So i replaced spark plugs, coils, injectors, and cam sensor. I have a 2001 laredo 4.0. The symptoms are 3 second start time (but when its warm it cranks right back up), slow shifting into second when cold, lack of power, randomly idles very low when stopping (but never does it in park). Weird shifting sometimes, like going back n forth at the end of a gear. Sounds like a lot of diffrent issues but ive replaced so much already im ready to give up. Pleeease help me out. Thanks in advance

 

From my knowledge it could be. Crankshaft sensor, o2 sensor, and possibly shifting sensor for the tranny. If these are incorrect or im missing something, let me know.

 

Check the fuel pressure, should be 49psi +or- 5psi. Low fuel pressure will cause all kinds of craziness, all of which you decsribed.

 

Hi guys, my girl is having the same issues (almost) and since I myself am a chick too I blame my Grand Cherokee of being on PMS almost as I figuratively hit myself on the head trying to find out what her problem is. At first she started to jump on rpm during idle: eg. during a stop when on Drive (from time to time on N or P). At 2500 rpm she would start vibrating like a ***** and then she would run smoothing when high up on rpm. I brought her to 2 Jeep garages already and what they've done so far is changing fuel filter, cleaning injectors, changing air controller valve, changing sparkling plugs, cables and getting myself poorer every time I have to go hopeless 'cause the problem is still there. Today I gave up the garages and went to the Municipality Car Inspection here in town and get a final diagnosis which includes:

1) Faulty O2 emission during high rpm ---> 5.05% when normal range should be: 0.00<=X<=3.00
2) Over emission of fuel during high rpm --->1,179.00 ppm when normal range should be: 0.00<=X<=649.99
3) Faulty O2 emission during idle --->5.52% when normal range should be: 0.00<=X<=3.00
4) Over emission of fuel during idle --->909.00 ppm when normal range should be: 0.00<=X<=649.99

They've recommended three thing to be checked:
1) Check engine for faulty valves, worn out pistons, etc.. however since my girl is a '97 with only 78,000 miles on her shoulders, this seems remotely doubtful, I've never driven her without oil or whatsoever.
2) Check for faulty injectors, as they have been cleaned using the ultrasound method and sometimes they might have busted them as a result of malpractice!
3) And finally to check on the car's brains... the last resource but often left behind... after all we all need therapy from time to time... hahaha.. well this means to check on the PCM of the car as it might have been sending the wrong signals for the right combustion. Which seems more plausible in my case but I would not know anymore.

So guys this is my story, check it out and see if this sound familiar to you. Now since I am sick and tired of going every time to the Jeep garages begging for a solution, I wonder if I have the solution under the tip of my nose and have not seen it yet. This is so I can bring it to the mechanics and stop making them spend on parts that I might have not even needed to change so far.

So what's your opinion.. I'd really appreciate any feedback...!
Thank you guys.

Grand Cherokee Limited 1997 ZJ 5.2 Automatic, 4x4, fuel injection.

 

i have the same problem. i have been told valves also dont think thats the problem maybe cam position sensor or crankshaft?

 

If youre getting to much fuel id check the o2 sensor or fuel pump. They tend to pump to much or not enough. As slow as work is now a garage will not solve youre problem sadly they need u to keep coming back. So their not gonna fix it properly. Maybe im in the wrong business. . Im yet to check anything else on mine...in need of a mechanic.

 

Does anyone know where i can find the crankshaft sensor and the cam sensor?

 

I assume you have a 4.0,5.2,5.9? Either way the crank sensor is on the trans bellhousing near the top. LH side on the 4.0, RH side for the V8's mentioned. Either one is a little difficult to replace and even tricky to see. Cam sensor on either engine is in under the distributor cap, just remove the rotor to replace the sensor.

For the above posts for running bad and/or failing emissions, probably the first things to look at are the typical tune-up items ( dist cap/rotor, plugs and plug wires) followed by a good injector cleaning and maybe decarbon the intake and cylinders, run a good cleaner through the intake, throttle body and IAC passage. Then its starts getting a little more complex, maybe a oxegon sensor, other engine sensor that failing, possible vacuum leaks at vac lines or intake gasket etc. V8's have been known to have a failed plenum (intake) gasket leak internally which causes the engine to breath crankcase vapors, this can usually be determined by opening the throttle plate and looking down past throttle body to see if there is a puddle of oil at the bottom of the intake.

 

I am having nearly the exact same issues. I drive a '98 2 Door XJ 4x4 w/ the 4.0, 5-speed. It's been harder(longer) to start cold lately, mileage has been crap, performance has been crap, idle isn't "rough" but it's very unsteady. Recently replaced the cat since it had stuff rattling around in it after only about 130k miles or so.

Replaced the crankshaft position sensor a year or so ago, replaced plugs, wires, dist cap, and dist rotor a few months after the CKS.

I'd really like to know if OP ever resolved his issue, and what it was.

So far I'm reading everything from Cam Shaft position sensor, bad dist, bad o2 sensor, bad fuel pump, etc.

Oh, also it backfires sometimes when downshifting or when floored, usually the latter when cold.

 

crank shaft sensor was my problem when it did a similar not starting thing...of course I just had to change out that damb fuel filter...which is by the way, in the friggen tank!! So you of course have to get a new pump/filter combo...man a live...but I did fix a problem with a yellow light that no one could figure out...here is the blurb I just wrote about...it is a long post...but kinda fun!
YELLOW LIGHT FROM HELL!!!
Did you ever fix this problem? I had a similar problem with a 4.0Liter 2001 Grand Laredo, it kept showing a yellow trouble light..every time I had to get an emissions check for my tabs done in Seattle Washington, no one could fix it....it took 5 years, and twice I paid the $150 to have them come up with nothin!!!! One guy said he would find it for free...than never happened! I did fix it..eventually...I decided that I wanted to upgrade the injectors with new Bosch 4 hole injectors.....I bought them on eBay for $92bucks plus shipping…great buy I thought! I had a garage do the work for get this $62 bucks...I thought that it was well spent money...So some history about that yellow light and ‘the code’….okay the code would always be the same, it showed the code for a back fire in various cylinders, but it never did 'back fire' and always ran great...so I had them there injectors a waiting their turn for the garage man to install...so one day I had to have a service call, window motor and relay of course...damb cars this is the second one, driver and then the passenger front....okay so I says how much for the injectors...the man says….$62 bucks – I says…....okay --- so I get this done and I get the Jeep back, of course they zeroed the codes.....next I am waiting for that darn YELLOW LIGHT TO APPEAR!!!!! And I am waiting…driving and waiting…baited breath and all…waiting and waiting…watching and waiting…as you see it would ALWAYS COME BACK!! And then… Lo and Behold, it has been over 120 miles and holding...no yellow light! So all along it was them darn oneholerinjectors! I had them even cleaned (injectors, and whatever else they clean) at one of them emission-bring-it-in-to-have-it-checked-and-send-them-off-after-paying-the-$150-bucks-so-I can-get-the-tabs...so so so - so the moral of the story is ...don't give up ...and someday do change them injectors..it will save you a huge bill, and a new this and that and the other thing! I had all kinds of stuff changed out, for naught! Good luck and the creek didn’t rise!!! Johnne in Seattle

 

yeah I have that year, they don't have plug wires anymore, it is a block that fits over the plugs that is now housing the conductors for the plugs, but the conductors are not wires as in the good ol days...hope you fixed your problem...and yes I did my sensor and bam worked/started great since...

 

I had a problem that kept the yellow light on without any garage figuring out that problem. I wanted to get new injectors, Bosch 4 holers just because, and that took care of the yellow light after having many garages try to find the problem....so if you seem to throw a yellow light for what appears to be misfires, then maybe it is, and maybe it is attributed to the injectors. No one and no ones brother came up with this idea, so having that thought to change out the injectors just because, has take away the dreaded 'Yellow Caution Light' and it has been over 300 miles and she still...the yellow light, won't come on~

 

After doing some research with local mechanics here in Syracuse, it seems that coil packs and injectors seem to be the cure for misfire codes. Neither of these parts are that expensive or hard to change, but most owners are reluctant to do so for some reason. In most cases, there is no way to clean and test injectors properly and it takes a test stand to do it. The test costs about as much as a new injector, so why bother? The coil pack is a molded epoxy unit that is difficult to visually check and may check out with a meter, but fail under load.

My 2000 WJ ran flawlessly for 180K miles until my 0331 head cracked. Then ran perfectly for another 5K but now I'm chasing misfire codes when the spark plugs look good. As soon as tax season is over, I'm going for a new coil pack and new injectors. My codes appear randomly and are not noticeable except at or near idle.

 

Low fuel pressure can cause multiple cylinder misfires.