Bigthoven370

As stated in the title my xj runs rough, and when it idles it idles really low. Usually between the first and second tick after zero. When I start the jeep it will idle up to around 1000 rpm, then back down to damn near close to zero, up just a hair, then it'll go down to zero and stall.

So here's a little background info. For these last few months my jeep has seemed to be running rich and idling up and down compared to it idling low and stalling as it is now. When I give it gas a black cloud will come out the exhaust, and when I let it idle in the mornings to warm up there will be a black mark on my driveway from the exhaust. While this was still going on, I took around a 370 mile round trip for drill. When I got back my clutch went out. (Had it fixed before from the PO not knowing what he was doing when he put a kit in it) Had a mechanic next door to my work fix it (just needed it to be bleed) and they noticed my jeep was running rich and idling up and down. He and I decided I should clean the TB and IAC valve to fix the up and down idling. So I did, pulled the TB off and took the IAC off. TB wasn't too dirty, mostly in the IAC valve's hole. The IAC valve was covered in carbon though, when I was cleaning it, the shaft came unscrewed (oops) I attempted to screw it back to it's original position and reinstall the TB and valve. With them reinstalled, I started up the jeep and it still didn't idle quite right. So I messed with the IAC valve's screw (I now know i probably shouldn't have done this) trying to adjust it. I reinstalled it and started the jeep again. Still didn't idle right. I did this until I got it to where i thought it was good, but it now idled low. I continued to drive my jeep and it seemed to be okay. I brought my jeep in one day after work to clean the floor mats. My boss (who is a retired mechanic) told me my jeep wasn't running right and seemed to be only running on 3 cylinders or so. He suggested that I clean the rotor cap and the spark plugs. Before I went home he took the cap off and it was dirty and told me to just take sandpaper and rub the carbon off. I wasn't able to clean them and then my jeep died on morning.At the end of November I went out to start my jeep so it could warm up before work. It started up, but it was idling really low and stalled. I started it back up and attempted to move it to the other side of my driveway. It stalled when I was in the street after backing up. Attempted to start it again and it wouldn't start at all. Had to have my neighbor help me push it into the driveway. Went to work and my boss asked where my jeep was, told him what happened and he expected that was to happen since I didn't clean the plugs and rotor cap. After work that day I attempted to start it and it wouldn't start, continued to try after work each day and still wouldn't start. Pulled a spark plug and it was quite fouled. So I went out and purchased a whole tune up kit. Finally had the time to install it, after it was installed my jeep started. Still runs like **** though. Installed the fuel filter that came with the kit as well, still runs like ****.

Now that you are caught up to speed, here's what I'm thinking may fix the issue. I have a can of seafoam and plan to pour half the bottle into the intake to clean out the engine, and the other half into the gas tank. I also have a bottle of HEET fuel treatment, which I plan to put in after I fill up my jeep with some premium fuel. (a coworker from the south who moved up north said that helped his car run smoother after it started running rough when he moved up here) I also think I should replace the IAC valve since it's probably bad now anyway.

Should I replace the TPS sensor too? I know that I DO have some CEL codes, and the last time I had them checked they were; Code 13 which is a MAP sensor code, (can't remember exactly what about the MAP) and a code for my speedometer which isn't working. Would this MAP sensor code be caused by what's going on with my jeep? Or could the MAP sensor have gone bad and it's contributing to how my jeep is running?

I'd really like to get my jeep running normally again so it doesn't have to sit and I can actually drive it!

Bigthoven370

An update on the situation with my jeep. A coworker of mine at work (same as before) suggested that it could be a vacuum line causing the idle issue and stalling. He and I took a look around the engine bay Friday after work, and sure enough the vacuum line for the MAP sensor (which I had a CEL for) was disconnected. Hooked it back up and the engine immediately perked up. Poked around some more and found that one of the hard vacuum lines was split and was causing a leak. Those were the only leaks we were able to find, so hoped into the jeep, check engine light was no longer lit and headed home.

Did some more thorough checking later that night in the garage, and found that more lines were cracked. The vacuum line going down to the vacuum ball was disconnected and there was a big tear in the line on the vacuum ball. The hard line was also split in more than one place.

So now the jeeps idling a lot better than before (actually idles high now, probably need to replace the IAC valve, since I broke mine) and it no longer stalls. Need to do some vacuum line repair, hopefully the hard lines aren't too hard to repair.

But I'm glad my jeep is running like it should and that it was such an easy fix!

peep

Good vacuum lines are a must.
Excellent you found them. When it's broke you know what to fix.
If you do the clean up, the IAC port, butterfly, and throttle body appreciate a good scrub. Carb or contact cleaner works. Even some WD40 will work.
I you scrape, be gentle.
My brother in law visits for New Years. A good thing, I need him to supply a fresh tooth brush to my tool kit. Of course I will return last years to him.
Glad you found the basic problems and have a fix in place.
If you've tweedled with the IAC you may need to replace. If it's working clean the pintle gently.
Best in the New Year.

Bigthoven370

I did indeed clean the IAC valve, its port, the TB and the butterfly plate. When i cleaned it is when the IAC valve came unscrewed as I was cleaning the pintle. I'll probably just buy a new IAC valve, which hopefully will fix the high idle and bring it back down.

I also did do the Seafoam treatment before I found the vacuum leak, seemed to help somewhat. Might pick up another can and do it through the brake booster vacuum line. Also still have to put some HEET in the next fill up.

Best in the New Year to you too peep!