Hey guys, I've been working on my cherokee all day and haven't come any closer to fixing it yet so I decided to turn to you fine folks for guidance. I have a 1996 cherokee country 4wd with the inline 6 4.0 . I've been driving it on and off for 3 months now and just recently have noticed that it will die if it idles and sometimes when I quickly decelerate. It started getting worse and worse but I didn't pay much attention to it because i could always drive it wherever I needed to go. Well yesterday I put more oil in it because it was reading no oil pressure or maybe just a little while I would drive so I put more in it and it went up to 40 no problem. Later that day the stalling problem got so bad I could barly drive it, I managed to get it into the workshop and I've been trying different things all day, first new plugs and wires, then removed the throttle body and cleaned it all up. Then new idle air control valve. Then new crankshaft positioning sensor. And finally new throttlebody positioning sensor. It still won't run, it turns over fine and will start but it dies right away. I can sometimes give it gas while trying to start it and it will run at like 2500 rpm and I can slowly let it down to about 1500 but any lower and it dies. I know my fuel pump works I can hear it and there's pressure in the fuel rail, distributor cap looks new. I'm lost I don't know what caused it and don't know why Nothing I've tried had made a difference. Any help would be appreciated, thanks.

 

Kind of sounds like you have a vacuum leak.

If you replaced the iac you might have to hold the RPMs up a bit till the computer learns it. Not real familiar with how the Cherokee computer sees that when you replace it.

I would definitely check your vacuum hoses if it were me.

 

As if you have a meter you may want to check for proper voltage on the tps.

 

Also is the battery fully charged or are you jumping it to get it going?

 

There are a LOT of possibilities here. Any check engine light?

So this like many repairs is a process of elimination. You rule the simple things in or out first.

The #1 cause of stalling at idle with the XJ is a marginal battery. How old is the battery in your XJ? And YES, you can have a battery strong enough to start the engine, but wounded enough to give the engine management system fits and stall the engine.

Have your battery LOAD TESTED. Any parts store will do this for free. Start there. Don't throw any more parts at it. Use a testing based strategy to determine the root cause of your problem.

 

That's what a mechanic friend of mine suggested, how would I go about troubleshooting a vacuums leak?

 

I don't know if there's a check engine light because the light has never come on not even when all lights come on when I start it, (I assume it's just not working). However I had and auto parts store check for codes and apparently the only code it was throwing was a o2 sensor for the cat converter and whoever owned the jeep before me redid the exhaust and cut that out. Also the batter is a few months old but I'm thinking about taking it in and having them test it. That battery has kind of been through hell since I got it. I had an alternator problem so on quite a few occasions the battery was the only thing running the jeep. Anyway I just charged it so if it is still ok it would be fully charged.

 

Well you can buy a vacuum gauge and hook it up and see what it says. Mostly vacuum hoses are brittle after many years of use and crack. If you took off your tub and replaced your iac ensure you have installed the proper gaskets and everything is tight.

Most people don't have a smoke machine around for a test. You can look up and see how to find it using soapy water or carb cleaner.

 

you mentioned it's missing an O2 sensor; which one or both?


If they removed the downstream sensor (on the cat) it will set a code but run OK. If they removed the upstream sensor (on the downpipe) the vehicle is running on defaults (limp home mode)...a bad thing


The best way to see if you have a vacuum leak is use a scanner that gives you live data and look at the O2 sensor voltage to see if the thing is running way lean

 

Ok not sure if anyone is ever going to see this but I wanted to post what the problem was so maybe if someone does they will know to check these 2 things. Number one is the ecu or the computer. After it was replaced it was running better. Next and probably the main problem was the distributor, if you take the rotor cap off you can see it was covered in mud, not sure exactly what went wrong but when that was replaced it solved the problem, hasn't run bad since, the bad distributor may have caused the computer to mess up or something and maybe could have been reset but it just got replaced anyway. Hope this helps someone!

 

Did you get to keep the old computer as a backup? There is likely nothing wrong with it.