Rough idle after cooling problem

[live24wheel]

Vehicle, 1997 XJ, 4.0, 5 speed.

Yesterday the upper rad hose started leaking so I took care of that. Out of stupidity and not paying attention I forgot to put the rad cap back on. My little brother drove it last night and said the jeep started loosing power and the shut down and he barely got it started. Then my dad took the Jeep today and broke down on the side of the freeway. Said it lost power and shut down.... So we get it started, gauge didnt show it to be overheating, we get it home. I get it filled up, Through my spare rad cap on since I lost the first one. temp is at about 220 - 230 now. I run it and it cools right back down to 210. It was blowing coolant right on to the 3 plug computer thing next to the airbox, right in front of the radiator neck... Im guessing that is why it was dyeing and running like crap....

So now it is all dried out and the idle is rough as heck and it starts hard. Above idle it smooths right out and has all the power it ever did. my dad thinks possible burnt valve.... There is no other motor noise than is normal.... What do you guys think?

P.S. He just called and told me the check engine light came on..... When he gets home, can I do the 3 key turn trick to read the codes? I dont know why but I could do it on our old 94 XJ and my old 03 TJ but I cant do it on my 00 XJ.

Thanks,
Tom

 

[hubs97xj]

I don't think you can do the key trick, but if you take to a parts store or a shop, they should be able to read the codes for you. Around here anyway, Autozone and a few shops would pull codes for free, while other places wanted half an hour at shop rates. Get the codes, then go from there. Driving it around with no coolant could have done any number of things.

 

[BPB]

ok, to see if any of the sensors on your throttle body are damp, if so, dry them thoroly. Also check to see if your oil is foamy, you could have blown a head gasket.

 

[live24wheel]

OK, checked oil, it looked fine. Hopefully it will clear up as it drys out more. I will check it when he gets back home. I know he checked the oil and said it was good but I will check it myself later. The other thing is that the 2 trips this jeep made when about 1/4 mile to the freeway and the motor shut down about 2 miles up the freeway both times. Just long enough for coolant to puke onto that computer. It was not ran for any period of time completely empty and both times I was told the motor didn't completely over heat.... but idk for sure. Thanks for the help!

Tom

 

[live24wheel]

Ok I took it over to autozone and the code it was throwing was a cylinder 1 misfire..... I took the plug out and checked it and it is sparking fine. I unplugged the battery to reset the computer and other than the check engine light going out for now, it has changed nothing. Any other ideas?

Thanks,
Tom

 

[hubs97xj]

No more CEL, and it runs fine, except at idle?

 

[live24wheel]

Right, it is still starting hard and idles rough. The only reason the CEL is out is because I discod the battery, im sure it will be back on. If your running it at about 2k rpm or higher it runs just as smooth as before.... I ran it hard and it runs great, just runs rough as can be at idle and somewhat noticeable during acceleration.

Since it is getting spark, could it be a fuel injector miss? I wonder if the code it threw could have meant the injector wasn't firing right in the #1 cylinder....

Tom

 

[99xjclassic]

This is a long shot, but it is worth a try.
Did the coolant spray anywhere else? Lets say by the distributor cap?? If so maybe it got wet. Pull the cap off and check. Like I said its a long shot, but easy to check
This happened to me when my radiator hose blew.

 

[live24wheel]

This is a long shot, but it is worth a try.
Did the coolant spray anywhere else? Lets say by the distributor cap?? If so maybe it got wet. Pull the cap off and check. Like I said its a long shot, but easy to check
This happened to me when my radiator hose blew.

I dont think that is a long shot and could have happened, since yesterday I fixed the upper rad hose.... Only thing is that I took the plug out and tested it and its sparking fine, yet throwing a cylinder #1 miss fire code.....

 

[hubs97xj]

Check your TPS, or have it checked. I've read on here several times that they die when they get wet, and yours could pretty easily have gotten wet.

 

[live24wheel]

I would guarantee it got wet. I will have it checked out for sure or find out if I can, by searching.... I did unplug it and the connection was very clean and dry, so i'm not too sure.

 

[live24wheel]

Hey guys, I just got back from Auto Zone as it is still running rough and the CEL came back on today, didn't drive it all weekend. This time it threw a TPS high input code. I did some research and everything pointed at the TPS. I bought a new TPS, put it in and no difference. It still starts hard and idles rough. I started looking and noticed the header is cracked. It is not a big crack at all like I normaly see. Along with that it is not loud at all, basically, it doesnt sound like a cracked header.

Any idea what I should check next. The CE hasnt come back on after I reset it when I replaced the TPS.

Thanks,
Tom

Edit: I tried to test the TPS but had trouble finding a correct way to do it. It also doesn't help that my meter doesn't have sharp prongs to get to the connector...

 

[live24wheel]

Any ideas?

I pressure tested the cooling system and it doesn't show that it is leaking down but I doubt that a head gasket would show much. The oil is normal and its not puffing any smoke. You can however hear a miss type sound from the exhaust at idle.

Thanks,
Tom

 

[Ecomike]

Based on my similar experience I would run a compression check next on Cyl #1, if it is low, you may have a small head gasket leak, how big depends on the compression. I fixed mine for a while with head gasket sealer additive for the coolant, brown fiber pellets. The newer systems detect low compression via a late appearance of the flywheel tooth passing the CPS. When that happens it throws a missfire code for that cylinder, and shuts of the fuel injector for that cylinder to avoid damaging the cat converter, which makes for a rough idle.

Rough idle seems to be a common sign of low compression on a cylinder, if all 6 cyl have fuel and spark.
You can usually test for fuel and spark by pulling the spark plug wire on the suspect cylinder. If it has no effect, but the wire sparks then it is fuel or compression.