GMC Jimmy fires all plugs all the time
Question:
– Hide quoted text — Show quoted text ->Hi Gregory, >hmmm…The first problem sounds like a fuel pressure problem, at least >that’s what I’d have checked for first. I’m surprised the dealer >didn’t. If not a pressure problem, maybe it’s sucking air. The ‘work >around’ they fixed has me thinking. It could also be a poor seal on >the tank ring, this is where the pickup and the fuel pump mount. But, >now that I’m thinking about it, it -could- be sometime goofy like a >bad gas cap. >The second problem sounds like somebody either didn’t know what they >were doing or was having a very bad day. My guess on the spark plug >mystery is a really cheap cap and roter was installed and it’s arcing >all over the place inside the cap. >eab
I have seen this with cheap cap/rotors before. The rotor will not be aligned properly within the cap causing it to hit and gouge the cap on one side and have a wide gap on the other. This can cause the cap to spiderweb crack and the firing will do all kinds of funky things. Also it may seem to be worse on rainy or very humid days due to moisture coming into the picture in there. I had a GM HEI on a SB chevy that was acting wierd like this and I looked under the hood at night in the dark. The cap was all cracked and was lighting up like a christmas tree as the car ran. Arcs all over the place. In the day though you couldn’t see it and the cracks were not really visible to the naked eye. Don’t know about all cyls firing at the same time though. This seems pretty unlikely on a standard cap/rotor. – Hide quoted text — Show quoted text -> I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. > I recently had a dealer replace my fuel tank after a light accident. The > mechanics there said there was a small problem with the hoses connecting > to the fuel pump, but that they worked around it and did not replace the > pump. > I commute 30 miles to work and back every day, at highway speeds. A few > weeks after the gas tank work, the engine started acting up. While > cruising, or while at low speeds, it would lose power very briefly, then > gain it again, sputtering frequently but intermittently. The engine did > *not* do this while idling. Despite not getting any trouble codes from the > computer, I thought it was a clogged EGR. I removed the valve and found > that the carbon wasn’t built up too badly, but cleaned it out anyway. > The problem continued and worsened. It stalled three times one night, each > time starting back up again after a 5 – 15 minutes. I took it back to the > dealer, who replaced the fuel filter, cap, and rotor. I also used some > fuel injector cleaner with a tank of 93 octane (I usually use 89). > After burning about nine gallons, the problem continued, and I had it towed > to another mechanic who I trust. I just spoke with him on the phone, and > he says that the plugs are *all* firing every time. The five that are > supposed to be dormant in a given instant fire light. > Any ideas?
Response:
> I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. > I recently had a dealer replace my fuel tank after a light accident. The > mechanics there said there was a small problem with the hoses connecting > to the fuel pump, but that they worked around it and did not replace the > pump. > I commute 30 miles to work and back every day, at highway speeds. A few > weeks after the gas tank work, the engine started acting up. While > cruising, or while at low speeds, it would lose power very briefly, then > gain it again, sputtering frequently but intermittently. The engine did > *not* do this while idling. Despite not getting any trouble codes from the > computer, I thought it was a clogged EGR. I removed the valve and found > that the carbon wasn’t built up too badly, but cleaned it out anyway.
With a timing light, look down the throttle body and see if you’ve got a nice dome-like spray (it’s difficult to explain what it’s supposed to look like and I have no pictures)while going through the RPMs. If it’s weird shaped, the injectors could be tired. If the spray is wimpy at higher RPMs, you have a fuel delivery problem. If the fuel filter has never been replaced, it’s definitely time to do so. I wouldn’t be surprised if the fuel pump were tired too. > The problem continued and worsened. It stalled three times one night, each > time starting back up again after a 5 – 15 minutes. I took it back to the > dealer, who replaced the fuel filter, cap, and rotor. I also used some > fuel injector cleaner with a tank of 93 octane (I usually use 89). > After burning about nine gallons, the problem continued, and I had it towed > to another mechanic who I trust. I just spoke with him on the phone, and > he says that the plugs are *all* firing every time. The five that are > supposed to be dormant in a given instant fire light.
Something’s fishy. A distributor type system will at most run a couple plugs at once due to carbon trails or a cracked cap. I don’t know how the heck it could get all six plugs at once. Well, time for a different cap and rotor (since buying new ones will cost less than $20, go buy them and put them on). A coil won’t be able to create a spark on all the plugs at once for long since it requires a tremendous amount of charge to do that. > Any ideas?
After making the mechanic fix it, offer to have him sterilized. He shouldn’t have let you leave with these problems. -Brian
Response:
I’ll help Gregory with your response. No-can-do with checking the feul spray pattern, he’s probably got the W engine which has the CPI system and NO WAY to see the injectors from the TB (mounted horizontally no less). I’m not saying he does, just that the truck having TBI can’t be an assumption… – Hide quoted text — Show quoted text ->I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. >I recently had a dealer replace my fuel tank after a light accident. The >mechanics there said there was a small problem with the hoses connecting >to the fuel pump, but that they worked around it and did not replace the >pump. >I commute 30 miles to work and back every day, at highway speeds. A few >weeks after the gas tank work, the engine started acting up. While >cruising, or while at low speeds, it would lose power very briefly, then >gain it again, sputtering frequently but intermittently. The engine did >*not* do this while idling. Despite not getting any trouble codes from the >computer, I thought it was a clogged EGR. I removed the valve and found >that the carbon wasn’t built up too badly, but cleaned it out anyway. > With a timing light, look down the throttle body and see if you’ve got a > nice dome-like spray (it’s difficult to explain what it’s supposed to look > like and I have no pictures)while going through the RPMs. If it’s weird > shaped, the injectors could be tired. If the spray is wimpy at higher RPMs, > you have a fuel delivery problem. > If the fuel filter has never been replaced, it’s definitely time to do so. > I wouldn’t be surprised if the fuel pump were tired too. >The problem continued and worsened. It stalled three times one night, each >time starting back up again after a 5 – 15 minutes. I took it back to the >dealer, who replaced the fuel filter, cap, and rotor. I also used some >fuel injector cleaner with a tank of 93 octane (I usually use 89). >After burning about nine gallons, the problem continued, and I had it > towed >to another mechanic who I trust. I just spoke with him on the phone, and >he says that the plugs are *all* firing every time. The five that are >supposed to be dormant in a given instant fire light. > Something’s fishy. A distributor type system will at most run a couple > plugs at once due to carbon trails or a cracked cap. I don’t know how the > heck it could get all six plugs at once. > Well, time for a different cap and rotor (since buying new ones will cost > less than $20, go buy them and put them on). > A coil won’t be able to create a spark on all the plugs at once for long > since it requires a tremendous amount of charge to do that. >Any ideas? > After making the mechanic fix it, offer to have him sterilized. He > shouldn’t have let you leave with these problems. > -Brian
– Reach me by ICQ. My ICQ# is 8023912 or, * Send me E-mail Express directly to my computer screen Download ICQ at http://www.icq.com/download/ For adding similar signatures to your e-mail go to: http://www.icq.com/email/emailsig.html
Response:
If this is the Central Port Injection, take it to a dealer as they would have the necessary tools to diagnose this very specialized system. Could be the central injector. But do the easy things first, like replacing the fuel filter.
– Hide quoted text — Show quoted text -> Hi Gregory, > hmmm…The first problem sounds like a fuel pressure problem, at least > that’s what I’d have checked for first. I’m surprised the dealer > didn’t. If not a pressure problem, maybe it’s sucking air. The ‘work > around’ they fixed has me thinking. It could also be a poor seal on > the tank ring, this is where the pickup and the fuel pump mount. But, > now that I’m thinking about it, it -could- be sometime goofy like a > bad gas cap. > The second problem sounds like somebody either didn’t know what they > were doing or was having a very bad day. My guess on the spark plug > mystery is a really cheap cap and roter was installed and it’s arcing > all over the place inside the cap. > eab
– Hide quoted text — Show quoted text -> I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. > I recently had a dealer replace my fuel tank after a light accident. The > mechanics there said there was a small problem with the hoses connecting > to the fuel pump, but that they worked around it and did not replace the > pump. > I commute 30 miles to work and back every day, at highway speeds. A few > weeks after the gas tank work, the engine started acting up. While > cruising, or while at low speeds, it would lose power very briefly, then > gain it again, sputtering frequently but intermittently. The engine did > *not* do this while idling. Despite not getting any trouble codes from the > computer, I thought it was a clogged EGR. I removed the valve and found > that the carbon wasn’t built up too badly, but cleaned it out anyway. > The problem continued and worsened. It stalled three times one night, each > time starting back up again after a 5 – 15 minutes. I took it back to the > dealer, who replaced the fuel filter, cap, and rotor. I also used some > fuel injector cleaner with a tank of 93 octane (I usually use 89). > After burning about nine gallons, the problem continued, and I had it towed > to another mechanic who I trust. I just spoke with him on the phone, and > he says that the plugs are *all* firing every time. The five that are > supposed to be dormant in a given instant fire light. > Any ideas?
Response:
I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. I recently had a dealer replace my fuel tank after a light accident. The mechanics there said there was a small problem with the hoses connecting to the fuel pump, but that they worked around it and did not replace the pump. I commute 30 miles to work and back every day, at highway speeds. A few weeks after the gas tank work, the engine started acting up. While cruising, or while at low speeds, it would lose power very briefly, then gain it again, sputtering frequently but intermittently. The engine did *not* do this while idling. Despite not getting any trouble codes from the computer, I thought it was a clogged EGR. I removed the valve and found that the carbon wasn’t built up too badly, but cleaned it out anyway. The problem continued and worsened. It stalled three times one night, each time starting back up again after a 5 – 15 minutes. I took it back to the dealer, who replaced the fuel filter, cap, and rotor. I also used some fuel injector cleaner with a tank of 93 octane (I usually use 89). After burning about nine gallons, the problem continued, and I had it towed to another mechanic who I trust. I just spoke with him on the phone, and he says that the plugs are *all* firing every time. The five that are supposed to be dormant in a given instant fire light. Any ideas?
Response:
– Hide quoted text — Show quoted text -> I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. > I recently had a dealer replace my fuel tank after a light accident. The > mechanics there said there was a small problem with the hoses connecting > to the fuel pump, but that they worked around it and did not replace the > pump. > I commute 30 miles to work and back every day, at highway speeds. A few > weeks after the gas tank work, the engine started acting up. While > cruising, or while at low speeds, it would lose power very briefly, then > gain it again, sputtering frequently but intermittently. The engine did > *not* do this while idling. Despite not getting any trouble codes from the > computer, I thought it was a clogged EGR. I removed the valve and found > that the carbon wasn’t built up too badly, but cleaned it out anyway. > The problem continued and worsened. It stalled three times one night, each > time starting back up again after a 5 – 15 minutes. I took it back to the > dealer, who replaced the fuel filter, cap, and rotor. I also used some > fuel injector cleaner with a tank of 93 octane (I usually use 89).
If it has a cap and rotor, it’s physically impossible for all cylinders to fire at all the same time. > After burning about nine gallons, the problem continued, and I had it towed > to another mechanic who I trust. I just spoke with him on the phone, and > he says that the plugs are *all* firing every time. The five that are > supposed to be dormant in a given instant fire light. > Any ideas?
Yes get another mechanic!
Response:
Hi Gregory, hmmm…The first problem sounds like a fuel pressure problem, at least that’s what I’d have checked for first. I’m surprised the dealer didn’t. If not a pressure problem, maybe it’s sucking air. The ‘work around’ they fixed has me thinking. It could also be a poor seal on the tank ring, this is where the pickup and the fuel pump mount. But, now that I’m thinking about it, it -could- be sometime goofy like a bad gas cap. The second problem sounds like somebody either didn’t know what they were doing or was having a very bad day. My guess on the spark plug mystery is a really cheap cap and roter was installed and it’s arcing all over the place inside the cap. eab – Hide quoted text — Show quoted text – > I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. > I recently had a dealer replace my fuel tank after a light accident. The > mechanics there said there was a small problem with the hoses connecting > to the fuel pump, but that they worked around it and did not replace the > pump. > I commute 30 miles to work and back every day, at highway speeds. A few > weeks after the gas tank work, the engine started acting up. While > cruising, or while at low speeds, it would lose power very briefly, then > gain it again, sputtering frequently but intermittently. The engine did > *not* do this while idling. Despite not getting any trouble codes from the > computer, I thought it was a clogged EGR. I removed the valve and found > that the carbon wasn’t built up too badly, but cleaned it out anyway. > The problem continued and worsened. It stalled three times one night, each > time starting back up again after a 5 – 15 minutes. I took it back to the > dealer, who replaced the fuel filter, cap, and rotor. I also used some > fuel injector cleaner with a tank of 93 octane (I usually use 89). > After burning about nine gallons, the problem continued, and I had it towed > to another mechanic who I trust. I just spoke with him on the phone, and > he says that the plugs are *all* firing every time. The five that are > supposed to be dormant in a given instant fire light. > Any ideas?
Response:
You should check fuel pressure. I’m betting it’s the filter in the tank. The dealer should have at least replaced the filter also called the sock —
– Hide quoted text — Show quoted text -> I’ve got a ‘94 GMC Jimmy (4.3L V6 Vortec) with 138,000 miles on it. > I recently had a dealer replace my fuel tank after a light accident. The > mechanics there said there was a small problem with the hoses connecting > to the fuel pump, but that they worked around it and did not replace the > pump. > I commute 30 miles to work and back every day, at highway speeds. A few > weeks after the gas tank work, the engine started acting up. While > cruising, or while at low speeds, it would lose power very briefly, then > gain it again, sputtering frequently but intermittently. The engine did > *not* do this while idling. Despite not getting any trouble codes from the > computer, I thought it was a clogged EGR. I removed the valve and found > that the carbon wasn’t built up too badly, but cleaned it out anyway. > The problem continued and worsened. It stalled three times one night, each > time starting back up again after a 5 – 15 minutes. I took it back to the > dealer, who replaced the fuel filter, cap, and rotor. I also used some > fuel injector cleaner with a tank of 93 octane (I usually use 89). > If it has a cap and rotor, it’s physically impossible for all cylinders to > fire at all the same time. > After burning about nine gallons, the problem continued, and I had it > towed > to another mechanic who I trust. I just spoke with him on the phone, and > he says that the plugs are *all* firing every time. The five that are > supposed to be dormant in a given instant fire light. > Any ideas? > Yes get another mechanic!
