rough idle- check engine light

[singleton8068]

the check engine light came on a few days ago and the engine immediatly started to idle rough. the engine tries to shut down when im not on the trottle ie. shifting or stopped. i replaced the relays, the plugs and wires, fuel pump and filter, air filter. i changed the fuel filter yesterday and it ran fine for about 2 hours then started back up again. any ideas?

 

[singleton8068]

the exhaust smells like straight gas. i checked the fuel pressure and its right where it needs to be. its running really rich tho.

 

[Earl43P]

http://www.therangerstation.com/tech_library/OBD_I.html

 

[singleton8068]

i picked up an obd1 computer reader from autozone and it worked once. now all i get it a continuous light and beep. theres no pauses or flashes to count. im not sure if its the computer thats shot or the scan tool.

 

[JustME]

Autozone and other chain part shops loan tools, bring your DL. They will let you use their OBD tester for free, just ask. Could be a O2 sensor

 

[JustME]

I don't see listed what you are working on, year, make and engine. Could be an OBD II and that is why your tester won't work.

 

[singleton8068]

its a 1993 ford ranger 4wd with a 4.0. i bought a new scanner to see if my old one was the problem. the new scanner worked the same as the new one. all i get is a continueous beep/flash. everyone ive talked to says the computer was to blame so i pulled it and ordered a new one. the new computer will be here on the 29th so hopefully thats the problem. if not im lost.

 

[GoGoggansGo]

Try cleaning you Mass Air Flow sensor that can cause an engine to run rich or run lean, and cause a bad idle. On OBDI it is very hard to find the problem, and figure it out. Trial and Error

 

[GoGoggansGo]

I found a TSB for a 3.0 but it an auto trans tsb for bad idle

 

[Duane867]

Pull the ICM off and have it tested.