maxmachz

Misses with the 4 wire plug hooked up. Unplug it so the ecm can't interfere with the distributor, and it runs nice and smooth. Fresh ecm with the stock PROM. No codes thrown, no check engine light. Light does come on at key up, so I know it works.

Hate to buy another ecm, but may not have any other choice?

Any other ideas? Could I replace the distributor with another, that has it's own advance, and leave the ecm hooked up for the trans and electric carb? Fresh plugs, wires, cap, rotor, distributor module......same result.

1986coupe

Is the timing set properly?

maxmachz

Yes; it is an intermittent miss / stumble, you only hear it at low speeds and idle. I beleive it is always there, but higher rpms make it harder to notice.

Unplug the 4 wire and it runs smooth as can be. I put quick disconnects on each of the 4 wires, and unplug one at a time and find it is the tan with the black stripe, "bypass" that causes the stumble / miss.

Thanks for your help.

7T1vette

Make sure the ecm has a clean, solid (direct) ground for the case. That case is the shielding for any stray electrical signals. It should ground directly to the frame.

wajulia

What about a bad HEI module? There used to be auto parts stores that could test them. I don't know if they can anymore?

maxmachz

Thanks for all the suggestions.

1st thing I did was replace the HEI module. I should have mentioned that.

I went out today, and just slightly retarded the timing......and it quit missing!

I don't get it, but will leave it there and run her a bit and see.

wajulia

May be telling you the obvious




81 comes out of the factory at 6 deg btd with the distributed connector disconnected. A lot of people have said it performs best at about 12 deg btdc.

Good luck

maxmachz

I had it at 10 BTDC, now with the gun it's at 8.

At 12 degrees, unhooked, it ran fine; plugged in it missed. I advanced it based on the folks on here syaing it was a cheap upgrade in performance, and WI is not a smog state I had no fear of test failure.