2000 Ford Escort Rough Idle CEL

Old 05-28-05, 03:28 PM
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2000 Ford Escort Rough Idle CEL

I have a 2000 2.0L split injection v4 Ford Escort with 71000 miles.

About a month ago I noticed the idle was getting a little rough. However, the roughness does not begin immeadiately when I stop the car. It takes 20-40 seconds before it starts. The roughness could be described as a cycling where it appears the rpms drop and the engine "coughs" and then it gets better for a second before cycling down again. If I don't give the engine gas it will stall about 30 seconds after the rough idle begins.

When I am driving at any speed, or even giving it gas in neutral, the problem does not exist. I recently replaced the air filter and the problem did not improve.

Additionally, I have experienced a decrease in gas milage of 5-8 mpg.

The check engine light came on about a week after the rough idle started. It stays on constantly. I took the car to autozone for a free code check, and it returned the code: 171 which is left bank lean.

The guy at auto zone said my O2 sensor is probably bad and quickly offered to sell me one. Is he likely correct? I have the Haynes repair manual and would like to try and fix this myself.

Thanks for any help!

Old 05-28-05, 07:56 PM
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Originally Posted by kansasnate
171 which is left bank lean.

The guy at auto zone said my O2 sensor is probably bad and quickly offered to sell me one. Is he likely correct?

No, but it certainly is possible

And AutoZone is #1 in o2 sensor sales
(sorry, inside joke)

That would be like shooting the messenger
Or at least dumping him in the trash and buying a new one because you didn't like what he told you

The o2 is reading that the engine is running lean, so the comp. is dumping more fuel in to compensate
By your fuel mileage seems to bear this out

I am more familer with the older 1.9s, but I assume the 2.0 (zetec?) is similar in this regard

I would look at the Mass Air Flow sensor, see if the sensor itself is gummed up
It can be cleaned with carb cleaner

I would look for a leak in the Air Intake Tube, specially after the MAF
Oh while you are at it check any vac hose for leaks, specially under the curved pieces

I would test the Throttle Position Sensor with a voltmeter

The Haynes should have the specs/procedures

There is also a chance it's the o2 going on you
At 71K that's a little unlikely (at least going bad enough to throw a code), but certainly a possibilty

I like to change o2s before they go, I consider them a maintenance item-not a failure item
I don't mind changing one after 60K just to keep on it
They do tend to slowly fade away
I'd just check the other stuff first
Old 05-30-05, 03:39 AM
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Given your symptoms, 'lean' and poor gas mileage and bad idle, you probably have a plug that is misfiring. That would account for all 3 symptoms. Replace your plugs.
Old 02-09-14, 11:18 AM
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Had this problem. PCV hose is hard plastic with rubber boot on each end. Boots were deteriorated. Couldn't get boots on Saturday, so l used an old spark plug wire. The spark plug boot fit the pcv valve & tube. The distributor boot fit the other end. Had to trim both boots a little but they are working fine. The distributor boot was the older type that has about a 5/8'' opening for the distributor. Hope this helps someone. Good luck!

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