Intermittent high-idle

Alex05

TJ Enthusiast
Joined
Jun 18, 2020
Messages
128
Location
Madison, WI
While stopped at a light, I noticed that my LJ was hunting around for it's normal idle RPM. When I got home, I shut off the motor, restarted it a couple minutes later, and it found it's idle normally.
I checked the vacuum line that runs from the manifold into what I assume is the ECM (vacuum line runs from a port on the intake manifold, across the firewall, and dives into a fitting near the 4 coil packs), and that seemed like it was attached normally. I've always been suspicious of this vacuum line because it seems really easy to disconnect from the vacuum port, and it doesn't feel like it's on there very tight, but it otherwise doesn't look damaged or cracked.
Any thoughts on some low hanging fruit items I can check? This was the first time this behavior has occurred. There are no CEL's.
 
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Idle air controller , research that
 
Thanks Andy, I definitely have read some about that. Is it easiest to pull the whole throttle body off? I saw that there's one torx screw fastener that's particularly tricky to get at.
 
Thanks Andy, I definitely have read some about that. Is it easiest to pull the whole throttle body off? I saw that there's one torx screw fastener that's particularly tricky to get at.
Mine was easy but has a spacer....I would only pull it if I had to but it sounds like yours is getting sticky and may just need cleaned.
 
Mine was easy but has a spacer....I would only pull it if I had to but it sounds like yours is getting sticky and may just need cleaned.
Definitely seems like something easy enough to try. This LJ only has 27k miles and is essentially stock, so I don't have a spacer. I guess I'd be surprised if this sensor is dirty, but it's also been in the elements for 16 years.
 
Definitely seems like something easy enough to try. This LJ only has 27k miles and is essentially stock, so I don't have a spacer. I guess I'd be surprised if this sensor is dirty, but it's also been in the elements for 16 years.
Low miles means ethanol residue and seals also dry out