Help with my F20B swap and PCB ecu

[deevergote]

PCB is the F20B ECU.

If it's not throwing a CEL, then I'd say you're right... everything that reports back to the ECU should be functional. That leaves a fair amount of potentially problematic stuff, though.

Given your attention to detail so far, I'd assume you're running the correct injectors, and not using the CB7's resistor box. Still, toycar's question is a valid one, as the wrong injectors (or using the resistor box with the right injectors) could definitely cause problems.

Since the other ECUs run the engine with the CEL on, they are running in open loop mode. Try disconnecting the o2 sensor and running the PCB with a CEL on to see if it runs properly. If it runs well, then I'd definitely suspect the ECU or possibly the o2 sensor (or its wiring.)

That is, of course, if the intake manifold gaskets don't fix the problem.

[toycar]

i personally think you have a burnt valve but was prodding and thinking about other possibilities.


do a leak down test on the cylinder, but i suspect you are getting combustion through the manifold, aka bad exhaust valve, but, dont want to be all doom and gloom.


its something specific to that cylinder, not the tune or the ecu or an o2 sensor or a bad gasket.

none of that stuff would affect only one cylinder, the problem would repeat itself across all 4 cylinder 99% of the time, and given the fact that the other cylinders are not getting hot, it cant be based on improper readout of o2 or a gasket leak. the manifold is glowing hot because the combustion is continous and happening outside of the cylinder.

if all 4 were getting hot than that other stuff would make sense. my guess is its related to injector behavior, or your exhaust valve isnt closing for the combustion cycle.


my .02

either way i would start with injectors though.

[Raf99]

ya. good point.

[ali954]

So I got the intake manifold gaskets replaced today and it is behaving exactly the same. None of the old gaskets appeared to be damaged either.

While it was running today, I put my fingers partially over the holes in the inside of the TB. The lower hole does nothing, meaning the IACV is closed I believe. The upper hole brought the idle down. With the idle lower, it began to miss. Could be the plugs getting too fouled or something else.

The injectors are the stock F20B injectors without a resistor box. Initially, one of them was not working. Found that out by switching around injectors and watching the one header pipe stay ambient temperature. Replaced the injector and all the pipes heat up together.

I have done a compression test and compression is good. I may have to buy or make a leak down tester. Just to be clear though, this is not an issue with just one cylinder. All cylinders are acting the same. All header pipes get cherry red evenly.

I will try to unplug the O2 sensor and see what it does next.

[Raf99]

Do you have a CAT on the car? Maybe she's jammed solid....

[deevergote]

A definite possibility.

[toycar]

guess i missunderstood and thought it was cylinder. my bad.


have you calibrated tps? black plugs usally = rich conditons, so whats causing that....

i feel like it might have something to do with your dizzy conversion or something that offers ignition timing reference data after googling your problem and reading what nightmares other people have dealt with

maybe verify firing order and dizzy conversion is correct again?

[ali954]

Yes the car has a cat and its not clogged. Had a look at it for the swap and header issues. The heat starts from the head and starts working downstream. The cat is not getting hot like the rest.

[Raf99]

Yes the car has a cat and its not clogged. Had a look at it for the swap and header issues. The heat starts from the head and starts working downstream. The cat is not getting hot like the rest.

Ok, so at the tail pipe you have plenty of pressure?
Toycar had a good point. If the dizzy isn't getting proper spark on one plug...

[deevergote]

The fact that it seems to run well without this issue when you use a P06 or PT6 with the CEL on really seems to suggest either an ECU problem or a problem with the o2 sensor or wiring.
The PT6 and P06 are not factory-programmed for the F20B, so if anything should be experiencing problems, it should be one of them over the PCB. Seeing as the only major difference between those two ECUs and the PCB is the presence of the CEL, that suggests that things are alright when running in open loop mode. That means the issue is likely to do with the fuel adjustments made by the ECU during closed loop mode, based on o2 sensor input. Either the ECU is getting incorrect input, or the ECU itself is faulty and providing drastically incorrect fuel mixture and ignition timing.
As toycar mentioned, the fouled plugs suggest a rich miuxture. The hot header suggests (to me) that the air/fuel mixture is igniting as it is being sucked out the exhaust valves. That could also lead to burnt exhaust valves, as mentioned (unfortunately, those valves are not equivalent to the H22's valves, so you'll have to find a US equivalent or source from some overseas if it comes to it.)

Once you pull that o2 sensor and run it with the CEL on, we'll know whether or not my thoughts on the matter have merit.

[ali954]

So I unplugged the o2 sensor and the headers still heat up. It throws a CEL for code 41, which is the primary o2 sensor heater. I have two PCB ecu's, both of which make the car behave the same way with hot headers. Also I unplugged the spark plug wires while it was running today and the idle dips on each cylinder, so I assume my spark is good.

The dizzy was apart of the continuity test. The sensor wires at the plug of the dizzy are connected to the right pins on the ecu conversion harness. I have a local friend with a h22a cb7, might ask to try his dizzy.

I have not calibrated the TPS. I'll have to test the voltage on it. Even though this is a JDM motor, the TPS is still riveted and doesn't have the torx screws.

With either of the PCB ecu's plugged in, the headers heat up and I see white smoke out the exhaust (assuming condensation). With the P06 or PT6 ecu's plugged in, I see black smoke out the exhaust and the headers are normal. If the issue is burnt valves, wouldn't the P06 and PT6 ecu's still make the header heat up?

[deevergote]

Weird. I hoped that by sending the PCB into open loop that it would stop doing it. I'm stumped now.
Yeah, I would expect the P06 and PT6 would do the exact same thing if it was something physically wrong with the engine. You may have valve damage, but there seems to be something else going on as well.

The only thing that seems to be questionable now is the distributor. Can you get your hands on an F20B distributor? Is it the same as a JDM H22A unit? In my experience, the more custom work you do to something, the more likely it is for that something to experience problems... regardless of your skill level or level of care.

[ali954]

The distributor that is currently on the car is the guts of the new prelude dizzy (TD61U) I bought, inside the F20B dizzy casing. The sensors are within the correct range of resistance. I did this thinking the sensors were mounted at slightly different locations, but they're not.

My friend's dizzy is an external coil so I don't think there would be an easy way to test it out.

I paid $60 for the new 2000 prelude dizzy. I could pay $60 for an internal coil TD60U dizzy from ebay, or $250 for a new dizzy from autozone. Both of these would be internal coil and I would not have to open them up. I don't care about the money if it fixes my issue but I don't want to be wasteful.

[Raf99]

wow, i really wish i could help. But I'm going to say assuming your sensors (TPS, MAP, ECT, etc.) are correct, then it's your distributor or spark plug wire order. Your plugs are firing at the wrong time, causing all the symptoms we are seeing here.

The car will not function properly with either ECU/PCB. What you need is a F20B PCB that is functioning and just work out the bugs.

Have you ever had this engine running properly in the past?

[dj_ender]

I saw this video and instantly thought of this thread.

https://m.facebook.com/story.php?sto...13741208636938