My 95 Neon is behaving oddly. When the outside air is below 25 Celsius (~90F) is runs fine. When the outside air temperature is over 25, it may stall. It has to have been running for at least 20 minutes, and it only happens when the car is going slow or at idle. It will just die. When I try to restart it, the engine bucks and shudders, and if it actually starts it will run rough and eventually stall. If I leave the engine sit for ahile, at least 10 minutes, it will start noramlly, but will stall quite quickly. If I leave it sit for a long time, the engine will start and run normally. It is showing no codes. I've had it in twice to a local (non-dealer) shop, and they haven't got a clue. Before starting the engine, I checked the oil level, and it was fine, but after the car stalled, when I checked the oil, it was very low. But if I waited for awhile, it would go back to halfway (started full). The front of the engine is covered in oil from about the middle on down.

Anyone have any ideas?

 

Your car is running in open loop which means it's running full rich, which is fine when it's cold but at operating temperature it will usually stall and be near impossible to restart until the engine cools down for hours. There is a bad sensor causing this trouble, so do the self check with the computer, here is a link to the details on how to do this (it's as easy as turning the key on and off a few times) and how to read it as well as what the codes mean: http://www.troublecodes.net/neon/

It is most commonly the forward O2 sensor or the idle speed control or throttle position sensor. Let us know what the code check comes up with.

 

I just checked, and I'm afraid that it is showing no codes (just 55). CEL is NOT on. Waht you said makes sense, but I wonder why outside temperature would affect this? If it is cool outside, it can run all day with no problems. Once is hits 25 (90F), then it willl likely stall.

 

The colder the air is, the denser it is, thus more oxygen content and that is what is needed when more fuel, or too much fuel, is added.

Check all electrical connections to the throttle body and it's components as well as all vacuum lines. I replaced my factory oil pressure sending unit with an aftermarket gauge in my '99 R/T and not having the factory wiring harness that was plugged into it hooked to anything it should have turned on the CEL, or at least one would think that it should have, but it didn't even show a code. So there is the possibility that a sensor could simply be disconnected or have a broken wire.

 

Now that you mention it, I recently had the oil pressure sending unit replaced. I wonder if they buggered something while they were under there. I'll look into it. Thanks very much for the help.