Engine intermittently dies and runs rough.

[JDub]

78 K10 350 th350

I have been trying to find my problem and I'm not sure where to look next.

Truck starts fine every time. Sometimes I can go a day or two with a of an issue sometimes I can't make it out of sight from the last time it died. It will seem to run fine then seemingly for no reason it will start surging and missfiring. This usually causes it to "diesel" a little then die. Some times I can bring her back by putting it in natural and putting my foot down on the gas. If that works she will rev strong untill I put her back in drive then she starts to miss fire again.

Once it dies sometimes she will fire right back up. Sometimes I have to wait a few minutes. Once that happens I'm lucky to make it a half mile before it does it again.

2 months ago I did a complete rewire of the truck
this problem stared about 2 weeks ago.
I have replaced the cap, rotor, coil, and plugs. Cap and rotor where obviously bad. Coil had some surface rust. Plugs seemed fine but I replaced any way; gapped to .045

After the repairs she would seem better for a short while then this would all start again. When she is running good she is strong and smooth.

 

[rich weyand]

Did you get the grounds right on the rewire? The cab, the engine, and the frame are all connected to each other with rubber bushings, so they need to have explicit grounds between them. The standard grounds are: battery to engine -- heavy battery cable to the alternator bracket; battery to frame -- second smaller wire of the battery cable to the radiator crossmember right above the battery; engine to cab -- a copper braid from the rear of the passenger side head of the engine to the firewall.

 

[JDub]

All the grounds are good. All new battery cables. Ground to alternator bracket is new and bigger then stock. Grounds from battery to frame and radiator are also new. All other electrical seems to be fine. I'm running duel batteries.

I'll have to check the engine to cab. I don't remember messing with that one. Not even sure I've seen it honestly. Thanks for the tip.

 

[rich weyand]

Missing that ground can cause all kinds of bizarre difficulties. Here is where it is. It should probably be connected to the power steering pump mounting hole (which appears on the back of the passenger side head as well as the front of the drivers side head) rather than to the valve cover bolt, but it's working OK for me so far.

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[350runner]

How about the spark plug wires, ignition module, or pick up coil inside the distributor.

Sent from the dust in front of you!

 

[JDub]

Thanks for all the leads. Based off what i see here and talking to a couple of other people I'm leaning twords the ignition module. I'll know in a few hours. I'm going to replace it when the parts stores open and see what happens. Considering the cap and rotor where visibly damaged it only makes sence that the module would be damaged too. This is my first vehicle with HEI so I'm a little out of my element here.

Thanks for everything.

 

[JDub]

I replaced the ignition module and now my truck is running worse then it was before. It's the same basic issue but now instead of making it down the road a little before it had problems I cant even get it out of my driveway.

 

[rich weyand]

Did you check for that ground strap?

 

[350runner]

Check the wires going to the pickup coil really good for cracks... That's where I'd start. You have good grounds. It sounds more like cracked wires inside your distributor since you say it got worse after you changed the module

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[79K10]

did you say you had to floor it to get it to fire up again? mine did that, tapped the carb with a LFH and knocked it loose, ran great again after that ...

i had a similar electrical issue and i found my positive battery wire had hooked up with a header and started cooking the wires a little at a time.

 

[MadOgre]

I would think its an intermittent vacuum leak or crud in the carburetor maybe clogged fuel filter too

 

[InjPerf]

This sounds more like a fuel issue than electrical. The symptoms sound like early warnings of a fuel pump failure. When it dies, pull the air cleaner lid off and look down the carburator primary and look for the accelerator pump shot when pumping the throttle. If you do not see this shot of fuel the carburator has no fuel which indicates the fuel pump failing. It can be a stuck needle and seat but that is not as common of an issue.

 

[chengny]

I wouldn't spend too much time diagnosing this one - it appears that after 4 posts back in October, that was it.
It seems that JDub has left the house.

Or maybe he's still in the driveway?

 

[Skweegle89]

Lol


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[350runner]

Haaaa!

Sent from the dust in front of you!