Have you tried leaving this disconnected from the distributor and plugging the supply side?

 

yes. Does not help the cause at all. I did that today to triple check the timing again

 

Curb idle is too low. Should be 650 minimum. Idle up until it stays at 650 minimum. Then in neutral or park if the idle is slightly too high turn in the idle mix screws bit by bit 1/8th turn at a time. They should be about equal in setting on each side too since there's one for each bowl.

Spray it good with cleaner and drive it hard. If that doesn't clean it out and allow you to set idle then look at rebuilding your carb. Did you open the top and inspect the bowls and floats? Clean or dirty?

Get it driveable then clean it out good on the freeway.

 

Yeah I’ve played with the idle screw and mixture screws so much it’s annoying. Problem is if I turn the idle screw up so it idles at 650 in gear then it idles at like 1200-1300 in park and that still doesn’t address the how much the rpm’s fluctuate. I tend to agree that I think it’s the carb but I know others think it’s vacuum.

 

Did you try to lower the idle in park or neutral by turning in the idle mix screws?
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How many turns out are they now?

 

I’ve tried everything there is to try with the mixture screws and idle screw. Nothing changes the huge drop and gap in rpm’s or the fluctuations. The screws are currently at 3 full turn out. Exactly where they were when the truck was last running well with none of these symptoms.

 

Just re-read my thread from 2 years ago on the exact same issue.

https://www.ford-trucks.com/forums/1...ion-issue.html

Replacing the carb ended up solving the problem. However I ended up getting the same edelbrock 1406 out of comfort. I mean… what are the odds I’m having the same exact issue 2 years later under the same circumstances and same model carb? Truck sat for 6 months before the issue)

Thinking of just replacing it all together and going with a summit. It looks like the M2008 would be the model. Would be nice if I could still use the 4 bore edelbrock phenolic spacer I just got with the summit. Shouldn’t be an issue right? Also I’m not sure how I have to adjust back to this style carb as it’s already set up for a edelbrock. Any tips on that?

 

That summit carb got good ratings. When you call Summit talk with the sales person and ask them any questions.

 

The important thing is to make sure your money tree is properly watered and fertilized. Check the soil pH, too. If your local university has an agricultural program, they may be able to help with the testing. These are all important factors to make sure your money tree thrives and produces a healthy crop. Never been much of a green thumb, myself. I tried planting a money tree, but it never bore fruit. Kinda like that time I planted bird seed. Didn't get a single bird out of the whole bag. What a waste of money.

The preceding was industrial strength humor to make a point. Is your present carb at fault? Heck if I know. Mostly we've had you work at ruling out other potential faults, until you end up at the carb by process of elimination.

You've ruled out some of the big stuff, such as disconnecting and plugging all vacuum lines on the carb and intake manifold. That's where I thought we'd find something.

Have you tested the PCV system? The PCV valve is supposed to be closed at idle. Try disconnecting and plugging the big line at the PCV valve. This should be about a 1/2" diameter line feeding somewhere at the carb base.

Did you ever test the distributor's centrifugal advance? Long thread, can't remember all the details. This is another quick and easy test.

 

Most spec idle screws are in the range of 1.5 to 2 turns out. When you got the carb what was the initial setting? How did you arrive at three turns?

If this issue started out after some sitting time hitting the highway for a tank of Techron might clear your carb out.

 

Just double checked under the cap. The centrifugal advance turned sightly and snapped right back. Seems that’s fine.

Pulling and plugging the PCV line at the valve had no change. It’s definitely not surging as much as it was before Deleted the EGR but it’s stalling when I put it in gear and wants to when I turn the wheel in park.

 

I don’t remember honestly it’s just where it was when it last ran well. 1 turn in or out doesn’t really change much anyway. The idle really only starts to drop when it’s around 1 turn or less.

 

The main issue at this point is the large drop in rpm’s from park to drive. It drops by like 500, so at the moment unless I have the rpm’s at like 1200 in park it will stall when I put it in gear. If it doesn’t stall it will as soon as I turn the wheel. Also, if it’s in park and give it some throttle the rpm’s drop really low and almost stall when I let off before going back up to idle. The surging seems like it might be a bit better after deleting the EGR but I haven’t really driven it to confirm.

 

Try setting your idle mix screws at 1-1/2 out. Adjust the idle in R to 650. What is the idle in park? Too high? Then try another 1/4 turn in on the mix screws and reset idle in R to 650. What is the idle in park? Did it go down? If so go 1/8 turn more on the mix. Repeat till you get your best idle in park with a 650 in R or D. Then at 650 can you turn with out stalling? If so you're dialing it in. Your rpm surge improved significantly by taking the EGR out of the loop.

3 turns out is just about to the point that the adjustment is jet orafice size limited. In other words max fuel. Are you sure no body kluged the seat or needle? If that's been done number of turns on the screw don't give the same results as spec.

 

I would pull the vacuum advance line off and plug it like Karl said. I know you said you did this several times with no results, but I get the feeling you pulled the line off and plugged it, got in the truck and put it in gear, it still stalled, so no luck. This is not how it should go.

If you have vacuum on the dist at idle, when you pull the vacuum off and plug it the idle speed should drop. After this happens you need a total retune of the carb. That would be let the engine idle down slow and re-adjust the idle mixture screws and then turn the idle speed back up to a reasonable idle. Leave the line unplugged and drop it in gear and see what it does then.