Running Rough - Out of Options - Send Help!

[NoRest92]

Hello Everyone,

I own a 1985 Buick Regal Limited with the 3.8L V6. After doing an extensive amount of work on the car over the last several years, it is running too rough to drive and I an running out of solutions.

Symptoms:
- Easy to start when warm, Hard when it's cold out
- It runs fine for short drives around the neighborhood, but on longer drives on hot days it begins to sputter, backfire, then dies and cannot be restarted until it cools for about 30 mins. Pressing the throttle makes it pop then it cuts out.
- Listening to the exhaust closely it sounds like it's skipping a beat or misfiring slightly. You can only hear this when next to the pipe's outlet in the rear
- When parked, if you rev it too high, it eventually comes back down then dies

- It seems to sit there and idle just fine in park, but that's about it. Lately it won't even make it down the driveway without dying.

After researching, some of these are symptoms of running lean, others are about running rich. I can't figure out what's going on.

New Parts:
- Gas tank w/ float
- Fuel Pump
- Some new fuel line
- Fuel Filter
- Spark Plugs & Wires
- Distributor Cat & Rotor
- Almost all new vacuum lines, but not every single one has been replaced

I've read that the carburetor on this motor is computer controlled and cannot be adjusted like an older model.
I honestly have no idea what to do next, and no local shops will help.

Any help would be very much appreciated!!!

 

[Wageslave]

I would check your ignition timing first. Cheap and fairly easy to do.

 

[pontiacgp]

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.

 

[Jeff L]

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

 

[Wageslave]

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

An easy way to check for heat soak if you are in a pinch is to either drive it until it runs poorly, then open the hood and run a water hose over the fuel line and fuel pump and up to the carb base to cool them off. Then try to restart vehicle. Don't use a sprayer nozzle around the carb itself as water intrusion is got good.

Another way is to just take the hood off of the car and go for a drive. The additional airflow through the engine compartment should tell you if heat soak is the culprit.

 

[Texas82GP]

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

 

[xitabl442]

Shouldn't the module have a nice film of dielectric grease under it?

 

[somaphox]

yes the bottom of the coil needs a semi light coating of either die electric grease,though i used thermal compound from autozone and it seems to be working fine and id imagine it would keep it cooler than die electric grease.we shall see after a few more good runs.might also check to make sure you replaced the odd shaped ground strap that sometimes gets left out.about timing not sure if you know but you need to ground the aldl connector in the car to adjust initial timing by using a paper clip bent to go into ports a and i think b on the aldl connector.,after that loosen distributor and advance or retard to i wanna say 20 degrees?

correction about 15 degrees though you could probably advance it to 17ish and be safe.all in at 2500 rpm

 

[jiho]

Disconnect the 4-wire computer harness at the distributor to sample base advance. It should be 15 degrees idling in Park. Make sure the cap is aimed the right way -- battery wire terminal pointed toward the radiator -- so you're on the right stroke. The computer will throw a code due to the harness being disconnected, but the code will go away after the harness is plugged back together. This is Space Age engineering.

 

[pontiacgp]

Shouldn't the module have a nice film of dielectric grease under it?

dielectric grease protects electrical parts but does not draw heat. You need some heat sink compound under the module.