Hey gang - it's been some time since I last posted here. A happy 4th to those of you celebrating.

I've been trying to track down the cause of some electrical weirdness on my '82 and could use some assistance.

This is a car I've swapped a 350 into, and I kept all of the Crossfire electronics (but now with the bigger 'vette injectors) to keep it looking original under the hood - I haven't been able to get it running/driving since the swap.

Here's what I've got and what I've done so far:

Following the instructions in the factory service manual, I've checked the Throttle-position sensor (between the top two points) and it reads 5.3 volts at idle, and goes down to about .5 volt at WOT. My understanding is that this is the reverse of how this circuit should function.

As such, I've tried unplugging both the MAP and CTS to see if the readings would change (and they don't)

I've checked ground for both MAP and CTS/TPS, and they are good (i.e. checked for voltage between ground on the sensor and "true" ground.)
I've checked 5v reference to ground at both the TPS and CTS and it is good.

I've checked for continuity between 5v reference and ground with everything unplugged (looking for a short) and there is none.

I've checked for stray voltage in TPS signal wire (blue) by checking it against ground, there is none.

When I checked for stray voltage from the MAP signal wire (green) and ground with it disconnected, it initially gave me 5 volts, but then it became zero. Which signal is correct? I assume zero?



With that inconsistent reading from the MAP circuit, I decided to bypass it. So I went into the wiring harness for the ECM and gently cut the 5-volt reference wire, and connected it straight to the TPS. I gently cut the ground at the TPS and went straight to the battery. Nothing changed, even with the 5v reference coming straight from the ECM and ground straight from the battery. I even tried disconnecting the blue signal wire at the TPS, and even with that circuit broken, I still get my 5.3 volt reading at idle between the 5v ref and signal wires.

I should also mention I've changed the TPS itself.

That said, with the MAP bypassed like this, I can get the car to start if I feather the throttle and hold it open (presumably because at mid-throttle, the TPS reading is close to accurate,) but it definitely will not idle and it will pop and fuss if I try to go too crazy with the throttle (presumably because it doesn't have a vacuum reading from the MAP to adjust fuel trims to.)

I have to assume this is some kind of weird grounding issue but I'm open to suggestions?

I've got a few tools at my disposal, but nothing fancy - DVOM, test-light, a basic cable tracker/transmitter.

If anyone's got some thoughts on this - that would be helpful.

I should also mention I spent some time polling a couple of CFI guys on the 'vette forums (since most of the world's CFI experts are 'vette owners,) and at the end of the day, it was just one guy who was pretty adamant that my problem was that my service manual was misprinted.

Thanks in advance!

 

awesome what did you use for heads and cam ?

 

Any update progress ?
Running a 747 ecm might be the way to go. Get a unhacked x fire harness and pin it to work with a 747 ecm.