Ok guys, im new here. Well here goes i have a 96 blazer that shut off going down the road at like 45 mph. Wouldnt start back so towed home,later that day tried it and it started but was knocking really bad from passenger side head. tore down and found bent valve on number 4. had a extra head so just replaced it. Also new intake gasket and being at 70,000 miles on 2 nd motor, checked timing chain and very loose, so replace chain and gears.lined up all my marrks and buttoned everything up. started it up and it misses like crazy and cuts off, no power with throttle open all the way, seems like out of timing so rechecked and it seems right, so may the cam position sensor, replaced and same thing. ok now crank position sensor and relearn of puter. still same thing. hooked up scan too and it shows timing advance at -6. i tried other vehicles and they show like 18 to 20, so there is a problem for sure.Now im lost and just throwing money away it seems. Sorry so long just wanted you guys to knowall i have did and tried so far. Please help.

 

I had a similar problem on a 99 suburban recently. I had a bad crank sensor so I replaced it and then it would run but missed and had no power. Turned out to be the part of the computer that controls the ignition needed to be reflashed.
But whats up with the bent valve? That indicates a mechanical issue to me, not sure the timing chain being real loose could cause the timing to be that far out.

 

as to what caused the bent valve i cant say for sure,but new head seemed to fix that. i relearned the computer with no difference in running, Think im going to try a compression check next. just dont know what to do.Also just tried a new computer and learning since last post and no luck.maybe im timing it wrong, haynes manual maybe wrong or something, i have tried 2 different ways here. first with all marks on gears lined up, #4 piston is tdc on compression, then i put distributer in with rotor pointing at the #6 notch on distributer for v6 4.3 . and i have tried bringing up # 1 tdc and pointing rotor to # 1 and nothing on # 1 just free spins.only thing with all this im confused about is the harmonic has two marks on it 90 degres apart, when turning engine in normal rotation i pass the first mark and put the next one in the middle of timing cover mark with the notch, then the other mark is lined up with the other spot thats lower. which i believe is correct from what i have read on here in a post from the moderator of this site.


96 s-10 blazer 4.3l vortec. 4x4 ls.

 

Check out the EDI Engine Timing thread in the Tech Articles (DIY) section for information on how to properly time the engine.

 

Thanks swartlkk, Thats the post i was talking about i read and tried already. i read it agian, and yep thats exactly what im doing.that dimple on bottom of distributer though i dont if if its staying lined up with the little white paint spot on dist. im pointing at the 6 for v6 for sure though, could that dimple still be 180 out? Swartlkk i have been reading alot of your post and all i can say you have some really great post and info on here. thanks in advance for any info. Man i love my blazer and hate to have sitting dead.


96 s-10 blazer ls 4x4.

 

well off to get a compression gauge and check that now,if im right i i believe i shouldnt have any cylnders under 100 psi, or any like 30% below the highest one.just start it up and pulled live data stream and spark advance is still minus 6. and the only other thing wrong with live stream is map sensor is reading over 30 which is high and throwing ses light. just cant get it to run long, start it up and push throttle all the way down to run, it shakes like its coming out of truck and pops back through intakethen dies. any ideas guys?


96 s-10 blazer ls 4x4 4.3


Update all cylnders showing 150 on compression test except number 3 and it showing 125. also good fire coming from coil, but nothing coming from distributer except for number 6 wire. the rest have no fire, gonna try another cap, but does that sound like possibly timing or something else?

 

I would say that you should not have any below 120psi, but every engine is different. And I have always gone with the rule that no one cylinder should be over +/-10% of the overall average.

Did you rotate the motor through an entire cam phase and recheck that the alignment marks on the cam/crank gears are still aligned? It sounds like your timing is way advanced and the PCM is trying to compensate, but cannot.

If, after checking the compression, everything looks to be in order, I would try skipping the distributor back one tooth to see how it runs.

*EDIT* - BTW, please use the EDIT feature to include additional information/questions in your post if another member has yet to reply. Consecutive posting is prohibited by the rules of the forum. You can thank some unruly people who exploited this to increase their post count...

 

Update all cylnders showing 150 on compression test except number 3 and it showing 125. also good fire coming from coil, but nothing coming from distributer except for number 6 wire. the rest have no fire, gonna try another cap, but does that sound like possibly timing or something else?


ok i think i understand that if someone answers and you reply u should edit instead of new reply?

 

Compression looks good. It would be lower if the cam was out of phase. Is the cap on correctly? It is possible that it is not sitting centered over the distributor body.

My note in my last reply was concerning your consecutive posts (back to back posts). So rather than just post again if someone has not replied to your previous post, please use the EDIT feature to include your new information/questions.

 

yes cap is on good and centered. This is just weird and doesnt make any sense. am i overlooking something or what. to bad there isnt a forum for out of work chevy mechanics for hire,lol. Well i dont know whats next to try, gonna put new cap on in morning too cold tonight. any other sensors that can cause this? new computer,cam sensor,crank sensor,coil. computer still showing -6 degrees timing advance, but doesnt run long enough to tell for sure, guess only runing on 1 cylinder.very confused here. thanks swartlkk, just ideas from someone helps so much to stay on focus, and you have been great. If it wasnt for emmission testing here in north carolina id drop a 350 with carb in lol.