F20, F22, F23
By BlcknPrplCoupe
#6908946 Like the title says, new to the Civic world. Bought a 94 Coupe with a, what seems to me, cobbled together F20B swap. Lots of jenky wiring going on all over the car. Plus weird issues with A/F readings and check engine light coming on whenever i get a little rowdy with it. Runs pretty good, but just a lot of weirdness going on. Any help would be appreciated. I know this is a bit vague, but any pointers of things to look for would really help.
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By EconoBox
#6908947 Welcome!

Is it a full F20b swap(F20b/H22 transmission with cable shifter and Prelude or Accord shift box) or is it an F to B (F20b engine with B series transmission, has shift rods and stock EG shifter)

The F20b swap is pretty straight forward. I know it probably has some hacked wiring that's really common for the F20/H22 swaps. The engine can actually use an stock Civic engine harness with a little finessing (aka removing the loom to reroute some wires) and extending the wiring for the alternator up to the front of the motor. Some pictures of the wiring would be a good idea for us to see what's going on all though none of that can be easily diagnosed over the internet.

Check engine light (MIL) is commonly setup as a shift light on the chipped ECUs. If the MIL comes on in high RPMS and then goes off once you shift or let out that's more than likely what is going on. The MIL can also be configured as an overheat warning to come on above a certain temperature and then go off if/when the temp goes back down. This won't leave a code stored on the ECU but unlike the shift light setting it usually won't just blip on and off.

Before diving into the funny air fuel readings there are some things you need to check.
- spark plugs? Use NGK V-Power resistor (ZFR6F-11) type spark plugs (if it has autolites or bosch or something else its junk)
- spark plug wire condition? again NGK plug wires or Honda OEM
-What fuel injectors? Check the impedance and then see if you need or already have a resistor box (a lot of people add it when it's not needed or don't have it when it's needed and funky things happen)
-Base fuel pressure?
-Check/Set timing with a timing light
-Check grounds (engine wire harness grounds on thermostat housing, chassis to transmission case, valve cover or head to frame/core support.

Once all that looks good and you know what your timing, fuel pressure, and injector size is. Pop open that ECU and see what you have. The common cheap method to get these running is to use a chipped P28 running something like Chrome. If you're lucky you'll have purchased a car that has Hondata S300 or a standalone ECU (like AEM) where you can get in and make some changes or have it easily tuned. Post a picture of the ECU when you can. If you are unlucky someone slapped in an adapter harness or moved some ECU pins around and stuck in the stock ECU that matches the engine.

Assuming you are running 93 octane pump gas your AFRs should be 14.7ish steady when cruising or at light throttle and they should slowly drop as you increase throttle. You'll want to see around 13.2 on a naturally aspirated setup at wide open throttle. AFRs will go full lean on off throttle conditions or deceleration until you are back down to idle speed. If you are seeing anything over 14 afr when hard on the throttle I'd stay out of it to avoid the chance of doing damage.
By BlcknPrplCoupe
#6908948 First things first, thank you.
Secondly, whoa that's a lot more info than I was expecting. So the car does have a Hondata ECU, I'm unsure of what model. I checked it the other day to see if it has a USB port in the case and couldn't find one. It is missing almost all of the screws on the case so it is electrical taped closed and I didn't really have time to dig into it.
I will purchase the plugs and wires that you recommended and see where i end up with that.
How do I go about checking the impedance of the fuel injectors?
I'm actually a little ashamed to admit that i didn't even think to check the timing with a timing light. I come from an old school V8 background and that is always one of the first things i used to check whenever i bought a new car.
I guess i need to buy an inline fuel pressure gauge so i can check the fuel pressure.
I'm pretty sure that the engine is grounded to all hell. There are grounding wires all over the place in the engine bay. lol
The MIL comes on and stays on. If my temp gauge is correct, it never even gets close to hot. It has a gigantic radiator that i have plans on swapping out for a dual core, half rad. If for no other reason other than freeing up space in the engine bay.
The A/F gauge never goes lean other than when I'm off throttle and decelerating. At WOT, I'm running around 11.0-10.0. At idle its anywhere between 13.0-15.0
Again, thank you for the help. This gives me a good starting point.
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By EconoBox
#6908950 No problem! Glad I could start you off in the right direction.

For checking the impedance you are just checking resistance across the injector itself. So just use a multi meter to measure the resistance (ohms) across the injector.