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rough running motor

nd4spdnd4spdMember
My GT5 has been running very rough. For a short period of time, like a couple of blocks, it will run fine. Then it feels like the ignition cuts out and in. It bucks like riding a wild bull. Has anyone else had this issue?

I took it to a local mechanic that works on older foriegn cars. He replaced the fuel pump (it was leaking), plugs, distributor, wires, and rebuilt the alternator (it wasn't working). He test drove it and it ran fine. Then went to start it and it would start. He replaced the coil for the second time. The car started and ran fine. I picked up the car and it ran fine for about 6 blocks and then it started acting up. The issue seems to occur randomly...doesn't matter what speed or if it's accelerating or not.

The only thing I can think of is that there is a short somewhere or that the ignition needs to be replaced. The mechanic thinks that the next thing to replace is the ignition. Has anybody else had this problem? Thoughts?
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garth66garth66"When speed is the only thing that counts"
What ignition system are you using? Mallory Unilite? How old is the module? Mallory revised the module a few years ago which makes it more reliable. Also, has the car been welded on before these symptoms started? My 6AL box was exhibiting the same symptoms when the box got hot (mounted on firewall above starter solenoid - car would die, pull over, sit for 5 minutes and it would start back up, then repeat after another couple miles.

I just installed the Pantera Electronics EIS - very well engineered, great features, and fantastic support from Jon! Costs slightly more than an MSD or Mallory box, but American made and many more features than either of the mainstream Chinese-made boxes offer! So, well worth the investment!
http://www.pantera-electronics.com/eis.htm

FWIW, I'll be adding the Pantera Electronics EIS to my Mustang as well.
bosswrenchbosswrenchMember
The ignition switch (electrical portion) is known to get 'tired' after 45 or so years and do intermittent things like you describe; also the internal spring gets tired.... When replacing an ignition switch, its best to deal with a vendor or someone that is intimate with the NINE POSSIBLE 'Pantera' switches you might find. Some will plug into the stock wiring loom(s) while others have extra wires or missing ones, wrong color codes. A few complete switches will not bolt onto the stock steering column, or are too short to protrude from the plastic covers. All in all, if it IS the switch, it may be smarter to send it in to an expert for a rebuild. Note- that will NOT be me!
panterachrispanterachrisMember
You know it sounds like a simple stuck float, lightly tap with the handle of a screwdriver on the side of the primary float bowl, if it's stuck it should let go and the car will run right, until it gets stuck again. When was the last time you rebuilt the carb? Sitting for long periods can turn that crappy gas into varnish and cause the needle and seat to stick.This will make your car buck, cut off then surge and even starve the engine to a stop! It sounds like your mechanic is fixing everything but the problem.
quote:
Originally posted by ND4SPD:
My GT5 has been running very rough. For a short period of time, like a couple of blocks, it will run fine. Then it feels like the ignition cuts out and in. It bucks like riding a wild bull. Has anyone else had this issue?

I took it to a local mechanic that works on older foriegn cars. He replaced the fuel pump (it was leaking), plugs, distributor, wires, and rebuilt the alternator (it wasn't working). He test drove it and it ran fine. Then went to start it and it would start. He replaced the coil for the second time. The car started and ran fine. I picked up the car and it ran fine for about 6 blocks and then it started acting up. The issue seems to occur randomly...doesn't matter what speed or if it's accelerating or not.

The only thing I can think of is that there is a short somewhere or that the ignition needs to be replaced. The mechanic thinks that the next thing to replace is the ignition. Has anybody else had this problem? Thoughts?
panteradougpanteradougMember
I vote on the ignition switch. The "run" contact internally is loosing it's ability to make constant contact.


I agree that the inlet valves can be an issue but what they normally do is stick open after the carb was permitted to evaporate it's fuel out of the bowls after the car sits for a while.

The dried ethanol gas acts like a glue until the fresh gas cleans it off, acting as a solvent.

The problem is that the valves are stuck open and the carb will flood big time, like Niagara Falls.

Holleys are particularly susceptible to this, Webers not so much but I don't see that in the description of the symptoms.


Ignition switch symptoms can vary. I had one where the car would turn over and start but when you released it from the start to the run position it would shut off.

Dried electrical grease internally was evident when I opened it. No sign of burnt contacts.

The spring loaded contact pins were no longer moving freely up and down because of the dried grease in the switch.
Last edited by panteradoug
panterachrispanterachrisMember
I can only tell you that I experienced the float stuck at the top or closed the car would run fine until it ran out of gas, this also can happen just while you are driving. It is so simple to check, you should try it.
quote:
Originally posted by PanteraDoug:
I vote on the ignition switch. The "run" contact internally is loosing it's ability to make constant contact.


I agree that the inlet valves can be an issue but what they normally do is stick open after the carb was permitted to evaporate it's fuel out of the bowls after the car sits for a while.

The dried ethanol gas acts like a glue until the fresh gas cleans it off, acting as a solvent.

The problem is that the valves are stuck open and the carb will flood big time, like Niagara Falls.

Holleys are particularly susceptible to this, Webers not so much but I don't see that in the description of the symptoms.


Ignition switch symptoms can vary. I had one where the car would turn over and start but when you released it from the start to the run position it would shut off.

Dried electrical grease internally was evident when I opened it. No sign of burnt contacts.

The spring loaded contact pins were no longer moving freely up and down because of the dried grease in the switch.

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