Howdy all,
I have a 400m in my 82 f-x50. I did an engine swap from an I-6 about 5 years ago. I have put about 70,000 miles on the engine (which I believe had about 20,000 when I put it in). I know the engine is getting tired, and pulling 19,000 lbs with it isn't helping.
My question is, I have aquired a severe miss. This started about 8-9 months ago, and I can not track it down. I have replaced plugs, wires, cap, and rotor twice. Rebuilt the carb, replaced intake gasket, set timing, etc. I have a see through glass fuel filter, and it has been checked. I have replaced the module in the distributor (I believe part of advance).

When I replaced the plugs the first time around, the miss went away for about 2 weeks, then returned. The miss is on low end, and especially when you lug it (leaving a light, or pulling in to high gear) it feels as if the engine is flooding out. If I stand on it, or clear it out, it is better. Once the engine hits about 2300 RPM (4.10 gears, and 33's) the miss is gone. However, when I stop at a light again, the miss returns.
When I replaced the intake gasket, the miss was gone for about a month, but it is back again. I checked the torque on the intake and they are tight and haven't changed.

I am at a lose. I am not sure where to even look now. I have tried everything I can think of other than replacing the fuel pump (which I am now on my 3rd one) an blowing high pressure air from the fuel pump back into the tanks (might be something caught in the fuel lines). I have also thought of the coil going bad, but haven't replaced it yet.

Sorry about writing a book, but I am at a lose and hoping someone here could possibly shed some light on something I may be missing. Thanks in advance.

Chris
cmercer@skylinecomm.com
http://www.mountaineers4x4.org/mercer
'82 F-350, '53 Dodge PU, '85 4Runner
Proud enough to stack hay, crazy enough to eat it.

 

Are you using a lot of oil? It could be oil fouling on the plugs that burns of with a litle RPM. Also maybe too much fuel pressure or too high a float level. Good luck!

1977 Ford F-100
280,000 miles
Stock on the outside
modified/rebuilt everything

 

Have you done a compression/ leak down test? These motors are known to burn or crack valves. Something to look into.

Nathan

 

It does use a bit of oil, but not any more than it did when it was running fine. The plugs did look a little bad when I pulled them last time. They have a lot of carbon buildup on #7 and 8 plugs. They have a white buildup on them. If I remember right, that is what happens when the truck is running lean. I have been told they will turn that color with an intake leak. I checked that the other day, and didn't find one.
I did a comp. test and they all are about 120-140. Didn't change much between dry and wet.
If the plugs are to hot, they will burn lean. Is it possible they are too hot? The type of plugs doesn't seem to matter much. Tried Autolites, NGK, Bosch, Champion, etc.
I'll try another set of plugs and see what it does. Thanks for the help.


Chris
cmercer@skylinecomm.com
http://www.mountaineers4x4.org/mercer
'82 F-350, '53 Dodge PU, '85 4Runner
Proud enough to stack hay, crazy enough to eat it.