99 Silverado Running Rough And Rich

[gto65racer]

I have a 99 Silverado 1500 with a 5.3. I sat for a month and when I first started it it was running rough and I could smelled rich. I tried to drive it and it starts to misfire and won't go over 10 mph. I checked the fuel pressure and it is at 58lb. I looked for vacum leaks and found none. I did a compression test and comp was from 167 to 175 over all cylinders. I un plugged coils as it was running ang number 2 and 5 made no differance. no check engine light is on.

 

Any help would be appreciated.

 

Adam

[Draenor]

Pulled and inspected the plugs?

 

 

My gues from you description of symptoms is the cats are clogged.

[gto65racer]

Pulled and inspected the plugs?

 

 

My gues from you description of symptoms is the cats are clogged.

 

I checked the plugs when I did the compression test. they were a little sooty. I hooked up my scanner and checked the mv on the o2s and they were fluctuatting from 800mv to 200mv on the upstreams and 900mv to 600mv on the downstream.

 

Adam

[bill190]

I'm trying to think of which sensors might get "stuck" if left to sit for awhile.

 

Perhaps check MAP and TPS sensors? Or any other sensors you can think of which would have some sort of mechanical movement to change the signal. (As opposed to say a temperature sensor which would have a solid state thermistor, etc.)