Can you test MAF?

Post by **amblerman** » 08 Sep 2018, 09:36

Hi Folks,

Recently my 1999 S70 Manual non turbo has been showing signs of the dreaded ETM/MAF issue.
Hunting idle that goes away, etc. But other than the occasional hunting at idle, the car ran fine.
However, last weekend I encountered significant skipping at highway speed that did feel like I was being blasted by wind. I know that is another sign of impending ETM/MAF. So I got off the next exit and when I pulled my car out of gear (manual), my RPMs went to 0 .
I reached down and started it again but when I came to a stop at the end of the ramp, the RPMs went to 0.

I started it up again and did got back on the highway back towards my house. I stayed in the right lane and I figured that if it did get worse, I could coast into break down lane.

I got home fine and the car ran perfectly. No hiccups at all.

The previous owner car already has a Xemodex ETM which aren't supposed to fail.

I went through the Xemodex flow chart and the very first question asks about codes. There are no codes reported on my OBD2 reader and no dash lights are on or came on when I had my 0 RPM issue.

Following the flow chart I end up pulling fuse 2 and confirming the ETM sounds right when the fuse if put back in.
That leads me to a MAF. I used starter fluid to test for any air leaks and couldn't find any.

The flow chart says "In the monitoring function of the scanner, select MAF and observe the MAF value." My OBD2 reader doesn't have a monitoring function.

Is there any other way to test if a MAF is going bad ? can someone recommend a OBD2 reader that can monitor?

Any other suggestions to hunt down this frustratingly intermittent issue?
Thanks
-A

Post by **matthew1** » 08 Sep 2018, 09:43

Best way to test is to put in a known good MAF. I don't know of a bench test, but I'm sure there's a way. I think I have one from my 1997 T5 that I can't guarantee is good, but I can guarantee I never knew it to be bad. Let me know if this is a direction you want to go and I'll dig for it and send it. I don't know if the part # is the same across 97 to 99 and T5 to NA however.

Post by **mrbrian200** » 08 Sep 2018, 11:24

The MAF signal output is an analog varying DC voltage that can be measured with a voltmeter. However, I've never seen a chart or graph that coorelates that signal voltage to air flow in g/min that the ECU converts it to. Which puts you back to comparing with a known good sensor. It gets more complicated when you consider that a malfunctioning ETM throttle plate or air leak in intake system will affect the amount of air passing through the MAF: an unexpected 'improper' reading does not necessarily indicate that the MAF is bad.
Under such conditions the ECU will often display the DTC for the MAF sensor. What that is telling you is that 1. The amount of air passing through the MAF is inappropriate for conditions expected, or 2. the MAF is bad. Most of the time its #1

Post by **misha** » 08 Sep 2018, 11:29

It's the same part across '96,'97,'98 na & turbo...t5 from '95.....every one with whole assembly replacement part. Inserts for earlier models & '99 are different.
Bosch # 0 280 217 107 up to '99.

Post by **abscate** » 08 Sep 2018, 13:54

I’ve got a turbo MAF KTBG but I don’t think it will play in an NA car

Post by **misha** » 08 Sep 2018, 14:26

abscate wrote: ↑08 Sep 2018, 13:54 I’ve got a turbo MAF KTBG but I don’t think it will play in an NA car

Bosch 0 280 217 107 is used in both...turbo(hpt & lpt) & na up to '99.
Motronic 4.3 & 4.4....Jetronic use different part and while insert fill fit into Maf housing from M4.3 & 4.4 it have different way of air metering and different values.