JDMZ28

94 Z28, 13.0:1, big cam.

I swapped the pcm and maf and still have the same codes.

The issue is, with the maf plugged in, the car is hard to start and it also will die when you let off the gas. I'm getting a very strange spike in the maf when the car stalls as well. The strange part is when I unplug the maf or run in SD mode the car runs just fine. I would like to retain the maf as I'm running open loop.

I think it has to be a wiring issue but I'm not super familiar with LT1 diagnostics.

Injuneer

DTC 16 and DTC 36 are for problems with the cam position signals from the optical module in the Optispark distributor. When you clear those codes, how fast to they come back? What brand distributor and how old? Have you checked the harness connectors for corrosion, damaged pins, damaged insulation or missing retainer clips?

With regard to the MAF, is it possible the intake elbow is torn, or not fully on the throttle body?

DTC 41 and DTC 42 relate to the ignition control module. Have you had the ICM tested under high heat conditions?

The EEPROM error is hard to explain. What scanning device are you using?

JDMZ28

They come back fairly quickly (within a few minutes). I'm scanning with data master. The car is an electrical nightmare, wires hanging here and there. It also would break up under wot to the point to where you have to let off. I thought it was the plugs so I changed them but haven't had a chance to testif it does it in SD mode or not.

Injuneer

DTC 16 would have to be intermittent, because if it is an active code, the PCM shuts down the fuel system, because it can't time the injectors and the spark. The engine wouldn't start or run. Must be a stored code, but the fact it comes back right away indicates it's a real problem.

JDMZ28

I swapped pcms and mafs and the codes came right back. The intake housing is solid. It's strange to see the afgs normal and then suddenly spike up to 200+ as it stalls. Since I know the Maf is good and the car runs in SD mode it has to be an electrical problem. Would a bad opti cause this or a bad ground? Would it help to see a datalog of the Maf spike?

JDMZ28

I'm sorry but how do I test an ignition control module and or wiring?

Injuneer

You have to take the ICM to an auto parts store, and let them test it. The important thing is it has to be hot to show up the typical heat soak defects.

There are no codes for the MAF, at least not that you listed. It should set a code when you disconnect it. Did it stall and show the same spike with the substituted MAF?

JDMZ28

It only showed a code when I disconnected it. Yes I got the same spike and stall with the known good maf, symptoms didnt change at all

JDMZ28

It still breaks up in SD mode. I think it's the ICM or opti. However, that doesn't explain the Maf issue.

Injuneer

The question is - is the MAF "spike" the cause of the stall, or simply a consequence of the stall, and it's true cause?

Do you have a data log that shows the stall? Can you post it to an FTP site so I can download it?

JDMZ28

I can post on hptuners. I'm not sure if the spike is the cause or not, I can only assume.

JDMZ28

I'm pretty sure that's an edelbrock opti, would that throw the 16 and 36 codes?

Injuneer

I've never heard of an Edelbrock Opti. Google search does not turn one up.

Doesn't matter what brand it is with regard to setting the codes. The PCM looks for the data it requires to run the engine, and if it doesn't get the data from the Opti, it sets the code.