Engine acts like its got a vacuum leak but I cant find it. Spark plugs are fouled though

[MadMax_636]

As the title states. My spark plugs are fouled and my engine wont stay running. Its acting like theres a vacuum leak. Ive used stater fluid everywhere and the only point that seemed to be a problem area was the EGR block off plate/gasket. I have since replaced it and it still wont stay running. the carb bowl is full (Fuel is pumping and getting to the bowl) but shes only "runs" if I put a rag/towel over the air horn. She doesnt like it when I pump the gas. It stalls out.

Me in my infinite stupidity decided to mess with it at 1 (When I got home from work) because the PCV was causing a high idle and kept causing my timing to go out of wack. So I decided to **** around with it until it stopped running....

 

[RonD]

When you Choke the engine, put a towel over the carb opening, you increase the Suction at the Jets pulling in more fuel
Thats what the choke plate is for, to run engine richer(suck in more fuel) when engine is cold

Yes, if there is an air leak(vacuum leak) below the throttle plate that also decreases suction at the Jets so blocking off the air intake would increase suction back enough to keep fuel flowing

But fouled spark plugs doesn't fit with clogged Jets or air leaks, unless they are OIL fouled

Clogged exhaust can also cause similar symptom and foul spark plugs
An Engine is a self powered air pump, if air can't get out(exhaust) then new air can't get in(air/fuel mix)
A Vacuum gauge can help test for this

 

[Shadowrider6661]

If your truck has a catalytic converter, it could be plugged causing your engine troubles. I went through this with a car I had many years ago. It's something you might want to check.

 

[MadMax_636]

When you Choke the engine, put a towel over the carb opening, you increase the Suction at the Jets pulling in more fuel
Thats what the choke plate is for, to run engine richer(suck in more fuel) when engine is cold

Yes, if there is an air leak(vacuum leak) below the throttle plate that also decreases suction at the Jets so blocking off the air intake would increase suction back enough to keep fuel flowing

But fouled spark plugs doesn't fit with clogged Jets or air leaks, unless they are OIL fouled

Clogged exhaust can also cause similar symptom and foul spark plugs
An Engine is a self powered air pump, if air can't get out(exhaust) then new air can't get in(air/fuel mix)
A Vacuum gauge can help test for this

Yeah, I couldnt find any sort of leak under the carb/throttle blades. I sprayed starter fluid all over it and nothing affected it. The only place that did affect it was the EGR block off gasket. Which i replaced after finding it. I changed it and it didnt seem to help. I just got my spark plugs replaced (As in, I took them to the auto part store and they tool the old and gave me new ones)

Im gonna gap them and install them and see what happens. I was thinking about maybe taking some carb cleaner and seeing if anything comes out the idle screw ports as well as the jet ports.

 

[MadMax_636]

If your truck has a catalytic converter, it could be plugged causing your engine troubles. I went through this with a car I had many years ago. It's something you might want to check.

Yeah, My truck doesnt have a cat and its also got a glasspack exhaust which is fairly new. So I dont think its clogged.

 

[RonD]

Block off PCV Valve port and Power brake port, see if either changes the symptom

 

[MadMax_636]

Block off PCV Valve port and Power brake port, see if either changes the symptom

Already did. When I remove the brake booster line. It just dies. So Im gonna leave it hooked up since its holding vacuum.

 

[MadMax_636]

UPDATE: I took the carb off, looked it over. the mounting gaskets are worn out (Turn and ripped) and the carb is a little dirty. Im gonna clean/flush out the carb's passage ways.

 

[Shadowrider6661]

It was just a thought. I hope your problem gets resolved quickly, it sucks having to chase down problems like that.

 

[MadMax_636]

It was just a thought. I hope your problem gets resolved quickly, it sucks having to chase down problems like that.

Thanks! Im hoping I can get this fixed. I ordered new fel pro gaskets and they are supposed to come Thursday...

 

[MadMax_636]

UPDATE: I flushed out the carb, rebuilt it 100%, and put brand new base gaskets.

It worked, I also hooked my PCV valve onto the vacuum Christmas tree. I mainly did that to help with keeping the carb clean, and removing any vacuum leaks on the carb level. I also set my timing with the PVC not hooked up. I set it to 12. Mainly because I can read 12 better on my harmonic. I also set my idle mix screws at the same time. I then re-hooked my PCV valve back up.

 

[RonD]

Good work

 

[MadMax_636]

Good work

Thanks!