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I replaced the UIM on my '99 SLE just after I bought it, and I also removed the throttle body and cleaned it (I first removed the sensors). Everything else seems to be ok, but I believe that the RPMs don't drop to where they should at warm idle. RPMs at warm idle are around 750 RPMs. Sometimes the RPMs will drop a little below that, but the engine then runs a little more rough and the RPMs go back to around 750. The idle seems a little rough at idle also.

There are no error codes, but I'm wondering if maybe there's a vacuum leak somewhere. I double-checked my work, and all hose connections are tight and connected to the same locations as before the UIM replacement.

Any ideas on what to check?

Thanks.

750 is about where my car idles when warm. the rough running could be a vacuum leak, or it could be you missed a sensor connection. check all the vacuum hoses, not just for proper connection, but to make sure you didn't nick a hole in one of them during assembly/reassembly. double check the torque on the UIM bolts also. you may have missed snugging one down and have a pinhole vac leak under the UIM.

From my personal experience, I'd say Steve is correct. - BC

I took a close look at everything today, and I didn't find anythng that I did incorrectly when I previously replaced the UIM. But for good measure I replaced the 2 pieces of hose connected to the solenoid that runs to the fuel vapor canister under the air box, I double-checked that the UIM bolts and throttle body nuts were tight, and I removed the IAC valve and the MAF sensor to make double-sure that the o-rings were there (they were) and the 3 throttle body sensors were connected correctly (they were). I didna't touch the EGR or its metal tubes at all when I replaced the UIM, and I didn't touch them today.

***Question: Where can I buy the rubber hose coupler that joins the 2 diffferent size vacuum lines going to the front side of the throttle body? I'm guessing that's a dealer-only part.

I learned something about this car today - my scan tool showed the RPMs varying between 630 and 650 when the RPM gage was showing around 750 RPMs, so the idle RPMs are in the normal range but the gage is off! I guess the way this car runs is the way it ran before I replaced the IUM.

Most of our tachs vary from the PCM/Scantool by 50-75 rpm's or so. 100 isn't abnormal.