Still have a bad miss

[chevydude1608]

I have posted on here before for this same truck and have done a lot of reading and repairs and am typically pretty good at repairing my vehicles but i just can't seem to do it with this truck. The truck is a 98 ec with the 5.7,4l60,2wheel drive with a little over 200'000miles. One day i cranked it up had a miss so i took it to mechanic the only code was random missfire so we did a new distributor, plugs, wires, coil, and crank sensor. He told me that i should probablly have a new timing chain and gears put in it pretty soon. He said thats why the crank sensor had some scratches on it (the new one had a spacer). Fixed for about two days then the fuel pump quit on me. I had it towed to my mechanic and he put a new fuel pump in it and did the timing chain and gears as well. So I get the truck back drive it for about a week and then it starts to miss reall bad again and after doing some reading i bought the upgraded spider injector and installed it. Cranked it up after doing this and the miss is still there not as bad but still there still idles rough and is rough throughout the rpm range. Checked the codes and still getting the random missfire and now the crank sensor code. So replaced that sensor again(lifetime warranty) and it was scratched up as well just like the first one. so to sum things up complete tuneup, fuel pump, timing kit, spider upgrade, 3 new crank sensors and i still have a po300 and po336. I don't know what else to do other than take it to an actuall shop and spread my cheeks. Any ideas other than mine would be greatly appreciated.

 

[trailer-trash]

u checked intake gaskets? both times that mine have been bad it gave a random misfire code...

 

[TruckinAin4Sissies]

I wonder if (by chance) the crankshaft's causing the 'gear to somehow scratch the sensor.

IDK, just a thought.






-Truckin-

 

[Tinbender59]

I wonder if (by chance) the crankshaft's causing the 'gear to somehow scratch the sensor.

IDK, just a thought.






-Truckin-

I would start with a compression test, next check for end play on the crankshaft, as "truckin" is hinting at. since you have done all of the upper end stuff time to check the bottom end. It could "by a long shot" be an over active knock sensor or a bad rod bearing, but not perceptable to you yet. ????

 

[chevydude1608]

the intake gasket was done last year and im not getting a milkshake anywhere or losing any fluid period actually. No smokey exhaust either. The motor has never had a tap sound or a knock or anything. prior to this all happening you could sit a open beer on the plastic vortec silencer thing and it wouldnt spill it it idled so smooth. Ill do a compression test this week and how exactly do i check for play in the crank