Weird 4.0 idle issue

bfabian76

bfabian76

Member
Original poster
Joined
Jul 8, 2021
Messages
56
Location
tampa florida
2001 4.0 auto

So I’ll start by saying this hasn’t been a big issues and i haven’t done much to troubleshoot it yet. (The jeep isn’t my daily) but. This is what it’s doing.

it will drive and idle fine all day. Cold or hot. Doesn’t matter. However, if i run up to the gas station. Shut it off. Go inside. Come back out and restart it. It will idle rough for about 30 seconds or so. And then it’s fine. It’s never done to it me at a stop light or anything other than restarting it after it’s warm and shut off for a few mins. I pulled the IAC and cleaned it. No change. My other other thought maybe an o2 sensor. But it’s weird to me it wouldn’t do it at a light or anything. Only upon restarting.
 
Your not driving it enough. When I first got mine it did that, but now that it gets driven frequently it hasn’t done it since.
 
After the engine is shut off the heat permeates the fuel injector body and fuel can drip out which when the engine is restarted it takes a while for the rough idle to clear.
If the fuel injectors are the originals and you have >125K on them; you should consider getting them chemically cleaned or replaced.
When I purchased this '01 4.0L the engine had the same problems of rough idle when restarted after sitting for 10+ minutes. I replaced the original 1 hole fuel injectors with 12 hole fuel injectors for a better spray pattern and installed the injector insulators and fuel rail insulation.
Even with the heat here in Florida; the problem has remained gone since replacing the fuel injectors and adding the insulation.
 
CharlesHS said:
After the engine is shut off the heat permeates the fuel injector body and fuel can drip out which when the engine is restarted it takes a while for the rough idle to clear.
If the fuel injectors are the originals and you have >125K on them; you should consider getting them chemically cleaned or replaced.
When I purchased this '01 4.0L the engine had the same problems of rough idle when restarted after sitting for 10+ minutes. I replaced the original 1 hole fuel injectors with 12 hole fuel injectors for a better spray pattern and installed the injector insulators and fuel rail insulation.
Even with the heat here in Florida; the problem has remained gone since replacing the fuel injectors and adding the insulation.
Click to expand...
That makes since. I’ll throw some new injectors In and see what happens
 
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