HELP HELP Stuttering and stalling

88 4.0 auto 115K miles bone stock

Driving down the road (40mph) and let off the gas to coast and when i do the speed drops along with the rpms which goes way low like to 500 and then engine dies. Coast to the stop sign and stop.......Scratch head in wonderment. I turn the key and she fires right up. Proceed down the road get on the highway drive for about 20 mins with no problems. Do some stop and go driving for 7-8 mins then some faster speeds for a few then some more stop and go......coasting to a stop sign and not even completely stopped maybe still going 10-15 mph and she dies once again. Turn the Key and she fires up agian and down the road we go.

On the way to an appointment I start really paying attention to things. I can cruise at 40 mph and let of the gas and the rpms really drop way low like i said down to 500 rpms.....get on the gas and they shoot right up. I come to a stop light and slow down and stop with no probs. Proceed down the road and hit the next light and she stutters and stalls. I make it to the appointment and pulling into a parking space she dies once agian. SO I pop the hood and start the engine and listen......and listen......and listen.....rev the engine a little and listen.....rev some more stumbles and stalls? Now i sometimes can duplicate the problem and other times i can't.

I have read some messages about CPS, EGR Valves and the such.....don't know where they are or what they look like. I have had the jeep for over two years......maybe time for a tune up would that help? What about changing the fuel filter??

Eagle your input is especially wanted. TIA everyone

No takers HUH??? thats surprising

It's pretty hard to diagnose an intermittent problem from a description. It's hard enough to diagnose in person. If you don't know what any of those components are, you better just take it to a shop. I've been doing this for a long time, and I run a mechanics shop, and I still take mine in occasionally to get a professional diagnosis.

Could be EGR valve or any number of things, or a bad vacuum leak.

check the map sensor and the vacuum line going to it.

I'd also check into having the throttle body cleaned. There was a TSB about modifying the Idle air controller so it will not close off completely. I had a similar problem to you in January and this is what my dealer mechanic did to fix the problem

I have the exact same problem. I have very bad hesitation to the point of stalling when the engine is cold. Then sometimes, when i'm under 10 miles per hour and let off the gas, it dies without even a stutter. I think it's the exact same problem. I replaced my EGR valve not that long ago, my fule filter is somewhat new. I'm thinking it might be the EGR solonoid, I'll have to check that out. Or possibly the gas control valve that sits on the end of the fuel bar could be clogged or broken....i've heard of that happening. Any idea on how I can do that IAC modification myself?

Is your Torque Converter unlocking?

and make sure the Mapsensor vacum line is not broken.

Ok, so i did some work today on trying to figure it out. It is not the EGR valve or the EGR solonoid. I did notice that my knock sensor was demolished by something....so that might be it. Anyone know what happens without a knock sensor? Other than that...the MAP sensor seems to be fine, I unplugged and plugged it in with the proper engine missing/stuttering when it was unplugged. Vacum lines look good except this one that used to go to my air filter box was just sitting there sucking air. I have a K & N cone filter now and that spare line used to control the thing on the air filter box that let in hot air off the manifold when then engine was cold. Well, i plugged that line, we'll see what happens. Cleaned out the TB, too. Then the rain came, so i'm inside waiting it out. I'll go test and get back to you all later. Any ideas if this stuff doesnt work? Maybe the IAC adjustment?

wolfpacker said:

Ok, so i did some work today on trying to figure it out. It is not the EGR valve or the EGR solonoid. I did notice that my knock sensor was demolished by something....so that might be it. Anyone know what happens without a knock sensor? Other than that...the MAP sensor seems to be fine, I unplugged and plugged it in with the proper engine missing/stuttering when it was unplugged. Vacum lines look good except this one that used to go to my air filter box was just sitting there sucking air. I have a K & N cone filter now and that spare line used to control the thing on the air filter box that let in hot air off the manifold when then engine was cold. Well, i plugged that line, we'll see what happens. Cleaned out the TB, too. Then the rain came, so i'm inside waiting it out. I'll go test and get back to you all later. Any ideas if this stuff doesnt work? Maybe the IAC adjustment?

Click to expand...

TC unlocking?

so i think i need to buy a repair manual... and check all the stuff myself....i don't have the dinero to go to a shop and have them "assume" that its this or that let alone just to run some dios on it.......well off to advanced auto parts....got a bro working there......Free manual for me

If my TC is locking at 10 mph, i think i have a problem anyways. I always thought it only locked at highway speeds. Anyways....the problem is much improved now. However I can still stall it out when it's cold and i try to rev. The idle is a little low for my liking. I think i'm going to make a whole new topic for the IAC mod, i want to try it.

RINGKONG....Is the mapsensor on the drivers side fender wall??? i traced down a vacum leak to a hose and it lead to a thing mounted on the feder wall...disconnected the vaccum line and heard the engine's idle get a little stronger. I left it disconnected and drove around and it ran like normal with no stuttering or stumbling. Or is the thing i am refering to something else>>

you're refering to the EGR solonoid. It should have vacuum lines going in and out, and the out line should go to your EGR valve on the side of the intake manifold. The MAP sensor is on the firewall behind the throttle body. Look on the left side of the tb and trace a vacuum line to the firewallabove the intake manifold, and there you have it. Mine has a green connector, I beleive.