2004 TJ - 4.0 - 5 speed manual
I've been chasing a rough idle for 2 weeks and am running out of ideas. It's only rough after the engine has warmed up and only at idle. I haven't noticed any loss of power, fuel economy, or fluctuating RPMs. At first I thought it was a vacuum leak, but every home test (other than smoke) had failed. So I started looking at the fuel system. I replaced the spark plugs and fuel injectors and this changed nothing. Pulled apart the throttle body and cleaned it as well as the idle air control sensor and both of the gaskets. I finally gave up on the fuel option and went back to looking for vacuum leaks. This time I was able to find something by putting the system under positive pressure and checking with soapy water sprayer and found the front PCB elbow gasket was leaking. After replacing this it seemed to help it a little bit.
After the engine warmed up I let it sit running idle for about 10 minutes and the "misfire" feeling started to come back. It's slight, but it's enough for me to notice..
Any other recommendations?
I should mention it was running perfectly fine when I parked it on a Friday. Saturday I fixed my winch and replaced the transmission mount, but still worked fine after test driving with the new transmission mount. Sunday I installed some bumper lights, but didn't test drive it and noticed the rough idle on Monday morning. RPM's used to be just above 750, and now they are just below 750. As soon as RPMs get over 750, the rough (slight misfire) feeling goes away.
I've been chasing a rough idle for 2 weeks and am running out of ideas. It's only rough after the engine has warmed up and only at idle. I haven't noticed any loss of power, fuel economy, or fluctuating RPMs. At first I thought it was a vacuum leak, but every home test (other than smoke) had failed. So I started looking at the fuel system. I replaced the spark plugs and fuel injectors and this changed nothing. Pulled apart the throttle body and cleaned it as well as the idle air control sensor and both of the gaskets. I finally gave up on the fuel option and went back to looking for vacuum leaks. This time I was able to find something by putting the system under positive pressure and checking with soapy water sprayer and found the front PCB elbow gasket was leaking. After replacing this it seemed to help it a little bit.
After the engine warmed up I let it sit running idle for about 10 minutes and the "misfire" feeling started to come back. It's slight, but it's enough for me to notice..
Any other recommendations?
I should mention it was running perfectly fine when I parked it on a Friday. Saturday I fixed my winch and replaced the transmission mount, but still worked fine after test driving with the new transmission mount. Sunday I installed some bumper lights, but didn't test drive it and noticed the rough idle on Monday morning. RPM's used to be just above 750, and now they are just below 750. As soon as RPMs get over 750, the rough (slight misfire) feeling goes away.
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