how to test or wiring diagram for 1999 s70 MAF [1275636]

Post by **amblerman** » 15 Mar 2021, 07:35

Folks,

I have been searching for a way to test the performance of my MAF and all the posts I found were for 98 and older cars.

Does anyone now how to test a MAF on the 1999/00 cars?

I have the Denso MAF with 5 wires. I can't find an wiring diagram that shows what each wire does or any process for testing it.

Any help would be appreciated.

My desire to test this is related to my recent post of the car just stalling out. I tool whole intake apart this weekend and there was no obvious issues.
My ETB is a Xemodex model and it passes their debugging flow chart.

-A

Post by **abscate** » 15 Mar 2021, 16:41

The Denso MAFS rarely go bad. I can send you my spare if you want to try swapping.
You do have an idle air circuit on an NA ETM P80 model, stalling at idle you can try cleaning that too. Be careful with those guys , they are not available anymore

Post by **amblerman** » 16 Mar 2021, 18:53

abscate wrote: ↑15 Mar 2021, 16:41 The Denso MAFS rarely go bad. I can send you my spare if you want to try swapping.
You do have an idle air circuit on an NA ETM P80 model, stalling at idle you can try cleaning that too. Be careful with those guys , they are not available anymore

I actually took that off and was planning on taking it apart to clean it when I discovered a new to be fastener head that I don't have. The pentalobular fastener.

More tools to buy.

If this isn't working right could it cause engine stall while driving and/or idle? I dont' know how it actually works.

Post by **abscate** » 17 Mar 2021, 04:14

Basically, it detects how fast a warmed wire is cooled by the flow of air over it. That is relayed to the ECU which makes an injection pulse to match the air flow. The pulse is fine tuned by the oxygen content measured by the first oxygen sensor in the exhaust in so called “ closed loop “ operation

When you unplug the MAF, THE ECU loses the signal, do it guesses the injection time based on rpm. This works pretty well, but the ECU makes the mixture a bit richer than optimal for engine safety.

Unplugging the MAF is not a good diagnostic for MAF health as anything wrong with the closed loop side components, or unmetered air , will be “ fixed” by the ECU running on rpm only.

Post by **amblerman** » 19 Mar 2021, 06:44

abscate wrote: ↑17 Mar 2021, 04:14 Basically, it detects how fast a warmed wire is cooled by the flow of air over it. That is relayed to the ECU which makes an injection pulse to match the air flow. The pulse is fine tuned by the oxygen content measured by the first oxygen sensor in the exhaust in so called “ closed loop “ operation

When you unplug the MAF, THE ECU loses the signal, do it guesses the injection time based on rpm. This works pretty well, but the ECU makes the mixture a bit richer than optimal for engine safety.

Unplugging the MAF is not a good diagnostic for MAF health as anything wrong with the closed loop side components, or unmetered air , will be “ fixed” by the ECU running on rpm only.

You're describing the MAF operation here correct?

I wasn't very clear in my last post. When I said "I don't know how it actually works." I meant the NLA Idle control valve.

I don't know when it comes on, what it does exactly, etc. I think I read (on another site) that it feeds air into the fuel rail and the air enters intake from the same channel the injectors are plugged into.