DFlintstone

If I had one plug go bad, I'd change them all. No Platinum's, also maybe no AC Delco. Champion Copper or NGK/NTK?

Yea, I've heard of noisy/buzzing Evap solenoids. I'm tot sure what they are suppose to do. Maintain a little negative pressure/vacuum in the fuel tank? IdK. Al I can think is sudden dieing can be the CPS. I might just give her a good run with known good plugs gapped to .035 and see if the miss clears up. I'm not sure regular injector cleaner is worth a 8888, but it you can find some Bk 44 I guess that might work..help. Don't forget our fuel separates and get's funky if it's been sitting.

Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep. ALSO, there is a large line coming off the intake, rear of the TB that goes back to the firewall, across, then forward down to the vacuum ball behind your right front bumper. You can pinch that off or unplug it and cap the nipple to test if you have a leak there.

fordraceboy

Lower injector O-rings.... I've been toying with the idea of bad injectors causing problems, simply because at 202k they've never been replaced to my knowledge- and I've owned it since 99k. The lower seals create vacuum leaks?

DFlintstone

Yes, they need to seal right or there will be a vacuum leak. Once I pinched a ring installing the injector and had a vac leak. A shot of starting fluid there is what let me know.

I have yet to try just plain water to "look" for vacuum leaks.

salad

The canister is indeed part of the evap system, it sucks up fumes from the gas tank and dumps them into the intake manifold via a vacuum line. Nothing fancy that would cause problems aside from a vac leak.

Slight misses can be caused by vac leaks, you got all 6 plugs new coppers and the right gap?

DFlintstone

At least until 90, the canister "vents" to the tube between tha air cleaner and the TB. (where presumably there is slight vacuum, unless air is "ramming" from the front grille).

I'd always assumed manifold vacuum was involved until I took a better look!

salad

Typical Renix voodoo... :P

weebur

That canister is for storing gas fumes from the tank that are later introduced into the engine. That clicking you hear is normal.

fordraceboy

I had never heard any clicking before- I suppose the new hearing aides are working... Lol

I put new plugs in and double checked the gap. It starts ok, but with extended crank time, sometimes. Then it simply won't start at all. I've resigned myself to it probably being low voltage/grounded wire somewhere. I'm going to go through the 5v circuit from the crank sensor again today. I get intermittent 0v at the green/orange wire on the coil harness at times.

That is fed through the ASR relay, which depends on the CPS circuit- correct?

salad

Yes. If the PCM sees a sane signal from the CPS it completes the ground path for the ASD relay, which powers the ignition coil and the fuel injectors.

fordraceboy

Has anyone ever had/heard of an intermittently bad CPS? This one has been in for maybe 10,000 miles, and testing it shows like 15,000 ohms IIRC.

salad

Most of them fail on an intermittent basis, yep. But again when that happens the ASD relay (and hence your coil and injectors) will have no power. I'd be very surprised if a Mopar unit went out this fast, though.

DFlintstone

Funny Salad! (it's the "good" Voodoo). If you are NOT Renix, here is the other Voodoo for the CPS. Nice knockers, but I guess you use a scope, or a meter that costs over $5. http://www.cherokeetech.com/VBull/sh...agnosis-Videos

salad

Huh. I always figured that was a payment method, not a diagnostic tool.

fordraceboy

Chased thr CPS circuit with a meter last night. I have 5.2v on the orange wires at both the CPA and TPS. There is 12v on the ASR posts 30 and 85, and there is 11.8v to the green/orange wire to the coil when cranking- 0v while key is just turned in the 'On' position.

Ugh.

CCKen

If you have 5.2 volts on the Orange wire when cranking but not when the key is to RUN, then I would suspect the Ignition Switch is bad. You should have the 5 volt reference voltage on the Orange wire to the TPS, MAP, Crank Sensor, Cam Sensor, and Oil Pressure Sensor in both the RUN and Start positions.

If the START-RUN A21 circuit in the Ignition Switch (RUN contact) is defective you would also lose the Instrument Cluster, Electric Radiator Fan, Fuel Pump and ASD, and HVAC functions with the switch in RUN, but have all circuits when cranking (START).