Engine juddery, loss of horsepower.

[None_zero]

I currently have the vac advance going to the middle port on the brown valve I will move it to the bottom. What goes on the middle?

[None_zero]

Ok let me see if ive got this.... from the carb front port connects to the hardline that connects directly to the vacuum advance. This line also branches off and connects to the bottom of the brown valve. The hose attached on the purge can(marked vac dist) connects through the hard line to the middle of the brown valve now the carb the vacuum adv. And the purge canister are connected to the brown valve via the two bottom ports and the top port of the brown valve goes to the air filter housing which is open to incoming air??

Edited February 23, 2023 by None_zero
Typed it wrong

[None_zero]

Does that sound right or should I try to take pictures 

[None_zero]

Then also the middle hardline connects to "purge" and then on the other side its on the bottom of the 3 port metal line coming out of the plenum just for the sake of being thorough 

[datzenmike]

Sounds right. The middle port on the TVV is for the EGR.

 

The TVV when the engine coolant is cold is open to the air and this leak destroys the vacuum signal. When the TVV warms up the air leak is closed off and the vacuum passes on to the vacuum advance or the EGR valve. When the valve cools down the blockage clears. I guess the vacuum advance and the EGR operate at different engine temperatures. In both cases the vacuum advance and the EGR are ported above the throttle plate and there should be no vacuum signal at idle.

 

I was hoping the top hose was connected to the intake vacuum and that was the source.

 

Anyway leave the vacuum advance hose off the carburetor for now, set the timing and we'll continue on, perhaps the cause will correct itself with something else we fix.

[None_zero]

It's warming up now idling first a bit fast then slowed down almost stalling so I upped the throttle a bit then it jumped up to 1500 rpms so I adjusted down. I'm just trying to keep it in a nominal range until it reaches operating temp so I can dial in the rmps and timing and then set the idle mix and see where we land 

[None_zero]

1 minute ago, datzenmike said:

Sounds right. The middle port on the TVV is for the EGR.

 

The TVV when the engine coolant is cold is open to the air and this leak destroys the vacuum signal. When the TVV warms up the air leak is closed off and the vacuum passes on to the vacuum advance or the EGR valve. When the valve cools down the blockage clears. I guess the vacuum advance and the EGR operate at different engine temperatures. In both cases the vacuum advance and the EGR are ported above the throttle plate and there should be no vacuum signal at idle.

 

I was hoping the top hose was connected to the intake vacuum and that was the source.

 

Anyway leave the vacuum advance hose off the carburetor for now, set the timing and we'll continue on, perhaps the cause will correct itself with something else we fix.

Oh sorry I jumped the gun I guess. You want me to cut it off and remove the vac adv line ?

[None_zero]

Ok i cut it off. Something still isn't right after it hit op temp I adjusted the timing back again and tach reading 600-700 but I think it's still reading wrong so what's the next move I remove the vac advance line from the carb and cap it? And then what?

[datzenmike]

Just disconnect the vacuum advance from the carburetor... for now. It's messing up the setting of the timing.

[None_zero]

8 minutes ago, datzenmike said:

Just disconnect the vacuum advance from the carburetor... for now. It's messing up the setting of the timing.

Ok did that. I set the timing at 5° and drove it a bit with the vacuum disconnected and capped but otherwise in the same set up it was after the adjustments. Just to make sure I'll be able to get to work tomorrow. I noticed while I was driving it that the voltage light is on but just barely you'd never see it in the day time or probably even in a well lit street 

[None_zero]

And still drinking gas. I'm starting to wonder if I'm not leaking gas somewhere I've done a perfunctory check around the tank and the lines but haven't really got up under there searching. Other noteworthy things I found a leak in the line that goes to the purge connection. On the canister. 

[datzenmike]

Faint charge light only seen at night is normal.

[None_zero]

18 hours ago, datzenmike said:

Sounds right. The middle port on the TVV is for the EGR.

 

The TVV when the engine coolant is cold is open to the air and this leak destroys the vacuum signal. When the TVV warms up the air leak is closed off and the vacuum passes on to the vacuum advance or the EGR valve. When the valve cools down the blockage clears. I guess the vacuum advance and the EGR operate at different engine temperatures. In both cases the vacuum advance and the EGR are ported above the throttle plate and there should be no vacuum signal at idle.

 

I was hoping the top hose was connected to the intake vacuum and that was the source.

 

Anyway leave the vacuum advance hose off the carburetor for now, set the timing and we'll continue on, perhaps the cause will correct itself with something else we fix.

So what is our next move. Do we focus back on. The carburetor and try to figure out why the idle mix screw isn't affecting the idle the way it should. Or should I do thorough search of the fuel lines from tank to carb? Or am I at replace the fuel pump and filter with appropriate replacement? And then what about the tachometer reading wrong. I suppose that suggests I've got multiple problems layered on top of each other? What's the best option you think? Don't think I even want to get into the wiring under the dash until I've got a fsm in hand to reference because that is a confusing mess  @datzenmike

Edited February 23, 2023 by None_zero

[None_zero]

Hey I just noticed the idle speed doesn't rise when I press the clutch now. Is that because we unhooked the connection over by the coils? 

[None_zero]

To add something positive, it's actually running pretty well, aside from the absolutely soul crushing gas mileage and maybe some loss of horse power in the upper range, it sounds ok and drives pretty decent up to 45 mph or so. Once you get up towards 55 mph it feels like it's struggling just a bit. I think it's safe to say not all 88 of the horses are in the coral, so to speak.

Edited February 23, 2023 by None_zero
Typo

[datzenmike]

14 minutes ago, None_zero said:

Hey I just noticed the idle speed doesn't rise when I press the clutch now. Is that because we unhooked the connection over by the coils? 

 

Probably that single wire on the distributor was unplugged.

 

Try lowering the float in the carburetor.

[None_zero]

1 hour ago, datzenmike said:

 

Probably that single wire on the distributor was unplugged.

 

Try lowering the float in the carburetor.

Ok I'll do it but isn't that going to unfix the Gas spitting issue? I checked and the wire is attached to the distributor 

Edited February 23, 2023 by None_zero

[DwayneOxford]

I'm wondering about timing chain and tensioner.

[datzenmike]

It might contribute some noise but does not explain the MPG and poor idle or the tach.

 

Lower the float some more, see if that helps the mileage. keep lowering till it affects the driving then raise it slightly to fix that. In the mean time gas smells so if there's a leak equal to half your mileage you should be able to see wetness under the truck or smell it.

 

48 minutes ago, None_zero said:

Ok I'll do it but isn't that going to unfix the Gas spitting issue? I checked and the wire is attached to the distributor 

 

WHAT??? I thought you took that off? If still connected take it off. Then check and set timing.

[None_zero]

44 minutes ago, datzenmike said:

It might contribute some noise but does not explain the MPG and poor idle or the tach.

 

Lower the float some more, see if that helps the mileage. keep lowering till it affects the driving then raise it slightly to fix that. In the mean time gas smells so if there's a leak equal to half your mileage you should be able to see wetness under the truck or smell it.

 

 

WHAT??? I thought you took that off? If still connected take it off. Then check and set timing.

Ok hang on I'm confused... I thought we were unugging the quick connection

Are you saying I was supposed to remove this

Or is that the same thing?

I'm pretty sure it's not the same but I've been wrong before 

Edited February 24, 2023 by None_zero

[None_zero]

I'm having a difficult time understanding the lowering of the float though, since there was an issue and adjusting the float solved that issue. Are you thinking maybe I went too far? Can you walk me through the logic I don't doubt you I just want to understand 

[None_zero]

I found something

I wiggled these wires on the fuel pump and it started bubbling and gas started coming out. Not a crazy amount but if while driving and the pump is running maybe it's just pumping it out onto the ground..... now that  thinking about this fuel issue in a new way I also notice there is a lot of oily residue around the carb right behind the line that goes to the needle valve and the short section of rubber fuel line looks pretty dry rotted.. I had assumed that residue was oil leaking somewhere but then only place I've had oil coming out is the back of the valve cover gasket by the fire wall though I think I fixed that yesterday 

Edited February 24, 2023 by None_zero

[datzenmike]

2 hours ago, None_zero said:

Ok I'll do it but isn't that going to unfix the Gas spitting issue? I checked and the wire is attached to the distributor 

 

This is what you said. So is that single wire on the distributor attached or not? If it's unplugged what wire were you talking about?

 

[datzenmike]

44 minutes ago, None_zero said:

I found something

I wiggled these wires on the fuel pump and it started bubbling and gas started coming out. Not a crazy amount but if while driving and the pump is running maybe it's just pumping it out onto the ground 

 

 

I think time for another pump. Get something that produces 3-4 PSI.

[None_zero]

1 minute ago, datzenmike said:

 

This is what you said. So is that single wire on the distributor attached or not? If it's unplugged what wire were you talking about?

 

I added photos. We disconnected that quick connect to stop the exhaust side plugs from cutting off. I don't remember you ever saying to disconnect the wire from the dizzy