M42 puzzle

[Boris3]

Well... Maybe solved.

Still same flashing cel issues this morning, cold and engine warm. Except when going up a steep hill with about 3/4 throttle. Let off and cel flashing.

Gas gauge showed about 3/8 of a tank and I hadn't added any since this mess began in case I had to pull the pump. So added a container of HEET, put in 5 gallons of 93 octane. No change for about 10 minutes then I got on the throttle hard, cel blinked for a bit then stopped blinking.

Drove around for about a 1/2 hour, fine. Turned it off for about 10 minutes. Started again and ran it again for a 1/2 hour. Side streets and highway. Fine. No cel.

Letting it sit for the rest of the afternoon and we'll see what happens later.

Like I said maybe...

[TobyB]

Jeezus that would be random.

Bad gas dicking with the o2 sensor, maybe???

t

[Boris3]

Let it sit for 5 hours. Restarted and ran it, all good at idle and on the road. Crazy. I'll put more miles on it this weekend to see if this is for real.

Best I can figure is that I had run the tank down to the empty warning light before filling up (Shell premium) which I had ever done before. Two days later at about 3/4 tank the problems started. Maybe condensation in the tank? We've had a lot of temp swings around here. Going up a steep hill under load tilts the car at enough of angle that the pump is drawing gas and no water? Anyway add in all the other things with the car: old O2 sensor, old plugs, a few vacuum hoses with cracked ends that I hadn't replaced, and there you go???

[wazzu70]

I was going to recommend testing the fuel pressure and watching for dips. If the pump is slowing down, under load it wont supply enough fuel and you will misfire.

When the engine misfires the mixture reading at the 02 sensor is off. This can trigger an out of range flag.

Just my thoughts, unfortunately the OBDI ECUs are pretty worthless for troubleshooting because they are so basic and easily confused :)

[bmwman91]

Weird. Hopefully it was indeed just something mundane like water in the gas tank. If that is the case, the good news is that you know that you have good sensors and no vacuum leaks now!

[TobyB]

they are so basic and easily confused

I am resembling this remark recently....

t

[Boris3]

No more than I am!

[wazzu70]

I am resembling this remark recently....

t

Recently? Dont humor yourself! ;)