KBZ71
Newbie
Hello first time poster, long time member, I have used this site to aid in troubleshooting but now I think I have a problem that only has expensive solutions. I have a 1989 chevy OBS CC R3500 454 TBI long tube headers, RV Cam, and TH400 with shift kit, 91k miles, about 2 months ago I was pulling my trailer (1850lbs) with 7500 lbs on it with 1500 lbs in the bed, at 60 mph, no problem. Truck is driven on weekends to prevent issues that occur when vehicles sit (learned the hard way) My girlfriends S-10 went down so she was driving the monster to work, called me after a few days saying its running like crap, she made it home, I found front drivers side cylinder (8) spark plug had backed out. Removed plug, cleaned with brass wire brush, reinstalled and truck was running great. After about 20 minutes of driving (empty) on the freeway it started misfiring like a ford and had my foot to the floor trying to keep it going, found if Ieased in throttle it would accelerate, turned around and was able to limp it home. Thought it may be thee cat so I bought a high flow the old one fell out (magic made it fall out, not me) and the new one was installed. Truck runs alot better but still not good, Ive never dealt with a burnt valve but I believe it is my problem but I wanted to see if anyone had a different opinion. I do not believe the problem is fuel related, to get it home from where it started its crap back to my house it disposed of a half of a tank. A parts store guy (all of them are car guru's right?) Said the plugged cat could have had excessive back pressure that pushed out spark plug. My immediate thought was no efging way, but then my second thought was can that really happen?? The plug was covered in black buildup when it was loose but I havent looked at it again. Planning to replace plugs and wires (just changed them almost exactly a year ago) but I appreciate any ideas / thoughts.