1992 Ford F-150 ROUGH IDLE

FORD TRUCK

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1992 FORD F-150

Engine Performance problem
1992 Ford F150 V8 Four Wheel Drive Manual

When the key is on but not started the check engine light will flash and rpm needle bounces around. When the vehicle is on and is hot the check engine light goes on and off, its idles rough and rpm needle bounces, and it sputs like its running out of gas, but is not. When its cool out and the vehicle has just started, it runs fine till engine gets hot. I had it tested under the obd1 tester. It said it was the map sensor. I've replaced the map sensor, along with the computer, spark plugs and wires, distributor cap and rotor, intake air temp sensor, tps electrical sensor, throttle positioning sensor, coolant temp sensor, fuel filter, fuel regulator, idle air control cylinoid, bypass air idle speed control cylinoid, thermostat, and have also had the electronic ignition module tested. Also, when hot tail pipe blows black smoke. After fixing all of these things there is still no change. Please help with any info you can. Thank you.

1 Reply

THIS IS MIKE

MECHANIC
686 POSTS

Check for any vacuum leaks or a partially opened EGR valve. A partially plugged catatytic converter could also cause this condition. The temperature of the exhaust should be cooler before the converter than it is after the converter. If it is not the converter is plugged or not working properly. Make sure you have at least 14-17 lbs of vacuum to the MAP sensor.