The Macinist
Newbie
I have a 1994 K1500 Suburban 5.7L. It has a Whipple supercharger that was installed by Canepa when it was new. They call for 92 octane, so I always run 91, the highest we have here in CA. Lots of other upgrades, but I don't think any of them are pertinent to this situation.
Some background info: I have had it since June. It has always run rich and blows smoke like a diesel under hard throttle. I recently replaced the PCV valve and installed a check valve to prevent positive intake pressure from the SC to flow into the crankcase. That seemed to minimize the smoke under hard acceleration. I am hoping that it will cut down on oil consumption. It currently uses a quart every 150 miles or so. Gas mileage seems to be on par with factory claims 8.5-12.5 overall mpg, depending on how and where I drive it. I found oil on spark plugs 1 & 2 when I did a tune-up in September.
It starts hard when cold. It cranks 10+ times before it fires up. Then it idles rough and will stumble or even stall if I am too heavy on the throttle before it warms up.
It was running particularly rough last night right after I washed it. I got on it pretty hard and it stalled out (OK, I tried to do a brakestand with the wet tires). Now it will not fire up for anything. There was gas in the throttle body when I pulled the intake plenum. I replaced the ignition control module, as that seems to be a pretty common problem (ICM went out on my 1991 K1500 a few years back). This morning it almost fired up after sitting all night. Today I put new spark plug wires in because the old ones looked bad and I seemed to be getting high impedance on the coil wire. Tried to start it with starting fluid and almost got it to start once, but not even a glimmer of hope after that. The coil seemed to be OK, but I swapped a used one from my old truck and nothing changed. Spark from the #1 spark plug looks very weak, orangish.
Frustrated and stumped. Blew most of my weekend on this thing.
Some background info: I have had it since June. It has always run rich and blows smoke like a diesel under hard throttle. I recently replaced the PCV valve and installed a check valve to prevent positive intake pressure from the SC to flow into the crankcase. That seemed to minimize the smoke under hard acceleration. I am hoping that it will cut down on oil consumption. It currently uses a quart every 150 miles or so. Gas mileage seems to be on par with factory claims 8.5-12.5 overall mpg, depending on how and where I drive it. I found oil on spark plugs 1 & 2 when I did a tune-up in September.
It starts hard when cold. It cranks 10+ times before it fires up. Then it idles rough and will stumble or even stall if I am too heavy on the throttle before it warms up.
It was running particularly rough last night right after I washed it. I got on it pretty hard and it stalled out (OK, I tried to do a brakestand with the wet tires). Now it will not fire up for anything. There was gas in the throttle body when I pulled the intake plenum. I replaced the ignition control module, as that seems to be a pretty common problem (ICM went out on my 1991 K1500 a few years back). This morning it almost fired up after sitting all night. Today I put new spark plug wires in because the old ones looked bad and I seemed to be getting high impedance on the coil wire. Tried to start it with starting fluid and almost got it to start once, but not even a glimmer of hope after that. The coil seemed to be OK, but I swapped a used one from my old truck and nothing changed. Spark from the #1 spark plug looks very weak, orangish.
Frustrated and stumped. Blew most of my weekend on this thing.
