VW Vortex - Volkswagen Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
598 Posts
Discussion Starter · #1 ·
so hears the deal, about a month ago one day i went to start my jeep and it fired up but didnt idle, it just turned off. so i tried again, fired up but died, wouldnt stayed idled. so i try again and pumped the peddle and it stayed idled.then would work for the rest of the day. then it did that every morning for a week. then didnt do it for a month, now it started again, same thing however only in the morning, cause when i get home from work and try to fire it up it seems to always start. You guys got any ideas, ive heard so many opinions, from fuel pump, to a sensor, to the carborator, to the gas i use. anyways its a 1994 grand cherokke V8. thanks in advance.
 

·
Registered
Joined
·
5,739 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (2003VeeDuBgolf)

I would say fuel pump, but I guess it could be an IAC valve or coolant temp sensor too though.
Try this: Turn your ignition to on and listen to the fuel pump run. If it's making a loud, nasty, whining noise, then it's probably your pump.
How long does it take in the morning before the symptoms go away? Do they ever re-occur after warm-up?
 

·
Registered
Joined
·
598 Posts
Discussion Starter · #4 ·
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (Brett92)

well it sometimes does it in the afternoon, but will start on the 2nd or 3rd try. the reason i dont think it might be the fuel pump is that it only does this **** randomly, some morning it will do it some other time it wont, it doesnt make sense to me, haha.
whats an IAC valve ? price of parts isnt a huge deal, i got wholesale on everything through my work and got gearhead friends, but i really dont wanna do a fuel pump cause its a 220 dollar gamble. and since its come up before, its not the fuel pump filter, only cause on these jeeps the filter is built into the pump, so u gotta do the whole thing, the pump looks crazy, looks like a mini robot, haha
 

·
Registered
Joined
·
2,143 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (2003VeeDuBgolf)

IAC = Idle Air Control - a motor which pumps in air into the intake to stabilize the idle speed. (Also called idle speed stabilizer.) Perhaps your spark plugs are worn out.


Modified by Winged Nut at 2:45 AM 7-23-2005
 

·
Registered
Joined
·
5,739 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (2003VeeDuBgolf)

I should've been more clear, IAC stands for Idle Air Control. They have different names(IAC,ISV, ISC, Bypass valve,etc) according to what manufacturer it is, but they're all the basically the same(a valve that lets air bypass the throttle body, driectly into the intake manifold, I think). Sometimes they can get dirty, or clogged, and affect airlow through the valve, or actually hinder the valve itself from opening and closing.
Did you say you had the 4.0 I6, or the V8? I know that I've cleaned one my brother's Jeep and his was the 4.0 I6. If you can post a picture of the engine, specifically the throttle body, I can point it out to you.
About the fuel pump, my 86 Jetta had a bad fuel pump, and it only had intermittant problems like your car. Some days it would run great and then other days it ran like crap.


Modified by Brett92 at 2:01 AM 7-23-2005
 

·
Registered
Joined
·
598 Posts
Discussion Starter · #7 ·
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (Winged Nut)

well the lame thing is that the 3 times ive towed it to repair shops it always works for them and they cant duplicate the problem cause it always starts for them no problem, im just hoping that maybe someone has experienced the exact same thing on here and has the solution. ive also heard there is a fuel sensor on the frame rails on these jeeps that regulates fuel to the engine, maybe a short in that... not clue i think its only a 15 dollar part....
 

·
Registered
Joined
·
2,143 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (2003VeeDuBgolf)

Quote, originally posted by 2003VeeDuBgolf »
well the lame thing is that the 3 times ive towed it to repair shops it always works for them and they cant duplicate the problem cause it always starts for them no problem....

Classic case of a bad fuel pump (not saying that it is the fuel pump though)
Quote, originally posted by 2003VeeDuBgolf »
ive also heard there is a fuel sensor on the frame rails on these jeeps that regulates fuel to the engine, maybe a short in that...

Fuel pressure regulator - it is a small cylinder on the return line (I remember this because of the two Rs: Return and Regulator) It should have a vacuum hose going to it to regulate the fuel pressure under different loads - it runs off of intake manifold vacuum/pressure.
Turn the key to the ignition position and wait until the fuel pump turns off. Repeat several times, you should be able to hear the fuel pump prime when the key is turned, and then shut off after a few seconds. This will build up the fuel pressure before you start the car. If the car starts normally everytime, you can suspect a faulty fuel pressure regulator. If the fuel pressure regulator is faulty, the fuel pressure will bleed off when the car isn't running and you will have a hard time starting it.
 

·
Registered
Joined
·
7,448 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (Winged Nut)

I know JGC's well. Your problem is one of two things. It is either the already stated Idle Control Selenoid (a small black box attached to the back of the throttle body), or the Crankshaft Position Sensor. Both are a very easy fix. The ICS is a $30 part and you can replace it.
One question I have for you is this: Before the Jeep started to die, did it have a problem with a surging idle? Meaning did the idle go up and down between about 500rpm's and 1500rpm's? If that is the symptom, it is the idle control. If it did not do that, it is the CPS. If that is the case, you need to get it fixed soon because sooner or later it is going to start killing the car while you are driving. This means that you might be tooling down the freeway and it is going to just shutdown. That can be a little unsafe. It is also an easy fix and not expensive.
You are not going to throw any codes BTW. So don't expect a CEL.
On the very very remote chance it is the fuel pump, you are most likely going to have the following symptoms:
1. It will not have this problem unless the tank is at 1/2 or lower,
2. You will be able to hear the pump when standing at the rear of the vehicle. It makes a very discernable noise.
 

·
Registered
Joined
·
7,448 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (jacobyb)

ANother symptom while I am thinking about it is this, when you are on the freeway say over 60 mph, does the torque converter keep unlocking and locking when you barely move your throttle foot? Like does it do the opposite of your throtle imput meaning, when you give it a little gas, the rpm's drop a little bit, then when you lift, they go up about 250-300rpm's? If it is that, it is the idle control. It is a very common "problem" for the GC.
 

·
Registered
Joined
·
2,260 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (2003VeeDuBgolf)

The other suggestions are good but check this too: The alarm system. My mother in law has a Grand Cherokee, and its alarm system is bizarre - does the exact same thing you describe here. I don't know what to do about it but on the occasions when I've borrowed that beast and been stranded by the side of the road, another Grand Cherokee owner always comes up and says "Alarm system problem? Yeah, mine does that too."
There is some sort of defect related to the "clicker" that locks and unlocks the doors making the alarm malfunction and shut the car down. It'll do just as you describe - run intermittently or start then stall.
Sorry I can't be of further help
Good luck
 

·
Registered
Joined
·
598 Posts
Discussion Starter · #12 ·
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (240nut)

the alarm system idea is kinda ironic, cause half the times it does this ****, once i get it started and going down the road the security light comes on, on the dash. i have an aftermarket alarm as well.
 

·
Registered
Joined
·
6,878 Posts
Re: problems with my jeep grand cherokke, please read, maybe u had same ... (2003VeeDuBgolf)

I am an ASE certified Jeep Mechanic here in Vermont...
Most likely the cause of stalling is a dirty throttle body, wich would cause the IAC port to become plugged and choke off the idle passage.
Pretty easy on V8's, just remove the 3/4" plastic nut on the top of the plastic throtle body assembly (its not a "carb" even though it is made by Holley) disconnect the 3 cables and then unplug the misc electrical plugs (IAC, TPS = Throttle position sensor) and gently pull off the MAP (manifold absolute pressure sensor) hose in front by hand. Then remove the four 13mm bolts and the whole assembly will come off easily by hand. Usually the gasket does not need to be replaced, but it is always good to get a new one from the dealer just in case.
Take an old tooth brush and some rags and a can of brake clean (green can made by CRC is my favorite) or genaric throttle body cleaner and clean all black soot or oil residue from the the throttle plates (also move plates open and closed and be sure to clean all surfaces, just dont pinch yourself from the huge hold down spring
)
The IAC wich is probably 1" round and 1.5" deep is held onto the throttle body assembly by two torx head screws (not sure on size, maybe T25?) carefully remove them and clean all soot and oil residue from the sensor plunger and the port inside the throttle housing. DO NOT try to pull the plunger in and out of the IAC valve as it will break in half. I find that the end of my pinky finger and a rag swirling the junk out of the passage way works best. There is no need to remove the throttle position sensor or MAP sensor. Re-assemble in reverse proceedure of course, and replace the gasket if necessary. The four 13mm bolts do not need to be really tight, only hand snugged about a 1/4 grunt as I like to say.
Now, to relearn the idle, having a Jeep scan tool is the best (obviously this wont work for you) DO NOT unplug the battery, as you you will trip the alarm and the lights will flash and its a pita to disarm. Doing it with either the optical remote (if you still have it) and or cycling the key in the driver's door or the hatch. This will work in most cases but in Vermont I find a lot of the time people get lazy, never lube the lock cylinders and they bind or the alarm trip wires break off from the inside the door or hatch, then the alarm will kill your battery. So, first off, chock one of the back wheels so it won't roll forward or back. Pull your e-brake (if you use it on a regular basis and you are sure it works ok) Put your key in and start the Jeep IN NEUTRAL then feather the throttle as you did before so it won't stall. You will probably have to hold it around 1100 RPM and slowly bring it down to around 600-700. If it holds idle for 10-15 seconds, try to put in drive (this is why you need to have wheels choked and e-brake on!) and if it does not stall, then let the car run for 5 minutes. Put the Jeep back in park, shut it off, try it one minute later and all should be good.
Upon normal start up the idle should flair to approx 1300 rpm and slowly drop down to a lower rpm that won't make it stall. If it still stalls you need a new IAC. A fuel pump would either not start and run, or idle all day long but studder hard on acceleration, so I rule this out a possibility to your problem.
Good luck and feel free to email me for any other problems
-Jason
[email protected]
 
1 - 14 of 14 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top