I bought a 1988 Civic hatchback with a '95 del Sol VTEC engine in it. It's got the original ECU. It had several error codes that I tracked down because I thought they were causing the emission problems, but it is still failing emissions for high HC and CO. Compression is good, 180 psi in all cylinders. The injectors appear to be older type, resistance is 2.5 ohms across the terminals instead of 12 ohms like in my stock del Sol. Injector wires go to a resistor block. Voltage at the injectors is 0.5 at idle, 2.0 volts at higher throttle. The engine runs great, no rough idle, good acceleration. Just bad emissions. CO is over 6%! Any help is appreciated.
High HC and CO from swapped engine
- Thread starter crodog
- Start date
- Replies 12
- Views 2K
We may earn a small commission from affiliate links and paid advertisements. Terms
Thanks for your advice. I checked the cat temperature after the engine warmed up this morning. The cat appears to be at about the same temperature as the inlet temperature so I think it is not working well, if at all. I had already checked the injectors by pulling the wires off each and listening to idle speed, checked resistance and voltage, clicking. All checked out OK. O2 sensor is behaving as it should according to a digital voltmeter. I may still check PCV valve and carbon canister but I'm hopeful that a new catalytic converter will fix the emissions. Thanks again.
The engine (1.6 L VTEC) has lots of power, more than my '94 del Sol or '94 hatchback (both have 1.5 L engines) and gets 35+ mpg. If a new cat fixes the emission problem, is there a good reason to get the original ECU?? That would be a rewiring nightmare since the ECU plugs are different. My questions: is my fuel mixture rich (high CO and HC) because the old ECU and injectors put too much gas into the engine? Or maybe my fuel pressure regulator is bad. Should I expect better fuel economy from this engine?
While browsing other threads, I found this comment: "if your car is tuned to an afr that is close to 14.7:1 and you have a working cat, youll pass most emission tests." Forgive my ignorance, but how do you tune the afr? This ain't the old days when you turned a screw on the carb.
Have you dynoed it?
No?
Then how do you know it has lots more power than your old engine?
A good reason to use the correct ECU is becaues it will have the correct fuel and ignition maps for your motor.
Also, by turning a screw on a carb, all you're affecting is the mixture at idle. Nothing else. Turning the idle adjustment screw on a carbourator ONLY adjusts the IDLE. If you want to change the fuel mixture throughout the RPM range you have to change the jets.
No?
Then how do you know it has lots more power than your old engine?
A good reason to use the correct ECU is becaues it will have the correct fuel and ignition maps for your motor.
Also, by turning a screw on a carb, all you're affecting is the mixture at idle. Nothing else. Turning the idle adjustment screw on a carbourator ONLY adjusts the IDLE. If you want to change the fuel mixture throughout the RPM range you have to change the jets.
its all good, most people dont know, but ill let you in on the REAL tuners most closely gaurded secret.
the thing is called a wide band o2 sensor. unlike a narrow band, it doesnt just switch on an off as it goes above and below 14.7:1, it tells you exactly where you are. If you monitor your tps and rpm in conjunction with the signal from that wideband, you will have the information you need to either tune your car for performance, gas mileage, or just to pass inspection.
Having the information is good, but then you need to know what to do with it. After you find someone with a wideband (or purchase one yourself....they are a smidgen expensive though) then you gotta change the maps in your ecu. Most of the people on this board do that by chipping their ecu (meaning removing the old chip, soldering in a ZIF socket to their ecu, and adding a new one with a new program on it). I would recommend staying away from things like the apexi VAFC or greddy emanage. They are called piggy back ecus, and the only time i condone their use are if there is NO WAY you can wire in an obd1 ecu.
So after we have our ecu chipped (btw, the p30/p28/p72/p06 are the most commonly chipped ecus), we need to write the program for the chip. Id suggest you use a program called crome (< C R O M E >) to write your new map. Basically you can see what the map is doing at different manifold pressures and rpms. Basically, if your running lean at 5000 RPMs and 30% throttle, you can adjust that spot on the map to run rich.
This is just a quick overview, we have a whole lot of tuning write-ups (as does pgmfi.org • Index page. I gotta go to work in a few, and going through a full write up aint gonna happen today....i bet you miss that carb screw right about now.
the thing is called a wide band o2 sensor. unlike a narrow band, it doesnt just switch on an off as it goes above and below 14.7:1, it tells you exactly where you are. If you monitor your tps and rpm in conjunction with the signal from that wideband, you will have the information you need to either tune your car for performance, gas mileage, or just to pass inspection.
Having the information is good, but then you need to know what to do with it. After you find someone with a wideband (or purchase one yourself....they are a smidgen expensive though) then you gotta change the maps in your ecu. Most of the people on this board do that by chipping their ecu (meaning removing the old chip, soldering in a ZIF socket to their ecu, and adding a new one with a new program on it). I would recommend staying away from things like the apexi VAFC or greddy emanage. They are called piggy back ecus, and the only time i condone their use are if there is NO WAY you can wire in an obd1 ecu.
So after we have our ecu chipped (btw, the p30/p28/p72/p06 are the most commonly chipped ecus), we need to write the program for the chip. Id suggest you use a program called crome (< C R O M E >) to write your new map. Basically you can see what the map is doing at different manifold pressures and rpms. Basically, if your running lean at 5000 RPMs and 30% throttle, you can adjust that spot on the map to run rich.
This is just a quick overview, we have a whole lot of tuning write-ups (as does pgmfi.org • Index page. I gotta go to work in a few, and going through a full write up aint gonna happen today....i bet you miss that carb screw right about now.
Last edited by a moderator:
I put a new cat on. It appears to help as there was some visible smoke before the new cat and no smoke after, but the car still fails for high HC and CO, at about the same levels as before the new cat. Very frustrating. I don't suspect rings since compression is good and consistant in each cylinder. Too much fuel. What can I do BESIDES replacing or reprogramming the ecu? I have the injectors from the Z6 engine (A6 injectors with resistor block are in the engine now). Can I use them? I admit I'm a weekend tinkerer with a limited set of diagnostic tools. No FI fuel pressure gauge, no fuel/air mixture gauge.
I have tried retarding and advancing the timing. Neither has any significant effect on HC or CO. I'm sure I'm dumping in too much fuel or the CO wouldn't be so high. I am not looking forward to replacing the ecu, but that might be my next step. I might try swapping fuel pressure regulators first...
Similar threads
