My jeep has a idle/start problem.?

Question

I drive a 1999 Jeep Wrangler TJ 4cyl manual transmission. Sometimes when I try to start it, she cranks until I rev the throttle a little bit and then finally she turns over. If I let go of the gas, it promptly dies, unless I've been moving down the road for about 300ft. She idles at a real low rpm unless I rev it at a stop or while moving in neutral. She runs fine otherwise. It seems really weird. Neither I, or even a mechanic, could find the problem with our quick searches. Any suggestions?

Answer 1

Your best bet is to go to the local parts store (advanced auto, autozone, pepboys, etc) and get them to hook up their scan tool.  Most major parts chains will do this for free (hoping that you will buy the replacement part from them.  You Jeep should give them an error code that they will cross reference, and tell you what's wrong.

Without a error code you're just shooting in the dark - this could be a fuel injector, computer error, heck, even a worn clutch.

Answer 2

I had this same problem with my 4cyl 97 wrangler the problem was my upstream 02 sensor the one under the intake on your exhaust is not reading fuel trim right the wiring for mine was rubbing on the intake and shorting out the sensor.  If you can get a scan tool and check for codes even ones not active and there is a 02 sensor code I would check that o2 sensor first.  I am a mechanic and a jeep enthusiast and have come across this same problem a couple times so  just take off the intake hoses to the throttle body to get stuff out of your way and find the connector for that o2 sensor and follow the wiring for any rubbing or melted connector.

Answer 3

Sorry, I don't know either?!?! Find a different mechanic I guess.

Answer 4

Two things come to mind.

1st, is it time for a Tune-up. New plugs & wires, cap & rotor.

2nd, the Throttle Body needs cleaning, to include the Idle Speed Motor and Throttle Position Sensor (both are attached to the throttle body).

Happy Trails!