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Re: air mass meter Posted by Ari [Email] ![]() ![]() In Reply to: air mass meter, dave, Mon, 12 Aug 2002 11:33:19 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The fact that the idle smooths out after it warms up says that the AMM is probably working. You won't see the element(hot wire) glowing under normal engine running - it just doesn't get that hot. There is a 'burn off' function - unplug the front hose from the AMM so that you can look in. Start the car, and let it idle for a minute. Rev the engine over 3000 rpm (2000 should do, but 3K works) for about 5 seconds. Let the engine return to idle, then shut off the engine. The wire should glow white hot for a second or two, between 5 and 20 seconds after you shut off the car.
If it doesn't, it could be the AMM, but more likely the engine control, because the engine control provides the burn-off signal.
The AMM does need to be adjusted. I'm pretty sure the '87 still has the -005 sensor, which does have an adjustment. Check in the archives for "AMM adjustment".
A bad AMM usually shows up both as bad idle, but also as real driveablity issues - lots of hesitation, especially coming off idle. If the only problem is the classic loping idle, I'd look elsewhere than a bad AMM.
The engine control schedules fuel based only on the AMM when the oxygen sensor is cold. After about 2 minutes, once the O2 sensor is up to temp, the AMM AND the O2 sensor schedule fuel. Since the idle is OK after the O2 sensor is at temp, it probably isn't a Bad AMM - the O2 sensor commands 25% of the fuel flow, the AMM 100%. A bad AMM would show problems all the time.
But if the AMM is mis-adjusted, you might be running a little lean before the O2 sensor comes up to temp.
Good luck!
posted by 140.157.4...
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