to of been the ICM..it runs great now and has no CEL light or anything.

 

When you get some down time you might want to do the up coil . heat sink compound under the icm. Age or hight resistance on the coil primary side can wipe out a icm. Or maybe your buddy dropped it and didn't say anything lol.

 

So there are some new-ish/different symptoms occurring now...

So before the car would run good cold and stall and run like crap when it was warm, but now it is pretty much opposite.

Now the car has a really bad surging idle when it is cold, but doesn't die nearly as much. It is running perfect when warm. Before I would push the clutch in and the RPM's would flatline and the car would die almost immediately. Now the car will idle down like normal, but once at a stop light it will surge really bad and try to die. Also when cold the car hesitates when it comes to power. I will be in first gear and pressing the petal and the car will feel really boggish and slow and then all the sudden shoot forward like it finally got the power behind it. Any ideas now? Ugh

^^^This is after replacing the ICM and thinking I fixed the problem. I will say I can actually drive the car and be ok now because it rarely will die even with the surging idle still occurring. It is definitely way better than what it was before, but I have to say I am confused.

 

The surging when cold sounds like its lean or the iac is hunting and the throttle blades on the throttle body need to be opened just a little. ya You might want to check the throttle shaft for wear and or vacuum leak.

 

Im glad my video helped someone lol

 

lmao , Thats awesome