Slight miss during idle, lots of new parts. What next?

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TXd150

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318
I have a '87 D150 with 318/auto 2bbl
I have installed new plugs,wires,cap,rotor,temp sensor,and EGR valve. The truck seems to run well on the road,smooth that is. I do feel a slight miss/fumble during idle after the truck has warmed up. I checked around for obvious vacuum leaks but haven't done any true vacuum testing. Any suggestions on where to start looking for the cause of this miss?
 

Deblackmon3

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I want to say that you're running a tad bit lean, and your engine missing is your engine soft seizing. Since you already replaced a lot of parts that could cause this, I'd say there is a vacuum leak somewhere in the line.

Again, I'm no expert so don't quote me on this repair. Honestly, I wish that was what's wrong with my engine. A slight miss during idle would be a dream, since I surge almost always and run incredibly hot all the time. If I don't rebuild my engine soon my engine will be ******.
 
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TXd150

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Did some checking around yesterday and found that my EGR was leaking around the gasket. I tightened it down and help a little. Plan on removing it and adding some gasket sealant to cure the leak. I still think its something else. BTW, like your truck. I wish I could see my grille. It's hiding behind a ugly ranch grille protector.
 

Deblackmon3

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Did some checking around yesterday and found that my EGR was leaking around the gasket. I tightened it down and help a little. Plan on removing it and adding some gasket sealant to cure the leak. I still think its something else. BTW, like your truck. I wish I could see my grille. It's hiding behind a ugly ranch grille protector.


Good job finding (part of) the leak. Question though, did you HAVE to replace the EGR? Sometimes the valve just gets dirty from carbon buildup, so you just have to clean it instead of replacing.

If it is still skipping, I think that would definitely be a vacuum leak somewhere, but not enough to be detected without equipment. I feel it's probably a hose clamp that isn't tight enough or was over-tightened and cut into the hose. Go ahead and get a vacuum pump. If the suction isn't as high as it should be, spray some soapy water around all of the hoses and components that use the vacuum, then start the engine. Any leaks will start to make bubbles.

Thanks for the truck compliment! I'm having to actually take it off the road because the engine is so damaged, I don't want to have it nuke itself. I saw a Ramcharger a few days ago that had the front grill off of one of those armored trucks that move around money for banks. He just welded it to the front bumper.
 

LB3711

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Sounds like not enough fuel.


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TXd150

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Good job finding (part of) the leak. Question though, did you HAVE to replace the EGR? Sometimes the valve just gets dirty from carbon buildup, so you just have to clean it instead of replacing.

If it is still skipping, I think that would definitely be a vacuum leak somewhere, but not enough to be detected without equipment. I feel it's probably a hose clamp that isn't tight enough or was over-tightened and cut into the hose. Go ahead and get a vacuum pump. If the suction isn't as high as it should be, spray some soapy water around all of the hoses and components that use the vacuum, then start the engine. Any leaks will start to make bubbles.

Thanks for the truck compliment! I'm having to actually take it off the road because the engine is so damaged, I don't want to have it nuke itself. I saw a Ramcharger a few days ago that had the front grill off of one of those armored trucks that move around money for banks. He just welded it to the front bumper.

Not for sure if the EGR needed replacement, it was the original 1987 valve. I still have it, plan to test it. If its good then I'll clean it and put it back on. Reason being, the new valve vacuum nipple is clocked on the wrong side. I prefer it the way it was originally.
 

Deblackmon3

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Not for sure if the EGR needed replacement, it was the original 1987 valve. I still have it, plan to test it. If its good then I'll clean it and put it back on. Reason being, the new valve vacuum nipple is clocked on the wrong side. I prefer it the way it was originally.

When you mean the vacuum nipple being clocked on the wrong side, what do you mean by that? Could I see a picture possibly?
 
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TXd150

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Don't have a pic but the nipple on the EGR valve that the vac line connects to is pointed towards the carb. The original is pointed towards the valve cover. At first I thought it went the other way but looked under the valve and installed it the correctly. Aftermarket EGR from autozone is pointed in the opposite direction.
 

Deblackmon3

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Don't have a pic but the nipple on the EGR valve that the vac line connects to is pointed towards the carb. The original is pointed towards the valve cover. At first I thought it went the other way but looked under the valve and installed it the correctly. Aftermarket EGR from autozone is pointed in the opposite direction.

As long as the hose is long enough to reach it, it should be fine. I still would try to clean the old one though if you can salvage it, then return the new one, again if you can. Make sure after you clean and reinstall it that it doesn't affect performance any.

Did you tune the carb after installing the autozone one? That may cause it to have a miss. If not, the carb may still be tuned to the old one, which will be great if you clean it and it runs well.
 

88rambigblock

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have you checked timing?
 
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