Another wiring check please

[88E30M50]

Hey Guys,

Sorry to keep bothering the group with this car, but can someone take a look at the wiring adapter I'm using? I'm trying to drop an 91 E34 M50 into an 88 E30 325is chassis. I've not gotten the thing to run yet and am starting to lose faith in it's ever getting to run. Here's the rundown on the situation:

91 E34 M50 with a 402 ECU with a stock chip. The ECU tests well in my 92 525iT.

88 325is chassis that ran well until I pulled the engine.
Ebay headers
K&N Filter
MAF runs on the 525i, but not as well as the 525's MAF sensor. The 525i MAF sensor does not change the situation when installed on the E30.
Crank and cam sensors are brand new and have been backprobed to the ECU connector.
The engine has not been apart since running in the donor vehicle, except to have new valve cover gaskets and pan gaskets installed.
Fuel pressure builds while cranking and holds at around 51 psi for hours after. There is still residual pressure in the system 48 hours after the last cranking attempt.
Coils check good. I've swapped coil packs out with the spares from the 5er and still no joy.
Using Bosch double platinum plugs (not crazy about them, but they are brand new)
With noid lights installed, injectors look to be firing correctly.
Checked spark and it looks good.
O2 sensor is not connected, but when I do connect one, it makes no difference.
Check engine light works fine with the stomp test (throws 1264 without O2 sensor relay and 1444 with)
Oil pressure light goes off while cranking.

When I try to crank, I get stumbling and misfires with an occasional backfire through the intake. Twice now, while cranking it seems to almost catch, but dies as soon as I let go of the key. The exhaust has felt warm to the touch after each of those times, but normally, it is the intake manifold that seems to get hot. The wiring diagram is:


I appreciate anything you guys can do to get this project beyond this point. I'm out of ideas and cannot keep throwing money at it right now.

Thanks,

[Jason89i]

When I try to crank, I get stumbling and misfires with an occasional backfire through the intake. Twice now, while cranking it seems to almost catch, but dies as soon as I let go of the key. The exhaust has felt warm to the touch after each of those times, but normally, it is the intake manifold that seems to get hot. ,

how much vacuum are you pulling?

cheers, jason

[JGood]

I had the same type of near start condition, it would stumble and burble, but wouldn't catch. I doubt this is your issue, but check your harness adapter connections. I was getting continuity across the adapter I made, on all pins, but the pins were corroded enough to not allow voltage/signal to flow properly (I had a old square c101 that was sitting around for a while). After 7 days and 50 hours of cranking with no starting, I cleaned the pins, the damn thing fired on the first try.

Make sure your cam and crank sensors aren't swapped (I think they read the same resistance, so even checking at the ECU won't necessarily prove this out)

I assume you've checked all your grounds, considering all the other testing you've been through.

[88E30M50]

I had the same type of near start condition, it would stumble and burble, but wouldn't catch. I doubt this is your issue, but check your harness adapter connections. I was getting continuity across the adapter I made, on all pins, but the pins were corroded enough to not allow voltage/signal to flow properly (I had a old square c101 that was sitting around for a while). After 7 days and 50 hours of cranking with no starting, I cleaned the pins, the damn thing fired on the first try.

Make sure your cam and crank sensors aren't swapped (I think they read the same resistance, so even checking at the ECU won't necessarily prove this out)

I assume you've checked all your grounds, considering all the other testing you've been through.

I'll check and clean the connectors tonight. I am sure I have the cam and crank sensors correct. I back probed the connectors to the ECU to verify which was which. Then, to be sure I was not screwed up still, I tried it with them swapped. With the crank and cam sensors swapped, it did not get fuel or spark.

I think the values on the cam and crank sensors are different. I check the ones on my 92 525 nv and got similar readings to the new ones. They were something like 1238 ohms and 540 ohms. My notes are at the house and I'm at work right now, so I don't remember which reading was which. I do remember that the Bentley manual is wrong on the crank test though.

[88E30M50]

how much vacuum are you pulling?

cheers, jason

I'll put the gauge on it tonight and check. What is a common vacuum reading when cranking? In the past, I just cranked and watched the needle to see if there was vacuum.

[88E30M50]

how much vacuum are you pulling?

cheers, jason

You have me thinking along the lines of vacuum issues now. I was thinking vacuum a while back and pulled the intake manifold to be sure there was nothing underneath that I missed or that I did not have a wire or something trapped at the flange. When I crank with the vacuum gauge attached, I get needle fluctuation in both directions. That is, there are spikes of positive pressure as well as actual vacuum.

Question is, what would cause this? I seem to get decent numbers on a compression test, although they do indicate a tired engine. I was thinking that the compression check would rule out any valve timing issues or bent valves that would vent back into the intake. Could a bad idle control valve kill vacuum? All lines are new, as is the brake booster.