4.0L idling
 

OK Maybe I should do more homework and search that.... but I am still going to ask.

-What would be considered a normal idling rpm ?
My 89 XJ laredo 4.0 with 200k miles idles smoothly around 500 rpm when I start cold.... but then gradually increases rpm to maybe 1500 when the engine starts warming up. Is this normal ?
I got it a month ago and because of electrical issues, the battery is disconnected all the time and I start it only from time to time to check stuff.
I know that disconnecting the battery all the time is putting the computer in relearning mode and I have not driven that car yet other than in and out of the driveway. What is you guys feeling on that ?

-Still idling when it reaches close to normal temp (about 180deg) I start hearing this noise that sounds like a very acute whistle.... I thought maybe a vacuum line that is bad, but they all look OK (as far as i can see)


Sorry again for these questions that most of you will find to be the ones of one that doesn't know anything about cars.... and they are right...

Thanks for your insights....

is there even such thing as normal idle rpm ?

do the RPMS settle after about 2-5 minutes or so? if they do then its your Throttle body relearning how much air to dump into your system. i am almost willing to be thats why it revs up so high. (mine idles around 650-750 depends on how cold it is outside) i have a 5 speed tho.

i wish there was... mine does roughly the same thing... but now it's smoking something ferice...

Thanks
it doesn't look like it revs back down after a few minutes.... but like you say, relearning is not an impossible answer I guess....
I will just keep looking and monitoring....

if it still idles high at normal operating temp,the culprit may be an Intake gasket leak, you say it gets higher after start up, it may be as the meatals heat up they are expanding causeing a vacuum leak spray carb cleaner along the intake and see if bogs down.

X2 -- My '89 was doing the exact same thing. Eventually I could hear the exhaust manifold leaking as well. It is one gasket for both the Intake manifold and Exhaust manifold. I tried replacing it myself but broke two studs and I don't have the tools or confidence to tap them out myself so I took it to the shop to have it replaced. Once the gasket was replaced it corrected the high idle and whistling at operating temp issues.

I will try that..... and that could explain the whistling sound ? It looks like it is coming from around there too...

OK I am going to do some research later, but just there... how would you rate the difficulty on changing the gasket for a beginner ?
I could take it to the shop and spend the money (well maybe not) but the whole idea of purchasing the jeep was to learn.... so how much learning will it end up be ;)

They'll charge about 4 to 5 hours of labor at a shop. So probably about $250 to $350. I don't think it would have been that hard had I not broken some studs, but on these '89's that happens a lot because the studs are old and get brittle.

A lot of guys will tell you to replace the exhaust manifold while your at it if it's the factory original because they are very prone to cracking. I didn't replace mine though as it was fine.

And yes, I was hearing that exact same whistle when it warmed up and started to idle high.

I guess I am in for that then, thanks...
Is it possible to replace/repair these studs when they break ? (because I am that lucky)

If you have the tools. I'd just never done it before and din't want too waste too much time on it and screw it up. There are several ways to do it, usually you drill them out and put a slightly bigger bolt back in. But that can eat up a lot of time if you haven't done it before, have to go get tools to do it, etc. If it's not your DD and you don't mind spending the time, the gasket is really cheap. You just might be spening a weekend or two trying to get it right. Ya never know.

PB Blaster everything a week before, then do it again the day before you start. you can let the engine warm a little before that can help expand the holes a little.

idling fun
 

Bought a 97 TJ that sat for 3 years before me. Learned quickly ( the hard way ) that the computer that was used by chrysler is a slow learner and will take a while to get itself back to normal. The dealer near me said let it idle, but watch it, for about a half hour and then it should go back down and be kinda normal. My 00 XJ idles around 650-750. Hope this helps.

At this point, any insight helps.... It is not the biggest problem anyway lol but those are things I will definitely consider when i am ready to get this thing on the road.... (after all the learning)