I just finished installing Pacesetter shorty headers on my '97 F-250HD, and aside from a broken stud on the passenger side, it all went pretty well. I have the EGR tube installed on the new passenger side header. But I had to cut off a pipe that was connected to the driver side manifold, which I could not for the life of me follow and figure out where it goes! Is it part of the EGR system, or part of the air pump system?

Right now the truck runs SO QUIET, it's amazing! But there's a faint stumble at idle and under light throttle that I'm thinking may be EGR/vacuum related, as I saw a hairline crack in the egr tube going from the valve to the front of the passenger side header. Right now the pipe that was going into the driver side manifold is just hanging in the wind, should I crimp it or plug it shut?

Then final question, to diagnose the stumble without firing the parts cannon, theoretically would a total EGR block between the intake manifold and valve eliminate any leaks from that system? I.e. if I block it and the stumble goes away, that means there's a vacuum leak somewhere in the pipe? Thanks for any help!

 

My guess would be part of the old air pump system, my 93 had one like that.

 

Maybe these will help - from the '96 service manual (which I believe '97 F250HD follow):

 

Thanks, that manual says it's a secondary air pump thing. Though it mentions it's for C6 trans models only (mine is an E4OD?). It shouldn't need to be plugged then.

Also, I replaced a few old crusty vacuum lines that I found, and also used the old carb cleaner spray trick to try and find any vacuum leaks, to no avail. There doesn't appear to be any. Could a bad spark plug wire or lousy contact between wire/plug or wire/distributor cap cause this kind of slight stumbling? It's not a completely dead cylinder, as I know what that feels like since I drove the truck accidentally with a plug wire unplugged once, and that was MUCH more pronounced than what it's doing now.

If it's a possibility, I may go ahead and replace the wires, cap & rotor just to eliminate all that as possibilities (they're all old anyway).

 

Sorry for the necro-thread but I thought I would give an update. I fixed the stumbling issue about 6 months after I posted this thread. I had replaced all the spark plugs at the same time I put in the headers. The guy who helped me put in the new headers, apparently did not fully tighten two of the new plugs; they were rattling around in the wells. It took me awhile to discover this because the new plug wires I put on were nearly impossible to pull back off the plugs. I bought special spark plug wire removal pliers, and ended up tearing two of the wires off, leaving the connectors still firmly seated on the plugs. So after getting new replacement wires and checking/torquing down all spark plugs, the truck runs brilliantly. Almost 3 years later and the truck is still very quiet, haven't had to re-tighten the header nuts/studs.

I used NGK 3547 platinum plugs, still going strong.

 

hows the seat-o-pants meter and the shorties, after you got stumble fixed

 

It's got a little bit more pep, nothing to write home about, but I'll take what I can get with a 22 year old small block going through 3.55 gears!

 

I just put bbk's on, after I did porting of intake earlier this year, puts a smile on my face every time I step off in it
5.8 upper/lower flow number results b4/aft dyno - Ford Truck Enthusiasts Forums

 

I think the porting would have a much larger effect, if I had the motivation to do such a thing!

 

That port goes to air pump. You might have something disconnected.