1989 C1500, EGR, Headers Question

[FullBlowncustoms]

Wow......not sure if you need a mechanic or a priest at this point!!!!! Lol
Ya.....it's behind the glovebox.
Good luck finding this gremlin!!!!

LMAO, she runs great, VERY quick at times on and off... Think I scared the crap out of it, now it hates me LOL.. Has a mind of it's own lately!!!

 

[FullBlowncustoms]

Put on so many new parts since it happened I have myself confused LOL.. Even though the puter gets no connection to read codes, I might even be looking in wrong area of problem. On my 95 Silverado at the EGR valve I put my finger under it and touch the diaphragm, on this 89 it is up FARTHER to touch it like stuck maybe? I have a new GM orig coming from Roc Auto and the EGR solenoid. But I have NO idea if from the ECM the solenoid itself is getting voltage at the two terminal plug with goofy ECM trouble... If I don't find the problem by time I store it for winter, It will be time to go old school something I understand, Tunnel Ram or 671... Just hate to cut the hood out, plus the TBI is pretty cool when it decides to all work at times LOL

 

[FullBlowncustoms]

I tracked down all grounds, all good. The ECM gets no connection or signal to a OBD 1 unit. So Have another ECM coming from Rockauto. BUT got to be a reason it ran awesome for like 2 hours when I installed the new distributor, sensors, coil etc... then acted up. Only thing I'm thinking is that I put on a 50K Volt Jegs coil with the United Billet distributor and I reversed the coil bracket closer to the dizzy cap so the wires would reach better. Maybe crossfire, or the Jegs coil took out the new United distrib ICM.. ETC.. Still fires right up, but not 100% power as usual. And I also notice that once it warms up I get NO signal from timing light, I took off NO#1- 8.5mm plug wire put on a small stock wire and still no signal on the light. Motor cools down overnight, come out and the timing light works. I tested that two different days/nights warmed up, then cold next day..

 

[Scooterwrench]

May have a carbon track or crack in the cap that acts up when it gets warm.
You may want to pull the terminals out of the ECM connectors one by one and check to see if maybe they've gotten spread and making intermittent breaks in the circuit. CAREFULLY! give them a little pinch with needle nosed pliers to tighten them back up. Don't squish 'em flat!!! May want to do it to all your connectors,no telling how many times they've been on and off.
Hi voltage coils are hard on caps and rotors and the back EMF can be catastrophic to primary ignition components. I've never seen the need for anything hotter that stock AC Delco coils. If you think it's blowing the spark out set the plug gaps a little narrower. Sometimes .002 in plug gap makes all the difference. What plug gap are you running now?
Avoid spiral wound plug wires like the plague. Good!!!! carbon core 8mm wires are all you will ever need for a street motor.

 

[Scooterwrench]

I had another thought last night,you may have a ICM starting to break down. They will act up when they warm up and get gradually worse until they quit altogether. Check everything else first,just throwing parts at it is a last resort.

 

[FullBlowncustoms]

What is the CORRECT way to use thermal paste on ICM? I seen guy's put just a circle blob in just the center, and I seen guy's spread it across the entire base like frosting a cake.. I assume the two screws are the ground? LOT of heat under there from the headers. I don't want to cook this one, GM unit, $82.00

 

[Scooterwrench]

A nice even film about 1/64 thick.

 

[df2x4]

What is the CORRECT way to use thermal paste on ICM?

I don't think it matters as long as you've got enough coverage (but not so much that a bunch of excess squishes out of the sides). Little dot in them middle, little X, even spread, whatever.

I prefer the lazy way, just put a dot in the center and let mounting everything in place do the work. That's how I do CPU/GPU coolers in PCs and I've never had an issue.

 

[FullBlowncustoms]

Am I to believe being a GM unit that IF it comes with the paste that it is NOT just Di E grease is all? I'm not so sure a home PC puts out the heat that the motor does?

 

[Schurkey]

What is the CORRECT way to use thermal paste on ICM?

I assume the two screws are the ground?

One of 'em, anyway.

LOT of heat under there from the headers. I don't want to cook this one, GM unit, $82.00

Ehhh. Under-hood temp is nothing compared to an electric circuit pulling 5-plus amperes in a tiny, concentrated area. The older modules were mounted to the aluminum distributor housing--fair amount of mass and surface area. Vortec modules are mounted to a small, but multi-finned heat-sink, even more surface area.

I don't think it matters as long as you've got enough coverage (but not so much that a bunch of excess squishes out of the sides).

What's important is that you don't have so much--or use a product that's so thick--that you'd have a blob trapped under the module preventing proper contact.

Realistically, I think that would actually be difficult. Any of the stuff I've used, squeezes around as the two module mounting screws are tightened. By the time the screws are tight, you've got whatever film thickness you need. In the old days, I'm sure we were provided with dielectric silicone grease as a heat-sink compound. Seemed to work, whatever it was. Now, I think they actually supply a true heat-sink compound.

Don't over- or under-torque the mounting screws. Wipe away any excess schlubba.