Acura Integra CEL 43. Stumped.

[Dylan Shrout]

I have been having a check engine light code 43 on my 1995 Acura Integra LS. It’s not on all the time, but it pops up sometimes when the car reaches operating temperature. When I first saw it come on, many seemed to suggest the O2 sensor, so I replaced it and I never noticed any significant performance issues, but the light still came back on. I will note, I have frequently reset the codes on the ECU by taking out the ECU fuses after every part I’ve replaced. After I realized the O2 sensor didn’t do it, I replaced the fuel filter and no change. I took a 3 hour trip to and from Atlanta and the code didn’t come on at all during either way. The next day when I got home, it came on while I was going to work. One day, I was driving around town, made a stop and then it wouldn’t start back up. My fuel pump went bad, so I replaced the fuel pump and the code still comes on. Up until this point, it does idle a little funny some times. I can feel a slight jerk when it idles, but it accelerates and starts up fine. I would greatly appreciate the feedback. Thanks!

Topic

[Billy]

I would start by testing the FPR and smoke testing the evap system.

[Andy]

In this order, I’d try:

fuel cap replacement
vacuum leaks/disconnected hoses
injector cleaning
fuel pressure
injector function

[Dylan Shrout]

Should I check the FPR even if the fuel pressure is perfectly fine? I loosened the banjo bolt on the fuel filter and turned the key to the first click and fuel sprayed everywhere.

[Dylan Shrout]

Well, I know the fuel pressure is fine, I’ve already checked for that. The fuel injectors seem to operate fine, I used the screw driver test on those. Is there a way to test the fuel cap? I do hear pressure release when I unscrew it, whether that means anything or not, I don’t know. Vacuum leaks may be the last thing I look at just because that seems so time intensive, unless I buy some expensive equipment to test it quicker.

[Andy]

Unless it has been done recently, I’d want to clean the injectors anyway just based on age and mileage. I don’t know of a way to test the fuel cap. The gasket could look fine and hiss, yet still not hold sufficient pressure. Make sure you’re tightening it until it clicks a few times.

Maybe clean MAF if present? (And check for leaks in the air intake after it.)

I think a 43 could indicate an O2 sensor wiring issue also–might want to check the wires and connections.

I think it could also be an exhaust or converter leak/obstruction giving your O2 sensor wacky data.

If there’s a noticeable rough idle which improves with increased rpm, that seems to point a bit more to a vac or air leak.

[Robert Robertson]

Encountering a similar problem with my 1995 USDM GSR / B18C1 OBD1.

4 minutes after driving, regardless of cold start or long warmup, CEL triggers code 43. Driveability normal.

If I cycle the key or turn the whole car off and on, code clears, STAYS cleared, Driveability suffers. Partial throttle input has intermittent (but persistent) cutout until MORE throttle is given, then it jolts to life. It’s a very rough ride.

Never stalls
Idles fine
Goes VTEC
Driveability usually eventually clears, but for not particular reason.

Spark plug 1 looks normal if not a little lean. 2-4 are sooty as if they are running too rich.

My AFR gauge always reads deep into the Lean, unknown 02 Sensor, but it is on the end of an extension harness that shoots good.

Cylinder 3 has a leaky valve stem seal that will be replaced this weekend. I will be changing the fuel pump and filter at the same time (it’s time for the filter and I wanted to put in a 255lph pump).

My suspicions are the pump or 02 sensor. What else could I be missing?

[Robert Robertson]

Changed Fuel Pump, Fuel Filter, and 02 Sensor. No help. Car drives great from cold start, but as soon as it’s restarted or the ignition key is cycled, the partial throttle bucking immediately returns, arguably worse that before I started troubleshooting.

There IS a serious exhaust leak pre-02 sensor from some prior owner hacking, but it shouldn’t contribute to this.

Injector?
FPR?
TPS Sensor?
EGR?
Evap?
PCV?

I’m almost out of ideas here

[Author]

Replies