out of ideas
 

History on my blazer. Got it last November with a blown head gasket. Spent the winter rebuilding it. Gave it a valve job with new seals, timing chain while I was in there, and new seals/gaskets all over the place. Got it back together and started it up, and it wont idle. It runs but had a huge random misfire and a code for the Crankshaft sensor so I took it and got that relearned with a TechII. No change and since I was back to class mon to fri and work fri to sun I didn't have time to mess with it, I took it to a mechanic. He has checked engine timing, injector timing/placement, fuel system, and rockers to make sure I had them all set up right. Nothing has been found that would be causing my problem and Im out of ideas on things to check. If it has fuel, air, and spark, that is what a motor needs to run correct? Other than the computer controlling things, so bad PCM? Any ideas on other things to check. Like I said, it runs, and will barely idle when it's cold, but once it has run for a few minutes it stops. The misfire is random, and happens a LOT.

My only other thought was if I managed to break, or knock the knock sensor around. Idk how it works on the 4.3 but with my gtp the PCM pulls timing when it detects KR. Is it possible that if this is loose the engine is pulling that much timing? And wouldnt that be more regular/less often at least giving me the ability to get it to idle?

ANY and ALL ideas are welcome and appreciated

Thanks guys

Distributor installed one tooth off? Any play in the distributor shaft bearings?

What codes are you currently getting?

Distributor should be in right, they took it out after I did and reckecked it to be sure. Not sure on the shaft bearings, I haven't had it in almost 2 months. Also unsure about codes being thrown. I will get it back Monday I believe. Just wanted tho throw the post up so I could get some ideas of things to check/how to check them before I got it back

Bump for any thoughts on if that much timing could be pulled by the PCM?

Also bad gas? The gas in it is almost a year old at the very least, and its had 175k miles of gas ran through it. Im thinking maybe the bad gas mixed with the amount of water potentially in the tank causing the miss?

That's a good possibility, especially if it has ethanol in it. Ethanol starts to break down after 1-3 months.

just wondering if the timing cover was replaced? aren't they plastic and recommended changing with the chain... i had a suburban that wouldn't run and the air gap to the reluctor was to big and if i pushed it just a little bit it smoothed out

Yeah we caught this the day I was supposed to pick it up, and he decided he wanted to keep it and see if he could check that out. It is a pioneer brand cover (made by dorman I've heard but unsure). He said taking the ckp sensor out it looked like too big of a gap. He sanded down the edge to move the sensor closer and said he feels like it runs better, but I don't notice much of a difference. Still a huge possibility im just unsure how to test it.

Checked fuel pressure, it checke out good. When I went to release it however it is the color of super concentrated urine. Nasty looking stuff. So I have drained it down to where the gas light is on (didn't wanna release all the sediment in the tank) and I am going to add some fuel/heet in there tomorrow and go run the hell out of it to see if that helps.

While scanning with Torque app on my phone I was unable to read any knock being picked up, but timing advance was in the 30-40tank) range consistently so im kind of ruling that out, seems decent enough?

I did notice that the majority of my misifres were being picked up on ccyls2,4, and 6 so im hoping the head isn't warped. Going to maybe compression test those cylinders tomo after I try the gas.

No fault codes at all in the ECM, althoug im unsure if they cleared them before I picked it up from the shop

Any other ideas to throw out guys?

Been a busy little man.

Dropped the gas tank, drained all the nasty out of there.

Started it up. Definitely ran better, and even kept itself running for a while but eventually died.

Changed the distributor because one of the bolt holes was gone and the cap was able to rattle around, no help.

Pulled a plug to check those, gapped correctly and plug looked normal.

Misfire is no longer isolated to cyl 2/4/6

Would a bad EGR cause this? If so how can this be tested? Manual says take it to dealer.

Also, Im still kind of caught on the CKP/Timing cover. I think I am going to order a GM timing cover tonight and throw that on there to see if anything changes.

Im about to give up and roll it down a BIG hill.

ANYTHING else I can go through? I am planning on trying to test the coil and CKP wiring in the next few days, but after that Im out of ideas again.

Anyone? Also, throwing it out there in case it helps anyone, the tach is pretty shaky all through the rev range. Is not smooth in movements like it should be, just jumps around. Leads me to think more into the timing cover/CKP sensor

Nobody?

Another question, is it possible for the cop to be bad and not send an error code? The distance between them doesn't seem unreasonable, 1/32 if an inch or so. The reluctor ring is not in the center if the hole fir the cop sensor, will this cause a problem? Its not terribly far off but definitely not centered

Ckp* sorry, cannot edit from mobile site