jeeps cold= ruff idle until warm, what gives

[288sunny]

I have been trying to trace this bug for awhile now, tried some sea foam in the gas, new spark plugs, etc..
When the jeep is cold like first thing in the morning, i start it up and the idle goes high( say around 1K), but then a few secs later it will drop off likes its going to die/rpms get real low, and then it will catch itself, idle goes back to around 1K but sounds/appears ruff, and it may frop down again, just depends on what kind of mood its in, Knock on wood it has never just died, idle goes up and down and is ruff..

Now the kicker, if the jeep is warm, or i just drove it to the store and then started it back up it runs fine, Very slight ruff idle but nothing like when its cold??? what else should i be looking for, or looking at?

 

[bobcat481]

Don't know. Mine does the EXACT same thing. I've always assume it was the nature of the beast. Mine only does it when it cold out side (30 or below or so). Does yours do it when it's warm out?

 

[xt master]

Could be something with the MAP sensor.It has to do with the air/fuel mixture when its cold.

 

[bobcat481]

Could be something with the MAP sensor.It has to do with the air/fuel mixture when its cold.

Hey...will a jacked up MAP sensor throw a code? My brothers got a reader. Wonder if it's worth hooking it up? Do you know if an '88 YJ is OBD1 or OBD2? Are the connectors the same?

 

[TerryMason]

What year Jeep? Assuming this is an older CJ, I'd bet your choke isn't working, or some of the carb jets are plugged up.

If it's a newer Jeep, I'd take it to the local auto parts store and have them pull the codes off of it.

 

[Bounty__Hunter]

288sunny, give a little info about your jeep so we know what we're looking at here.

 

[288sunny]

Sorry fella's, its a 2003, 4.0 automatic 4x4

 

[Bounty__Hunter]

I would remove the throttle body, remove the sensors, and give it a good bench cleaning with carb cleaner and a toothbrush. Pay special attention to the half-round housing on the side where the idle control motor attaches.

 

[jps4jeep]

also the rough running could just be the oil not coming up to temp. what oil are you running? 10W30 is about the highest I go in the winter.

 

[xt master]

also the rough running could just be the oil not coming up to temp. what oil are you running? 10W30 is about the highest I go in the winter.

I use 5-30 in the winter and 10-40 in the summer.