1998 Jeep Cherokee Only Runs With Foot on the Gas

UPDATE: I got a new IAC which ended up not doing much. I was then just messing around with things and removed the rear breather tube (?) from the intake manifold which would allow the Cherokee to stay idling but when I put it in gear it would die out. When the breather tube was connected I would have to leave my foot on the gas for it to idle. Progress? Lol

Sorry that this is so long, I figured I’d just say everything that I’ve done and the outcome. So in short I recently bought a 1998 Cherokee with around 170,000 miles that will only run if I leave my foot on the gas. I replaced the crankshaft sensor, cleaned out the throttle body and IAC, cleaned up some grounds, replaced spark plugs and replaced a PCV valve(?) along with the hose.


For those of you who would like more information. I bought the Cherokee non-running, it would run for about two seconds and then just shut off but if I left my foot on the gas it would run but die when I put it in gear. Also while running it just sounded really bad and not healthy, sometimes I would let it idle with my foot on the gas and it would pop and then I would see white smoke coming out of the exhaust. The first thing I did was replace the crankshaft position sensor as the check engine light was on due to a faulty one. This did not help much if at all. I read that if the throttle body is clogged up it will cause a similar issue so I decided to clean it along with the IAC. This did make it run a lot smoother and it started quicker but it still sounded really bad. I then cleaned up some ground wires, although probably not all of them. It sounded like the previous owner had messed with the timing so I figured I’d check to make sure that the plug wires were going to the correct plugs, they weren’t, 3 and 5 were switched which was causing it to run very rough. Once I did this the engine was a lot happier and was much quieter, I then decided to check out the condition of the spark plugs, it looked to be running lean but also it wasn’t burning off oil on the plug. I replaced them and it turns out they weren’t even the correct spark plugs.... Correcting people’s mistakes made it run a lot better and just sound healthy. I was able to shift it into gear while leaving my foot on the gas and drive about 6 feet before it died out. I decided that I would attempt to mess with the timing, as I was removing the valve cover I realized that the PCV valve(?) on the back of the cover had been broken off and someone tried to JB weld a fitting onto it but it was very very loose. I replaced the valve along with the hose which helped a lot. After doing this I was able to drive it around the block (about half a mile) as long as I kept my foot on the gas, when I let off the Cherokee would die out. After feeling very productive I decided to take a break, I came back later to try to drive it again just to see if I would have the same results. It started out well and about 1/8 mile in it just died so I went to start it and nothing at all, waited a minute and it started up fine. Drove a few hundred feet and same thing, I was able to drive it home though. Also I should add that on the final homestretch I did let off the gas to see what would happen, it was still running fine for a few seconds but I could tell it was having a hard time. Once I got it home I charged the battery and went back to drive it a few hours later. I started it up and went to put it in gear and it just died out, tried it again and same thing. Then I just let it idle for 10 seconds, it then backfired and was wanting to die out so I just shut it off and quit for the day. I have a list of things that could potentially giving me problems but I just figured that I would make a post to ask for some more input. Anything helps, thank you.

 

I would start with checking for a vacuum leak and compression test. Knowing when you last replaced the crank sensor is a good thing.

 

Only because it was not mentioned...fuel filter, fuel pump, air filter?

 

okay I will do that, thank you!

 

I did check to see how much PSI I was getting at the fuel rail which was 50. The air filter looks pretty good still and I haven’t checked on the fuel filter.

 

UPDATE: I got a new IAC which ended up not doing much. I was then just messing around with things and removed the rear breather tube (?) from the intake manifold which would allow the Cherokee to stay idling but when I put it in gear it would die out. When the breather tube was connected I would have to leave my foot on the gas for it to idle. Progress? Lol

 

How is it when you take off with a cold engine? As the idle speed should be increased until it warms up. The breather tube should not really be a factor here.

 

I just checked the RPM's with my OBD2 scanner as it doesn't have a tachometer. It's idling around 2000RPM and it seems to be running rich.

 

That would be pretty much normal, as a cold engine needs to have a high idle and run rich. So does the idle just seem be be too low when the engine warms up? A guess would be that the pedal linkage stop is worn an needs adjusting.

 

replace IAC again???????????????????????????????????????????????????? With the $75 one?