In need of a little help please !!!!!!

[Chief_Cherokee]

Hello. I know this is a long one but i am in need of help so i would really appreciate it if you could take the time to read through this one! I have recently been having some problems with my 1996 Jeep Cherokee Sport. It has the 4.0 Litre, High Output, In-Line 6 engine (Fuel Injection). We have taken it to the shop 3 or 4 times already now and they are even stumped by this one. Sometimes it will start normally and other times it won't. When it won't start, it turns over, but it just won't start up. Other times it will turn over and begin to run for a split second then it will hesitate or sputter and it won't start again. Sometimes when you start it, it hesitates, like it isn't getting enough gas or something but then it runs normal after a few seconds. It seems to take longer to start it recently as well (You have hold the key in the ignition longer so that the starter motor is going and then it will start, but you never had to do this before). Other times it will start somewhat alright, but then when you turn it off and try it again it won't start anymore. When it won't start, you have to depress the accelerator to the floor to get it started. The second problem is that when it is idling it will sometimes idle higher than normal. Also if you depress the accelerator a little bit and let it off right away, the engine won't rev down right away. It is like your foot is still on the accelerator. After a few seconds it will start to rev down. It does the same thing when you are driving. If you let off the accelerator the revs do not come down right away. It is like something is getting stuck. There has been a brand new (Jeep) distributor put in, and the idle control arm has been cleaned. When it is put on the scope, it shows that nothing is wrong, and no codes or anything come up. Can somebody please help me and give me some tips?!?!?!?!?!? Thanks for taking the time to read through this long description. I would really appreciate any help or tips whether they are small or big.

THANKS
JASON

 

[MudderChuck]

I´ve had most all of the problems you discribed at one time or the other, but never all at once.
Have you taken your Jeep swimming lately, or washed the engine compartment, with a high pressure washer?
I´d pull every connector I could get my hands on, carefully and take a look (blow them out with air), maybe spray out he contacts with some sort of contact cleaner (WD 40 not recommended, contains wax). I´ve had no starts, because of moisture in the connectors, on another occasion the wire to my CPS flopped over on the manifold and was crispy. CPS is the heart of the system, if it´s acting up, it could cause numerous proglems.
The high idle reminds me of a dirty, TPS sensor connection I found. Couldn´t keep the TPS in adjustment. I don´t believe the 96 adjusts, but a dirty connector or water logged TPS, will cause some of the problems you´ve discribed.
Good grounds and clean connectors are important for the sensor imputs. Most of the sensor imputs are very small voltages, dirt or faulty grounds, cause wrong or changing values.
Many of the problems I´ve found were traced to a moist, dirty or partly unplugged connector. Second most common was a battery to engine ground and/or engine to firewall ground.
Many times the computer will only throw a code, when a sensor is out of the envelope, it can be somewhat wrong, or reporting somewhat false values and not show a code.
What your discribing sure sounds like a wet, loose or corroded connector. Flacky contact somewhere. I sometimes change the relays around in the relay box, to check if a problem disappears (or moves), many of the relays are interchangeable (look close and make sure).
The 96´s have a rep for questionable fuel pumps, but the fuel pump sure shouldn´t make you have a high idle. May have something to do with the other problems though.

 

[XJNick]

Hi,

It sounds like a Crankshaft Position sensor (CPS) problem to me. If the computer doesn't receive a signal from the CPS, it often won't start the vehicle. Likewise, If the signal from the CPS drops out during engine operation, a number of things could occur, such as stalling or high reving, as the computer looses vital data such as the engine Top dead center (TDC) location and engine RPMs. :mrgreen:

Though note that the Throttle Position sensor also can cause high idle. But I'd replace the CPS first. It shouldn't be too expensive of a part.

-Nick :!:

 

[Chief_Cherokee]

need used YJ parts in GR Mi. area

Thanks for the advice. I hope it helps. Also just recently change the spark plugs and it seems they might have had something to do with it.....not too sure though. Anyway thanks. Hey Nick, 409, 618 miles or kilometers??????

Jason

 

[XJNick]

Hey Nick, 409, 618 miles or kilometers??????

Hi,

Yes it's got around 409,618 miles on the dash!

355,xxx of those miles from the original AMC 242 4.0L engine. :mrgreen:

-Nick :!:

 

[jeepmaster]

my jeep has the EXACT same problem. i had nearly every sensor replaced on that thing and nothing fixed it. oddly enough i ended up "fixing" the problem by switching keys. i switched to one of my spare keys and my jeep hasn't sputtered since. i know this makes no sense and couldnt be possible but it seriously did it. down to the point where i cant get it to start in the rain with one key, and it fires right up with the other. the one that works looks more beat up than the one that doesnt. im stumped but at least my jeep works... so try using one of your spares