1995 Ford Contour Car dies occasionally at idle and loses p

NAPPINKAT

MEMBER
1995 FORD CONTOUR
4 CYL
2WD
AUTOMATIC
91,000 MILES

I have a 1995 Four Contour GL. It is a four cyl with an auto trans. The car runs decently but it seems to have a high idle and a bit rough but not bad. The car runs fine at higher speeds. When I come to a stop or coast for a peroid of time the idle abruptly gets rough and then dies unless I tap the gas pedal. It seems like something deenergizes or causes this to happen quickly. I can be at a stop for thirty or foutry seconds and its idling fine then it quickly changes and the idle gets rough. Then it seems to lose power when I step on the gas and abruptly accelates when I push the pedal to the floor. Then the symptoms go away and then return if I am doing a lot of stop and go driving. Putting it in neutral does not stop the car from dying at a stop. Thank you

5 Replies

MATHIASO

MECHANIC
1,209 POSTS

Hello nappinkat

Welcome to 2carpros. Com

You probably have a vacuum leak or fuel delivery issue.

An EGR valve that is stuck open at idle can have the same effect as a vacuum leak
Or a loose PCV hose. You can use a carb cleaner or propane to check suspected vacuum leak around the intake.
The important thing to keep in mind about vacuum leaks is that they have the most noticeable effect at idle. At part and full throttle, there is so much air entering the engine that a little extra air from a vacuum leak has a negligible effect.
If you have a scan tool, look at the Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT) values. Normal range is plus or minus 8. If the numbers are +10 or higher for STFT and LTFT, the engine is running LEAN. If you rev the engine to 1500 to 2000 rpm and hold it for a minute or so, and the STFT value drops back down to a more normal reading, it confirms the engine has a vacuum leak at idle. If the STFT value does not change much, the lean fuel condition is more likely a fuel delivery problem (weak fuel pump, restricted fuel filter, dirty fuel injectors or a leaky fuel pressure regulator) than a vacuum leak

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Wednesday, January 27th, 2010 AT 12:45 AM

NAPPINKAT

MEMBER
3 POSTS

Thanks for the quick response. This only happens when the car is run for a little while and it is intermittent. I was told to look at the IAC? Could that be the problem?It idles fine when I start it. Then all of a sudden I will be with my fooot off of the gas and the idle drops abruptly. I hope this makes sense. Thanks!

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Wednesday, January 27th, 2010 AT 7:37 AM

MATHIASO

MECHANIC
1,209 POSTS

Hello nappinkat

If your engine is idling too fast, too slow or stalling, the problem may not be the idle speed control system, but an engine vacuum leak. Check for vacuum leaks first to rule out this possibility.
A common condition is to find the idle air bypass solenoid extended all the way out (closed). This usually means the engine has an air leak and the PCM is trying to bring the idle speed back down by closing the idle air bypass circuit. If there is an open or short in the idle air control solenoid, Wiring or driver circuit, or the idle speed is out of range, it will usually set one or more fault codes and turn on the Check Engine light. If the light is on, you need to plug a scan tool into the diagnostic connector and read out the codes that set the light.
The diagnostic procedure involves disconnecting ISC motor, then starting the engine to see if the idle speed increases (it should). Turn the engine off, reconnect IAC and start the engine again. This time the idle speed should return to normal. If it does, the problem is not in the IAC circuit or motor. Check for vacuum leaks or other problems that would affect idle speed.

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Wednesday, January 27th, 2010 AT 7:52 AM

NAPPINKAT