All out of ideas

[capri debris]

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This is a deperate plea for help, mostly from those who understand ECUs. I've been exhausting myself trying to track down this problem and hope someone can shed some light. This isn't your average, "My car won't idle" thread, this is waaaaay worse.

Subject:
An '86 Capri 5.0, C4, mass air conversion with an A9T ECU, Trick Flow top end kit, 24 lb injectors, 70mm TB, 75mm Pro-M mass air meter, 255 pump, smog delete, EGR and charcoal canister removed.

Problem:
1. Car will idle when first started COLD and in open loop, but starts hunting and dies as soon as it switches to closed loop.
2. Can pull KOEO codes and only get ones that pertain to the smog stuff being unhooked.
3. Can't pull KOER codes. Car just dies out half way through the test and reads: "Vehicle not responding" on my digital code reader.

What I've done so far:
1. Replaced the original A9P that came with my M/A conversion kit with an A9T and problem is still there.
2. I have cracked open both ECUs and there is nothing burnt or messed up that I can see.
3. I've checked all my wiring to make sure I didn't get anything crossed or hooked up incorrectly and as far as I can see it's all as it should be.
4. I've run continuity tests on the mass air wires, sensor wires, ECT ground and power wires, O2 wires and all wires that go to the self test connector... all checks out fine. All chassis grounds are good also.

Hopefully someone's had this same problem and can point me in the right direction because like the title says, I'm all out of ideas and I'm about to swap it to a carb.

 

[jrichker]

To get the engine running codes to dump, you will need to temporarily ground computer pin 30 to the chassis. Computer pin 30 uses a Lt blue/yellow wire. Remove the passenger side kick panel and then remove the plastic cover from the computer wiring connector. Use a safety pin to probe the connector from the rear and jumper the safety pin to the ground near the computer.

The computer wants to make sure the A/C is off due to the added load on the engine for the engine running tests. It also checks to see that the transmission is in Neutral or the clutch depressed (T5, T56, Tremec 3550 & TKO). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

If that does not work, start checking the signal ground black/white wire for continuity back to the battery negative terminal. You should see 1.5 ohms or less between the black/white wire on the TPS, ECT, ACT and EGR sensors and the battery negative terminal. Do all resistance checks with the power off to avoid getting erroneous results.

If you find a sensor ground reading that is greater than 1.5 ohms, measure between that sensor black/white wire and pin #1 of the white 10 pin connectors. Pin #1 is the center pin and is labeled sig-rtrn on the diagram

Here's a diagram that shows what the black/white signal ground connects to:

 

[Cobra912]

wow what he said