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Discussion Starter · #1 ·
OK, everyone, this is my first trouble post: 1990 240 GL wagon, auto, after starting, after the engine warms up a little, we get a surging at idle as follows:
rrRRRRrr chug-chug-chug rrRRRRrr chug-chug-chug rrRRRRrr chug-chug-chug
it almost stalls on the chugs. The car has been sitting since xMas and my 16-year-old has been sitting in it playing the radio, waiting to get his license. We've started it up, briefly, but only put it on the road this week. On it's maiden voyage, this stuff started. Eric got his license this week, so he is frantic to get everything fixed so we can get an inspection sticker. Thanks in advance for your advice.
 

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You need to try cleaning the throttle body and idle motor first and see if it helps.
If not then try unplugging the mass flow sensor and start it and see if it idles better.
 

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Discussion Starter · #3 ·
Could it be the oxygen sensor? Is the "mass flow sensor" the same thing? I'm at work and the car's at home, so I can't look under the hood, but I recall oxygen sensors are on the exhaust manifold somewhere. This surging is very rhythmic, by the way, and it doesn't start until the engine is warmed up a little, so I'm thinking that some startup sensor is feeding xtra fuel until things warm up and that masks the surging.
 

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The mass flow sensor is located on the drivers side in the hose from the filter housing to the engine.
It is possible that the coolant temp sensor is bad.
The O2 sensor I don't really think it would cause the problem.It really doesn't work till the engine is warmed up all the way.

I would try cleaning the throttle body.I have seen it cause these problems before as well.
 

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One other thing to look at is the PCV valve. If blocked, it will respond this way. Very inexpensive to change. May take you 5 min. GOOD LUCK
 
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