Hmm, no change in idle when you unplug the MAF has me thinking the MAF is dead and your already running without it. When the engine switches from real time data to table data it will stumble. No change, tells me the MAF may be bad.

Good point. I will confirm if what I recall is true. Probably a good test would be to remove the connector *with* the engine running and see if it hiccups.

Once again, I really would like to know if normal operation is voltage decreasing with air flow decreasing, or even better: acceptable voltage ranges for certain specified conditions (idle, etc.).

ANY idea where I might find that info.

Darn it - I meant "voltage decreasing with air flow *increasing*".

This chart shows the MAF in hz, it goes up as air flow increases.

I don't know if the '97 Bonneville MAF sensor works the same as a '99 Century one - the pictures on aftermarket sites show a totally different looking part (see photos below), and the info. I get from Googling MAF sensors has conflicting info. on whether a given year or engine GM is hot wire or thin film type sensor, and whether the output is a voltage or frequency. There is an indication in what I read that they used different types in different years and engines.

Your Bonneville one is obviously one that puts out a varying frequency, but looking at the schematic in my AllData 1999 Buick Century account, which I believe is taken right out of the Buick FSM, its circuitry appears to be a varying analog voltage level, not varying frequency. I do know that they sometimes show simplfied representations of circuitry internal to the sensors, so - yeah - it too could be a frequency output.

I have a feeling that you guys are right - that the MAF needs replacing. Again, if the part was only $20 or $30, I might be willing to gamble on it and just replace it. But it being over $100, I am going to try to get more info. specifically on what to look for as normal outputs for the 1999 Century sensor.

I do have an FSM on order, so maybe it will have enough information in the MAF sensor description to say how it operates.

'97 Bonneville replacement MAF sensor:


'99 Century replacement MAF sensor:

Oh yeah - if I should happen to get a new sensor, are there particular brands that you guys have found out to be good to go with or ones to avoid?

I do appreciate the information and help.

The information going to the PCM should still be the same.

OK - thanks. Still a couple more days before I will be able to get on it.

Any brands of sensors to avoid? Any brands that are known to be particularly/consistently good and/or best bang for buck.

I don't know of any differences.

Well kudos and a big THANK YOU to both of you for your help.

Today, I finally felt up to taking a look at it again (remember I had hernia surgery last Friday). Went to Advance and bought a can of MAF cleaner, came home, removed and disassembled the MAF sensor from the intake tube housing, and cleaned it thoroughly - just kept cleaning until there was no more left in the can, re-assembled it, and cranked her up.

It sounded really different (in a totally good way) right off the bat with the hood open when I goosed the throttle. Took it for a drive, and there was no sputtering. It had immediate throttle response, and that nice WOT spunk that I hadn't seen in it for the last 3 years was back!!

I let it sit for a few hours and then took it out again this evening (before I cleaned the MAF, the symptoms were worse before it was fully warmed up, so I wanted to see how it would do driving from a cold start and on thru the full warmup cycle). Still good - didn't miss a beat.

So - YAY - I saved some money today not having to buy a new sensor!

Thanks again.

BTW - Advance has an in-store deal going on where if you buy a can of CRC brand MAF sensor cleaner, you get a free can of Thottle Body and Intake Cleaner (they sell for $7-$8 each).