are all Air Mass Meters created equal?

[steve roche]

Hi-

I've got a 1985 240, it's really crusty, but it runs pretty solid, at least 3 days out of the week.
Until lately.
I'm suspecting the AMM because of extremely hard-starting, poor idle, and choppy acceleration.
I've corrected all the vacuum leaks, but I've not checked out all my corroded electrical connectors.
The AMM connector came away once, but I put it back(with ign off) and all was well.

Question: is it characteristic of a bad AMM to cause bad running at high speeds as well as low speeds?
One blog I ran across mentioned that if your performance is poor, esp. over 2000 rpm, then yes, your AMM
may need to be replaced. Mechanics love to do it because it's expensive and it takes five minutes of labor.

My performance is terrible at idle but very good over 2000 rpm; if I can get out of that engine stumble upon starting from
a standstill... it will take off. So, I wondered if defective AMM issues control low-speed and idle only,
or if their failure means 'no performance at any speed'... are they consistent?

Disconnecting the AMM will put the engine in "limp" mode which is exactly how it felt today when driving...
except when I gunned it and got up to speed (40-50 mph) and then it's all good. Idling and accelerating
are the scary parts.

Hours of google searches reveal "Replacing the air mass meter" as the definitive fix
for misbehaving Volvos.. until the owner realizes the problem has not gone away.
I hate to go buying another one unless I can reasonably suspect mine to be bad..

sr

[billofdurham]

All AMMs are not created equal BUT all AMMs can cause problems at idle speed. Poor performance at higher engine speeds is usually down to other things.

For both issues I would suggest that you check, clean or replace all the earth (ground) connections on the intake manifold. Replace the connector that came away, not just put it back on. Clean all the corroded electrical connectors. The AMM is a sensitive item and does not respond well to poor circuits.

Having sorted out the electrics check for an air intake system leak. This could be a leak at the intake manifold gasket or it could be a hole/tear in the intake hose and would be a factor in the poor idle up to the 2,000 rpm mark.

Have you tried to clean the AMM? You can get a cleaning spray at most good parts outlets.

Bill.