wilson007

First off, hello guys! I'm new here.

Anyways, I own a '98 base prelude and have been trying to troubleshoot these codes for quite awhile now and desperately need some help. Although at the beginning I was also pulling an EVAP code, currently I have P0170 (fuel trim malfunction) and P0172 (system rich). The codes don't stay on all the time, by the way. They will turn off for a few minutes maybe once a week. Also, I took the exhaust off and it doesn't appear to be running rich due to normal/lean markings on exhaust valves and O2 sensors. Here is a list of what I've done so far:

-replaced both O2
-replaced fuel pressure regulator (was running a LITTLE higher than spec, now at normal levels)
-new fuel filter
-new plugs, wires and dist. cap
-new gas cap
-cleaned injectors
-checked for vac leaks
-swapped the ECU
-went through the entire HELMS flow chart for solenoid malfunction, etc...
-cleaned carbon deposits from IM 2 years ago
-brought it to the Honda dealer for a diagnosis and they came up with nothing after about 10 hours with it

Currently, the Honda dealer wants me to just drop it off and leave it with them to fix it but I'm a little hesitant to do that because they've had it for so long already without any results. Also, labor adds up REALLY quickly when trying to troubleshoot something like this. If anyone has an idea of what might be causing the problem I would greatly appreciate the help.

TIA!

gstrudler

I would suggest trying to swap injectors with known good ones and see what happens. If that doesn't help, I would probably next check the wiring to your primary o2 and measure resistance and all that good stuff to make sure the wire isn't killing or modifying the signal before it hits the ECU. I believe with a good OBD2 reader (like the PGM tester the dealership has) you should be able to read a/f ratios live while the engine is running and that will tell you whether it's actually running rich or just a sensor malfunction.