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chevy1500z71 07-23-2010 01:11 PM

help with my timing!
i cant get my truck timed, its a 95 k1500 so its tbi fuel injected with the late model efi style distributor where you disconect the est wire behind the gloevebox to time it at 0 then plug the est wire back into the ecm. the problem is that i disconnect the est wire and set the advance to 0, i plug the est wire back in and the truck still runs at 0 degrees across the board, it may drop back a few degrees in the negative as rpms change, thats about it. i just dropped in a parts store reman distributor w/ module and a new coil, could this be a bad ignition module? i dont know what to do. i tune the truck with my laptop so i pluged it in and played with the timign to see if i can see any response and i get nothing no matter what i do, when i data log the ecm i read the proper timing advance, so the ecm is functioning properly.its just not making its way to the distributor, the distributor just wont respond to the ecm is what the problem seems like. there are no breaks in the wiring that i know of, it worked fine before the coil went out and i started throwing new parts at it.

sqzbox 07-23-2010 02:55 PM

First of all, why did you change the dist?

chevy1500z71 07-23-2010 10:35 PM

well its one of those parts iv been wanting to change, i put a new motor in about 10,000 miles ago and kept the original 200,000 mile old distributor. the distributor was worn, had some play in it and the truck started to give out when it got hot, then the other day it finally quit for good so i figured the modue was bad, ended up being the coil but i wanted the distributor anyway because of how worn it was.

anyway, turns out im a total retard, i made a mistake by assuming the first 0 mark on the dampener was the right 0.thanks, but i figured out my problem which wasnt what i though at all. my fluiddamper has many markings, not just a 0 mark like a stock dampener, a little after 50 degrees theres another 0 mark(not sure for what, 0 degrees for another cylinder?, couldn't be bottom dead center, wouldnt run.) but it was not the right one obviously, so when the advance worked i was thinking it was dropping back the timing becasue i was looking at the markings wrong when really it was advancing it beyond the markings, its hard to tell how little movement is so many degrees when theres no more marking i guess, so between that and me not realizing you need to turn the truck off in between unplugging and plugging back in the est wire i was just chasing my tail all day like a fool. so i set it to the proper 0 degrees and was on my way, after 5 minutes of spitting and sputtering with severely fouled spark plugs that is. the plugs look real bad, probably from slipping performance from the old coil and hours of screwing with the timing watching it spit black smoke, the neighbors love me.

after logging the truck to make sure it wasnt knocking i noticed i definitly have a knock issue, but its not from me timing it wrong becasue now that i notice it, i know iv felt the same thing before, pretty much ever since the manual transmission swap. when i hit a certain point during normal acceleration the motor feels like it hits a wall, and after dataloging it, its clear that the power loss is from 8 degrees of knock retard, during a normal light acceleration i will reach 0 vacuum, maybe even a pound of boost, so the timing gets pretty low, around 12 degrees and its still taking timing out? my debate is weather this is some form of preventative burst knock or if my knock sensor is really reading any knock... makes me wonder about the quality of the fuel im running, 8.9:1 compression and 93 octane and i get a knock at 12 degrees of timing? somethings not right.

sqzbox 07-23-2010 10:41 PM

Sounds like an incompatible issue between the ECM and Dist. :boxing:

cobalt327 07-24-2010 03:02 AM


Originally Posted by chevy1500z71
my fluiddamper has many markings, not just a 0 mark like a stock dampener

Your damper is degreed in 2 degree increments from 0 to 50, with additional marks at 90, 180, and 270 degrees.

LATECH 07-24-2010 08:39 AM

Test IC Module circuit
Your truck has tan with black wire for timing adjust as you stated. during start up when the engine is being cranked there is no voltage present on this wire and the module grounds the circuit timing stays at base ( O degrees) after the engine starts the and PCM sees around 400 rpm ( during upstart) it supplies a 5 volt signal to this little tan with black wire. This causes the ignition module to switch to computed timing effectiveley switching from base timing. Here is what you do... backprobe the tan/blk wire with a DVOM of good quality at least 1 megohm internal resistance hook the red lead to the cicuit and the other to a suitable ground. Turn key on note the reading should be zero or real close then start the truck and watch to see if it changes to 5 volts, if it does not your pcm is defective if it does the module is defective.If you scan it you may see a code 42. this is the code for that circuit. It will set when you unplug the connector and remain for a certain amount of key cycles. clear it out and see if it reappears under normal conditions.this manuever along with the DVOM reading should tell you what you need to know

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