So lately my truck is stuttering and idling really really rough. It only happened after I cleaned the air filter.

I've run fuel treatment, iso heet, and checked vacuum hoses and wires. The only thing i can think of that I modified is the VAMF. My truck has been running fine up until a few days ago. And up until a few days ago, it was warm outside. The past few days have been 30 degrees outside. So I was thinking maybe the cold air was causing an intake/compression issue with the way I adjusted the VAMF a few months ago.

Could this be the case? When I adjusted the gear and spring, it was summertime and it was still running fine. Here I am, in winter, and now it's idling like crap. I was thinking maybe I adjusted it to the point where the cold air was causing better compression and not enough fuel was being mixed in, which was causing a rough idle. So basically, it was breathing, but not burning fully.

-EDIT-
some people know the VAFM as the MAF (if i'm even calling it by the right name)

 

yeah, if you adjusted it earlier, it might help if you put it back where it was.

 

Lol. I don't know where it was, but I'm trying to set it back. I do have some scratches on the gear where it was originally and where it is now, so somewhere between that range is where I have to look to adjust it.

Originally it was burning too much fuel. I could smell it on the exhaust. So I adjusted it and it was all good.

If it helps narrow down the problem, I also had to open the idle air screw a bit more. Originally I had it set to iudle at 800rpms, but lately (since the sputtering and rough idle) I had to open it up to about 1100rpms. After I opened it to idle at 1100rpms (it should still idle at 1100rpms) it now idles at 800-900 rpms now. It's confusing, yes. But I had the screw all the way in. All the way in, it should idle at 800. I unscrewed it 3 or 4 turns, and it SHOULD idle at 1100 rpms (which it was for a while) and now it's down to 800rpms (as if the screw was turned all the way in)

Does this help any?

 

the idle screw should be somewhere between flush with the top of the bore is sits in or down a few turns. if you have had to turn it all the way in that's suggesting that either the throttle isn't closing all the way or you have a vacuum leak somewhere letting air around the throttle.

if you turn the gear the same direction the vane in the afm moves, you will richen the mixture; the opposite direction leans the mixture.

 

Yes, I had it turned too far clockwise, I think. I've been adjusting it counter-clockwise little by little until the rough idle goes away, or back to a halfway decent position.

As for a vacuum leak, i think I have one on the intake manifold. When I did the head job, I realised I had a stripped hole. I think maybe only one was stripped, maybe two. Could be three. Anyway, it used to have silicone gaskets, but when I did the head I put some regular gaskets on it. Could putting RV gasket material instead of regular material help form a seal and fix the vacuum?

 

a sealant applied to both sides of a gasket may help, but you have to follow the recommendations regarding skin and cure time, etc., but will probably not last very long. and you should fix the damaged bolt holes with helicoil or similar.

 

I'm working on it. Looking to buy a heli-coil kit. Until then I have to MacGyver it to get it fixed.