Fast idle after tire change WTF

[Co-MAAAN-cheee]

Hey @cruiser54, It been a while. Remember me? I wrote an addendum to your c101 delete.

 

Anyway, My air filter was saturated with oil and the engine bay was filthy. I took her to the car wash and thoroughly cleaned it. Then I did an oil change and added one of those cheap oil catch cans. I also updated the headlights to LED. Installed the relays years ago. Everything was working fine for a couple of weeks. Drove it exclusively during that time. A couple of days ago I had new tires installed. When it came back from the tire shop it started fast idle. What? I'm assuming it's just a coincidence, but maybe the that guys bumped a vacuum hose. I unplugged the TPS and the idle dropped to normal. Plugged it back in and it held. Turn her off and back on, fast idle again. 

 

I'm planning on doing a smoke test to eliminate a vacuum leak. Tempted to remove the TB for a good clean and maybe just replace the TPS. Neither have been done in over 10 years. 

 

Where would you start? Why do you think it started after a tire change? 

 

Appreciate you, you are my jeep hero.

 

Dave 

[89 MJ]

1 minute ago, Co-MAAAN-cheee said:

Hey @cruiser54, It been a while. Remember me?

I hate to break it to you, but Cruiser passed away in May of last year.
 

To answer your question, the high idle after the tire change would be completely random, unless a vacuum line was bumped in the process. Start with cleaning the TB and adjusting the tips, per Cruiser’s instructions and double checking your vacuum connections. Maybe start with the CAD because that’s near the wheels. 

[Co-MAAAN-cheee]

I'm so sad to hear that. Thank you for letting me know. He was such a great guy. 

 

And thanks, I totally forgot about the vacuum at the cad. I'll smoke the vacuum system first. I think I'll clean the TB regardless, its due 

[pizzaman09]

I do agree that this sounds like a vacuum leak.  A smoke test will prevent you from chasing your tail.  It is worth checking the header bolts, make sure they are tight. 

[Co-MAAAN-cheee]

I did a smoke test and found a couple of cracks in vacuum lines. One at the TB and another near the air box. They were barely perceptible. The TB, especially the IAC, were extremely dirty. The IAC was so caked with hardened oil I don't think any air was getting past it. I cleaned it up and patched the vacuum lines and she is purring like a kitten. I ordered new vacuum lines and a new IAC and will finish the job tomorrow. 

 

A couple of years ago I rechecked and repaired all the grounds, and I cleaned and treated every electrical connection with deoxIT. I'm thinking I'll follow more of Cruisers tips to ensure all the sensors are in spec.

 

 

[89 MJ]

Glad you got it taken care of and it sounds like you’ve got a good plan going forwards. 

[pizzaman09]

Well done.

 

I also recommend Cruisers tips of using Oxgard on connections where it makes sense.  It protects the connections from oxidation and maintains conductivity.

[AZJeff]

3 hours ago, pizzaman09 said:

Well done.

 

I also recommend Cruisers tips of using Oxgard on connections where it makes sense.  It protects the connections from oxidation and maintains conductivity.

If Oxgard is not available, dielectric grease (or plain old silicone grease) is quite effective in sealing out moisture and oxygen at the microscopic level where the electrical connection is actually made.  
 

I use this on ALL electrical connectors under the hood where the environment is less than benign.