Rough Idle

Godless Nature

Godless Nature

Member
Joined
Jan 30, 2020
Messages
27
Location
Indianapolis, IN
2000 Sport 4.0 5 Speed

Idle bounces around 5-700. Spark plugs changed recently, no change. I took off the throttle body and cleaned it all last night, as well as the IAC and housing. No change. Vacuum lines seem fine.

It threw a warning light last month reading high voltage on the downstream O2, but then went away a few days later.

Anyone have a recommendation before I inevitably start throwing parts at it?
 
I just went thru this with mine. Was throwing code for cam position and TPS changed both then it ran like a bag of hammers. Started throwing codes for Crank sensor and Coil Packs. Ended up having to turn the cam sensor gear ahead to advance timing some and now it idles around 750-900 but smooth and no codes. I'd try just advancing timing ever so slightly. The o2 sensors are weird cause I have my cat gutted and haven't had any issues with o2's yet.
 
I'd suggest replacing all your O2 sensors per this thread:

The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

O2 sensors are general wear-and-tear maintenance items and should be replaced every 80k miles or so, regardless of whether they are bad or not. They pre-cat O2 sensors affect how the engines run, so they could in some way be contributing to the idle possible.
 
  • Like
Reactions: Godless Nature
Chris said:
I'd suggest replacing all your O2 sensors per this thread:

The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

O2 sensors are general wear-and-tear maintenance items and should be replaced every 80k miles or so, regardless of whether they are bad or not. They pre-cat O2 sensors affect how the engines run, so they could in some way be contributing to the idle possible.
Click to expand...

I replaced the upstream sensor tonight (correct ntk part) and it cleaned up a little. There are only two O2 sensors on mine.

There still is an intermittent bounce between 6-700, mostly when it is coming off of throttle.

I have the other sensor for the rear. When trying to drop the TC skid plate to get a decent angle on it, I came across the front nutsert broke loose on both sides. Just another thing to address once I find the parts.

How clean of an idle, and at what RPM, should a guy be content with?
 
Godless Nature said:
I replaced the upstream sensor tonight (correct ntk part) and it cleaned up a little. There are only two O2 sensors on mine.

There still is an intermittent bounce between 6-700, mostly when it is coming off of throttle.

I have the other sensor for the rear. When trying to drop the TC skid plate to get a decent angle on it, I came across the front nutsert broke loose on both sides. Just another thing to address once I find the parts.

How clean of an idle, and at what RPM, should a guy be content with?
Click to expand...

Your idle RPM sounds normal to me. It shouldn't be lump while just sitting there idling though, so if it's doing that, something is up.

The nutserts are easy to fix. Blaine sells replacement ones you can install, as it's a very common issue.
 
Chris said:
Your idle RPM sounds normal to me. It shouldn't be lump while just sitting there idling though, so if it's doing that, something is up.

The nutserts are easy to fix. Blaine sells replacement ones you can install, as it's a very common issue.
Click to expand...

I agree, something is up. The only thing I can think of is to replace the throttle body sensors and/or coil rail... after I get that bastard o2 sensor.

Looking through the forum, Blaine runs Black Magic Brakes?

I saw the replacement nutsert/bolt package on that site. I suppose I probably should do them all rather than just the two. If that is him, the guide on making the installation tool looks solid.
 
Godless Nature said:
I agree, something is up. The only thing I can think of is to replace the throttle body sensors and/or coil rail... after I get that bastard o2 sensor.

Looking through the forum, Blaine runs Black Magic Brakes?

I saw the replacement nutsert/bolt package on that site. I suppose I probably should do them all rather than just the two. If that is him, the guide on making the installation tool looks solid.
Click to expand...

Yep, that’s Blaine. And he will tell you to replace all the nutserts at once, which is solid advice.
 
Top Bottom
Back