I'm in total agreement with your theory - seems like getting the vacuum patched up should help on some level. I don't have a clue about the thermactor system's function, but I assume it can't hurt to have it operational.

I cleared the codes, and we'll see how it does tomorrow. By the time I get back home from work I have a good 'seat of the pants' idea, and I'll pull codes when I get back home. Hopefully this was the missing link, and I'll get a resounding 1... 1... (I doubt it, but I can dream!)

 

Basically, the thermactor pumps air all the time. The only way the computer knows if it's working is through the solenoids. If you have vacuum in the solenoid but not out the computer doesn't know and assumes it's working, unless the solenoid is the reason no air is coming out. The TAB (thermactor air bypass) vents the always pumped air to the atmosphere when it's not needed. Fresh air pumped into the exhaust at deceleration causes backfiring. The TAD (thermactor air diverter) channels the always pumped air to where it's needed when it's needed. During cold start and hot restart air is pumped into the exhaust manifold to help reduce hydrocarbons, but if not switched from there causes driveability problems such as surging and pre-ignition. Air is pumped to the catalytic converter to keep an oxygen rich environment to burn off hydrocarbons but since at cold start up the catalytic converter isn't up to temperature the air isn't needed. Also, at hot start up and periods of extended idle where fuel rich exhaust may be present for extended periods, the air must be bypassed from the catalytic converter to prevent its overheating.

 

What do you think #33 means as to EGR function or non-function?(EGR Fault/Specifically:not closing properly) Which means there's crap built up around where the plunger seats w/ the inner port orifice, so the position sens. notes the plunger is a hair out of position. Through all those posts, I'm not sure, are you useing a new one or the same one?

 

Actually, in the F150 manual 33 is defined as no EGR movement detected. He dissected the old one and found a bunch of crap in it, so he has the new one on.

 

Strange there always seems to be slight variances on code defs. I'm refing from Ford OBD 1 Fault code Definitions for EEC-IV Sys. #33 = EGR Fault/ Not closing properly (Trucks only) ??? Beats me!

 

Yea, my generic code book lists 33 as EGR valve not seated or EGR valve not opening. Totally opposite ends of the spectrum.

 

Thanks for the info!

My optimism was short lived - the old girl drove like crap again this morning. Idles much better, but surges and stutters under load. It's also registering low oil pressure now if it's idling in gear, even though it's full of brand new oil, which hadn't happened before.

Maybe I need to check out those TAB and TAD solenoids... The surging may be related to that? I dunno - I'm grasping at straws here.

 

Based on your explanation above, the more I think about it, the more I think maybe this is part of the issue. I've only had the truck for 6 weeks or so, and have no idea if this problem was 'bypassed' by a mechanic with the pull of a vacuum plug, or if it was worked on and the fitting just missed the port (it is kind of hard to see what you're doing back there). Seems like a mechanic taking a shortcut would at least cap the vac line that they disconnected... who knows.

I'll take a closer look tonight, and try to figure out from the chilton manual or the web how I can test those. It just seems like there should be other codes popping up - I'll check again when I get back home to see if there are some now that it's plugged in.

 

When I got home, I pulled codes and only got the 33 again. Even though the truck has no power, shakes, chugs, stutters, and now the oil pressure drops every time it idles in gear.

Per my other post about the ticking noise, I ran sea foam through the intake this afternoon, and got quite a bit of smoke while pouring the sea foam in, but after letting it sit and starting again, it didn't smoke like I expected. Didn't really run any different either...

Anyway... that process led to some questions.

When I pulled a vac line of the intake vacuum tree to do the sea foam treatment, the idle went up quite a bit - is that a normal thing? I assumed it would drop or at least get rough.

I've also been looking over the thermactor stuff - I think part of mine is missing... The diagrams on the web are just not plentiful, nor are they accurate.

Pulling the vac back off the TAB solenoid doesn't make any change.

Humor me this - from the pump (driven by the serpentine belt) there is a hose running to a canister (air cleaner?) mounted on the passenger fender beside the vacuum can. Is there supposed to be something connected to that canister? There is a tube sticking out toward the cab, but nothing connected to it, and a small hole on the top with nothing connected.

All of the diagrams I can find show some sort of line from that empty fitting to a valve on the intake manifold? Maybe the air bypass valve? ...and I have no idea where that valve is (or if it's gone). It looks like from the other end of the pump, the lines run to the valves on the back of the cylinder heads and all that like the diagrams suggest.

I don't know if the valve is still there or not, but there is definitely no hose from it to the air pump air cleaner on the fender.

Any clues?

 

this is the closest diagram I can find - I labelled the parts that are missing (I know the hose is missing, just not sure where the valve is if it's there).