96 Grand Cherokee Stalling

Hi Bill, Well, the spark plugs are certainly "vintage". But given the intermittent nature of my problem, and the fact that it can also happen to some degree at highway speeds, would you think the plugs and/or a dirty throttle body would be the root cause? I'll certainly try dropping in some new plugs and cleaning the throttle body. Can't hurt.

Thanks, Doug

That is telling you something.

Take your nice new shiny filter off. Put your fingers over the holes and shake it. Turn it input side down over a glass and see what comes out.

You might have a tank full of crapoline

Staling when cold with it stumbling at other cold times implies a dirty connection on the TPS or throttle position sensor. Ours acts like that when dirty anyway.

I recommend using a spray contact cleaner that electronic stores sell on all the plugs and sockets on the throttle body. It can't hurt and that fixes ours.

There is also an idle air passage that can get carboned up and need cleaning, but that usually just stays as a bad idle.

Mike

Well, when I changed the old filter (which had been in place far longer than I'd like to admit), I was a bit surprised at the dark brown goo that poured out of the inlet side of it. However, this has been going on for a couple of months now (happening more and more often), so if it's crapoline I must have an uncanny knack for finding it. I usually fill up with cheap gas at Walmart/Murphy, so maybe...

A new wrinkle to add this morning: After driving about twenty minutes this morning, I stopped the vehicle to go in and run an errand. Came back out about five minutes later, and it didn't want to start. This is a first. I've never had a problem with a "cold" start. It would crank fine, of course, but not start. After about 2 to 3 minutes of trying, it did finally start. If it does this again, I'll tap the fuel pressure valve and see if it has pressure.

Solving this mystery would be fun if it weren't: A) An expensive pain in the butt, and B) leaving me stalled out in rush hour traffic frequently. Most of the time it idles and runs fine. But these random problems always occur at the worst time. :-)

Thanks for all the suggestions, guys. Hopefully, I'll have time to nail it over the long weekend.

Doug B.

If you happen to be low on gas this would be an opportune time to drop the tank and clean the gunk out of it.

You have to remember that it, most likely, isn't just crapoline from one tank fillup but many (unless that load was particularly bad).

FWIW I got a tankfull of bad Shell gasoline back in the earlier '80s but that Shell station pretty much told me to 'drop dead creep' when I asked about a refund. After I drained out the 20 gallons and replaced it with some Chevron from the lawn mower gas can and a new $1.99 filter it fired right up.

I've only bought gas from Shell a few times in the intervening 20+ years... not that they miss my business all that much. That particular station might have.... I got 20 gallons three times a week (100 mile round trip to work) and the business went to the Chevron directly across the street.

Maybe the cat is going bad.

Later Mike

Oh, the "cat" is definitely bad. It's getting replaced for free in the morning via a recall notice DC just put out on my Grand Cherokee. It's been rattling like a box full of cans tumbling down a staircase for about a year now. Sometimes procrastination pays off.

I'm off to get contact cleaner and spark plugs.

Doug B.

When you pull the old plugs note which cyl they are for and in what condition the ends are. A little grey or black stuff is fine.

If you haven't done it before, the cap/rotor/wires are also way past expected lifetime. Also take a look in the distributor and see if there is any oil down there. Oil indicates the lower bushing is worn and if the rotor wiggles at all from side to side then you should get a new distributor. (cheaper than rebuilding) I did mine a while back.

The saga continues...

I've changed the spark plugs and wires, and added some fuel injector cleaner. I've checked the fuel pressure at the rail; it's got plenty of fuel pressure. Nevertheless, sometimes it will just up and stall out on me. It can be at idle, or at 35 mph. I can even get a quick buck or hesitation at 50 mph or higher. If I really give it a ton of gas, I might keep it running, but when I do that it usually sputters, coughs and chokes, acting like it's running on one or two cylinders. When it stalls, it rarely wants to start right back up. I have to keep trying and praying for several minutes. After the last episode, it set five separate code 43's. Yes, five of them.

I also put in a brand new crankshaft position sensor. Obviously, that didn't do the trick, even though the old one showed considerably less than infinite resistance across terminals B and C (suggesting it was bad).

I guess I'll pull the distributor cap and take a look at the rotor. Grrr....

Doug

Have you replaced the ignition coil?

It doesn't sound like fuel delivery is the problem, especially if it will not restart immediately. Translate a code 43 for me: it doesn't sound like the OBD that I am accustomed to.

Regardless of what code it is throwing, basic ignition continuity should be checked. Intermittant problems are difficult to diagnose and are labor intensive. Wiggle testing might be your next assignment.

Yes. That was the first thing I tried last weekend. I replaced the distributor cap just now, and still got it to stall out. This time I had a fuel pressure gage with me. Right after it stalled, I hooked up the gage, but saw zero pressure. Then I turned off the ignition and back on, and got a full 49 psi. It started back up, ran less than a minute and cut off again. This time the fuel pressure gage was still reading 49 psi. I started it again, and it ran very rough for about a minute, but the fuel pressure was rock steady at 49 psi.

If not for that initial reading of zero, I'd be confident that it was not the fuel pump. Naturally, I haven't been able to get it to stall again while sitting in the yard. I'm really getting tired of having to do this out in traffic.

Doug B.

According the engine code chart on Doug Wilson's excellent web page, a code 43 can be either of the following:

What in particular should I try wiggling?

Thanks, Doug B.

How long will it hold fuel pressure?

Leaking fuel injectors will make restart difficult....... do you get an initial puff of black smoke when it does start?

No, no black smoke on a restart. I haven't timed it, but it holds fuel pressure pretty well. At least 15 or 20 minutes.

Doug B.

Your fuel pressure is good, possibly even a bit on the high side. How's the hose look that connects the intake rail to the pressure regulator at the front of the fuel rail? Measure the pressure then take that hose off and see if it goes up. It should go up a few psi.

(it's going to be this one)

This is telling me the coil circuit is having problems. It could be the connector, the engine ground, or the coil. The only other thing it can be is the computer. That's not likely. What coil did you use?

When I was having problems in my 93 I found out the napa part with harness was needed. This was the same coil Jeep installed to solve an earlier idle problem. The harness has an internal resistor.

The coil gets 12v from the ASD relay, make sure it's pins are clean. Actually you might swap that relay with the AC or Fog relay just to make sure.