Cold start, bad idle. 92 S10 4.3L TBI, 4x4

[Wags391]

I have a 1992 S10 4.3L, TBI, 4x4. When starting in the mornings or after getting off work, the idle is rough and then when driving I don't seem to have any power going up hills.

Recent repairs: Reman. long block from Jasper, EGR valve, CAT converter, fuel vapor canister, and I checked all vacuum lines.

When driving with the A/C on and accelerating up a hill, the vacuum pressure decreases and I can hear the A/C doors flapping. Once I let off the gas, of course the vacuum returns to normal. I have the same problem with the 4x4 actuator. When using 4x4 and accelerating hard, I loose the light indicating 4x4 is engaged. I would think there is some sort of vac leak somewhere, but I can't find one, or another part somewhere is bad. I've checked everything I can, except for the EGR solenoid. I replaced it within the last year or so, so I'm hoping it's not bad. Any ideas?

Jason

[MT-2500]

Originally Posted by Wags391

I have a 1992 S10 4.3L, TBI, 4x4. When starting in the mornings or after getting off work, the idle is rough and then when driving I don't seem to have any power going up hills.

Recent repairs: Reman. long block from Jasper, EGR valve, CAT converter, fuel vapor canister, and I checked all vacuum lines.

When driving with the A/C on and accelerating up a hill, the vacuum pressure decreases and I can hear the A/C doors flapping. Once I let off the gas, of course the vacuum returns to normal. I have the same problem with the 4x4 actuator. When using 4x4 and accelerating hard, I loose the light indicating 4x4 is engaged. I would think there is some sort of vac leak somewhere, but I can't find one, or another part somewhere is bad. I've checked everything I can, except for the EGR solenoid. I replaced it within the last year or so, so I'm hoping it's not bad. Any ideas?

Jason

Plug all external vacumn ports/line.
And check main engine vacumn.
Post back engine vacumn at idle and at 2K rpm.

Late ign /valve timing and EGR valve leak and intake manifold leaks and brake booster and weak compression and pluged exhaust can cause low vacumn.
Post back engine vacumn reading with every thng pluged up .