Help baffling CE light 98 E320

P0170 and P0173 are fuel trim codes, one for idle and the other for part throttle. The adaption at idle and part throttle has reached the end of its limit. That is part of the answer. However, your mechanic is not saying WHICH end of the limit! Most of the time, the MAF sets P0173 because the part throttle adaption has reached the end of its LEAN limit, the LEAN limit is 1.32. But P0173 can be set if the adaption reaches the RICH limit. If I remember right, it is 0.62 but it may be 0.82. Very rare to reach this unless you have an injector pouring gas in a cylinder. Since you have both trim faults, have him get a print out of the freeze frame of what set the failure. Self adaption works up to a point. It will lean a rich running or richen a lean running engine up to its limit. But you need to know what it is trying to accomplish. If you are too rich, it will try to lean it. The weakest link for too rich is the pressure regulator on the fuel rail. Shut the engine off and pull off the vacuum hose that goes to the top of the regulator. Is it wet with fuel? Let it sit and watch it. Does fuel dribble out the nipple? If the lean limit has been reached and the self adaption can no longer richen the engine, check for vacuum leaks. 2 prme contenders are the purge valve [stuck open] and the shut-off valve on top of the charcoal cannister [stuck open].

I cc'd this to you. I got an auto response that I would need to go to another link to get you to accept my email?!? Screw that.....if you get it, fine; if you don't, read it here....

throttle. The adaption at

answer. However, your

P0173 because the part

but it may be 0.82. Very

of what set the

lean running engine up to

too rich, it will try to

rail. Shut the engine

wet with fuel? Let it

the engine, check for

shut-off valve on top of

Thanks, Karl. I read your post here. I watched him run a diagnostic on the car with a handheld computer that plugs into the port under the hood. I didn't recall the fuel trim limits so I will check that out.

Another question: After a MAF meter install, would ONLY the MB dealer be able to reset the fuel trim adaptations or would my independent be able to do it with his computer unit?

Thank you.

another link to get you to

throttle. The adaption at

the answer. However, your

sets P0173 because the

is 1.32. But P0173 can be

frame of what set the

a lean running engine up

are too rich, it will try

fuel rail. Shut the engine

Is it wet with fuel? Let

richen the engine, check

shut-off valve on top of

You should not reset the trim. IF the MAF is the culprit, then a 10 mile city drive will show the adaption moving back to center: close to 1.00. This is a good test to see if it is fixed. If his scanner shows fault codes only and no actual values, then he is just guessing with your money. This is the SWAG method of repairing cars.... one step up from the Mossberg method.

No, his scanner, a Snap On, and shows far more than simply fault codes. It's quite extensive, with page after page after page of detail and readings.

Thank you for your replies.

city drive will show the

if it is fixed.

just guessing with your

Mossberg method.

and throw everything at it,