Hi everyone,

Recently, when I first put my car into drive, it develops a rough idle, doesnt rev(then suddenly jumps in rpm), and when i hit the gas i get a faint gas smell. What's strange is that the problem goes away after 15-20 seconds and it runs perfectly smooth after. I took it to my mechanic, he plugged his reader into the obd port and nothing came up out of the ordinary. No check engine lights either. A couple times the revs dropped so low the engine shut off. Anyone have any idea what it could be? What makes no sense to me is why it goes away after 15-20 seconds.

EDIT: JUST FOUND THIS OLD POST, EXACTLY THE ISSUE I AM HAVING, PLEASE READ:
"I have a 1998 Cherokee Sport, 4L 6 Cylinder engine. 146,000 miles.

For about a year and a half I have an issue with jerky acceleration at lower speeds. Around the same time I started experiencing some problems with a rough idle. When the engine is cold it idles very loudly and the RPMs oscillate in an inconsistent pattern. During this, the exhaust system is very loud and is shaking underneath the vehicle. On several rare occasions the engine has shut off because the RPMs have dropped so low.

I'm not sure if the two problems (idle and acceleration) are related. It feels like the same thing because my RPMs also fluctuate when driving at lower speeds. When this happens and the RPMs drop, it feels similar to running out of gas. Also when the jerky acceleration happens, I hear a clunk/click and I can feel that clunk/click in the gas pedal. Spark plugs were replaced just a few months before this all started.

This happens very inconsistently. I had a mechanic look at it, but it wouldn't happen when he was in the car. Lately, it has become less inconsistent and happens almost every time I drive. Outside temperature seems to have no effect. It almost always stops after a few minutes and the engine is warm. But even this is inconsistent as sometimes I will drive for a long time, stop the car to gas up, and the problem is back even though the engine is plenty warm. The only consistency is that it's always at the beginning of my drive. This never happens after accelerating away from a Red light for example.

Things I've tried:
- Tested fuel injectors (all fine)
- Manually cleaning fuel injectors
- Manually cleaning idle air control
- Using a fuel conditioner/additive somewhat regularly for the past 6 months.

Any ideas? Thank you! First time poster, long time reader."

 

More info, year, miles, etc.

 

4.0, 1999, 128k miles. Recently changed serpentine belt and idler pulley. This has been going on for about two weeks or so now. hasnt gotten any better or worse. My mechanic said it could possibly be a leaky injector.

 

Could be. Could also be your O2 sensor. It won't set a code. Check that first.