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'90 Comanche Running Rich And Idle Too Slow

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New to club - first time Comanche. I picked up a 1990 project truck. 4.0 2WD Auto with a paint-bomb finish. I've been going through the prelims. Wires, plugs, cleaned TB, filters, cap/rotor, etc. I had some leaky injectors that O-rings didn't fix, so I replaced them. Other than checking the vacuum lines, that's all I've done. The seller was not the one who drove it, so not a lot he could tell me about the servicing except that the cat. conv. had been removed from the pipe. All that being said for background I guess.


I'm running rich... and was before I "tuned it up". Also, the idle seems to cycle a bit. It goes from normal to almost stalling. When I unplug the vacuum line coming from the rubber grom in the back of the valve cover (ccv)to the manifold, the idle stabilizes.

Is this due to a clogged (thingee) on the valve cover? and is there any way to clean it without taking off the valve cover? Does this relate to the rich condition?

Can any one tell me what I have gotten into and (for God's sake) WHY?!?


Rev. Chris


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Check for vacuum leaks and that the hose from the rear fitting of the valve cover to the intake manifold is clear.


Intake manifold bolts must be snug.


The hose/tube from the throttle body to the MAP sensor on the firewall must be flawless.  


Click on this link and go to posts 1, 3, 4, and 5 and perform the outlined procedures. Preventative maintenance and a good investment of very little time. 


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I have found no vacuum leaks. Not saying that they aren't there hiding.

I removed the ccv hose and checked it. I can feel the gasses coming from it when it is running, and can blow through it when it is off... but I don't know if it is restricted from the norm.

I would have figured it would run poorly when it was unplugged, but unplugging it improves the idle.

I will get on those connections right away, thank you.

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