AFM temp sensor test

[jase007]

My iX is running ... OK but I have a rich warmup condition that I have been investigating over the last "many" days. Symptoms are 1. rich exhaust smell 2. galloping / lopping idle like a V8 with BIG bumpsticks (aka camshafts) until almost out of the blue on temp guage. I have replaced the fuel pressure regulator (FPR), drawn a vacuum on the new one (to test), chased down air leaks and tested for potential others with soapy water and carb cleaner. Have rebuilt throttle body, gapped plate, replaced gaskets, JB welded 90degree fittings, etc... and various other "preventative" maintenance tasks.

The coolant & cylinder head temp sensors are new and I have been busy with my voltmeter performing just about every test in the Bentley manual on anything else under the hood. Everything electronic checks out OK, including the TPS, C191 connection, fuel injectors, evaporative charcoal cannister venting valve, yadda, yadda, yadda, etc... ad naseum.

Then ... I come across this posting from Bill Taylor's BMW site on testing the temp sensor IN the air flow meter (AFM) I didn't know one was in there.

"and,,,i add to the other two, who shared how to's on repair of the afm.... the temp sensor....

it is located at the intake side of the afm,
looks like a neon indicater...when this thing goes, your engine is
either extreemly rich or lean,

i went and bought a used afm , bosche, for $40.00, removed the temp
sensor, via the black top where the wiper arm resides, r& r temp sensor
and was back on the road....

you can check your temp sensor by spraying the unit with compressed
air,or butane, from a canister to make cold and heat from a propane
torch , held close but not too close...

and reading with a VTM...you should see a swing in resistance, as the
temp varies...no variation...bad temp sensor...replace, varying
resistance,ok.....look some other place

richard, euro wrench"

I think it might be worth a look however, my car isn't running extremely rich and gas mileage is "OK" for the cone / chip / exhaust / heavy foot modifications I have done. It seems "richard" may have had a not-running condition when this temp sensor failed. Definitely not my situation.

Asides from doing a compression / leak down test (in the works)any thoughts from you DIYers?

TIA

Jason

[jase007]

Almost a week and no guesses from anyone ...? Come on ... where are all the DIYers on this board?

Well, in my research I discovered that our AFM is similar to the Ver. 1.X used in Porsche 911s ('84 - '8?)

In tracking down a miss in my friend's '85 911 I was using his Bentley manual ... in there was a resistance test for the AFM temp sensor (also a Bosch unit). I'll have to go back and check but ... I wonder if the E30 Bentley has a similar test. If so ... all I need to know is the resistance range at X ambient temperature to see if it specs out.

FYI

Jason