Serious Idling Issue - (Resolved)

[Zenobian_84]

The MJ seems to have caught a serious problem. Here's the story :fs1: Sorry for the ridiculously long post, but I figure if anyone's going to help, they should know exactly whats going on.

 

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Drove to work last night around 10 pm. The last few weeks, nothing amiss has happened while driving it. Shifted flawlessly, idled where it should, never overheated, oil pressure was in the good.

 

5 minutes of driving down the road (my job is only about 10 minutes away from my house) the truck started to get a high idle of around a constant 1400 when I was sitting at a red light. Seeing as how this sometimes happens randomly (has been doing this since I first got the truck) I didn't think too much of it. Instead of fluctuating back down to around 900/1000 where it usually idles, it stayed at 1400, and began to climb. Needless to say, I started driving again and shifted gears, noticing that each time it seemed as though I had the gas pedal 3/4 of the way to the floor, even though I didn't. When shifting gears, I noticed a slight clunk when going into second, but figured it was due to the idling. I got to work and parked the truck, where it sat for 9 hours.

 

I got off work about an hour ago, and started it up. Everything seemed back to normal. I drove about a half a mile, and, what a shocker, it started acting up again; but worse than it was last night. Instead of idling at around 1400 at a stop light, it idled at 1900, and kept climbing. I had to turn the truck off at least 5 times because of my fear of the engine blowing due to this happening; with each time upon starting, it would be at a higher RPM rating. The final time I turned it off before I got home, the idling at reached 3400 RPMs.

 

I pulled off the side of the road about a 1/2 mile from my house to check the engine compartment. Other than it being a little hotter than normal (I contribute this to the idling, because the truck ran at about 200 degrees the entire time) everything was fine, and I couldn't visually see anything wrong. I did notice however the last day or two that the truck's oil gauge ran over the OK line once or twice (about 65/70) for about 10 minutes, then would go back to where it usually is at around 55. Lastly, when I pulled into my house, I opened the hood for another visual check; I decided to check the throttle cable because I thought something might have come loose because the pedal seems to be slightly lower than it usually is. When I pulled the throttle arm, I noticed it gave off a clunk, and the cable shuddered when I let go.

 

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So... I'm at a loss for ideas right now. Here is what I know. :wall:

 

1. Something like this just doesn't happen unless something has gone out or has failed. If the truck ran perfectly ok up until last night when I drove it around (I drove it yesterday morning as well with no signs of a problem) what could be making it act like this?

 

2. I was thinking it could be a vacuum leak somewhere that has grown bigger. I've been thinking of replacing the manifold gasket with a new one, seeing as how I had a similar high idle problem right before I replaced the O2 Sensor a few months ago. Could this be a possible culprit as well?

 

3. Could the throttle cable have gone south? Or could there be something wrong with the gas pedal? What keeps the pedal from falling to the floor, because it doesn't seem as resistant as it used to be.

 

4. Removed the cover off the throttle body to check if anything was wrong. Opened the flange all the way and white smoke poured out. Am I correct in guessing this is just excess fuel smoke being burned from the still hot motor?

 

As always, especially now, help is appreciated. :dunno: I have 3 days to fix this problem before I have to go back to work.

 

UPDATE:

Had my dad speak to 3 mechanics where he works at within the last 20 minutes. They all agreed it was a vacuum line that either got disconected, or has rotted out. I believe I know which @#$%ing line it is. It's the line that runs to the vacuum ball behind the front clip. Could this line be the culprit?

[cruiser54]

On the 2.5, there are a few vacuum lines around the throttle body that tend to rot. You can find vacuum leaks by spraying an oxygen sensor safe carb cleaner around the suspected areas. You'll know when you hit it. The idle will change dramatically.

 

Don't rule out a bad TPS.

Also, while you're at it remove the bolt holding the ground strap to the firewall. Scrape the paint off the firewall, clean up the connector and bolt it all back together.

[JeffN]

I take it it is an automatic? Could be your downshift cable sticking once it gets hot. Check that it isn't near the exhaust

[Zenobian_84]

I take it it is an automatic? Could be your downshift cable sticking once it gets hot. Check that it isn't near the exhaust

AX-4 Tranny. 4 Speed on the floor, if you don't know the AX Family of tranny types. Do manuals even have downshift cables? I've never heard of such a thing (D-Shift cable)

[JeffN]

no, only automatics so ignore my answer

[Zenobian_84]

Scoured my engine bay today checking all the vacuum lines. The only line I could find that was in terrible shape was this one.

 

It runs from the Heater Core to some little vacuum connector doohicky. Does the HC even affect vacuum for the truck?

 

The Doodad in question. What is this thing? Can't seem to locate it in my repair manual... :dunno:

 

The only other line that's in questionable shape. Connects at this Y-Joint; left side goes to the vacuum ball, the right goes to the air box, I believe. I was told previously that the part blocked off controls the HVAC for the non-existant 4x4; correct? Will be replacing this ragged line down the road, to avoid more problems later.

[cruiser54]

Fix the vacuum leaks for sure. A little piece of vacuum hose as a splice will be fine for the small plastic line.

[MJCARENA]

I had the same issue with my 89 XJ, 4.0, auto. After about 15 -20 minutes of driving it would idle around 1300 rpm, turn it off and restart it, it could go up to 2500 rpm. It would do this till it cooled off.( sat for a couple of hours or over night). Found that if I disconnected the TPS when this was happening it would drop down to around 600 rpm. Could not get it to idle high as long as it was disconnected. Replaced the TPS and adjusted it,have not had the issue return. But I would fix your vacuum leaks first and see what happens. Hope this helps.

[cruiser54]

Carena, not an unusual fix. Thanks for your input.

[Zenobian_84]

Replaced the worn out / cracked lines. Seemed to make a slight difference in the idle. Idle's around 2500 right now instead of 3000, so it's getting there. Next on the agenda is this, the ticking time bomb.

 

I have no idea how long the gasket has been like this. The arrowed part juts up above the manifold/intake ports and doesn't sit flush against everything like the rest of the gasket does. I'm going to just ASSUME here, that it should not be doing this, and that a properly installed gasket should sit completely flush against the block?

 

I'm also going to go ahead and assume that there is supposed to be a bolt here? Again, I have no idea how long it's been like this. It could have been like this since I got the truck to begin with. If there's supposed to be a bolt here, then that would 95% likely explain why the engine shimmies and shakes around while it runs. :headpop: I blame both the PO and myself for not realizing this sooner. :fool: :thwak:

 

Going to go buy a new gasket, along with a bolt.... possibly. Can the bolt that's still there (@ end of manifold, closest to firewall) be used again, and if not, should I go get a new set from the dealership? Or can I use bolts from the hardware store? Grade 8 I assume. Not sure if I have to get them heat treated, but I would think so.

 

Also on the to get list, a new Exhaust Manifold to replace this one. Won't be for a while though...

[cruiser54]

There's a special washer for under the bolt. Look at the other ones and you'll see what you need.

[Zenobian_84]

Have a feeling it's a combination of the ISA and Manifold.

 

Anybody have pictures of the IAC on a 2.5, and how to check / remove it / clean it? There's quite a number of little things around the TB, and most of the descriptions I've read through forum searching on what the "IAC is, and how to remove it" don't help much. Thanks.

[cruiser54]

The ISA wore out inside. Little gears and such. I know of no service that can be done to one. But, vacuum leaks can drive the eCU crazy trying to keep the ISA in the right spot. Fix the intake leak and check the crappy hoses around the throttle body.

[MancheKid86]

I'm with carena on this one,

Because this problem happens to me,

Unplug your tps, remove the green weather seal,

Plug it back in :thumbsup:

 

Works for me

 

your IAC is on the throttle body beside your TPS,

you can remove it, 2 torx,

check to see if it goes in and out (its a soleniod)

if not spray it with solvent, and put in vice and pry with screwdrive (sounds nuts but it frees the soleniod)

IAC wouldnt bring it to 2500 rpm tho,

your TPS on the other hand will,

like i said before it happens to me,

took me a while to figure it out but as above that fixes it.

 

 

***EDIT***

 

just happened to me again,

shut it off, turned it on VROOOM 3000 rpm,

shut it off pulled the tps and cycled the throttle lever on TBI until i heard a distinct click,

started just peachy :D

[Zenobian_84]

For anyone following the thread with the same problem:

 

Removed the IAC. Solenoid was slightly sticky. Pulled out a bit and it seemed good to go. Cleaned the springs and little bushing pins. There was also carbon buildup on the electrical pack itself. Re-assembled it and installed back where it belonged.

 

Started the truck up, same idling speed; removed the vacuum line from the EGR valve. That didn't make any difference, so I removed the connector from the TPS. Didn't make a difference at all; I even ran the truck with both the EGR and TPS connectors removed with no improvements. Any thoughts on what's next? Both the EGR valve and the vacuum lines running to and from the Throttle Body have vacuum, so I can't say there's a leak somewhere.

 

My next guess would probably be the TPS, so that's what's going to get checked / adjusted. :fs1:

[ComancheKid45]

That manifold being loose and leaking like that definently is playing into your problems. I bet once you get that straightend out this issue might resolve itself ;)

[cruiser54]

That manifold being loose and leaking like that definently is playing into your problems. I bet once you get that straightend out this issue might resolve itself ;)

 

More than likely. That needs attention first and foremost.

[Zenobian_84]

-Update-

 

Turns out it was the IAC after all. Unplugged it completely from the truck, and it idles at 4-500 RPMs. Can give it some gas and everything works and idles like a dream.

 

Even though I gave everything a good cleaning inside and out, the solenoid just isn't activating inside the chamber due to old age and being worn out. Next stop is cross referencing numbers to find a suitable replacement.

 

My advice to anyone having this problem is: Check, check, and check everything again. Even if you are 99% sure that it couldn't be something you've checked before, don't ever rule it out.

 

Will post results as more progress is made. If replacing the IAC fixes the problem, I'll leave the manifold gasket for another time.

[Zenobian_84]

Woke up this afternoon to find this at my door. :hmm: Couldn't have come at a better time. Now if only the tropical storm would co-operate with me for 20 minutes.... :wall:

 

 

 

[Zenobian_84]

Turns out the IAC was the culprit after all. Installed the new one, and hooked everything back up. Started the truck up, and had to give it a little gas to keep it going at first (combo of new ICA and 2 weeks of sitting) and then drove it around for 10 miles. Babied it for the first 5, then romped on it for the last 5. Got back and parked it at the house, and noted the 900-950 RPM. Shut her down and waited 5 minutes and started her up. Revved high for a second but immediately calmed down to 900. Repeated and the same result happened again.

 

Am very pleased, and wanted once again to thank everyone that commented on this thread with suggestions. :bowdown: :bowdown: You don't know how good it feels to be able to drive a Jeep again. Almost stalled out at a red light though :oops: ;) :cheers:

 

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On an off note, my gas gauge works now. When I started up for the 1st, 2nd and 3rd startups, it didn't peg out like it normally does. In fact, it went right to the 1/4 tank mark and hovered around there. Fluctuated when I took off and when I braked like it should. Does the ICA have anything to do with the Gauge itself? Seems kind of wierd, but if it's going to work now, I won't be complaining. :yes:

[cruiser54]

Happy for your success. I don't see the corrolation between the gas gauge and the ISC unless they somehow share a ground.