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Topic
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1999 cougar with a 2.5 engine.
When the outside temperature falls below around 25 to 30, the engine alternates between surging then loping (sometimes dieing).
This goes on no matter what the engine temperature is. Granted it is worse when engine is completely cold but never quite goes away.Here are things I have checked –
fuel pressure good (42’ish), PCV valve replaced, MAF sensor cleaned and electronically tested, IAT sensor clean and test, no fluids being lost, IACV recently replaced, no black smoke coming out, no “new” codes (same codes it has had for months), battery is 12 V engine off and 14.5 when running, IMRC not holding open secondary runners at low RPM, Engine temperature “normal”, and the hoses LOOK ok, none are broken at least, not that I can see. Self-diagnostic test shows engine temp to rise as expected (unless it is taking a reading off the separate sender unit instead of the Coolant temp sensor itself which signals the PCM) Anti-freeze is proper mix and not losing any.It was suggested that maybe the extreme cold was causing a hose or line to contract and open a leak. I don’t really relish the thought of standing outside when it is 15 degrees to inspect every hose with a magnifying glass. Besides, some hoses are way too fragile to be messing with.
As i said, this surging/loping is a problem ONLY when the outside temp gets below freezing like 30 or less. Funny how this seems to coincide with real close to the freezing point of water…
Well folks, that is pretty much it. I am hoping yesterday was a fluke but I don’t think I will be that lucky. i am open to any suggestions.
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As far as checking the hoses, the easiest way is to take any aerosol can (or source of pressurized air) and spraying under the hood at various hoses. If the engine suddenly surges or dies, then you’ve found your vacuum leak (because vacuum connects throughout, and engine RPM is based on vacuum pressure, you can use this to find your leaks).
Other possibilities include checking the throttle body – just buy a gasket kit (maybe $10, not gonna look it up, but it’s cheap), remove the TB, clean with TB cleaner, install new gaskets, reinstall. I’m sure Eric has some video on how to do this, not gonna go into much more detail, but for someone familiar with working on cars, it shouldn’t take more than half a day over the weekend or something. If nothing else, that’ll clean up the engine and get you some more power and a cleaner operating engine.
Trying to think of anything else, but I’m sorry, been working WAY too many hours lately, and I’m just plain tuckered.
I would be checking the coolant sensor.Thats a major
player when the car is cold. What code did you have?Coolant sensor seems OK.
Not sure why but after i cleaned and and inspected a few things, it has not done it again, and last night it was 24 degrees and car ran without incident.Only thing I replaced was the PVC but I somehow doubt that thing was bad, the new one rattled the same as old. For $3 though why not just swap.
Well, I appreciate the feedback here, I guess time and weather will tell if this car starts acting up again.
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