Help with my F20B swap and PCB ecu

[ali954]

I ordered a full F20B swap including LSD trans, wire harness, ecu etc. My plans were to run the factory PCB ecu that came with the swap. So I got an OBD1-OBD2B ecu conversion harness, which I had to add 2 wires for the EGR. For the engine harness, I started with the harness of the F20B that went all the way to the ecu. I took the accord engine harness and followed each sensor back to the factory shock tower plugs for reference. An extra plug for additional wires like vtec and knock was added to the passenger side. I bought a new prelude distributor and converted it to internal coil and made it 2 plug OBD-1 style with the tach signal.

I did the timing belt job, with a manual tensioner conversion, new h22 timing belt and water pump. I also replaced the seals while I was there and put in a Skunk2 cam plug on the other side that was leaking. Compression is good on all cylinders.

Once the swap was installed, I had trouble starting it due to the reassembling the distributor 180 degrees out. Once that was fixed it fired right up. Then I lost spark, which ended up being my coil. Replaced the coil and it started back up. Noticed one of the header pipes was not warming up, which turned out to be a dead injector. Replaced the injector and now she is firing on all cylinders.

So that's the back story, now I need help.

The PCB ecu starts the car fine with no CEL beside initial priming. However, the header gets very hot very quickly. Within idling for a minute, the header is cherry red. It is turning the NGK plugs black. I ordered another PCB ecu to try and it does the exact same thing, again no CEL. The car also runs on a PT6 and a chipped P06 without the header heating up. Both throw a CEL 12 for CYP.

I've seen almost nobody actually use the PCB ecu, but I would love to have this engine running with ultra low emissions and a functional egr.

[Raf99]

I was thinking clogged CAT up until i read that you can try another ECU and the symptoms go away. But it's running rich and implies that it's the ECU and only th ECU.

The only thing I can think of is that you're using a non supported O2 sensor (non-denso) and the different ECU's can't read the data, thus dumping fuel or limiting O2. Could be MAP or other sensor too.

[ali954]

I put a new denso o2 sensor for a 2000 prelude and it didn't help. And for the MAP, im using the F20B TB with its MAP and TPS. Ive tried an CD5 TB and it was the same result as well.

I'm thinking its running rich on the PT6 and P06 where i see black smoke out the exhaust, and super lean on the PCB ecus with all the heat.

The motor is all stock except a IAB stack which I've always had and I doubt would affect it like this.

[deevergote]

If the CYP is faulty, your fuel/ignition may be WAY out of whack, and the ECU may think it's right. Hot header and fouled plugs make me think that the fuel mixture is igniting late, basically as it's exiting the exhaust valves. I could be 100% wrong, as this is beyond anything I've ever dealt with myself... but that was my first thought after reading your description.
Was the distributor used? I would try another one.

[Raf99]

Well I'd stick with the OEM ECU and troubleshoot the car. Your issue reminds me of the below video I seen recently. All it took was one little air leak.

[deevergote]

Definitely stick to the OEM ECU. If it's not running right on the proper ECU, it's not running right.

I'd think that running lean would result in chalky spark plugs, though. If they're black, they're being fouled by too much fuel rather than too little. That's why I suspect ignition is taking place as the gas is exiting, leaving the plugs with nothing but soot.

[ali954]

The video that Raf posted is the same symptom. This makes me want to replace the intake manifold gaskets again. I put a thermal gasket between the head and runners, while the other gaskets are the paper style.

Deev, the distributor is a new one from ebay for a 2000 prelude that I converted to internal coil. I checked the resistance of the TDC, CYP, CKP, all of which are within spec. I still find it weird that the PCB ECUs don't throw a CEL for CYP while the others do.

[Raf99]

Spray some brake clean or whatever around the gasket and see if you hear a difference. But when the manifold is getting cherry red hot the car is running like shit right?

[ali954]

I've tried using brake cleaner to searching for vacuum leaks with no success.

The car starts easy and idles around 1500 rpm. I never leave it running long enough for the FITV to close and bring idle down. But it does idle smooth, no misses or anything.

[Raf99]

Stupid Question, what's the OEM ECU for a F20b ? (I mean, i only read of people using chipped ECUs)

[dj_ender]

The PCB that's being discussed.

[illinois_erik]

I'd get pin outs and continuity check the conversion harness to verify its made right

[ali954]

I'd get pin outs and continuity check the conversion harness to verify its made right

For pin outs, it's just an OBD2B ECU thats missing things like EVAP and a second O2. All the wires that were connected to the ECU with the swap are accounted for. I did verify all my wiring with a continuity test. I have continuity from the conversion harness to the sensors on the motor. Checked the distributor, MAP, TPS, IACV, O2, etc. That's how I found out it was missing 2 wires for the EGR. Again there is no CEL, I would assume if something was not connected, it would throw a code.

I got the IM gaskets today and hope to put them in tomorrow, weather permitting.

[toycar]

what injectors are you runnig? pretty sure f20b = saturated and cb7=peak and hold


check injector pulse and swap injectors around to see if problem follows the injector

[Raf99]

The PCB that's being discussed.

And the name of it is?