After about 8 years of engine rebuilding, paint process, tranny rebuild, today was the first time I drove my 1986 Iroc on the street.

I drove about 2 miles to a friend's house. First test to the tranny too. Only shifts 1-2. Bummer. Although it drives fine, when I got there, the car was overheating. Radiator fan is hardwired to be on all the time. Have a 16lb radiator cap. Also the engine has been hard to start, and needs a little gas in order to fire up. It won't just start without the help of the throttle as most FI engines to.

Almost everything is new in the engine, but have been sitting for years until today. So my friend and I waited for it to cool and then removed the thermostat just in case it had stuck closed. It wasn't.

We assembled everything back and checked for vaccum leaks. Couldn't find any. The plenum has MAP and FPR connected, brake booster, hose to PCV, hose to other valve cover hole with no PCV valve or anything. Just the hose inserted into the valve cover hole. Vacuum diagram shows it to be like this. Is this OK? Then hose to charcoal canister.

Next we checked timing. I expected the idle to go rough when I disconnected the brown wire, but it didn't. We checked with timing light and timing was at 0deg as I had set it a couple months ago. Tried connecting and reconnecting the brown wire and no change.

I wanted to check wiring harness but was too hot to get my hands in there. It was also getting dark so had to drive back home. Driveability was fine again. Maybe not as much power as I would expect. But still haven't tuned the newly swapped 730ECM either. It's just running the unmodified S_AUJP bin v3 I think.

So for my question, when the computer tries to control timing to my distributor, what kind of signal does it send? If I find the distributor is the culprit, and not the harness, Is there something I can replace?

My distributor is like an old HEI one, but with no vacuum ports and the connectors to the harness hanging from the module. I think 1986 got a lot of oddballs, because I've seen 87s and up use the smaller external coil ones. If I swap a newer, external coil distributor type to my Iroc can the 730E ECM control it, considering I might have to change the connector? I did a search on Summit Racing, but the MSD ready to run electronically controlled distributor 8366 was not listed for a 1986 Camaro.

Are the external coil type distributors more desirable? Maybe I can get one from a junkyard.

Sorry for the long book, but I'm very excited as if this was the 1st day of owning a Camaro

 

If you try to adjust the timing without the ESC (Electronic Spark Control) connected the ECM should try to adjust it on its own back to where it was. If you can adjust it and the timing always reverts back, then the ECM is doing what it's supposed to do to at least some extent with regards to timing.

Disconnect the ESC plug, and set timing for... I think the TPI cars it's supposed to be set to 6 BTDC

 

Thanks for your reply InfernalVortex. That's how I did it, except I put it at 0deg.

But shouldn't disconnecting and connecting the ESC change something when checking with a timing light?

 

The EST wire has to be disconnected and reconnected with the engine off - has no effect (much) with engine running.

 

Yeah, 86 is an oddball. Plenty of one-offs that year. Even in 87 there were still some odd things (like the accessory belts).

Is there a single EST wire poking out of the wiring harness above the heater box or is it the older-style 4-wire flat connector coming out the back of the distributor going into the wiring harness above the trans bellhousing?

All the large cap compute controlled HEIs I've worked on used the 4-wire flat connector out the back of the distributor for communications with the ECM. Have to unplug that flat conector before checking the base timing. Maybe 86 is different in that respect, but I thought I'd share that with you.

Electrically speaking, the small cap HEIs have some very minor upgrades over the older large cap ones. Little higher peak amperage allowed through the coil, little better adaptive control of dwell. Nothing worth writing home about.