citRon

1996 4.0 4x4 Aw4, 186,000 miles.

My troubles started a couple weeks ago. Jeep started running hot, then overheated when I shut it off, blowing the cap off the flush-T, spewed coolant all over under the hood. (I had done a full flush and fill and changed the T-stat a week earlier, too.) After that it wouldn't start, stranding me in a parking lot. Got everything dried up the next day, cleaned off the battery terminals, got it started up and got it home. Turns out the clutch fan was very weak. Replaced that. Then still ran hot and started clanking- water pump. Replaced that.

^^^don't think that has anything to do with it, but...

Seemed like everything was ok for a couple weeks, then started randomly dying while driving. It would re-start instantly. This happened only a time or two, then would go days without doing it. I did a tune up a month ago (Mopar cap, rotor, wires). Both O2 sensors new NTK's.

Last week, I drive 15 minutes, park. 15 minutes later, crank, crank, crank... no start. Finally starts up. Dies while driving. Re-start, repeat, etc. Get it home. Repeats this pattern for a few days, then 3 days ago I barely got it home. I got the P0340 code when the CEL lit up. I replaced the Cam sensor, and noticed that the distributor shaft had a lot of side-to-side play...the next day it started out running right, then bam- same symptoms. I figured the distributor to be the culprit. Replaced that with a new Duralast from AZ. The old distributor indeed had a lot of play in it...
Finished up- wouldn't start, backfired through the intake. Crap.
Today, tried again. I must have had it 180* out, because it fired right up when I finished today.

Then stumbles. Idles for a few seconds, stumbles again...
I put a meter on the CPS, and it was reading low resistance, so I figured that was crapping out as well. It was a matter of time...

I got a new Borg-Warner CPS, and for the heck of it also got a new TPS and IAC. I got the new CPS installed without too much hassle, got the TPS in.
Losing light, I figured I'd do the IAC tomorrow.

So I turn the ignition, it starts up. Then quits. Re-start, it is bucking like it wants to quit, surges, bucks, dies. Re-start, repeat.

Double-U, Tee, Eff...

Any ideas? This is my daily driver, so I've been taking the kids to school and the wife to work, and picking up and trying to spend a couple hours each day doing this stuff...I need it figured out!!

- I can hear the fuel pump come on when i turn the key...

I'm going to shoot a video of it here in a minute...

300EXC

You need to check your fuel pressure. Had similar issue when my fuel pump went bad.

Thax

If your CPS is showing low voltage you need to check the MAP sensor as well as it is on the same 5v circuit. Try switching the fuel pump relay with another similar relay and check fuel pressure on the injector rail both at idle and at 2k rpms.

citRon

fuel pressure good, 49-51 or so at idle and at 2k.
tested the coil, too, checked out.

citRon

here's a video- I'm holding the throttle steady, too...

DFlintstone

I'm likely not much help, some ideas though. Was it pretty much the same between dizy swaps? It's easy to be one tooth off. The rotor should be just leaving #1 terminal at TDC, (so when the puter advances the spark it still reaches). Did you get a new cap, or wash the origional well with dish soap after it's bath in coolant? (in the dark, see any sparking?). You haven't mentioned plugs. If you clean and gap them, you can check the color of the porsiln while you are there. Might tell you something.

That said vacuum issues come up. If you pinch off the large line to your brake booster, or the one feeding vacuum to the "Ball", does that change anything? Check a few of the easy to reach manifold bolts, see if they are loose. If you find some that ARE, stop, and tighten them all starting in the middle and working out.

See that your EGR valve is functioning as it should. That could cause a vacuum leak. Try it with that air filter off.

You might google "noid light" for fun. Besides telling you if the signal to the injectors is there....that tells you that the CPS is indeed sending a signal to the PCM. (there can't be injector pulse, without a CPS signal). Oh, and try un/repluging that new CPS, see if that changes anything. Just some thoughts!

citRon

I re-used my 'old' cap with the new distributor, as it is a Mopar part - I did cap, rotor, wires (Mopar) and Champion plugs all together a month or so ago.

I know I have a small crack in the short vacuum tube-ish thing that comes off the cruise control solenoid (?) -by the passenger fender- I have duct tape wrapped on it right now...

Tomorrow I am replacing my new APN header. It didn't fit without grinding on the intake runners and also whacking on the #6 pipe, as well as the flange being thicker than the intake mounting surface. I'm replacing it with a Dorman stock replacement. -If there's any leaks from there it should solve them. It's been on for over a month, though without any symptoms...

I tried checking for vacuum leaks by spraying various liquids around everywhere, and never got a change in RPM's.

No EGR valve on a 96. MAP sensor- and that's the only one I havn't changed!

I started it up in the garage, in the dark a few minutes ago. I saw a very faint arc light near the coil...maybe saw it for a split second one time...

DFlintstone

The spark from the coil will look for anything better than the air gap on the plug. If it finds a path of less resistance it will take it. I bring my cap, rotor and wires right into the kitchen and scrub them like any greasy thing, then dry well and install. The cap and rotor are high temp plastic. If the cap is not black, (making it about impossible to see a carbon track), I'll reinstall it, if looks OK.

I'm not sure what a bath in coolant does, but you might want to clean anything near the secondary spark! (any film may attract dust or something that conducts better than air) Not a bad idea to have all that clean anyway.

67 GMC

I'm wondering if it's a bad injector-The NOID light will tell you if it's getting power but you don't know if the solenoid is working. I had this issue with a fuel pump on its way out. It would be fine one day and the next you would get that backfire out the intake if you stepped on it. You said it kept pressure even when you gave it throttle so it should be ok. I'd change the fuel filter too to be sure.


When I first got my Jeep, it ran really crappy and I had a valve on #1 cylinder that the rocker had come off the rod so it was staying closed (exhaust valve). It was still spraying fuel in there and that wasn't a good thing. If you get really desperate, take off the valve cover to make sure all the push rods are under the rockers. I attached a pic of that:

citRon

I had replaced the fuel filter a few weeks ago...maybe I need to do it again- the old one had been on there for years

citRon

...and injectors were replaced at the same time with the Bosch 4-hole Neon's that were rebuilt and flow tested from a reputable seller

citRon

so the new cps I put in was a BWD from Advanced Auto...I keep reading on the 'net (so it must be true) that the cps should only be Mopar because the aftermarket ones have a high failure rate right out of the box.
If the new cps is bad, would the Jeep still even start up? I thought if the cps was bad it wouldn't even start...?

67 GMC

Apparently, if the CPS doesn't put out enough voltage, you can get intermittent no start condition. I have one now that is just under 0.3VAC. From the forum, this is supposed to put out 0.5-0.6VAC. Mine is running fine but will occasionally not start up if it's warmed up. It will take a good 5 seconds of on and off cranking to get it going. When it's cold, it starts right up so I'm thinking the CPS is on its way out.