99 Cougar V6 rough idle

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Old 01-11-05, 06:14 PM
Handyman1950's Avatar
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99 Cougar V6 rough idle

My daughters 99 Cougar V6 started running rough at an idle...like it was running on 3 or 4 cylinders. After it gets up to about 2000 rpm, it starts running fine. I pulled the plugs and they were all a nice tan color with a good gap.
A friend of hers put it on an analyzer and said the front three cylinders weren't firing at an idle. He couldn't figure out what was causing it without spending more time on it--which he didn't have. The plug wires go to what looks like a distributor in the back of the engine. Not being a Ford person, I don't know what type of ignition system it is. I can't imagine what would cause the front three to cut out at idle unless maybe it has separate coils for the front. If it's something simple, I would like to try and fix it before I put it in a basket and take it to a garage. Any help would be greatly appreciated.

Hm1950
 
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Old 01-11-05, 07:07 PM
Master101
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Old 01-11-05, 07:59 PM
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Have the computer codes read by a place such as auto zone (should be a free check) and post back here what the code(s) are. Or your daughter's friend may have checked the codes so you could try asking him if he knows what they are. It could be a lot of things. It would be odd for 3 plugs or wires to all go bad at once.
 
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Old 01-11-05, 08:20 PM
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Check for vacuum leak

Check for a vacuum leak on the lower intake manifold. O/rings leak on intake.
 
  #5  
Old 01-12-05, 05:00 PM
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Master 101: Thanks for the link but none of those symptoms exist.

Hogfan: He did mention something about a possible vacuum leak but I haven't had a chance to look for one...that's next. I'll let you know what I find.

Something else I noticed that may have a bearing--there is a strange 'trumpeting' noise that started happening a couple of weeks before the rough idle problem. Now, when the noise is occuring, the engine runs smoothly. When the noise stops, the engine starts running rough. It doesn't happen very long though. Once, when the car was in the driveway and started making the noise, we popped the hood and it seemed like it was coming from the air cleaner. I unfastened the bail wires around the box and the noise stopped. I don' know if this is a cause or a symptom or if it is even related.

I'll keep you posted.

Hm1950
 
  #6  
Old 01-29-05, 09:25 AM
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Smile Happy ending

I went to O'Reilly's and borrowed their code scanner. It had about ten codes stored. All cylinders were misfiring, both banks were lean, and some H02S1(?) switches were not present.
Sounds like 02 sensors to me! The parts guy tells me there are two...one before the cat con and one after. I buy them and crawl under the car to find that there are actually three! The one on the rear bank is the same as the one under the cat con in the front...and the parts guy sold me the wrong one. Back to O'Reilly's to get the right one from a different parts guy that knew how to read and found that the first parts guy didn't even offer me the OE item for the top sensor, just the universal fit. Traded the universal for the custom fit. Much better. Installed both and re-read codes. Only codes were for misfires on 1,2, and 3 -- the rear bank - now we're getting somewhere. Back to O'Reilly's for the third sensor. Car runs great. Cleared all codes ran it for a while and scanned again...no codes. It's been a week and the car is still running good. Total cost...$172.00.
Thanks everybody for the input. Given the reviews I've read on this car, I'll be back.

HM1950
 
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