Anyone?

 

Water is a product of combustion. Pic looks like "acid rain" and mold.

 

I can understand it being moist, but it was puddled in there.

 

Do you HAVE to have the EGR valve? I took mine off my 77 351Measly,, sooo much happier with it off,,, it is a needless part to things,,, although I have to put it on every 2 years for the smog *****,,, it drives like a pig with it on,, the rest of the time I have a nice running truck! Ditch it!

 

Well, Im not going through the trouble of recurving the distributor and trying to get the a/f mixture set correctly. Yeah, its a needless part to an engine, BUT, the carb and dizzy on my truck are set up for an EGR, and Im not changing that. Ive put the valve back on and I'll take the truck for drive later to see if the miscellaneous moisture buildup was the problem.

 

Just went for a test drive, ran terribly with the valve hooked up. Engine makes a sort of a empty rattle can sound and hardly has any power. Same stumbling problem, except on both acceleration and deceleration now. Hmm, come to think of it, I only let the engine warm up for 2 minutes before driving it. The egr shouldn't be receiving vacuum, should it? Bad 2 port PVS?

EDIT: Both valves are closed, so those are fine. Which begs the question, how the heck is the egr getting vacuum? No vacuum should be supplied before the engine reaches operating temp. Maybe the vacuum lines are routed incorrectly. But then why did the truck run fine for those few months and why did this problem slowly develop? So many questions, so few answers...

 

Ok, idea:

Looks like vacuum is switched on/off to the EGR by the TVS (see diagram below). Im just not seeing how this thing works, looks like a piece of rubber with two nipples on the air cleaner. Maybe the truck ran fine for a while because the egr passages had clogged, but getting a new valve slowly freed up the clog and started this problem.

 

The part Im referring to, BTW:

 

Forget the jet idea, ..... get a tee and tie into the "Ported Vacum" tube on the carb and she'll start easier.

Distributor gear on cam will always be pulled tight as it drives the distributor AND oil pump.

Any variation seen in the timing marks is a result of some slop in the crank to cam timing chain as it will slap some and vary the timing (both ign and cam, but you only see it with a timing light) some at lower RPMs as the crank shaft pulsates with power pulses and vacum pulls on intyake straokes of those 8 cylinders.

 

I went to a Edlebrock performer 400 4bbl intake, and Holley 600cfm carb,, never recurved it, runs great,,, adjusted the timing to 8* I think, and have the advance on ported vacuum,,, no stumbling or coughing,, he does like the choke in the cold mornings though,,,

 

It's a possibility of four problems...

1: Plugged exaust or non factory exaust: The EGR valve seen in the pictures is a pintle type backpressure activated valve. The EGR valve needs both vacuum and exaust backpressure to open. If you have too much exaust backpressure it will cause the problem you are describing as the valve will open more than it should.

2: Vacuum to the EGR valve when it shouldn't have it. I would check the vacuum hoses for proper routings. The EGR valve should not be open with the engine cold, or the engine at Wide Open throttle. Check all hose routings, and make sure all components are plugged in. Make sure the proper vacuum restrictor is in the proper vacuum lines: (Some people mistake these for vacuum splices,) they are not, and are usually color coded depending on restriction.

3A: The TVS is a (Thermal Vacuum Switch) and it opens when the ambient air in the air cleaner reaches a certain temperature. It's a secondary activator for the EGR valve but it's not the main one. The main purpose for the TVS is to control the thermactor system air bypass valve for the Air Pump. If you are missing some of the Thermactor system, IE: Bypass valve, lines etc, and the vacuum lines have been plugged in an odd way, this could cause a problem.

3B: There is a four port vacuum check valve (VCV) at the front of the engine. (This is the one I'd be checking.) AKA as Ported Vacuum switches, these are controlled by water temp. Some of the ports remain closed when cold, and then other ports open and close when the water temp warms up. These can fail in a same way a thermostat remains open all the time. These valves are color coded for temps. According to your diagram, your vacuum advance as well as your EGR is controlled by the same vacuum source. Depending on how the VCV is switched, when the engine is warm it increases the vacuum to your vacuum advance, and turns on the EGR valve. When the engine is cold it restricts your vacuum advance and turns off flow to the EGR. If this VCV is malfunctioning then this can cause your problems, especially in cold start conditions. If the VCV has never been replaced in the entire life of the truck, or if all four nipples let vacuum through at the same time when hot or cold, or doesn't change with engine temps, replace them as they do go bad, but make sure they are exactly the same color as original.

4: Defective EGR valve, Mis-application EGR valve, carbon buildup in valve, or improper washer restriction. Make sure the EGR valve is of the exact same part number required, and make sure you used the right washer.

 

WOW. I am curious and would like to know where those four vacuum lines off the ported vacuum switch on the thermostat housing lead to?

 

Ok, Ill try that. Its gonna idle nice and low then, right?

I'd love to do that, but its just not in my budget at the moment.

Reps sent.

1: Hmm, too much backpressure? Could be. Exhaust set up is 2-to-1, then cat (with guts cut out), then flowmaster 40 series 1-in 2-out. The whole system is rusting out. When I first got the truck(It had been sitting for 3 years), there would always be little rusty bits scattered over the driveway from when I started her up. Maybe little rusty bits have flaked off and are plugging the system.

2: Only potential problem area is the TVS on the air cleaner housing. I'll check that later to see if it has closed up when the truck cools down.

3A: Thermactor system is intact and routed correctly.

3B: 4 port PVS was replaced a few months ago, verified working. Other PVS is a 2 port and also verified working. Now that I think of it though, maybe the lines arent connected to the correct nipples.

4: There was a block-off plate on the spacer when I got the truck. I bought a new valve and found the possible part numbers online. Two possible washers and the one I put in was the smaller of the two.

Too many things and too many tee's for me to explain in words. See vacuum diagram above. NOTE: The two lines on the end have been taken off and connected together (manifold vacuum and dizzy)


TVS: D5AF-CA

Currently open, which seems strange to me cause my drive home is a half mile or less, and its been 45 minutes with an air temp of 65*F.


Yeah, this is being a pain in the ***, BUT, think of all the random tid-bits of information Im leaning

 

Pulled the TVS off, stuck a tube on one of the nipples, and blew through to tube to verify openness. Then stuck it in a freezer for a few minutes, cant blow through it. Used a heat gun to warm it up, got it to open up. Measured the temperature of the valve right after it opened, infrared thermometer said about 95*. So it "works", just not sure how well.

EDIT: Bubba says it closes at 50°F, opens at 76°F. So then I guess it should be getting vacuum. Ughh...

 

Well I can rule out the problem being associated with the engine cold. Hooked the valve back up after a drive and once again, it ran like crap. Sorta leaning towards 81-F-150-Explorer's back pressure idea. Its running good enough now, and Im gonna replace the exhaust this winter anyway.