Thanks so much for that last post. It gave me the info I needed to rule several things out. I had not managed to find info like that anywhere doing google searches, and I wonder how the scan tool in the examples can be hooked up to my ECU. I don't have a connector that can allow ECU parameters to be sampled.
1. TPS was .453v at idle. That's in spec, and it's a good thing because these TPS sensors are riveted on; therefore, not adjustable. Just for giggles, I even took the old cx throttle body and plugged its TPS in (without bolting that TB to the manifold), started the car, and at idle, it still surged. I know THAT throttle body/TPS was good because the old motor didn't have idle problems. That ruled out the bad TPS sensor issue mentioned in the tech article.
2. Idle screw - this didn't change anything as far as the surging is concerned.
3. IAC - I had already tried the old cx IAC and even though it didn't fit right, I managed to make the gasket seal to the manifold using only one bolt and two big tire straps. It still did the same thing. That IAC is also known to be good, yet it's for a much different motor.
4. I've swapped ECU's (P05 A00 and a P06 A01)
5. Swapped thermo sensors (both of them). The one on the head, and the one in the thermo housing. Voltages changed on both of them as the car warmed up, so they work. The only time it seemed to normalize was when I pulled the electrical connector from the coolant temp sensor on the head. It still surged when my foot was on the gas, but the idle seemed better.
6. I grounded the o2 sensor (no effect).
7. I clamped and pulled every vacuum line, and even leak tested the manifold with my boost leak tester. All of the vacuum lines are new, so none of them are blocked.
I can't find anything wrong with this thing, yet it's rejecting this transplant. Maybe my car is type O- and this engine is AB-? No? I thought that would be silly, too.
I just printed out page #182 and 183 of the service manual which details the coolant flow of the D15B7 and the D15B8 motors. They're different. The water pipes are different. The flow path through the AIC motor is different. I'm pretty sure I have it right, but this is the last thing I have left to verify aside from the wiring harness. If it's all plumbed properly, I really don't know what to do.
Is there any reason a CX wiring harness shouldn't work on a DX motor? The only difference I can see is the length of the wires that go to the idle purge solenoid, and the cx uses a 1-wire o2 sensor instead of a 4-wire. The other 3 wires on the o2 sensor are only used for a heating element, so it shouldn't affect the o2 reading. There is no provision for using a heated o2 sensor on the cx wiring harness.
I do appreciate the help that has been offered with this so far. I'm sure I just have an oddball problem that would stump the most avid of mechanics. It's done that to 3 of them already, anyway. I guess this is what I get for swapping a car that already runs to start with. Thank God it's my car. Thanks again.
Jafro
95 GSX
92 cx hatch w/D15B7 transplant