My 2000 blazer LS 4wd is having an issue i am struggling with, I just put the motor in the beginning of the year from a 2001 astro van with 120,000 miles on it my truck has 360,000, its been running great sence the swap but recently i have been having issues it started out with the tach would rarely just go nuts and jump around like crazy jumping, peged out to nothing but all the while the truck was running fine, just a twich ya know, it was very rare. more recently and mostly when the trucks at operating temps after running 10-15 min maybe the same condition with the tach going crazy but with it comes a crazy misfire like it is way out of time, this continues for a minute or so then the tach will drop to zero completely dead, the misfire is gone, all is well, but not really there remains a powerloss not to bad but i can tell, my fuel milage is sorry. Im worried she's gonna laydown leave me walkin. I have some codes i dont recall them all but i have for sometime had one for the trans the component slipage one for my tcc pwm thing but now new ones i dont remember the numbers but, caltilyst inefficentcy, random missfire, and maybe one more ill go to advance and have them print them up for me tomarro. I have a new distributor, cap, rotor, plugs, wires, coil, all new from the engine swap most of the sensors are origanal to the new motor exept the knock sensor I had to drill and tap the block to use the one for the origanal motor. I appriciate anyones input, i am thinking maybe somthing about the crank or cam sensor, just hope its not some uber hard to find electrical problem that i will never find short of replacing everything, maybe sombodys encountered somthing of the sort.

 

Anybody able to help? I have inspected the wiring to the crank sensor and they appear fine idk how test the sensor itself. it always takes a few minute befor it starts to act silly, when its at temp it does it almost immediatly. i know for sure it is not a slipping tranny it is obvious, it is like a sudden change in the timing. my entire distrib is new plus cap and rotor, so not a bad gear or somthing. and i dont think the tack would jump for a missfire unless it had somthing to do with the crank sensor. idk it still runs just drinks a little more gas.

 

I have a customer's vehicle in my shop with the same symptoms. Code P0335 ckp circuit A I know it is not the ckp, cmp, or cap rotor or related stuff. I also get a knocking sound like detonation when it starts it's issue. Really giving me a headache. I feel your pain. Am trying to work out the issue. Customer being really understanding.

 

We had an issue like this on a coworkers' 1992 Cadillac STS. It was actually an improperly installed ground.

 

Try doing a crankshaft relearn with a tech II

 

Hi, i had the same problem on two of my trucks. after many swear words and afew $$$$ i finally figured it out what gm and my local mechanic could not. recently i had changed out the cam sensor,cap, wires etc. so i backed track and found that the cap was slightly off, not completly seated. since then mpg had returned to normal, no crazy tach and misfire had disappeared. this may or may not be your problem but is worth checking.

 

*UPDATE* got it fixed a few months ago sorry for my tardiness but after a trip to a local shop (plug time thanx to dennis at auto excellence inc in troutman nc) it turns out there was a defect in brand new distributor i got from advance auto parts and after a few chosen words they replaced my Lifetime warranty part (they weren't going to, freakin jerks) and it has run like a dream ever sense.