Runs really rough when cold?
Thread Starter
|
Posting Guru
Joined: Jan 2005
Posts: 1,749
Likes: 0
Runs really rough when cold?
It's my 78'.. 400, 4x4 - I don't have the stock distributor, it's an aftermarket HEI.
It use to idle perfect on a cold morning when I bought it.. it would slowly creep to 2k RPMs from about the 1.5K RPM fast idle until it warmed up, but it would run pretty smooth.
Now it feels like there is a 8.0 quake outside when I start the truck..
It starts and with the choke closed it idles rough at about 1k RPMs, that's understandable.. hit the gas and it shoots up to fast idle speed with the choke slightly open. However, it still runs really really rough until it hits 190F (it improves slightly every bit it increases in temps, until it gets to operating temps and idles and runs perfect)
What would cause this? did I set my carb up wrong? is it the new distributor? Oil looks good but it's a bit on the heavy side (20-40), with my engine running as good as it is I doubt that weight of oil would cause it to run *this* rough.
It isn't a slight rough idle, it scares me to run it long enough to warm up.. it almost feels like it's not sitting on any mounts and is ready to pop out of my hood. When I first started it today, I thought I had blown a rod or something, it was pretty scary.
It use to idle perfect on a cold morning when I bought it.. it would slowly creep to 2k RPMs from about the 1.5K RPM fast idle until it warmed up, but it would run pretty smooth.
Now it feels like there is a 8.0 quake outside when I start the truck..
It starts and with the choke closed it idles rough at about 1k RPMs, that's understandable.. hit the gas and it shoots up to fast idle speed with the choke slightly open. However, it still runs really really rough until it hits 190F (it improves slightly every bit it increases in temps, until it gets to operating temps and idles and runs perfect)
What would cause this? did I set my carb up wrong? is it the new distributor? Oil looks good but it's a bit on the heavy side (20-40), with my engine running as good as it is I doubt that weight of oil would cause it to run *this* rough.
It isn't a slight rough idle, it scares me to run it long enough to warm up.. it almost feels like it's not sitting on any mounts and is ready to pop out of my hood. When I first started it today, I thought I had blown a rod or something, it was pretty scary.
Thread Starter
|
Posting Guru
Joined: Jan 2005
Posts: 1,749
Likes: 0
Curb is at about 700rpms, timing was fine when I set it.. I think 14degrees base at 650rpms.
I'll check choke spring tension but I'm not sure it will help.. unless, is it possible the extreme cold is causing the spring to tighten too much? I'll try adjusting it when it's cold to see if I can't improve it somewhat. I set it in the summer and didn't spend too much time on it because it would start and run well no matter what.
My intake never really warmed up even at operating temps (to the touch, I'd guess, at most it was 90F).. my choke has no electric assist, that really might be the issue.
I'll check choke spring tension but I'm not sure it will help.. unless, is it possible the extreme cold is causing the spring to tighten too much? I'll try adjusting it when it's cold to see if I can't improve it somewhat. I set it in the summer and didn't spend too much time on it because it would start and run well no matter what.
My intake never really warmed up even at operating temps (to the touch, I'd guess, at most it was 90F).. my choke has no electric assist, that really might be the issue.
Cargo Master
Joined: Apr 2001
Posts: 2,364
Likes: 3
From: Eustis FL
Sounds to me like the choke could still use some messing with... Did you set your carb mixture needles with idle set at spec? Also, do you have the exhaust stove pipe still in place, or did you remove it? If it's there, check the vacuum hose and one way check valve to see that vacuum opens the air intake flap when the engine is warm. Do you have a closed air cleaner, or is it open? Open cleaners are not good for winter months.
