1992 Ford F-150 rough cold idle

JDCARTER

MEMBER
1992 FORD F-150
215,000 MILES

First start up very rough idle need to keep idle to 2000 rpm when gets warm(5mins or so) runs great seams to be hard on fuel mileage blocked egr replaced plugs, injectors, fuel pressure reg, coolant temp. Sender(to pcm), does have purge can. Codes have run some live data not sure what values should be. 2or3 years ago had blown head gasket and bent rod replaced rod truck did set for awhile

3 Replies

HMAC300

MECHANIC
48,601 POSTS

Try cleaning the throttle plate with choke cleaner and iac hole. Clean on both sides. Check for a vacuum leak. Check to see if vacuum goes through purge at idle it shouldn't. Or block off purge line to test if idle straightens out then replace purge valve.

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Monday, November 11th, 2013 AT 8:33 AM

JDCARTER

MEMBER
2 POSTS

1992f150 rough idle more input check map sensor no help engine runs when cold with a dead miss clys.2, 7, 8;(cold engine;have noted that on scan tool intake air temp. Iat starts with a value of 4.0 when value gets to1.0 engine has run long enough to begin to run better when completely warm could not ask to run better also when cold seems to spit back not sure if in exhaust or intake driving when this happens) does any one other than I think it could be a valve or head issue taking head gasket and bent rod issue or is it electrical or sensor problem this one has made a lot of seasoned mechanics rub their heads without ideas have also tried to clean intake by through vacuum lines sucking sea foam into intake no help what do you think jd carter

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+2

Wednesday, November 13th, 2013 AT 6:05 AM

HMAC300

MECHANIC
48,601 POSTS

What engine? If this had a bent rod you would know it. Check your distributor either worn bushings or a pickupcoil problem maybe. This really sounds like a vacuum leak however. Check your pruge vavle for being open it has one vacuum line and shold only have vacuum on one side not both. Or block off the line and see if it stops the rough idle. Check compression if a 20% variance then it's a cylinder problem.

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Wednesday, November 13th, 2013 AT 6:46 AM