Guttrshark

I have a 99 sport 4.0. This is my first jeep and I'm not very happy so far. I've only had it a couple weeks. The day i got it i was at a stop light and it stalled. I hadn't even realized till i went to give it gas. I put it in park and it started right back up.That's usually what it does, although sometimes it doesn't start right away. I might have to wait a little bit longer.

It doesn't matter hot or cold, it does it. More so when hot.
the RPMs will rise then drop sporadically.
When idling in park the RPMs usually stay right over 900. Then it will go up over 1000 then come back down and it will start to sputter. then usually it dies.
Once it dies my check engine light comes on for a few seconds then turns off. No code stored.

I've read a couple old threads and determined the problem to be the IAC and/or the TPS. I've replaced both. I have also cleaned the throttle body.
I just changed the IAC about 20 mins ago and it died once so far while idling. I haven't driven it yet! But the rough idle and everything still persists.

I'm at a complete loss.


Any ideas?


Also, this being my first jeep. What should i keep an eye out for? What are some common problems?

ZINGGG

I'd start with a tune up. Champion copper spark plugs gapped to .035, quality spark plug wires (NAPA wires are recommended), distributor cap with brass contacts and ignition rotor.

As for what to look for, have you noticed any oil leaks? These things are leak monsters. Are you lifted at all? Or are you at stock height? If you are lifted, I'd look at motor and trans mounts. Also, the cooling systems on the XJ are mediocre at best so all components need to be in good condition. Have you had any overheating issues?

Guttrshark

Thanks. I'll give it a shot. I was also thinking of maybe renting a code reader and just driving around with it till it stalls and see if i can get something from it then.



Im all stock. I had a little oil leak when i bought it, but i tightened a few bolts and hadn't had any leaks so far. and no overheating issues.

tjwalker

1. Agree that a tuneup for a "new to you" vehicle is absolutely in order. Fresh Champion copper plugs gapped to .035, new quality plug wires, distributor cap and rotor. Even if this is not your problem, you need to do this. You most likely have no idea how long the existing tuneup hardware has been in there and new tuneup hardware will maximize efficiency of your engine as well as establish a baseline for future tuneups. A bottle of quality fuel system cleaner is also not a bad idea as it can help with your fuel injector spray patterns. My favorite is BG44K and Techron is my 2nd favorite.

2. The crankshaft position sensor could also be in play. They create symptoms like you describe and oftentimes do not set a code. SEARCH for lots and lots of light reading on the crank sensor. It is the most common engine management sensor failure on the Jeep 4.0 engine. If you buy a new one, please do yourself a favor and buy a genuine MOPAR unit from a Jeep dealer. Plenty of issues with aftermarket sensors.

3. Stalling is a very common symptom of a marginal battery. And before you ask....yes, you can have a battery strong enough to start the engine, but marginal enough to give the engine management system fits and create stalling symptoms. Have your battery "load tested" at a parts store. They all do this for free. Load testing is the ONLY accurate way of determining battery condition.

I own a 99 and the above is how I would proceed if this were my vehicle. Good luck and keep us updated!

Guttrshark

Thanks a lot. I'll try to get it all done as soon as possible.

I've driven about 25 miles so far and no stalling yet, but I'm not gonna get excited just yet. ha


but thanks again. Ill keep updating as best i can!

THENNING

2. The crankshaft position sensor could also be in play. They create symptoms like you describe and oftentimes do not set a code. SEARCH for lots and lots of light reading on the crank sensor. It is the most common engine management sensor failure on the Jeep 4.0 engine. If you buy a new one, please do yourself a favor and buy a genuine MOPAR unit from a Jeep dealer. Plenty of issues with aftermarket sensors.


^^ this.....had the same problem your experiencing awhile ago ended up having to replace CPS

VTJeep

Idk about the 99 having a CPS. I've got a 99 sport and have never encountered it...? Either way, I know some of this has been covered already, but here's everything I can think of that may be associated with your issue...

-Starting at the battery terminals, make sure all wires are clean and well grounded.
-Cap/rotor
-Plugs/wires
-TPS
-IAC
-o2 sensors- both of em..
-Injectors (but prob not)

My next thought is that it could be a lack of fuel delivery from the pump itself.. I dropped mine (with as little fuel as possible) and low and behold there was all kinds of swag floating in there; leaves, mud, sand, a small spring and a gasket from the (barely) existing fuel pump... Gnar-gnar!!

So if it's stumbling and hesitating and/or popping from manifold, I'd say it's worth checking if nothing else on the list helps.. Hell, if you've got the ability just drop the tank for free and check it. Make sure to have a gallon or two on hand so you can get back to the gas station..

THENNING

the 99 does have a cps I'm not sure why you would think it doesnt?....although its a pain in the *** to get to its there

Thekid320

Mine was the idle air control valve! Pull it out and look at it if there is carbon all over it it is probably that give it a good cleaning or throw a new one in iirc they are cheap

VTJeep

Either way, good to know about the CPS... So when you get the CEL cleared, there are no code/s that come up?? How good of a code reader?

tjwalker

All 4.0 Jeep engines have a crankshaft position sensor. And all 4.0 engines will (eventually) have their crankshaft position sensor fail. It's just a matter of "when". It is a very common failure.

Guttrshark

I already replaced the IAC and the TPS

Im gonna have my battery checked tomorrow. Hopefully.

It stalled about 4 times in about 2 miles earlier today. My frustration is almost overwhelming.

My initial thought was the fuel pump, but everyone seemed to point towards to other things and not the crankshaft sensor.


and the way this thing burns through gas i should be low...
tomorrow haha

(my last car was an acura integra. Almost 40 mpg. Cost $35 to fill up where i live)


So ANYWAY... depending on the weather tomorrow, i might drop my tank and check it out. Can't hurt, right? Even if that's not the problem.

OH, one more thing! Would it be fine to get a CPS from junkyard, i know someone said to get one from the dealer, but thats gonna be a bit more pricey.




Thanks again for the feedback. I really appreciate it!

Guttrshark

Don't know what CEL means haha

but the code reader was a guy from autozone. They do the diag for free.
i don't know anything about the reader they use.

Guttrshark

Also i found this thread a couple days ago about replacing the CPS

https://www.cherokeeforum.com/f51/je...-sensor-17310/

THENNING

well if you have it narrowed down to the CPS i would suggest getting a brand new one OEM from the dealership....grabbing one from the JY is just asking for more problems in my opinion.