Vehicle Not Driveable Unless Disconnect Base Timing Wire

[polter6stowtel]

1995 GMC C3500 Redgular Cab 5.7L TBI 4L80E, Cruise Control (stays off)

 

About a month and a half ago I had the motor replaced. The rpm gauge jumped around at least after the motor was replaced, maybe before. I don't recall.

It ran fine for maybe a week, then I noticed what felt like slight misfires only on the highway. At this point, I replaced the plugs, wires, cap, and rotor. It had some more get-up with the new parts. However, the problem got worse. Soon thereafter, I replaced the ignition coil. Around town or idling, the vehicle would sputter intermittently and jar around. I could hear the skips in the exhaust when this happens. It generally would run fine for a few minutes, then sputter for a few seconds.

Next, it ran out of gas, so the fuel pump went bad. I replaced the whole pump and sender assembly, and filter. It persisted and got worse. I then installed a different, and very clean, throttle-body assembly from a '94. It had a bad TPS, but I just swapped it out for the old one. It continued to sputter and get worse. Then I realized I had water in the fuel tank from some old gas can I took fuel from. I disconnected the lines, ran the pump until empty, and put on a new fuel filter. Problem gets worse yet. Although, at this point, I pressed the rotor down on the distributor a little more, and it cleared up noticeably, but not for long.

It would typically drive worse at night. 0 - 20mph in two minutes. At this point, it would idle well for a few seconds, then sputter for almost a minute. This whole time, it would much better in the rain; hardly a miss. Throughout all this, it either sounds fine, or sputters terribly. It wasn't until later that it would pop loudly out the tailpipes after sputtering for a few minutes at a time.

Later, I found a sort-of remedy. If I disconnect the base timing wire (the tan wire under the glovebox which you disconnect to set the base timing) before I start it, it will run smoothly. I understand that it gets way too much fuel if I do this, but it is the only way it's driveable. I reconnect the wire before driving just in case it makes a difference. The vehicle sound is deeper and the gas mileage is terrible. Also, fuel enters the oil, so I change the oil rather frequently.

When I start and drive it after disconnecting the wire, the rpm gauge works perfectly, but now the speedometer jumps around. I just replaced the distributor with a Cardone reman., and I tried setting the timing a few different spots, but to no avail.

I think there may be a bad computer ground or something, but there is nothing I can find. It hasn't rained in a while, so I don't know how that would be. I just continue my wire-disconnect trick until I can learn any more. The exhaust does not have any cats, so there shouldn't be any problem.

I looked for another post that could address this, but I couldn't find any using search, and 370 is a lot to cover haha. I think this situation is rather unusual, but I could be wrong. Nonetheless, I thank anyone for advice.

 

 

P.S.

 

 

I'm curious exactly where 0 degrees BTDC is because the timing indicator above the harmonic balancer has several aeros. Thank you.

[rockcrusherrevived]

sounds like one of the wires on the pick-up coil is just about broken clean through pull the distributor and change the pick-up coil

 

 

 

1995 GMC C3500 Redgular Cab 5.7L TBI 4L80E, Cruise Control (stays off)

 

About a month and a half ago I had the motor replaced. The rpm gauge jumped around at least after the motor was replaced, maybe before. I don't recall.

It ran fine for maybe a week, then I noticed what felt like slight misfires only on the highway. At this point, I replaced the plugs, wires, cap, and rotor. It had some more get-up with the new parts. However, the problem got worse. Soon thereafter, I replaced the ignition coil. Around town or idling, the vehicle would sputter intermittently and jar around. I could hear the skips in the exhaust when this happens. It generally would run fine for a few minutes, then sputter for a few seconds.

Next, it ran out of gas, so the fuel pump went bad. I replaced the whole pump and sender assembly, and filter. It persisted and got worse. I then installed a different, and very clean, throttle-body assembly from a '94. It had a bad TPS, but I just swapped it out for the old one. It continued to sputter and get worse. Then I realized I had water in the fuel tank from some old gas can I took fuel from. I disconnected the lines, ran the pump until empty, and put on a new fuel filter. Problem gets worse yet. Although, at this point, I pressed the rotor down on the distributor a little more, and it cleared up noticeably, but not for long.

It would typically drive worse at night. 0 - 20mph in two minutes. At this point, it would idle well for a few seconds, then sputter for almost a minute. This whole time, it would much better in the rain; hardly a miss. Throughout all this, it either sounds fine, or sputters terribly. It wasn't until later that it would pop loudly out the tailpipes after sputtering for a few minutes at a time.

Later, I found a sort-of remedy. If I disconnect the base timing wire (the tan wire under the glovebox which you disconnect to set the base timing) before I start it, it will run smoothly. I understand that it gets way too much fuel if I do this, but it is the only way it's driveable. I reconnect the wire before driving just in case it makes a difference. The vehicle sound is deeper and the gas mileage is terrible. Also, fuel enters the oil, so I change the oil rather frequently.

When I start and drive it after disconnecting the wire, the rpm gauge works perfectly, but now the speedometer jumps around. I just replaced the distributor with a Cardone reman., and I tried setting the timing a few different spots, but to no avail.

I think there may be a bad computer ground or something, but there is nothing I can find. It hasn't rained in a while, so I don't know how that would be. I just continue my wire-disconnect trick until I can learn any more. The exhaust does not have any cats, so there shouldn't be any problem.

I looked for another post that could address this, but I couldn't find any using search, and 370 is a lot to cover haha. I think this situation is rather unusual, but I could be wrong. Nonetheless, I thank anyone for advice.

 

 

P.S.

 

 

I'm curious exactly where 0 degrees BTDC is because the timing indicator above the harmonic balancer has several aeros. Thank you.

[polter6stowtel]

Do you mean there may be a broken wire on the new distributor?

I just installed it today and didn't notice anything that looked in poor condition or out of place. I even just completely disassembled the old one, and it looked fine. I've been stumped for a while on this one haha.

 

I probably should have mentioned that it sputters no matter how much or how quickly I give it throttle.