Running Rough - Out of Options - Send Help!

[xitabl442]

Hmm, didn't know that. We've been using dielectric grease for a while now on DRL bulbs to prevent them from melting their sockets. I wonder if it's been working? I got the tip from our Napa salesman.

 

[330 uhc]

Dielectric grease is used on the metal plate underside of the module because it prevents oxidation, but more it helps maintain ground from the plate to the housing completing the circuit...not sure temp compound is right for that...I agree it has symptoms of timing...so why look at the box first?... how about timing gear setup?...another thing I've seen at least three times is a clogged cat convertor or a collapsed inner wall of a double wall exhaust pipe...does exactly what you said...starts cold, runs good, short time later...undriveable...easy check with a vacuum gauge...hold it running at mid range rpm, then release the throtte and watch how the gauge reacts...the test is listed in most basic manuals...also, early gm modules can fail as others have described, however in my time I've sold a couple hundred, almost all just quit completely...I remember only one or two doing what you describe...but it is possible...

 

[pontiacgp]

Dielectric grease is used on the metal plate underside of the module because it prevents oxidation, but more it helps maintain ground from the plate to the housing completing the circuit...not sure temp compound is right for that....

the hundred of thousands GM products that have a module in a distributor came from factory with heat absorbing compound under the module. Dielectric grease is neither conductive or insulative. It is specifically formulated to lubricate and protect electrical connections from corrosion that will ultimately cause higher contact resistance. The grease has a tendency to lower its viscosity at elevated temps, or could completely evaporate if temps are high enough.

 

[330 uhc]

Always willing to learn...but I gotta say every module I sold came with a packet in the gm delco box full of lube...my boss said at the time it was dielectric grease, which is what the packets said...our techs at the chevy dealer I worked at all had the big tubes of dielectric and used it for the modules as well. I asked them...we never had a failure or a comeback, whether it was right or not...in any event I worked there in early 1976 when hei came out...the v8 module i still remember was a 1875990...used to get a white powdery crud on the bottom plate, and the car would quit running...I worked there 20 years...we did not have any heat compound anywhere in the place...never...right or wrong it worked fine...never saw two techs who fixed the same problem the same way...all had their own ideas ...thanks for the info...

 

[airboatgreg]

I am leaning toward no fuel. Don't worry about cold drivability until it runs good hot. Carefully spray some carb cleaner or starting fluid into intake while someone is working key and throttle. If it runs then we know it is fuel and you can go from there. All good previous suggestions. I have seen a few times when the carb is mis-adjusted and a metering rod will stick in the jet. Rare but not unheard of causing a lean condition on 4 cylinders. Buy an HEI spark tester (Looks like a spark plug with an alligator clip to hook to ground. Stay away from the adjustable one) and hook to plug wire. That will tell you spark or no spark as it will bridge or not. Basically go or no go. Trust me on this. It eliminates any idea of is it enough spark. Put your hand on EGR valve as it could be stuck open. If it burns you it is open. Maybe a piece of carbon or mis-routed vacuum hose routing.

 

[pontiacgp]

Always willing to learn...but I gotta say every module I sold came with a packet in the gm delco box full of lube...my boss said at the time it was dielectric grease, which is what the packets said...our techs at the chevy dealer I worked at all had the big tubes of dielectric and used it for the modules as well. I asked them...we never had a failure or a comeback, whether it was right or not...in any event I worked there in early 1976 when hei came out...the v8 module i still remember was a 1875990...used to get a white powdery crud on the bottom plate, and the car would quit running...I worked there 20 years...we did not have any heat compound anywhere in the place...never...right or wrong it worked fine...never saw two techs who fixed the same problem the same way...all had their own ideas ...thanks for the info...

I know you can't believe everything you read on the internet but this is a good article...

http://www.superchevy.com/how-to/67498-hei-coils-modules/
"All performance modules come with a high-heat-transfer white grease that conducts heat away from the module to help keep it cool. Heat is the biggest enemy of the HEI module."

 

[NoRest92]

it could be the coil is overheating and/or the ignition module is breaking down when it gets hot. If a coil overheats it can affect the module.

The thing that stands out at me is driving awhile and the problem starts and you need to wait 30 minutes to cool down. I agree with pontiacgp something is getting too hot. I would think about changing out the coil first and then maybe the module to see if the problem still persists.

The sputtering makes me wonder if something is up with fuel delivery. Could the carb be getting some kind of vapor lock while driving long distance? I know 30 years ago my 85 SS was recalled to change jets in the carb because of a hot soak/ sputtering/dying while driving issue. Are any of the fuel lines near a heat source? Just because you changed the fuel pump, the new one might be bad. Had that happen a few times. It will seem ok when you test it but after the long drive it might be acting up?

Timing as wageslave said is something to look at. If it is messed up the car will run like crud. I am not sure if that motor in that year had timing controlled by the computer yet? Others on this forum would know this better then me.

Good luckmand hope you get it fixed soon.

Jeff

I agree with pontiacgp. I would suspect the coil or module.

Thanks a for the help everyone! I replaced the coil and module and it runs better than ever. The coil wires were brittle and falling apart, and the module had white residue underneath it. I was actually able to take it out for the longest drive yet since I've started bringing the car back to life! I appreciate everyone's replies. They're a huge help for someone like myself who is learning as I go.