indiana

 

what are the chances of the autozone timing cover being junk? like the hole for the ckp sensor being too deep thus making the sensor too close to the reluctor, it still backfires through the intake even with everything set correctly. is there a relearn procedure for the ckp sensor?

 

well i took the timing cover back off today to check it out and i measured the bore for the CKP sensor and it was .052 inches deeper than the original. so the sensor was actually too far from the reluctor. im not sure what the tolerances are for it but im sure its less than .052. its gotta be atleast part of the problem. INSPECT YOUR AFTERMARKET TIMING COVER CLOSELY BEFORE YOU INSTALL IT! ESPECIALLY THE DORMAN (PIONEER) ONES!



i get bored and tired of messing with it alot so i just work on it when i feel like it, but i thought i would post all of the info on here for others and my own future reference.

 

Im curious, If the truck backfired through the exhaust before you replaced the timing cover, why do you think the new one is the cause?

I bought a 2000 for $500 that back fired so bad through the exhaust it blew the muffler to smitherings! Wouldnt run at all. smelled like raw gas. a shop condemed the spider injector. I replaced the cap and rotor plugs and wires. It was cross firing inside of the distributor cap. I drove it the same day. All the problems youve described makes me think its cross firing. Good luck!

 

the timing chain was stretched really bad and it was basically a tooth off when i took it apart, and it blew a head gasket also. ive checked out everything else that i can think to check, i know that cover has to be bad b/c im sure the tolerances have to be tighter than a .052 difference.

Edit: it backfired when it died, but now it does it through the intake( i know it probably sounds like its 180 out but its not. lol)

thanks for the input i appreciate it.

 

Have you tested the ICM (ignition control module) to make sure it's not defective? We had a Jimmy in the shop one time with the same symptoms (felt unbalanced during cranking/no start/backfire) and that was the problem. The unbalanced cranking was due to a cylinder firing at the wrong time. Good luck...

 

I do not mean to insult your intelligence at all. But I didnt not know there were 2 timing marks on the harmonic balancer until just recently. I now own my 4th blazer. Ive done 3 intake gaskets on these motors and have been fortunate to never have to time the motor from ground zero. But I was curious about something once and read up on the timing procedure. If you use the wrong timing mark the ditributor will be WAY off but the valve timing will still be correct.

I understand the concern about the new cover and the crank sensor....but what actually causes the plugs to fire at the correct time? I dont believe its the crank sensor. I believe (May be wrong) that the pick-up in the distributor creates the signal for the ignition module which in turn fires the ignition coil at the correct time.

I believe the crank sensor and cam sensor MAY be used for timing on distributorless engines.

I would hate to see you spend alot of time changing the cover if it isnt your problem.
Good luck!

 

Hubert;

In your early posts, you mentioned smelling gas. Is that still the case? Have you checked the coolant temp sensor? When this circuit gets open (broken connector usually) the computer mistakenly believes the motor is -40deg F and so pumps way too much fuel.

Just a thought.

 

01blackbeauty: I checked the ICM when i first put it back together and it was out of spec on the ohms so i replaced it. (cant remember what the reading was anymore, its been awhile.lol)



kristoph30: I understand. lol yes i am aware of the 2 timing marks. Yeah i've had a few of these myself. done intake gaskets, lifters, spiders, everything on the top end including the heads, so im pretty familiar with these engines. actually when you intall the timing set and line the marks up on the gears the #4 piston is on TDC (well these engines dont fire exactly on TDC but its close).

The CKP sensor sends signal to the PCM in return sends signal to the ICM in the distributor which makes it fire at the correct time. If your CKP sensor goes bad it wont run. (its new b/c the old one was out of spec).

The new timing cover is already back off and the bore for the sensor is .052 inches deeper than the original making the sensor sit further from the reluctor. its is noticeable by just looking at it, if i would have noticed it before i put it on the first time i would have taken it back to the parts store. lol




billbobagns: the really strong gas smell is gone, and the ECT sensor reads correctly.


Thanks for all of the input on this i really appreciate it!

 

So after i put the old cover back on it helped but still backfired through the intake, but not as bad, a friend and myself noticed that there was a burnt spot on the inside of the distributor and it was arking inside the cap, changed it and it fired right up. No more aftermarket timing covers or cheap distributor caps.