1990 240 white & black exhaust poor MPG

[billofdurham]

I'll start with the good news - socket 6: 1-1-1 means no faults.

Socket 2: 1-1-3 check fuel injectors and fuel pressure.

1-2-1 Mass airflow meter and/or heated oxygen sensor.

2-1-3 Throttle switch (full load).

With luck erasing the codes will do it but if they should return the attached shows how to check most of the bits. The heated oxygen sensor needs an exhaust gas analyzer.

Tests.pdf

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Bill.

[rainbowwillow63]

I erased the old codes that I got earlier today. I went for a 4 hour drive and retested the codes. This is what I got:

port 2- 121 & 322

port 6- 111

If I read my Haynes right they are both for the AMM?? Not good, right?

[billofdurham]

They are both mass airflow meter (MAF) codes. You can check it using the instructions in my last post. Try cleaning it using a proprietary MAF spray cleaner.

Bill.

[rainbowwillow63]

I fixed it!! Jeeze I really love this place!!!

I bought CRC MAF cleaner, CRC Throttel(?) cleaner and CRC electrical cleaner. I disconnected the plug to the MAF and man was it corroded. I cleaned that with the spray and I also used an emery board to get more of the stuff off. I than figured if that was like that than the MAF is cruddy too so I took that off too.
I took the screens off and sprayed them, yuk! I looked inside and it was covered with black carbon. I sprayed it a couple times, let it dry, and put it back together.

WOW! What differance it made! No more black smoke, no jumpy ideling and it runs just as smooth as a baby's rump

BUT, now I'm getting a 311 code. The speedo is working fine so now whats wrong???

Thanks so much for helping me out!

[billofdurham]

Progress at last.

Before tearing the speedo apart check down the rear of the engine to the differential. The speedometer sensor is located on the top of the diff and it is possible that the lead has come off. There have also been cases, on older cars, of the insulation on the lead breaking down. It is worth checking.

Bill.