Tomak

Hey guys, thought I would ask here...

Working on a 1989 Iroc with 383. The tuning of the AF was great, at the end, got an error code 12.

Re-checked base timing, everything was ok, for the heck of it, I thought I would check total timing (reconnected the EST wire), and low and behold, timing still did not change off base.

ie, at 2000 rpm free rev, Tunerpro and Winaldl shower 40 degrees.... timing light showed actual 10 degrees.

Any ideas? Wiring harness looks like it is in great shape....

Ideas?

merc3065

I don't think anything is wrong.

Code 12 is no distributor reference pulse according to Haynes.

But that is the code that blinks 3 times when key on engine off.
It will then blink any additional codes after the 12, three times each, before blinking 12 again.

Tomak

Hmmm... well, it was the only code that flashed...

also, after driving the car... something is definitely wrong with the timing... it is sluggish till about 2500 rpm or so, then pulls ok.

I rechecked timing with a light,... it sits motionless around 10 degrees till about 2500 rpm or a little more, then jumps to 25 degrees or thereabouts.

It has an MSD GM EFI drop in distributor... the tan wire has continuity at the 'timing' connector... where else should I be checking its integrity?

Can anything else cause this problem>?

Thanks guys

merc3065

Im not too sure what else can cause the sluggishness other than the spark curve in the chip, and the fuel curve to match it.

But im still a novice programmer so I cant really say what you need to adjust from there. I just know from driving experience that not enough fuel or too much fuel can cause it to run like crap at the lower rpms as well as too much spark can cause it to chug or surge at certain rpms under heavier loads.

Hopefully someone with experience can help out here.

But code 12 is the default engine off code.

RBob

iTrader: (1)

What you are seeing for at-crank SA is what occurs when the BYPASS connector is open. Or, if the BYPASS connector was re-connected and the engine not shut-off and restarted after a 10 second wait.

Double check that the BYPASS connector to firmly connected. Do this with the key-off. Then start the engine and check the at-crank SA again. If still the same open the BYPASS and re-check. There should be no difference.

Note that code 42 should have been set when you ran the engine with the BYPASS open. That is an EST error. The SES light should also be on while the BYPASS is open and the engine is running.

It may be that the ignition module or ECM is bad. A wiring issue will most definately set code 42. You didn't mask out that error in the calibration?

RBob.

Tomak

Opening or closing the bypass has no affect on the timing while running. I also tried numerous times, shutting the engine off, restarting etc.... Not sure on the check engine with the bypass open... I am not 100%, but I do not believe it tripped a code, 42 and 43 are enabled in the swithches section... so I'll double check.

So, bad PCM (it is a delco replacement PCM, not an actual 165, service number starts with 16 something or other).... or bad module in the distributor? The memcal has been tampered with (soldered replacement chip), but I am using a Moates adapter anyway... can a bad memcal do the same thing? If so, the only Memcal I have is out of a 730 ecm... would that work in a 165? I don't have a spare ECM... just a couple 749's and a 727 I think.

The car runs beautifully otherwise, AF is spot on etc, but on start, it blips to life, then dies if you don't feather it for a few seconds... I imagine this is probably due to the timing not advancing on start.

Thanks for the help.

Tomak

Hey! RBob lol... Just noticed your website... I was gonna order a unit or two of yours to keep in stock for the more radical engined guys. I think I spoke to you about a Grand National I had in, but we got it to work on the stock ecu 'good enough' for the customer and his budget.

Small world lol.