At Wits End.....

[jefflewis]

 

hello all....let me start by telling you i have a 1990 chevy silverado k1500,5.7 auto.. my problem is that when taking off from a dead stop. i have a miss like its hitting a rev limiter.also doeas it again if i hit the passing gear. idles fine ,cruises down the high ok but under a hard load,towing or hard excelleration the rev limiter issue is there. i have replace pcm,prom, distributor ,coil,new wires and plugs ,fuel pump. battery is charged and holds charge. altenator is charging......i discovered today that 6 month old pcm will not communicate with modis scanner when it is running. communication is ok with just key on engine off.any help would be appreciated and thanks in advance.

[dlobi]

possible plugged cat?

You can check backpressure at the o2 sensor by unscrewing it, that way you will be in front of the cat.

just a possible thought.

[jefflewis]

possible plugged cat?

You can check backpressure at the o2 sensor by unscrewing it, that way you will be in front of the cat.

just a possible thought.

 

 

sorry should have included that in the start...duall exhaust no cats...36" glass packs. also odd thing is that pcm only stops communicating with scanner when the truck is running..key on enngine of i have com, running i dont.