Jooman07

So I just got back from a deployment this week and of course my XJ sat most of the time I was gone. I had it on a battery tender so the battery would be no issue. When I started it up and got it running it ran just fine (after replacing a seized alternator). The idle was normal, around 600-700rpm. I took it for a drive and when it was up at operating temp (180-190F) I noticed when I came to a stop light that the RPMs were really low at about 250-300 RPM. It wouldn't die immediately but it kept acting like it. I put it in neutral and gave it some gas until the light changed. Everything drives like normal. All the "power" is there and it gets up to highway speeds no problem. On the way home it did die a couple times. The idle only drops low when I stop completely. It starts right back up no problem after it dies. I let it cool back down and took it for another drive and when I started it up the idle was fine until it got to temperature. Does this sound like a IAC issue? Once I get a break in the crappy weather I'm going to try and take it off and clean it. 30*F is pretty cold when you come from a place where its close to 100*F everyday. Is there anything I should look for in addition to the IAC? Like I said, everything else seems to work just fine. Only the low idle seems to be an issue at this point.

Kogulanathan Kasinadan

What year??
Sounds like TPS problem.check for code first. Also check ignition coil to spark plug.

CurrySoSpicy

Your on the right track, I would take the whole throttle body off of the intake manifold and clean it in addition to the IAC. 4 bolts, a few sensor wire harnesses to remove, and a few mechanical cables that pull right off. Just be mindful when torquing the TB back down to the intake, it is made of aluminium.

You can get a new TB gasket at the auto parts store. My advanced auto also sells CRC throttle body cleaner. Some people use carb cleaner, some advise against it. I just bought the stuff that was designed for TBs.

tjwalker

Cleaning the idle air control is a good idea, but the first thing I would do is to have your battery LOAD TESTED. I know you had it on a battery tender during your deployment (thank you for your service BTW) but the #1 cause of stalling of the 4.0 at idle is a faulty battery.

Any parts store will load test your battery for you for free. And yes, you can have a battery that is plenty strong enough to start the engine, but marginal enough to give the engine management system fits.

I'm not saying this is your problem, but it needs to be ruled in or out. I've seen guys throw a lot of parts and time at a problem that turned out to be battery related.

96er

yeah, check ur battery man. ive owned 2 xj,s over the past 20yrs an have had several issues that i came to find were battery related. good luck

Jooman07

It turned out to be the TPS after all. I took the IAC out and cleaned it but it wasn't all that dirty. I took the TPS off and looked at it and it seemed to still have the motion and didn't seem to bind up at all. I figured I would try the TPS first so I went to autozone and took my battery with me to have it tested as well. If it passed the test I was gonna buy the TPS. It passed fine so I bought the TPS and after I installed it I tried it out. It's been on a few days now and so far no issues like I was having before.

CurrySoSpicy