'95 Integra GSR, Intermittent Code 43 (Fuel Supply System)
 

Hello,

Occasionally when driving my Integra, the CEL comes on. Using the "paper clip jumper" method (yes it is OBD-1), I have discovered the code to be 43 (fuel supply system) which means there is an issue with either A) fuel pressure or B) O2 sensor, according to the factory service manual.

Here's the odd part though; I can never get the light to stay on. Let's say I am driving along, the car has just warmed up (about ~3 mins of driving) and the CEL comes on. If I pull over to the side of the road, turn the car OFF and then ON again, the light goes away. Basically, the light disappears every time the car is turned off and sometimes doesn't come on again for a while, then comes back on. The only similarity is that I am usually driving at a steady highway speed, say 80-90 km/h and/or the car has not been driven in a while (it is cold).

There are no driveability issues associated with the CEL. Fuel economy is good, no stumbling, bogging, or hesitation. Car runs great.

The previous owner replaced the fuel pump, I might do the fuel filter this week when there's time. But was looking for some helpful input as to what the problem might be. A buddy of mine says to replace the O2 sensor, just wanted a second opinion before I shell out $100 for a new one.

Thanks!

$100 is not the hard part.. getting the O2 sensor out after many years makes paying money seems easy.

It is easy to test a O2 sensor with a multimeter though, unplug the sensor and apply a torch to it and check for voltage.. it should change with heat.. another thing to test is its heater element.

Fuel filter would be my bet though.. make sure it is in in the correct orientation too!

how long ago was the fuel pump replaced?
i'd check to see if the fuel cap is properly pressurized as well.

Fuel pump was allegedly replaced by the previous owner 2-3 weeks ago. And when I open the gas cap, there is an audible "hiss" sound.

I replaced the fuel filter today, sprayed carb cleaner through the old filter after removing it and it was pretty gross, it was almost a brown color... tried blowing air through it and it felt seriously more clogged than the new one.

Took the car for a short drive afterwards, butt dyno feels a bit more pep and no CEL. I'll have to wait to drive the car to work tmrw (longer drive cycle) to see what happens...

from what i've experienced in the past, 41 and 43, fuel delivery, point to the O2 sensor. Again, from my experiences, i would suggest a Denso or NGK (NTK)

Yup that's the next one to tackle if the fuel filter doesn't fix the CEL. Already bought an NTK sensor just in case. Will probably install that on Thurs.

UPDATE: Drove home from work today and the CEL came on about 2-3 minutes into my drive, holding even at 2500rpms in 5th gear. Guess it's time to replace the O2...