I have a 97k, z71 k1500. I bought with 217k miles, it currently sits with 255k. I’ve driven it cross country, I’ve done basic mechanic repairs as well as larger repairs such as a tranny rebuilt since I’ve had it but at this point I’m lost.

At times the truck is perfectly fine, and then some days it gets into a mood and decides to fall face first. It’ll start idling super rough, almost like it’ll stall out but doesn’t. Gauges all read normal. RPMs may bounce slightly while it does it, but not always. The entire truck will begin to violently shake when accelerating at any speed, whether its slow accelerating or I’m slamming my foot to the floor. But as soon as I take my food off it smoothes out, but still shakes a little bit. Shortly afterwards, not all the time but sometimes, a misfire will pop up on the dash and it reads Cylinder 1 misfire. We’ll pop the hood, check the plug and it’ll be fine. Heres the kicker;

I’ve replaced; Distributor and cap, all wires and plugs (yes made sure they were gapped correctly), fuel pump, fuel filter, fuel pump filter, I just had the cats completely removed because they were clogged. So there are no cats on the truck now. The o2 sensors are on the truck still, they currently have extensions but they are all bad. I am replacing them this weekend. The truck does have a tranny leak (yes I just had the tranny rebuilt roughly a year and half ago). Tranny fluid lvl is fine, I am keeping up with it until I can replace the seals thats leaking. Oil lvl is fine. Is there anything else that could cause the truck to act like this? I’m thinking its about to time to possibly replace the engine itself. I’m not sure what kind of maintenance was kept up on the truck prior to me but when I bought it there were already all kinds of issues I’ve done replaced and fixed, and at the time of purchases it was throwing o2 sensor codes and all kinds of misfire that I’ve done replaced and fixed.

Any recommendations or help would greatly appreciated.

 

Fuel pump going south?

 

Fuel pump, fuel filter, fuel pump filter, wires and plugs, distributor and cap all have been replaced since this started happening. I had the old cats removed since they severely clogged as well. Still nothing seems to be resolving the issues.

 

I would suspect it has to do with the missing cats. To me that is the only thing that is immediately standing out.

 

Yeah but the thing is, I just had the cats taken off last week. This rough idling/misfiring issue has been going for a month now if not longer. I’m thinking it has something to do deep within the engine. Thats where the shaking feel is definitely more prominent. And the compressions are off on all the cylinders, way off. Which the engine being as old as it is, makes sense, its not going to have perfect comp. But still.

 

I didn’t know you had just removed the cats. That would definitely not be it then. I just don't know why it would start acting up so suddenly. Unless something literally broke inside the motor, but I doubt it. And wear the problem would come on slowly.

 

Thats why everything is bizarre. When I was stationed in NY, i kept having a cylinder 7 misfire. Again, distributor and wires and spark plugs were all replaced. The same cylinder continued to misfire so I had fuel injectors completely replaced and it seemed to resolve the issue. I wonder if the fuel injectors gone bad again? Or possibly one is sticking?

 

Although it is possible, I doubt that the same injector failed in the same cylinder, again. Have you put something like a borescope down that cylinder, to see if there’s anything unusual in there? Also, if I remember correctly, there is a way that you can have injectors tested, or if you wanted you could swap injectors around, and see if the misfire moves.