Engine falter or stops after 30 minutes, intermittent

3.1 Engine: On morning commute engine stalls when warm, no immediate restart, no service engine light nor trouble codes. Allowed to cool for 15 minutes, starts fine, parked outside and return trip falters near end. Neighbourhood garage cannot duplicate.
- Suspect electrical problem, last problem was fuse holder powering ambient light sensor and daytime running light module. Just adjusted fuse contacts an seems ok.
? What can cause this without engine troublecode? Happened twice now but rest of time engine operates beautifully. Cannot tell whether problems is caused by heat buildup under dash or engine compartment.
? can faulty DRL module cause this?

I've had a similar problem for about 2 yrs, that kept getting worse. I have a 1992 Lumina APV, 3.8L, 4T60E Auto Trans. 132K miles.

It would start up fine when cold. After it warmed up, it would die on the road. I found that if I waited at the side if the road, it would start again. I flashed the check engine light and found no trouble codes. I suspected spark or fuel, but always had it when I checked it at home. Also, when I got on the freeway in 3rd or 4th gear, the engine/trans would buck and hickup and randomly stall for a split second when the torque converter would lockup (TCC solenoid). I thought I may have more than 1 problem going on.

I removed the ignition module thinking that may be causing the stalling problem and had it tested several times at a local Autozone parts store. It passed every time. No progress on the stalling.

So I switched problems and focused on the bucking. Having read before that sometimes the TCC solenoid goes bad, I inquired at the AutoZone about a TCC for this car. The counter salesman said he did not sell this part and the only part he sold was a vehicle speed switch. He then said "sometimes the motor will stop if this sensor goes bad". I bought it, $45, and installed it. It goes in the tail shaft of the trans. I noticed, when I pulled the old one out, it had a build up of band/clutch debris on the face of the sensor pickup. I installed the new one anyway but the clutch debris accumulated on the pickup face could have been the whole problem with the VSS sensor.

Now the van does not buck and has not stalled for a couple weeks. I would have never guessed this one.

Thanks. I have taken out the ignition module as well with no progress. I forgot to mention it is a 1997 Lumina with 3.1 litre, automatic. Good suggestion on the VSS sensor I will try cleaning it first.

hey, if its caused by heat build up, simply removing the ignition module and testing it wont cut it. You need to test this sucker when its hot. I suspect it is in fact the ignition module. Let your car cool down, so you know it will start, and then heat the ignition module with a hair dryer or something, and then try to start the car, if no start, replace and be happy. Good luck with it, keep us informed.

Understand. When I took it to the AutoZone, they tested it 8 times in a row to "heat the sucker up". It was as warm as any hair dryer would get it. It's only been 2 weeks since the VSS change but, It's been running great so far with an immediate improvement after the VSS change.

hmmmm, I had no idea auto zone did this good of a test on it for free, never mind then, Good luck with your problem. (if its still there)

hmmmm, I had no idea auto zone did this good of a test on it for free, never mind then, Good luck with your problem. (if its still there)

Well, I took out the VSS sensor and tested it before and after cleaning it. Seemed ok but no way to test pulse shape. Not too much fine metal sludge around the magnet but some. Anyway no problems that last two days. I will probably replace the Hall effect 7X crankshaft sensor (don't think I can get it out without breaking it) as my son reminded me that that is how we fixed a similar problem with his 87 Cavalier a couple of years back. It had a minor crack in it, which was sensitive to heat and and baffled up the ignition module (I have a spare ignition module if anyone needs one;-). Thanks for your help guys. I will try this over the next week or get back to you if I have problems again.

Well, I took out the VSS sensor and tested it before and after cleaning it. Seemed ok but no way to test pulse shape. Not too much fine metal sludge around the magnet but some. Anyway no problems that last two days. I will probably replace the Hall effect 7X crankshaft sensor (don't think I can get it out without breaking it) as my son reminded me that that is how we fixed a similar problem with his 87 Cavalier a couple of years back. It had a minor crack in it, which was sensitive to heat and and baffled up the ignition module (I have a spare ignition module if anyone needs one;-). Thanks for your help guys. I will try this over the next week or get back to you if I have problems again.
we had the same problem,we replaced the module,that didn,t work, replacing the crankshaft position sensor cured the problem. it will probably break when you take it out,ours did!

Interesting about the VSS. I've never run across any issues with them, but that doesn't mean it couldn't happen. Tblake is right, it is hard to "bench test" an ignition module under the stress and temps that it operates under in service environment. But the CPS sounds most likely to me here. Good luck!

I've found that the best way to remover the CPS is to soak it liberally with an aggressive carb cleaner, wiggle it around a bit, respray, and repeat, until all deposits are loosened, and it will usually come out in one piece.

Was just wondering where the CPS was located on a 99 LTZ with a 3.8.
Thanks