engine stumbling bad, need help
Thread Starter
|
Junior User
Joined: Mar 2005
Posts: 74
Likes: 0
engine stumbling bad, need help
ok, first I will never be mistaken for a mechanic, so any help here would be great. 78 f-250 300 with a t-18. My truck idles nice and smooth, and when I run through 1st,2nd and 3rd it runs pretty good, but every time I shift from 3rd to 4th I start to have some issues. The truck starts to backfire real bad, stumbles and barely runs. Now if I can get through that (sometimes I can't and I have to keep it in 3rd) and get it back up to 50mph+ things smooth out real nice and it runs fine 70mph. It dosent matter when I shfit from 3rd to 4th, at the low rpm range, or nearly redline, same thing everytime. I've done a complete tune up, new carb and checked all the vacuum lines, everything looks good. I'm thinking exhaust valve, but could it be a transmission issue that I have overlooked? Any help would be appreciated.
Tuned
Joined: Jan 2006
Posts: 290
Likes: 1
Exhaust system. Check for the Exhaust Valve for movement with your hand when the motor is cold. The valve should move freely. Spring still on the valve? Next, look for smashed exhaust pipe. How old is the muffler and does it look like it can still pass air? I test drove a van years ago that could not get out of it's own way. The modified exhaust system looked like a person did it at the end of a 10 year drunk.
Thread Starter
|
Junior User
Joined: Mar 2005
Posts: 74
Likes: 0
Thanks for the input....have been so busy at work I really haven't looked at all of what you are suggesting, but I do know the vacuum is good, checked that. The exhaust is fairly new, along with the fuel filter. I had a friend of mine come listen to it with me, we both came to the conclusion maybe it was a timing issue. From idle to almost redline the engine purrs pretty nice for the age. It only struggles with a load at the low rpms, like an upshift from 3 to 4 trying to gain some speed. I put a cheap autozone dizzy on it (a $6 valucraft, its all they had) last week, and I think that could be the source of the problem. So I'm gonna start there and work out. Any other ideas would be great though, this is getting old, I want to drive my truck.
Thread
Thread Starter
Forum
Replies
Last Post
Turbo442
1997 - 2003 F150
14
Mar 25, 2015 08:43 PM
jbielenda
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
7
Sep 18, 2009 11:44 AM
