Still having problems

As I've posted previously, my 1993 Lumina 3.1 was stalling randomly after warming up and finally would not even start. I've had the ECM, prom, plugs, plug wires and injectors replaced. Now the car starts right up in the morning after sitting all night and runs great after it's warmed up. No stalling at stop, starts right up after sitting for 10 minutes or so. New problem is I can't start the car after it sits for an hour and a half or two. Cranks, sometimes starts then dies right out. If I wait another hour or so it will start right up and run fine after it warms up. I'm in the Detroit area so it's cold outside right now. Shop where I had it fixed now wants to put in a new crankshaft position sensor for free since they seem to have no clue now. The problem seems to be temperature related more than anything since it starts fine when cold.

The windings in a bad CPS can be affected by heat soak and loose continuity after the engine is stopped, then regain after cooling off, like you describe. That would be my first guess as well...

Car started right up this morning after sitting all night. Drove around for about a half hour with no problems. Waited 2 hours, car cranks, won't start. Tried again after another hour, cranks won't start. Should be plenty cold by now.

See if the CPS is providing a pulsed signal when the engine is cranking...hit it with some ether and see if it fires on that...if so, it's not the CPS, gonna be fuel related...

Where do I "hit it" with ether?

Ether...starting fluid, spray into airbox or straight into intake.

Went out after 5 hours, car started right up. Let it run for a couple minutes and shut it off. Waited 5 minutes, started right up again. I'll check in an hour and see if it still starts since I didn't let it warm up.

Car started right up this morning. Drove around for 20 minutes with no problems. Stopped a couple at couple stores, started right back up. Came home and parked it. Went out half hour later and won't start. I can hear the fuel pump and can smell gas when I open the hood. Could someone explain to me why it would take at least 4 hours for something to reset or whatever before the car will start again? It's been in the 20's all weekend so it should not take long for the car to cool off.

Does the engine start if you hold the throttle open while cranking?

CPS replaced at shop this morning, no change. Car starts, hour later, only cranks. 4 hours later starts fine. They are still trying to figure it out.

It would really help if you could verify whether it will fire on ether when it happens, and if so get a fuel pressure reading/verify injector pulse, and if it doesn't start on ether, test for spark, which will probably not be present.

Then we could narrow down the possibilities. Otherwise, we're shooting blanks. Might as well throw a parts store at it.

Some odd problems can prove very hard to find...I got lucky with the wife's Ford ZX2 back a few months ago, it would suddenly start running on two cylinders instead of four after it had been running a while. Once it cooled off, it was fine. First thing I did was start grabbing wiring/connectors and tugging. I found when I got to the coilpack wiring, I could produce the problem by barely pushing on the connector.

Turned out to have a bad connector. When the wiring got warm and softened up, it would sag just enough to make that connection break. Cut one off a junk car, and it's fine now. But if it had gone to a shop, they might have suggested wires, plugs, coilpack, etc...and $600 it would still be doing it...see what I mean? A little bit of investigation can save you a lot of time and money...

I'd try this when it's running fine. Move the wiring harnesses around, push/pull on the connectors to everything you can reach, etc....see if it stumbles or stalls...you may just have a wiring sag issue or something dumb like that...

Shop said it was getting fuel and spark when cranking. I wasn't there at the time so I don't know any readings. All I know is, it starts in the morning and runs great. Park it and after half an hour it won't start. Wait 3 1/2 to 4 hours, starts right up no matter where the car is parked, inside a heated garage or outside in the cold. We've spent hours tracing every wire and find nothing, when it's hot or cold. Since the problem is time sensitive I believe it's pressure related but since I'm unemployed and have no more money to spend on fixing this car(my only one) I give up.

The injectors need a minimum pressure to open, so even if there appears to be pressure at the rail, doesn't mean it's spraying into the motor...

Need a fuel pressure reading when it happens. You can borrow a fuel pressure gauge at Autozone. Not feeling real confident about your shop you're using. You need someone who knows how to attack this.

Shop I've been using gave up. Says they fixed initial problem and I need to take it somewhere else. I've already spent $500 and have no money to take it any where else. Car stalled 3 times while driving 35mph after running for about an hour. Had trouble starting back up but would start. Car is parked now so I will have to wait at least 3 hours before I can drive it again.

Was it getting fuel and spark when cranking when it wouldn't start, or didn't the shop get it to repeat the problem? It sounds like a bad ignition module or ECM. Both will work when cold, and fail after the car has run a while. You can access the ECM under the plastic cover in the passenger side fender just ahead of the wheel well. Try starting the car, and lightly tap on the top edge with the handle of a screwdriver. If the car stutters or stalls, then the ECM is bad. If the service # on the ECM is 1227727, it is a high failure part due to water intrusion issues and could very well be your problem. The ignition module is under the coils (a pain to get at as it's mounted to the front of the engine under the front exhaust manifold), and can be tested at Auto-Zone/Advance for free. Make sure they run the test enough times to get the module warm.

ECM was replaced due to water intrusion on old one. I'm going to pull the ICM myself and get it tested.

Car is finally fixed. Was towed yesterday to an auto electric shop where they diagnosed this morning the ICM was bad. Runs great now. No stalling, no problems with starting. Here's everything that's been replaced in the last 3 weeks:
ECM, prom, plugs and wires, injectors(free), fuel filter, CPS(free) and ICM(free).