ravener622

My friend talked me into buying a 1997 jeep grand cherokee spot 4wd 4 door when my stratus broke down and when I first got it it had a pretty bad stalling problem. We found out it was the throttle positioning sensor and after we replaced it it ran like a chap. Now aboit a week ago I noticed a random knocking under my feet when id be driving and found I had broken the brakets for my exhausted. Now that we fixed them my jeep started stalling out again and wouldn't idle correctly. We took it to autozone and they put the compuetr on it and told me the code said it was the manufacturing code transmission but both of my jeep mechanic friends told me it was the air intake valve. So I bought a bew valve and we replaced it to but now when I'm in park it idles at over 1 grand and doesn't seem to pick up speed like it used to and its shifting pretty hard. Can someone tell me if this is an easy fix or if I bought a lemon.

Jmb94

I'm not sure that the exhaust brackets and the knocking were related.

Odds are the code was right, if it's shifting hard it isn't going to be anything on the engine. The TPS issue is pretty common, so try tapping it with a hammer and seeing if you get any results (did that when mine went out, and it worked. Percussive Maintenance). Actually, the exhaust has to be completely unrelated. It sounds like you're dealing with two different problems here:
1. Your transmission is starting to slide downhill.
2. Your TPS or Air intake Valve or any one of the other 30 bazillion sensors on your engine are having problems. Maybe even try a bottle of Heet, maybe you got into some bad gas?

RB89XJ

I am having a similar problem in my jeep. I have an 89 4.0L. Mine is stalling out at really low speeds, like driving in parking lots, or just creeping in traffic. I had the IAC valve replaced not too long ago, and that fixed it for a while. Then the jeep quit out on me and it would crank and but not start. I had the throttle body cleaned, and a new crank sensor installed. It starts now, but is giving me the same stalling problem. I had all the vacuum lines checked and they are fine. My resting idle is about 500. I am wondering if the jeep is idling improperly, and that is causing it to stall out. Maybe i need to replace the IAC again? I also have an emissions mat light on, so i was also wondering if that may have something to do with the issue. Maybe O2 sensor, CAT Conv, or something else?? Any ideas????

Decemberist

Please use spell check, or at leased proof read your frikin post.

P.S There's your problem, you bought a Grand cherokee.

Skunkape

Decemberist I think you meant to say atleast not "at leased" maybe check your own spelling Bro before becoming a spell check ****.Hope the Op doesn't think everyone here is a A hole.Welcome and enjoy your Jeep and don't pay attention to guys like Decemberist.Wish I could help but just don't know GCs very well

ravener622

Mine has been doing that a lot lately also...the whole cranking but not turning over thing lol. but my boyfriend believes it may be the fuel pump since when it finally does turn over it tells me i have no gas and when i go below 15 mph my oil gauge goes down and the check gauges light comes and thats when it tries to stall out...oh AND my exhaust brackets broke AGAIN!! we replaced another sensor and the water pump since i first posted this. Now i love my Jeep and i was planning on rebuilding it from the ground up and making it a beautiful girl's Jeep lol but that was gonna be over the next two or three years...not everything in the first 3 months so needless to say i'm ripping my hair out over this. hopefully someone will give me a good clue do to the fact its again costing me $80 just for a car dealership to tell me whats wrong..i really don't want them to charge me for fixing it

tjwalker

The throttle position sensor is responsible for a good percentage of transmission shifting problems. Where did you get your TPS from? No lack of cheap-charly engine management sensors around. The TPS can be tested with a meter and a manual.

Your IAC (idle air control) valve and a vacuum leak are the two primary suspects for a high idle. Perform a comprehensive search for a vacuum leak and also clean your throttle body and IAC. They get carboned up over time and miles. Here is more.
---------------------------------

The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

ravener622

could that also cause a bucking effect?? i would just really like to rule out that its the tranny

91armygreenXJ

IAC valve

mcguyver_xj

you are not very observent op's picture is of a cherokee so obviously op is a bit confused to which they have...

and i am a parts guy and have seen similar problem from jeeps and the iac almost always solves it...don't bother cleaning it just replace...

ravener622

we have already replaced the IAC and it was fine for about a week and then it started stalling again and now whatever it is is screwing with my transmission.

dukie564

ok so after reading everything posted so far:

1) when you say "air intake valve", what's the actual part you replaced? That part name doesn't make sense on a cherokee.
2) IAC will not contribute to your problems while driving, only at idle.
3) The fuel gauge/no start issue sounds like your fuel pump may be on the way out, or a poor ground (see below).
4) Throttle Position Sensor is the main culprit for transmission shifting issues / bucking - may have a poor ground (see below).

My suggestion would be this - you have quite a few problems that may be attributed to poor electrical grounds. Bad grounds are big causes of electrical gremlins in our vehicle. My first course of action would be to clean and freshen these ground points. The main ones are:
1) Battery (-) to the fender (wire)
2) Rear post of the valve cover to the firewall (strap)
3) Oil dipstick attachment bolt.

in each case, unbolt the wire and clean up the terminals/contact surface really well, and scrub with some sandpaper until they are shiny (bare metal) and reattach. Also inspect the cable/strap metal condition (peel back the insulation as needed), if it's green and crusty replace it.

I would also seriously consider replacing the battery terminals.

CoffeeCommando

I am currently experience similar symptoms. I have a manifold leak somewhere along the bottom of mine though. All the rough idling from poor spark plugs must've worked the bolts out of place.
My vacuum leak continues to get a little worse each day. I can smell the gas fumes now.

I recommend hooking up a vacuum pressure tester on the manifold (disconnect and unimportant vacuum line, not the brake booster though because it causes the revs ro go way up) and seeing where you're at. Mine had a free spot that I had a vacuum cap over so I didn't have to disconnect anything (I bought a jeep grandcherokee 2002 manifold for better airflow).

I was pulling 10 Hg when I should have had about 20-25. Everytime I slow down (put on the brakes) the brake booster bleeds so much vacuum (of what's left anyways) it drops down to about 400 RPMs and almost stalls out on me.

I've also replaced my IAC, MAP and TPS. The problem I just mentioned didn't change one bit.

So I recommend having a look at the vacuum since it's free to do at A-Zone.

ravener622

thanks everyone for your input!!

but we took it to autozone and the same code kept coming up about the transmission and now i'm paying $80 so get it looked at just to tell me exactly whats wrong..i'm hoping its something small since i really don't have the money to replace a trannsmission

dukie564

what is the actual code?

did you freshen the grounds as I suggested?