Po 170 & Po300

[cmbennett]

I have a 96 E320 80,000 miles
I replaced the MAF with new part from dealer.
Check engine light came back on.
I took car to very good mechanic. (he works on everthing foriegn ferraris-to-fiats)
He replaced all spark plugs and connectors.

Car ran like a dream Although check engine light came back on during trip.
I went on a 12 hour trip, parked car in very cold, zero, weather.
Ran rough and gave codes PO170 & PO300.

I have read that this indicates a MAF, but I just replaced it.
Please help me!

Im going to drop it off to the shop, but I want to go in fully informed.

[Raylee177]

I would just try to reset code with OBDII and see again. PO170 is MAF, I believe.

[cmbennett]

The book that came with the OBDII said PO170 was fuel trim malfunction, any ideas?

[tirona]

are you closing the fuel cap tight enough? did you fill the tank while the car engine was still on before the error message showed up? that thing happened to me, i filled up the car while the engine was running and the next day i got the check engine salute. i reset the codes at autozone and the message hasn't showed up since then (1&1/2 years ago). that can cause error messages.
or maybe you need to replace the fuel cap or the fuel filter???

[cmbennett]

I have replaced the fuel filter,
yes I fill up with the car running, its cold!! lol
I will check into the cap, but the car runs rough, very rough; thanks for your insight.