Loping idle

[Finnegan1008]

If my truck is in gear and warmed up my idle starts to chop. It’s a fairly consistent and rhythmic lope.

Like a brap-brap-brap-brap and it rocks the truck slightly.

The previous owner supposedly installed a very low mileage engine out of another CUCV. Other than that I have no idea what the history is.

Any idea what may be causing this? Is it something I should be concerned about? Or can I live with it?

 

[Barrman]

Try moving your idle up or down just a bit. A little change makes a big difference with all the rattle noises inside the truck.

If all your filters are newish and your Injection Pump timing is close. Then idle or the IP itself are about all that is left if you have no weird knocks or smoke of any kind.

 

[87cr250r]

That sounds like a misfire. Are you getting any bubbles in the radiator?

 

[Finnegan1008]

Try moving your idle up or down just a bit. A little change makes a big difference with all the rattle noises inside the truck.

If all your filters are newish and your Injection Pump timing is close. Then idle or the IP itself are about all that is left if you have no weird knocks or smoke of any kind.

If I give it just a hair more idle from the throttle pedal it smooths out. Zero smoke

 

[Finnegan1008]

That sounds like a misfire. Are you getting any bubbles in the radiator?

I’ll check, not seeing any coolant smoke from the exhaust.

If I give it even a hair more throttle she smooths out.

 

[Finnegan1008]

That sounds like a misfire. Are you getting any bubbles in the radiator?

Crap… just did a cold start this morning, pulled the radiator cap off and sure enough it’s bubbling. I assume this is a head gasket problem?

What are the odds this will be fixed with just a R&R of head gaskets?

 

[87cr250r]

From your picture, I don't think that is enough bubbles to indicate a misfire causing head gasket leak.

Crack injector lines to see if you can pinpoint the misfiring cylinder. There will be no change in idle when you hit the bad one.

 

[Finnegan1008]

From your picture, I don't think that is enough bubbles to indicate a misfire causing head gasket leak.

Crack injector lines to see if you can pinpoint the misfiring cylinder. There will be no change in idle when you hit the bad one.

So if I ID a bad injector does that mean replace just the one? Or do I need a set?

 

[87cr250r]

You can replace one. They're expensive right now. 3 years ago new injectors were $25 a piece. They're closer to $50 each right now.