How can I fix a check engine light (CEL) in a pre-modified honda prelude?

Question

so i bought this car a year ago and found that the check engine light wont go away no matter what i replace or fix. it comes and goes, but its always the same codes, P0172, P0170, both are for "Fuel trim bank one".....or atleast thats what comes up for Autozone OBD-II readback. I bought the car with mods already done to it....DC headers, Cold air intake, short-shift......

Answer 1

I don't know what year your car is but I can't find the P0170 tied to a prelude. The P0172 is for a fuel system that is too rich and the car's on board computer can't lean the mixture out enough to keep it running in the normal range of operation.

your oxygen sensor is working if you are getting this code; its not an O2 sensor problem. Your problem is too much fuel. More likely than not you've got a leaing fuel injector. You can test for that but you need a fuel pressure gauge to do that and most people don't have one of them lying around. The fuel pressure could also be the cause of the problem if you have too high a fuel pressure but that is very uncommon.

the code means the condition is affecting all cylinders, not just one. You may also have oil that is diluted with gasoline if you have a leaking injector; you would be able to smell that on the dipstick when you pull it out to check teh oil. If you have gas in the oil the gas would get pulled up into the intake through the PCV and be a second source of fuel. If there is gas in the oil change the oil and filter before you go after the injectors and that may solve your problem. Gas can get into the oil if you flood the car trying to start it (yes, fuel injected cars will flood out).

The leaking injector, too high a fuel pressure or gas in the oil are the three most probable causes of your concern.

hope that helps

Answer 2

Were there any fuel mods done? The header (singular), intake and short shifter wouldn't throw the codes your getting.
These are some of the possibilities I've found.

Probable causes for fuel trim bank one:
1. Mass Air Flow Sensor (not it-mechanic tried)
2. O2 sensor
3. ignition misfire
4. fuel injector problem

I hate getting a CEL, I hope you fix it soon.

Answer 3

I would make sure you have a O2 sensor. sometimes other people will put headers on there car but there will be no bun hole for the O2 sensor. if you do have one it will be on the very end of your header. look under your car and see. if it is there replace it. i bit that will fix it right up. after replacing it dont forget to clear the code. pinding on what year your lud is you can pull the back up fuse and the ecm fuse for about 2 min, and your code should clear.(fuse box under the hood) good luck.