Causes for an AMM failure code?

[Geronimo]

Re: my 89 740 B230 non-turbo Gl sedan that is down: Very hard to
start, you have to give it LOTS of gas, it won't idle at all. It dies
when you put it in gear:

It has a code set for "air mass meter failed". But I have a bad
air duct that really needs replacement. It doesn't have a rigid
plastic duct like the turbo has, it is flexible/corrugated. it has
gotten soft and was collapsing, and because of the rediculously high
price of a new air duct, I wrapped it up with metal tape. The ends of
this duct are different sizes...so I couldn't just buy a generic flex
*metal* one off-the-shelf from a local parts dealer. I need to go back
out to the car and unwrap the duct and see if maybe it has split or
something, which would let unmetered air into the intake. If this was
happening, could this trick the computer into thinking that the air
mass meter is bad? Seems like this would cause it to set the mixture
completely wrong, at the least, right?

Yea, this engine doesn't have a "limp-home" mode in reality,
because when the car was working OK, I once pulled the conn. off the
AMM, and the engine didn't just run badly--- it wouldn't idle at all,
and was undrivable!

Does anyone have a spare used AMM, P/N 281101A? Even if it proves to
be just a matter of fixing the duct, I still need to get one to have
around for when the AMM really does fail, if it turns out to be in
fact good now. The local junkyard doesn't have any89-92 740's.

Thanks, Jim

 

[Randy G.]

Re: my 89 740 B230 non-turbo Gl sedan that is down: Very hard to
start, you have to give it LOTS of gas, it won't idle at all. It dies
when you put it in gear:

Bad AMM

It has a code set for "air mass meter failed". But I have a bad
air duct that really needs replacement.

Is it the one before or after the AMM? If after, repair it with epoxy
for plastic or RTV to see if that is it. If before, it will have
virtually no effect on the AMM.

It doesn't have a rigid
plastic duct like the turbo has, it is flexible/corrugated. it has
gotten soft and was collapsing, and because of the rediculously high
price of a new air duct, I wrapped it up with metal tape.

Ya- that will work temporarily. Go to a wrecking yard and get a
replacement.

The ends of
this duct are different sizes...so I couldn't just buy a generic flex
*metal* one off-the-shelf from a local parts dealer. I need to go back
out to the car and unwrap the duct and see if maybe it has split or
something, which would let unmetered air into the intake. If this was
happening, could this trick the computer into thinking that the air
mass meter is bad?

No, I don't think so.

Seems like this would cause it to set the mixture
completely wrong, at the least, right?

Yes, but wouldn't cause the code. The code states, "Bad or missing
signal to or from the AMM."

Yea, this engine doesn't have a "limp-home" mode in reality,
because when the car was working OK, I once pulled the conn. off the
AMM, and the engine didn't just run badly--- it wouldn't idle at all,
and was undrivable!

You might have other problems as well. With the AMM disconnected it
sould run- very rish and not over about 3500 RPM.

Does anyone have a spare used AMM, P/N 281101A? Even if it proves to
be just a matter of fixing the duct, I still need to get one to have
around for when the AMM really does fail, if it turns out to be in
fact good now. The local junkyard doesn't have any89-92 740's.

I think the number you need is the Bosckjh number, like xxx xxx xx 012
or such. Post the number here- maybe someone can find one at a yard
for you.

BE SURE to check the air box heat riser control thermostat for proper
opreration. IT MUST NOT allow hot air in once the car is warmed up or
in a temperate climate. If in doubt- replace it! The hot air will kill
a good AMM.




__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"

 

[Geronimo]

Randy......

I didn't remember exactly what the code said. Come to
think of it I think it did state" signal from AMM missing" for that
code. So it looks like I need an AMM.

The part number I gave in previous post is correct, that
is what this car has installed! It's Bosch # 281101A
It's not xx012 or xx016, it is exactly as above.

Thanks!

 

[Robert Lutwak]

It's the hose.

--
-----

-RL

Randy......

I didn't remember exactly what the code said. Come to
think of it I think it did state" signal from AMM missing" for that
code. So it looks like I need an AMM.

The part number I gave in previous post is correct, that
is what this car has installed! It's Bosch # 281101A
It's not xx012 or xx016, it is exactly as above.

Thanks!