T-15 Jimmy (again) cutting out on freeway

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'91 T-15 Jimmy, 4.3L/700R4, 4x4.
Lil Jimmy has aquired another nasty problem. On the freeway (100+ kph) and once around town (60-70 kph) the truck has kinda bucked a little bit, kinda
feeling like the torque converter unlocking and locking a few times per second for a good two to three seconds at a time. It has been pretty intermittent, although it has usually occured on the skyway (a fairly steep bridge). It got to the point last Wednesday that just as I came off the skyway it did the little stumble and as I was moving over to get off the freeway as soon as possible the CES light flashed for half a second and the engine quit. The engine cranked for a few seconds before restarting (usually restarts on the first crank when shut off normally), got me maybe twenty feet, and quit again. Restart again after another cranking session and it quit again at the bottom of the offramp. Again, cranked it back up and it made it to work with no more problems. Once there I checked for codes and found nothing.
Since I had one waiting to be installed I changed the fuel filter before heading home that night. The old one had a lot of crap in the inlet side so it was pretty clogged (as far as I'm told, the older guy helping me had pitched it before I crawled out), and Jimmy ran quite a bit better on the sidestreets, but I swear I felt it stumble for half a second once on the way home. Any ideas? How the hell am I supposed to diagnose this? I figure I should check the fuel pressure for a possibly dying pump (once I find a gauge for my TBI setup, damn useless parts stores) and maybe throw a cap and rotor at it (it does tend to go through them every once in a while), but other than that I'm left scratching my head.
I'm awfully close to just scrapping the damn thing...
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Sounds like a plan, if the fuel pressure looks good, you could just for insurance replace the module and pick up.

-
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Check the electronic module under the rotor in the distributor. Make sure it's screwed down tight. Can't remember which sensor it is - maybe spark sensor? Anyway, it might not be the problem, but I've seen one truck where it WAS.
JLarsson
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Hmm... I do have a spare one from a junkyard truck I could swap in... I wonder if I have any thermal compound left.
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SBlackfoot wrote:

I wasn't thinking so much that it was bad, just that maybe it was loose, hence the intermittent nature of your problem.
JLarsson
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I know it sounds weird, but you should remove all the battery terminals and clean them WELL. wash with baking soda paste(mixed with water) and scrape them clean. Then rinse off the soda paste with clean watter and make sure all are clean. This has happened to me 1999 tahoe and friends other chevrolet(and ford) owners. it would still turn over and start, but run rough and die momentarily. the cleaning fixed it for three years now.
old john do it!

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and
clean.
I guess it's worth a shot. The worst part is that to see if the problem is solved I'll have to take it back over the skyway. I'd hate to have to call my Jeep buddy for a drag back home. :(
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snipped-for-privacy@comcast.net wrote:

All you did was RESET the computer !!!

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again

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SBlackfoot wrote:

    First NAPA should either carry, or be able to order for you the Proper fuel pressure tester, with adapter. You might have to ask to see the tool catalog and look for it your self.
    First check should be your Spark System. Check the cap,rotor, plug wires. Check the plugs. Then check the coil, and the plugs/termials on the coil.
    Then check the TBI. A bad or dirty TPS can cause "Bucking". If you go to WOT after it bucking, if you see black or grey smoke the engine is loading up. This is caused by the TPS sending a signal for more fuel then needed. Charles
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To update, I pulled the plugs one by one and took a good look. None were wet and they all looked exactly the same, definitely good. Slight oil smell (maybe gas, but smelled more like oil). Just for the hell of it I swapped in a coil I grabbed from a junkyard truck a while back, sanded down any little deposits inside the cap, and replaced the #1 spark plug with an odd plug I had lying around (broke the damned thing while pulling it, an hour after the parts stores closed. What a week...). A little later I think I'll head out to the Skyway and see what happens...
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SBlackfoot wrote:

Well? What happened? Hope you're not still out there some where.:)
JLarsson
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lol I didn't think anyone was still paying attention. ;)
I chickened out that night. The Skyway sure would be a crappy place to break down. I did try it this afternoon though, with a buddy and his XJ with me just in case. Jimmy made it up and over without so much as a puff of smoke. Maybe it was the fuel filter after all. It'll take a week or two of making that trip every day before I'm 100% convinced.
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Had a similar problem on a '90 burb 5.7 and after trying to find it for over a year and a half, I finally stumbled onto it by accident. Turned out to be a fuel injector that was acting up intermittently and then finally died about a mile from the house.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% There are two classes of pedestrians in these days of reckless motor traffic - the quick and the dead. ~ Lord Dewar 1933 ~
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Hmm... I do have a spare junkyard throttle body lying around... If it acts up again I'll try swapping injectors.
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Well?Any thing good or bad?

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Good, I think. I've went over the Skyway three times with no hiccups. I still bypass it in the morning just in case, but it's been fine in the afternoon. I hate intermittent problems. Who knows if it's actually fixed or not. <shrug>
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Well it wasn't the fuel filter...
'91 T-15 Jimmy, 4.3L/700R4, 4x4.
Jimmy and I just made it home from work. It made it over that scary-ass bridge a good twenty times since it's last bucking and cutting out incidence, all the way back to town. Idling at a red light, no problems. Light turns green, give it a little gas and blah, no revs. No smoke, no stuttering, no CES light, no warnings of any kind. Luckily it gave me enough of a kick in the ass before it died to coast out of the way of that 18 wheeler breathing down my neck.
Just like last time, once stopped it cranked over until it fired, and died again with a quick CES light flash (no codes, and I checked only seconds later). A few more cranks and it fired up and made it home with no further issues.
Jimmy and I are close to parting ways (he's looking pretty tired) so I'd hate to have to dump a sizeable amount of money into it, but I might try to get the winter out of it if my plates don't get yanked for being "unsafe" first. I'm going to try swapping in a few more of my spare parts just for the hell of it and hope for the best (ignition module, injectors, MAP sensor, etc.. some of the stuff suggested before), but considering that this is the first recurrance in around three weeks I'm not sure if I ever know if I've fixed it or not. Any other ideas before I start looking into that Grand Cherokee again? Thanks.
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SBlackfoot wrote:

Computer !!!! gotta be it since it doesnot store any codes
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SBlackfoot wrote:

You've certainly had your share of trouble with this. I HATE intermittent problems. I have been known to go so far as to push everything that I can push in hopes of making the problem permanent so I can find and fix it.
That said - I never read whether you checked the module under the rotor. If those screws are loose and the thing raises up a little on one side occasionally - it will do exactly what you describe here. If you checked that already, then perhaps it is that module that is intermittent and when you swap it out you will be okay.
I'm hoping that's the case for you. I'm feelin' your pain here, man!
JLarsson
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