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3.8L '92 Cougar Low Compression

2K views 18 replies 7 participants last post by  Soduka 
#1 ·
If the V6 engine on this car has a cylinder that has low compression and is triggering a misfire, shouldn't that in turn trigger the CEL?
 
#2 ·
With the OBD-I systems, I'm not sure exactly what conditions triggerthe SES light for a misfire.

What you can do, however, is run the OBD self diagnostic and cylinder balance tests. That will tell you which cylinders, if any, aren't firing normally. In short, you ground the small single gray plug near the test port by the air cleaner, start the car and wait for the check engine light to flash at you. At that point, it wants you to jerk the steering wheel 1/2 turn, then do a quick WOT snap on throttle. It'll do some more tests, then start flashing codes at you. After the last code flashes, you can tap the throttle lightly and it will then do the cylinder balance tests.

http://oldfuelinjection.com/?p=13

http://oldfuelinjection.com/?p=94
 
#3 ·
Not on a 92! I think that only happens with newer OBD-II systems & coil-on-plug ignition that a misfire is sensed by the computer.
 
#4 ·
#5 ·
Thanks everyone. I'm just trying to figure this car out and make sure the other systems were working. Didn't know Ford's OBD 1 didn't detect misfires.

One of the cylinders is down to something like 60 psi. Probably not a good thing. Don't know what to do about that right this second.
 
#9 ·
Well I changed the oil a few days ago and nothing out of the ordinary came out, no foam or coolant or anything. The car will idle rough/really misfire when it's cold now. As it warms up it calms down. Above 40 MPH and below 25 mph you can't tell anything is amiss with the car. It seems to be at its worst in between that range.

Out of curiosity's sake and from a mechanical standpoint, does continuing to drive it affect the rest of the cylinders? Will the engine implode in the near future?

Only did basic compression test as of now. Haven't done leakdown/wet yet.
 
#13 ·
Alright, just trying to get an idea of the repercussions. Thanks.

I'm no moron, I can't imagine driving on 5 cylinders is IDEAL nor advisable, I was just trying to figure out if continuing to drive it will start causing other cylinders to shut down and eventually brick the car and leave me stranded in a field. If I am right, to fix the problem properly the engine will most likely have to come out, correct? If that is the case then I would just find another engine to plop in there, no point in putting this old thing back in. This one has at least 300,000 miles on it.
 
#18 ·
Just my 0.02 here, but with what you just posted, I would point to sticking valve (badly sticking in some instances) Highway driving will help an engine run better, whereas city or stop and go driving, if there is a problem with the engine already will probably make it more pronounced. But with 300k on it, baby it, then when you have the money and time to replace/upgrade it. Send it off with a bang - Rev limiter until boom imo. Then you replace your mounts and drop in the new power plant. All is well again in your world :D
 
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