rough idle

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Oct 10, 2010 | 04:22 PM

kirbykoon

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rough idle

1992 f150 4x4 5.8 efi
this truck has been running fine til i let it set for a couple days, now it idles rough(almost like i have a big cam) and wont idle at all when cold.
I cleaned the iac and tb with no change, if i let it idle while spraying carb cleaner in the tb, the engine smooths out, could this be caused by a sparkplug? maybe...help please

Oct 10, 2010 | 05:57 PM

DBGrif91

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From: Des Moines

It could just be a matter of air in the fuel lines.

I've had issues in the past w/ my 91 F150 where after I let it sit for a couple of days, the fuel lines seem to completely drain. If I don't give the fuel pumps enough time to prime the fuel lines before turning the key to start it, it will run rough.

Are you familiar with how you're supposed to hear the fuel pumps run for a second after the key is turned to on? If so, repeat this procedure about 5 or 6 times before attempting to start it. If you get it started, use the gas pedal to prevent it from dying if it's still running rough.

When I experience this problem, it takes a good solid 1/2 hour of running the truck before the issue straightens out.

Oct 10, 2010 | 09:36 PM

kirbykoon

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ok i will try the 5 or 6 times thing and see if that works...i drove it 28 miles today and it tried to die everytime i stopped, but it drives normal and it smells like it is running real rich

Oct 10, 2010 | 11:06 PM

bustech81

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Try disconnecting the IAC and see if that helps. Pinging under acceleration? Poor throttle responce?

Oct 11, 2010 | 01:34 AM

kirbykoon

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no change when i unplug the iac and it hesitates . when i am sitting in 1 spot revving the motor, it doesn't seem like it has full power

Oct 11, 2010 | 07:11 AM

kentuckyredneck

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TPS? If it's bad, it can really screw up the idle.

Oct 11, 2010 | 09:43 AM

rla2005

Fleet Owner

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From: Kentucky

It is always a good idea to do a tuneup if you do not know the age/mileage on the plugs/wires/cap/rotor/filters. No sense spending money on other parts until the basics are taken care of.

Many times there can be a code stored without turning on the Check Engine Light, therefore I would also check for stored codes or other problems with the KOEO tests.