In my last post I was calling this a vibration. I've now determined its a rough idle. It does not miss and never has. The injectors were pop tested and shimmed accordingly and cleaned 1.5 years ago. I determined this by adding a liter of 2 stroke oil to one full tank of full. Within about 200km's it was idling smoother. It's still not great but a huge improvement.
The fuel screw is not near being maxed and everything else is as stated in my sig.

I'm wondering what could cause this. A bad lift pump causing the VE to have to suck and possibly cavitate?

Im still looking for the cause and would appreciate an input.

Thanks again to everyone who replied to my last thread

 

mine idles weird also. sounds like it has a radical cam at cold start up

 

Low idle speed?

Air in the fuel can cause this too, but it is usually accompanied by a hard starting problem.

 

Idle speed is higher than it should be but I don't have a tack. This was compared to a truck with a tack. It`s 50 to a 100rpm higher than it should be.

I park on a down hill slope. always starts up in less than 1 revolution unless I back into the driveway, then it can take up to 2-3 rev`s before catching. I suspect its`s bleeding back to the tank.

Also I checked the fuel pressure at the air bleed screw and was getting 7 psi the problem I have with this is that it was pulsing really bad. At idle it would pulse between 5-7psi. If I hammered the throttle pressure would steadily drop but still pulsing. Lowest I saw was three psi but I suspect under load...long pull up hill it would drop more. The pulsing I think might be normal due to the mechanical lift pump... it`s not constant like the electric but I didn`t think it would fluctuate that much.

 

If it dropped to 3psi siting in the driveway, I'd say replace the lift pump. It WILL drop into vacuum- pulling range under load. I had a 92 that started hard if I parked around back (nose up), but fine on the level. Replaced the lift pump, and all was well.

 

With the mods in my sig should I be doing the big line kit and a fuel pump up grade...Second gen lift pump of electric pump. I worried that the IP is damaged due to this. Should a stock lift pump be able to keep up with what I've done.

 

You have an air leak. Find it and the truck will start on the first hole unless you park it upside down. It'll idle better too.

A healthy stock pump will keep up with stock injectors.

 

Don't forget about your throttle linkeage. My truck had similar symptoms, and after confusing the mechanics, I realized that the weighted arm that pulls the arm that comes off the injection pump had a bad bearing, and was over-center, keeping the governor from opening the throttle up. It was very bad in cold weather. Not sure how to fix it, but have to before it gets cold.