Hi guys,

Ran into a prob that is driving me absolutely crazy. Any advice on how to isolate this problem would be much appreciated.

I built a 350 using a block from a 77 corvette (4 bolt main, non-roller). This is a long story I will make short.

Eventually, I had this thing running pretty smoothly. But I had not yet installed bigger fuel injectors and or a 350 chip, or switched out my ESC. Logged data for a while ... O2 sensor switching fine except of course when really pushing the engine. WINALDL showed me a few spark counts at startup and a few every now and then. Nothing that looked all that bad.

So off to the junkyard I went ... emerged with fuel injectors, ESC, knock sensor, and 8746 ECM from various 350 Caprices. (I hung onto my original 8746 ... planning modifying that one to support EEPROMs for tuning.)

Well, I immediately noticed more oomph. But right after warm up, opening up the throttle produces a hesitation followed by the Service Engine Soon Light.

A little research ... looks like the ECM will try to test the ESC and kock sensor by advancing spark in an attempt to produce engine detonation. If it doesn't hear the engine ping it asserts code 43. Other things can cause code 43 but this explanation appears to fit the pattern best.

So I checked the wires and they seem good. I soldered in a new KS connector and I have 100 KOhm from the ESC connector through the KS to ground ... looks right. I checked the KS by connecting a sensitive voltmeter and banged on the block ... got a signal in the 10s of millvolts.

I went back to my original ESC ... same behavior.

Now, before I changed all this stuff, winaldl was showing me a few sparks on startup, and then a spark every now and then. But now I never see a spark ... except dozens or more on startup. I am wondering if my "new" 350 ECM is having a problem reading the ESC logic signal.

Anyone got any ideas?

 

Hi guys ... problem solved. As usual, the problem was caused by my own misunderstanding.

My 91 RS came equipped with a L03 306 ... roller cam. The car came equipped with a ESC module - GM p/n 16126761. The ESC I salvaged off the Caprice Classic with the 350 TBI setup came equipped with a 16128261. I also salvaged its knock sensor.

A little research at the GM parts site confirmed what is said in the sticky 305-350 swap ... these 16126761 was used in a lot of 84-92 applications, including both the L03 F-Body (305 roller cam) and various 350s ... with hyrdraulic flat tappett cams. Well, what I have is a 77 block and a flat tappetts so I restored the original ECS module and knock sensor to the configuration and have been getting reasonable knock counts (low rather than zero) and no Service Engine Light.

So I was able to get a clean data run and I see my BLMs are tending high ... 136-150 in a lot of cells. But that is another issue. I suspect I am heading toward the realm of DIY prom burning.

Thanks for viewing my question and for help on past matters ...

Rob