Mechanics

STALLING

1998 Jeep Grand Cherokee • 188,915 miles

My jeep keeps stalling on me, I keep getting engine codes that say bad ignition coil and catalyst system below thresh hold bank. I keep replacing the ignition coil and catalytic converter but the vehicle still stalls out when driving and idling. I've also replaced. Plugs and wires, map sensor, both 02 sensors, cam position sensor, cap and rotor, checked and replaced multiple dry rot hoses. I've had it t two different mechanics and a jeep dealer and no one can seem to figure out my problem? My next attempt was going to be to change the EVAP canister, does this sound like it could be my issue? I am at wits end with this vehicle, its an awesome jeep except for this one issue and when it runs good it runs awesome. Both mechanics and the jeep dealer I had it to did compression tests, fuel pressure tests, checked to see if the fuel pump was working properly everything comes back good. Why am I having this problem? HELP. PLEASE. Also at times there is a faint smell of gas and I think I heard the evap canister ticking once
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Luthiertom
August 21, 2013.



The ticking you're hearing is most likely the valve that controls the purge flow. It will cycle on and off about twice per second.

Since you didn't list the engine size I don't know if yours has one or multiple ignition coils. If you have one for each cylinder you should get a fault code stating which coil circuit has the problem. You can switch that coil with one of the other ones to see if the problem moves to that new cylinder.

Most mechanics have scanners that display live data AND have a record / playback feature. The record button is pressed when the stalling occurs, then the event can be played back slowly later to see what is changing or happening. Because that data travels through the scanner's memory, the recording actually starts a couple of seconds before the button is pressed.

You also didn't say when this stalling occurs. Is it while driving at a steady speed? Just when coming to a stop? Will the engine restart right away? One common but elusive problem is stalling just as you start to coast from highway speed.

It's not very likely the evaporative emissions system can cause stalling. That system mainly takes care of gas fumes from the gas expanding in the tank.

Caradiodoc
Aug 21, 2013.
The jeep is a straight 6 4.0, and it has only one ignition coil, the stalling occurs at anytime there is no rhyme or reason for when it does it. Before the last time I replaced the catalytic converter it was backfiring horribly and its never done that before but now since I replaced the cat again and replaced some bad vacuum lines that went to the Evap canister it drove great for a day then the next day started up again but the codes for the cat haven't come up and don't backfire anymore. Also no codes for the ignition coil as of yet. But still stalls out when driving and not. It seems to be starving for air or fuel when it acts up

Tiny
Luthiertom
Aug 21, 2013.
If the engine stalls while driving at a steady speed that is almost always due to the crankshaft position sensor or camshaft position sensor. When they fail intermittently it is because they are failing by becoming heat-sensitive. The engine will not restart until they cool down for about a half hour. Most commonly this occurs right after a hot engine has been stopped for a few minutes. That gives the heat time to migrate up to those sensors. A mechanic would see this on his scanner during the restart attempts. One sensor signal would be listed as "present" and one would be listed as "no".

Unlike GM fuel pumps that typically fail while you're driving and let you sitting on the side of the road, Chrysler pumps will fail to start up when you start the engine. Once they DO start up they rarely quit while you're driving. If you drive with a fuel pressure gauge clipped to the radio antenna, (as I've been doing for the last year on my '88 Grand Caravan daily driver), if you see the pressure slowly drop, particularly when coasting from highway speed or when pulling a heavy load, suspect a plugged pickup screen. In my case it was snapped onto the fuel pump assembly and was real easy and cheap to replace.

If the stalling only occurs when you come to a stop, and the engine will start up again right away, that is due to the battery being recently disconnected or run dead. There's an easy fix for that.

Caradiodoc
Aug 21, 2013.
I've replaced the camshaft position sensor (if that's the one right on the bell housing) and when it stalls out it usually will start right back up but sometimes it takes a minute of two, and I went and bought a code reader that has live data. But I don't know what im looking at?

Tiny
Luthiertom
Aug 21, 2013.
Simple code readers don't do live sensor data. You don't need a code reader anyway. Chrysler makes reading Engine Computer codes real easy. You cycle the ignition switch three times within five seconds from "off" to "run", leave it in "run", then watch the code numbers show up in the odometer display.

There are some code readers out there that are getting a little more involved and may provide sensor data, but all I've ever used are full scanners. I have a Chrysler DRB3 because with extra plug-in cards it will work on the older stuff I drive and it can access emissions-related data on all car brands sold in the U.S. After 1995.

The camshaft position sensor is in the distributor. You replaced the crankshaft position sensor which has had a higher failure rate. Was there a thick paper spacer stuck on the end when you installed it, or was there a thin plastic rib molded onto the end? Those set the critical air gap. If that gap is not right it can cause intermittent stalling with no set pattern. I had one that I thought I was too smart and I didn't use that spacer. The engine ran fine for two weeks, then started stalling intermittently. All I had to do was reinstall it with the spacer.

The spacer will slide off as soon as the engine is started, and the plastic rib will wear down over time. With either design, if you reinstall a used sensor, if it has the rib you are to cut the remaining part off, then use a paper spacer.

Caradiodoc
Aug 21, 2013.
Yes it had the little paper spacer or plastic don't remember which but it had it and I installed it correctly, do you think I would be better off installing a new camshaft sensor before thinking seriously about the whole EVAP canister idea

Tiny
Luthiertom
Aug 21, 2013.
You shouldn't be thinking at all about the evaporative emissions system. That won't cause stalling. If your scanner or code reader shows the camshaft position sensor and crankshaft position sensor states, monitor those while you're driving and when the stalling occurs. If you see one of the signals suddenly listed as "no" or something equivalent, that is the circuit to diagnose. Replacing the sensor will only solve the problem about half of the time. The other times it is due to a corroded splice or stretched terminal making poor contact in a connector. Often those will not set a fault code because they don't act up long enough before the engine stops running. You're also unlikely to get a crankshaft sensor code when the air gap is wrong. The signal generated will be too small to keep the ASD relay on but big enough to be detected and prevent a code from setting.

You can also monitor the automatic shutdown (ASD) relay. It will turn on for one second after turning on the ignition switch, then again whenever there is engine rotation, (cranking or running). That relay is turned on by the Engine Computer when it receives signals from those two sensors. If the relay turns off while you're driving, that is due to a problem with one of those sensors. That relay supplies power to the ignition coil, injectors, and fuel pump or pump relay.

Caradiodoc
Aug 21, 2013.
Ok cardiodoc, I ran my diagnostic tool last night while I went for a ride, scanner didn't show any (ASD) setting. Maybe its called something else on my particular scanner but as I watched the live data I saw that there was a Fuel sys 1 and a Fuel sys 2 and the number one showed that it was closed and the number 2 said it was N/A?

Tiny
Luthiertom
Aug 22, 2013.
That sounds like a generic display where they are filling in the available information. I don't know if "fuel system 1" is for the automatic shutdown relay or the fuel pump relay. Either one should turn on for one second when you turn on the ignition switch. That can be hard or impossible to see with a scanner because they stop receiving information when the ignition switch is off, and even when it's on they respond too slowly. The display updates WAY slower than the information that is transmitted between the computers on the car.

Of more importance is what happens to that value when the engine stalls? That can also be hard to catch because the ASD relay and the fuel pump relay WILL turn off when the engine stops rotating. Your best hope is to have the engine stall at highway speed. The engine will keep rotating down to about 15 - 20 mph giving you time to watch the display. If that fuel system 1 stays "closed" while you're coasting, you have a spark OR a fuel supply problem. If it switches to "open", (off), and the engine is still rotating, you have a problem that is affecting spark AND the fuel supply system, which usually means the cam or crank sensor.

Caradiodoc
Aug 22, 2013.