1994 Acura Integra 4 cyl Front Wheel Drive Manual 180000 miles
----------------------------------------------------------------
I have a 1994 Acura Integra with 180,000 miles that I bought recently. It has a GS-R (VTEC) engine from a 1997 Integra in it, as well as some after-market parts installed (headers, cat-back exhaust, cold air intake, Apexi V-AFC II).

My problem is that I can't get the car to pass emissions. The car is producing 6 times the legal limit of CO, but the other tests are OK. The mechanics where I got it tested tried to work on it, but they got nowhere and told me to ask a Honda professional. They also said the high CO is because the car is running rich. The car does idle funny in the morning, but after driving it a block everything is OK.

I disabled the V-AFC before going to emissions testing the second time, and still failed. (A V-AFC is an aftermarket computer that fits in between the engine sensors and the ECU. It lies to the ECU and can be programmed to adjust the fuel/air mixture)

The emissions mechanics did replace the water temp. sensor as well as installed a new cat and O2 sensor (there was a testpipe and an O2 sensor before).

I should also mention that sometimes the check engine light goes on when I start driving, but if I park and shut the engine off for a few minutes the light goes away. This only happened 3 times in the past month.

Any idea what to look at first? Tomorrow a friend of mine is coming to look at it but I would like to have more input. Thank you in advance.

Hi andkorn,

Get a scan done to find out what is causing the CEL to show.

Since there are a lot of modifications, you need to isolate the possible causes.

When the engine is running rich, you need to check the TPS, MAP, O2 sesnor, injectors (have they been replaced with over sized units), fuel regulators, ignition timing, spark plugs, catalytic converter.

The ECU is ODBCI, so my mechanic was unable to check it. He did preform a trick where you short out 2 pins on a connector under the dash and the CEL flashes a certain number of times, thereby giving a code (by counting the flashes). The CEL did not flash though.

I took the car to another mechanic, where they connected an oscilloscope to each sensor to check the raw data that the sensor was reading. They ended up replacing the O2 sensor (right before the catalytic converter) and the water temperature sensor (the previous mechanic put in sensors that didn't work). These new sensors were outputting correct signals now, and they reported the rest of the sensors were working correctly.

They also replaced the timing belt and corrected the timing, replaced the spark plugs, and checked if the fuel injectors were stuck open (they were not).

The fuel injectors are stock according to a friend of mine who is a Honda mechanic. The catalytic converter is brand new.

The mechanic I took it to last (the one with the oscilloscope) said that under 25% load the car won't pass emissions, but once you get it up to 30% load or higher it is OK. However, the emissions test requires the car to be under 25% load. He also says that the car doesn't go into closed-loop under low loads. They also did a compression test, which came back as 200 on every cylinder (200 _what_, I'm not sure).This mechanic had the car for two weeks, and he called everyone he knew for advice.

Could it be that the previous owner did not replace the ECU when they swapped the engine? Remember the car is a '94 Integra LS (ODBCI) and the motor is from a '97 Integra GS-R (ODBC-II). Maybe the previous owner replaced the camshafts with racing cams? Or perhaps they had a Hondata (or similar) reflash to the ECU.

I am drawing a blank, as is every mechanic that has worked on this car.

Thank you for your help so far! I will post my last emissions results when I get home.