My TJ 2000 Sahara is driving me crazy with one problem, high idle and it is affecting my gas milage really badly. The worst part of this that there is no error codes or check engine sign.
1-I have cleaned my throttle body and IAC twice so far and replaced the gaskets.
2- Changed the O2 sensor #1, as I had a code error.
3- Changed my serpentine belt as I had a noise coming from the pulleys.
4- Changed the battery as it started to be weak and on Monday morning it wouldn't start in the morning. It took two hours from the time I removed the bad one to the time I put the new one back in.
That bad battery it was bought in February, 2013, meaning it served about 9 months.
5- I SEA FOAM'ed my fuel this past Friday.
I'm planning on rebuilding my alternator, maybe the pulley needs to be replaced, also I'm inspecting my vacuum lines, but I haven't found a thing yet.
I should also mention that when I shut-off the engine, it shakes and it takes more time that it would normally take.
My spark plugs are a year old and I changed my crankshaft sensor about six months ago.
What are your suggestions?
Just took the jeep back from work, as I started it, it started with the same problem, I shut-it off and back on and it idled within normal range, I drove it and as I came to the first red traffic light, it was revving at 2000 and throughout my way, I stopped for gas and when I was done, it started normal and then went up as before.
In brief, if it doesn't idle high at start up, it does it as I go along.
Sounds like the vacuum issue i just fixed. The vacuum line that affects idle speed also has Cruise and dashboard air flow on it. I traced the issue down to the section between the T at the firewall and the connection at the vacuum reservoir (under battery tray). Since the part from Morris 4x4 was so cheap, I just replaced the entire harness. 30 min job tops...
I haven't have the chance to check for vacuum leaks, it has been really cold lately -18C.
When I have noticed in the past three days that my engine revs smoother after each fill-up, which makes me think that the sea foam is cleaning my injectors and as my tank gets empty, it starts revving back to 2000.
My TJ is a 2000, so the A/C was an option and I didn't take it, thus it doesn't have a recycled air option.
All the ideas you guys gave me are valid, just it is hard when one got no garage and it is my daily driver, cold weather isn't helping and getting darker as I leave work, doesn't give me enough time to get started.
tank and injectors are not going to have anything to do with the higher RPMs. You got a vacuum leak. Get a can of carb cleaner one with the spray noozle, crank jeep up, and go to spraying around every line and hose. When you here the engine change RPM ANY look there. But dont just stop in one spot unless its obvious. Brake booster lines and brake boosters cause these issues also.
Get someone with good hearing and see if they can help you find the hissing noise.