Stalls at operating temp

I'm getting really confused with my 93 4.0. It runs fine when it's cold, but when the temp guage gets up around 210, it will just die. It will fire back up after a minute or two, drive for 100 feet, and die again. When I let it completly cool, it will run fine again till it gets hot. I've never run into anything like this before, and I have no idea what's wrong with it. It seems to have good fuel pressure, and has a brand new coil. I just changed the oil the day before it started doing it, but I don't think it's related at all.

Any ideas?

Thanks,
-Joel

Sounds like your crank position sensor is on the way out so replace it. It's in the 1 o'clock position on the bellhousing when viewed from the front, and a real PITA to get to unless you have a socket wrench with swivel joint and extension. There's only two bolts to remove so once you're there it's fairly easy.

it could also be the coil, just because its new doesnt mean its good .It does sound like it could be the CPS to.

i just had this happen to me twice.there is an auto shut down relay under the hood .i had to replace mine all is good again.

I originally thought coil, that's why I replaced it. I also switched out relays to make sure it wasn't the Auto shutdown. CPS was a thought, I just didn't know if temp would affect that. I'll try that next, thanks.

How about oxygen sensor? When cold, the injection runs in open loop mode -- uses a pre-programmed fuel map in the ECU and ignores sensor feedback. When it warms up, the system switches to closed loop mode and uses sensor data to control the fuel map and ignition.

If it runs okay cold, it appears the ignition and injection should be okay but once it changes into closed loop mode one of the sensors involved is sending funky data.

Well I put in a new CPS today, but its still doing the same thing. I guess I'll try the O2 sensor next.

Long shot - but maybe the cat is clogged such that as everything expands as it heats up, it becomes blocked?!?! Again, it's a long shot......

Flashover said:

Well I put in a new CPS today, but its still doing the same thing. I guess I'll try the O2 sensor next.

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Eagle suggested that originally and he may be right. If nothing else, changing the CPS leaves you with one headache less to worry about. You can keep the old CPS as an emergency spare.

Did the O2 sensor this morning, still not good. If nothing else, I'm building a decent collection of spare parts. Can anyone think of anything else? Thanks for your help so far.
-Joel

Sorry you spent the money on an O2 sensor for naught. Seemed like a good guess at the time. :dunno:

Have you taken it to a shop with a good diagnostic computer and hooked it up? It still sounds like a problem relating to when it goes from open loop to closed loop. Now I'm wondering if it might be in the ECU itself.

Flashover said:

Did the O2 sensor this morning, still not good. If nothing else, I'm building a decent collection of spare parts. Can anyone think of anything else? Thanks for your help so far.
-Joel

Click to expand...

It sounds like for whatever reason, your engine runs fine when cold but becomes too lean when hot.
The coolant temp. sensor (CTS) in the t'stat housing might have been one candidate but if that was shorted out, it would cause the engine to stall or have a low idle when cold, and run fine when hot. The same also applies to the MAT (manifold air temp.) sensor (or IAT sensor, same thing). If these sensors were dead and giving infinite resistance, the engine would run rich all the time which is OK when the engine's stone cold but as it warms up, it begins to run very poorly, bog, and splutter as the plugs get fouled up with unburnt fuel.
Now that I've ruled out two sensors (CTS and IAT) as being the culprits, I've saved you from collecting more spare parts.
Since you've already changed the O2 sensor (the most logical candidate), check the wiring coming from it. Since the wiring is very close to the exhaust manifold, the insulation might have broken down causing it to short out.

When I pull the codes I get either a 32 or a 12 and an 11, I'm not sure which. 32 doesn't seem to be a valid code for that year, so I guess it's not that. 12 makes sense since I disconnected the battery when I did the coil last week. 11 is the code for a CPS error I think, but I just replaced that as well. Also, if the CPS is completely toasted, it shouldn't run at all, should it? Thoughts?

Thanks,
-Joel