Hey,
I own a 1998 Mitsubishi Mirage with about 190,000 miles on it. The engine light has started coming on and I get three codes:
P0170 Fuel Trim Bank 1
P0136 Oxygen Sensor Bank 1 Sensor 2
P0301 Cylinder 1 misfire
I’m hoping that this is all really one problem. Any guesses from you car experts on what the problem would be?
Thanks,
A misfiring cylinder makes a mess of the exhaust - that’s read by O2 sensors, and the P0170 is based on upstream O2 sensor reports. I’d ignore anything downstream of the cat (P0136) until the upstream thing is in order. And I’d ignore a bad fuel trim report as long as I had a misfire.
So anyway…I’d chase the misfire first and keep in mind that misfire codes are not exclusively about spark. They’re really mis-combustion codes. Starting with plugs and wires always makes sense though. How old are the plugs and wires? Check all of that out. I think this car has coil on plug, so it should be easy enough to swap the #1 coil with another and see if the misfire follows.
While the plugs are out, I’d want to check the compression. If you don’t have a gauge handy many of the auto parts store “loaner tool” programs have them. While I was messing around and greasy I’d also pull out the MAF sensor and clean that.
If you don’t come up with anything on spark or compression you can swap the #1 injector with another to see if the misfire follows. (If you have access to a scantool though you can check injector balance without removing any. But you do need a live data stream for that. Of course, if you DO have access to a scantool start by looking at the fuel trims and O2 sensor signals).