Hey guys
i got this 2wd 89 s10 with a 4.3L vortec with a th350.
it's a TBI motor, so computer and all that crap. But the kid i got it from changed the coil cuz the last one arked out on him, he said after that he had to unplug the spark advance timing because it backfired when u matted the gas, but with it unplugged you dont. And with it unplugged i think thats whats causing me to run a bit rich. AAnd tonight i just plugged it in to see what happens and it backfired when i was in park and just revv'ed it up a bit.

Any clue what this could be?? could he have bumped the distributor while installing the new MSD coil?? someone told me msd coils cant run on stock ignition, but i just need to see if anybody has a clue what this could be. Thanks

You can`t run it without it connected, it has zero timing advance without it. Your lucky it hasn`t run hot or did worse damage from lack of timing advance, I`m betting it sure don`t have much power. First I would check the spark timing, it should tell you where the problem is, the timing could be over advanced or likely too retarded. In some cases you can reset the timing and the problem is solved. Set the timing to the proper spec with the wire off and then disconnect the battery cable so the computer will dump the current setting, then reconnect. If it still runs bad then replace the module, if you replace the module make sure you clean the mounting pad the module bolts to, and use the correct grease to assure it doesn`t overheat the new module. The MSD coil will have no effect on it, I have one on my 4.3 and it runs fine.

ive never dealt with Tbi before, so i dont exactly know how to check where the timing is at or even advance or retard timing if it needs to be. Is advancing and retarding the timing just like setting the timing on a v8 with HEI?

also when i plug in the spark advance, when i fire the motor it rev's at about 1200 rpm and then drops under 1000rpm after about 15 seconds and idles smooth, but when i mat the gas for a split second it backfires, and last night i tried it, and the motor died.

Yes its just like you HEI distributor. Disconnect the EST wire, this is your spark advance wire that you call it. This wire should be a tan with black tracer, located on the firewall it will be hanging outside the wire harness or on the passenger side under dash area by heater box.

once that wire has been disconnected, set timing to specs. IIRC should be at 0*

Then plug EST wire in and clear codes by disconnecting the battery for 15 seconds and take it for a test drive.

Steve

thanks so much

do you think thats my problem? when the EST wire is plugged in the timing seems way out and keeps backfiring? thinks theres a possibilty he could have hit or bumped the distributor when taking the coil out resulting in timing advance/retard?

im goin to do the timing today, and i will plug the EST wire in and do the battery thing. Will post results. Thanks again