Hey, just picked up a '93 f150 300 5spd 2wd with 122k.

Truck runs idles rough and has a miss if I hold it at a steady rpm. Exhaust smells rich and if I let it set and idle when I get on the throttle I get quite a bit of white smoke which clears out through driving or holding rpms up, if I let off the throttle suddenly it stumbles bad at idle but does usually catch itself and speed back up.

Also while driving it seems to generally lack power. I pulled codes 173 and 538 with you folks instructions here.

So far I have done a general tune-up (cap/rotor/wires/plugs/oil/fuel and air filters), new O2 (was missing when I got the truck), changed a few vacuum lines, fuel press is around 45 at idle.

Forgot to mention it had a tank of old gas in it when I got it which I've run out and then added 10 gals of fresh with some heet and fuel injector cleaner (makes me think this truck has been sitting a while).

Possibly unrelated I took it for a drive and when I got back let it idle for a bout 10 mins and it started to get hot.

Anybody have any ideas for me? I'm running out.

 

Driving it a little bit again, serious lack of power... When the muffler let loose I noticed the cat is one of the most beautiful shades of cherry red steel I've ever seen. Was thinking, maybe that tank of bad fuel coupled with whatever might have been in the cat already has made for one clogged up son of a gun? I don't have much experience with them. Anyone have thoughts?

 

Could be well over due for a new Cat considering the age of your vehicle. Also, check the vacuum...you may still have a leak.

 

A lot of times a cherry red cat is caused by unburned fuel running down the pipe to the cat to feed a nice little fire. Lots of things can help this to happen. A plug or wire, cap, rotor, TFI, pick-up coil cutting out for example. Since you mentioned rough running and smells rich I would rule that out before hacking the cat/pipe. I just found out that both AutoZone and Advanced can check your ignition module for free. If it is fender mounted, just remove two bolts and it pops off. No need to remove the module from the heat sink for testing.

My original TFI failed at the low RPM operation. The new one from Autozone failed all eight checks. If you replace the module have the new one tested before installation. Ford module is $180. Autozone is $50 with lifetime warranty.

 

I would probably put a set of wires on it unless you know they are good! And like Harte3 said, check your vacuum hoses. There is one buried under the intake plenum that is easy to miss. It gets warm where it is and can crack! Sometimes the connections on things can look fine but they are not. It takes time to trace intermittent down sometimes but you will find it.

 

All good points, guys... but I'm starting to think that it's got quite a bit more to do with the lack of compression on cylinders 1 and 3.

Not a bad idea about the cat, too bad the pinch bar was faster than your post--but it did pick up quite a bit of power after I punched a test flow hole in it.

Will keep you updated.