87 Buick V8 307 Stalling after driving 20-30 Minutes

[Built6spdMCSS]

Definitely heat and/or fuel-related! Next time this happens, open the gas cap and listen for a whoosh sound. This would indicate a need to replace the cap. Next, candidate is the insulation under the carb which would contribute to fuel starvation due to fuel-boiling and evaporation.

Vented Cap is not the fix when it's a Fuel System Vent issue, these cars have an EVAP System in them and that needs to be fixed properly.

 

[86 Salon]

Did you check/readjust the new TPS? It shouldn't cause your issue, but it won't help your carb feedback to the ECM if it's too far off.

To me, if it repeats like this, it doesn't sound like a carb problem or a dirty fuel sock. Very unlikely since it seems fairly repeatable.

Although you haven't done much diagnostics at this point, I tend to agree with MrSony on VERY LIKELY the ignition module. Your 87 307 uses a 7 pin module. And as stated, you need THERMAL paste as a heat sink seal between the distributor housing and the bottom of the ignition module. If some paste is left under the old unit that isn't full of dirt, you can re-use it. It doesn't go bad as it's not like a greased bearing. You don't need much. Make sure if you put new on it, that it's THERMAL paste. It can be dielectric thermal paste, but make sure it's for heat sink application. Or you'll fry the new one, too. If it's dry underneath the module, that's a problem.

Carry a friend and a timing light with you. The timing light means you don't have to disconnect anything to test for spark. As soon as it dies, get to the side of the road if possible, have a friend crank it after you hook up the leads to the timing light, any cylinder will do, doesn't matter which spark plug wire but preferably #1. Have them crank it over ASAP and check for spark by seeing if the timing light will flash when cranking. If none, it's the ignition module AND/OR coil. I've heard of coils conking out after they get warm. Kinda rare, but possible. If you DO have spark, then it may be time to focus on the fuel. If it does crank and fire up, then check the timing mark and see if it's steady or fluttering around. If it flutters badly, it may be a timing chain telling you it may be going bye bye. If it's original, it has nylon gear teeth which are notorious at that age of breaking off and ruining people's fun. If you get it back to the house and it's running, do a timing check on it and make sure it's at 20 degrees with the A&B terminals on the ALDL under the dash jumpered to lock timing while you check it. With the terminals grounded you should see 20 degrees BTDC. And it should be pretty steady.

If you put new plugs in it and set them to proper gap, the 87 307 uses a 0.060" gap. You can use that and shouldn't be a problem, but probably better to again probably reset those to 0.045 to 0.050" max. JMO. It'll run just fine that way and not overtax the ignition system.

Again, try the 7 pin module. Various GM p/ns, but also you can get Standard LX315.

You didn't say WHEN you changed the coil. Was it before the issues or after? As far as any coil change, you HAVE to make sure the polarity is right. Not all HEI coils interchange. Did you just buy a coil from AutoZone or something and let some counter jockey without experience make the call? Depending on what's in the computer, they MIGHT have gave you the wrong coil. Just feeling out possibilities. Still got the receipt or box it came in? Part number? This can help me determine if you got the correct one.

For your 307, 12498336 is the GM part number you seek (or aftermarket equivalent, like Standard DR-32). RED AND WHITE wires. If there's a yellow wire in there, it's the wrong one.

Excellent diagnostic strategy but I would also bring along a can of either or flammable brake cleaner. If it starts on one of these, start checking the fuel system. He's actually lucky that his problem isn't intermittent.

 

[Tore]

Alright, so changed out ignition module and still stalling after 20 min drive. When I started to feel it stalling I let off throttle a bit and kept running for a little while until I pushed throttle harder then stalled. When I got it back home I let idle and after about 10-15 min stalled out. And of coarse let sit for a little while fires right back up but will stall after about a mile of driving. Car only has 27,000 miles on it if that matters.

Changed out plugs 0.0600 gap along with wires, coil, and now ignition module. New TPS. Fuel filter is clean. Fuel pump changed maybe 9 months ago.

 

[Clone TIE Pilot]

Sounds like it stalls when it enters closed loop operation. Are you getting any trouble codes? Best to get either a analog dwell meter or OBD1 scanner and see how the ECM is responding as it enters closed loop. Also I would install a inline fuel pressure gauge and see if the fuel pressure is too high. Replacement fuel pumps these days often have excessive pressure that upseats the needle valve, especially high flow performance needle seats.

 

[Tore]

Sounds like it stalls when it enters closed loop operation. Are you getting any trouble codes? Best to get either a analog dwell meter or OBD1 scanner and see how the ECM is responding as it enters closed loop. Also I would install a inline fuel pressure gauge and see if the fuel pressure is too high. Replacement fuel pumps these days often have excessive pressure that upseats the needle valve, especially high flow performance needle seats.

No codes are coming up

 

[69hurstolds]

Almost sounds like it's loading up with fuel as Clone TIE Pilot was alluding to. When it dies, did you take the air cleaner top cover off and see if there was excessive fuel anywhere? Choke fully open?

Appears the parts cannon ran out of ammunition here. If fuel is getting to the carb, and it's clean, then that's probably not it. Ignition system is virtually all new. Gaps set right. Hmmm. Less likely it's spark, but who knows doing this long distance?

Still haven't answered the question if it's still getting spark immediately after the car dies. That would narrow it down to spark or fuel. If it's getting spark but not starting, then it's gotta be the fuel/air.

 

[Tore]

Almost sounds like it's loading up with fuel as Clone TIE Pilot was alluding to. When it dies, did you take the air cleaner top cover off and see if there was excessive fuel anywhere? Choke fully open?

Appears the parts cannon ran out of ammunition here. If fuel is getting to the carb, and it's clean, then that's probably not it. Ignition system is virtually all new. Gaps set right. Hmmm. Less likely it's spark, but who knows doing this long distance?

Still haven't answered the question if it's still getting spark immediately after the car dies. That would narrow it down to spark or fuel. If it's getting spark but not starting, then it's gotta be the fuel/air.

Have not tested for spark after it dies will try that this weekend.

 

[Clone TIE Pilot]

Have not tested for spark after it dies will try that this weekend.

For that you will need a HEI tester, a regular spark checker will give a false good reading on a fa7ling HEI system because its so powerful. A HEI spark checker has higher ressistance to reduce false readings. If its not the ignition then its a fuel air mixture issue as 69hurstolds states.

 

[Tore]

I am still getting spark when car stalls

 

[Clone TIE Pilot]

I am still getting spark when car stalls

Then you have a fuel issue. How do the sparkplugs look? As I said before it sounds like the car stalls as it goes into closed loop.