Raceit

I'm 95% sure mine is bad. And with a cost of 3-400 bucks I'm curious if there is a way to rebuild these or clean them or something?

I've been having some issues with the car stalling and not running well past idle. The check engine light stays on all the time now. I did the little "tap dance" with the gas pedel and got an engine code of 1121. The shop manual says that my Air Flow Sensor could be at fault. Upon further testing I would have to agree. It says that with a voltmeter hooked up and at idle (with the plenum closed) it should be like 250mv. Which it is. Then once you move the plenum by hand it should gradually increase to around 4 or 5 volts. Then it says during the change if there is any sudden jumps or drops in voltage that the Air Flow Sensor is probably bad. And that seems to copy the problem my car is having. At idle it's fine (wich the CEL still on), but once you give it any amount of gas it will start to die out and sputter.

The reason I say only 95% sure is that my little voltmeter isn't the best. It is digital, but it's no Fluke.

pete944

I've heard (but I'm not absolutely sure) that the AFM on the S2 is the same one on the NA just flipped upside down. If so you could get one from a parts car fairly inexpensively.

Luis de Prat

They can be repaired, but you need to open them and bend the butterfly so that it makes good contact again.

I have a writeup somewhere if you're interested. Problem is, they tend to go bad again. I ended up replacing the whole unit and guess what, it wasn't the problem. The Ignition Control Module was causing the erratic behavior and it's a $45 part!

Raceit

That would be nice if that's correct. For example here's one on ebay for around 30 bucks. Then another 20 for shipping...ya right. Who's making money there.

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2426096734

Because that black angled piece looks just the same as mine. At least from the picture.


If you have a write you could find I would be greatful! Also if you have any further info on that Ignition Control Module that would be nice too.






Too bad S2's are so freaking rare. It would be nice to just swap one out from another real quick and see what happens. But if an older N/A 944 uses the same AFM that would save me a ton of money if that's the route I have to go.

Luis de Prat

OK, the ignition control module is quite easy to access. It's a triangular plate-shaped unit, located behind the driver side headlight, bolted to the fender wall, right below the coolant expansion tank.

You can take it out and have it checked at an electronics shop. Mine was bad and gave me all kinds of ignition trouble, like cutting out and erratic acceleration. It's worth a shot.

HY M8NC

You can't have the one off of my car. However-
Call Wren at Avenue Auto Wrecking
816.861.5055
2500 Manchester Trafficway
He's got 8 or so 944's, and is always getting more. He's also a stand-up guy, and will treat you right.

I've heard the same thing about the early cars AFM, but I'd want to confirm that with someone smarter than myself. The good news is that person will be easy to find.

pete944

Ok, I just checked PET and the Turbo and NA use the same AFM-part # 951 606 121 01 and the S2 uses part # 951 606 124 00.
Sorry but the S2 does use adifferent one.

Raceit

I'll check that Ignition Control Module out!


I've talked to Wren before. I'll see if there's anything I can use off his cars.


I checked PET as well, I'm wondering if it's different part numbers since the design of the plenum is different. It kind of looks like they both have the same Bosh part stuck to the bottom.

Luis de Prat

Steve, I was able to dig up that write up from waaay back in 1998. I've been hooked on Rennlist for too long... I'd try the ignition control module first, since it's S2-specific and the regular NAs and turbo cars don't have it.

=====

SUBJECT: [Fwd: Stuttering acceleration problem (help), Check the Air Flow Meter?]
From:
Date: Sun, 15 Nov 1998 09:45:59 -0500

Have you checked the Air Flow Meter? The 944 engine management system (Bosch L-Jetronic) utilizes air flow measurements only for low to mid RPMs. At higher RPMs or WOT it uses a lookup table to calculate fuel delivery. If the air flow meter's moving vane is mechanically sticking, or if the resistive strip inside is corroded or worn, it's output will be noisy and will not directly correlate to air flow. One of the first warning signs is rough acceleration and hesitation. You can perform some simple tests on your air flow meter. It is easiest to perform these tests with the unit removed from the vehicle, but I have tested the AFM while installed by removing the air filter for access to the moving vane.

First, check the mechanical movement of the vane. Using a soft object
(wood), move the vane through its range of motion. (Be carefull not to
damage the temperature sensor which is located on the inlet side on the top of the air passage) The vane should move smoothly, with no roughness, and should return to the closed position on its own. If it doesn't move smoothly, there is a mechanical problem. This can sometimes be caused by gunk (oil, dirt, etc..) that has deposited with time. You can try cleaning to restore movememt.

Now, the electrical tests. There are 5 electrical connections to the air flow meter as follows:
Pin # Function
1 Temperature Sensor Signal (1.45->3.3 k-ohms @ 15->30 Deg C)
2 Air Flow Signal (250mV -> 4.6V)
3 Power (5 +- 0.3 volts)
4 Ground
5 No Connection

o To test the temperature sensor, simply connect an ohm meter to pins 1 and 4. Compare your reading to the range shown above. You can also try heating the sensor to see if the resistance changes. You can use a hair dryer or heat gun, just don't heat for too long.

o To test the check the resistance of the unit while you move the vane
through its range of movement, connect your ohm meter between pins 2 and 4. Resistance should change smoothly as you slowly move the vane, there should be no sudden drops or peaks in resistance. If there are, you need to service the unit. You can try cleaning the resistive strip internally, but it may be too worn.

To clean the resistive strip, you will need to remove the air flow meter from the vehicle. Using a sharp object, carefully cut around the cover and pry the cover off. Carefully examine the black resistive strip to make sure it is not worn through in any places. If it looks to be intact, you can remove oxidization and dirt with a spray cleaner sold for that purpose. Although not the best, Radio Shack sells a contact cleaner and lubricant advertized for cleaning volume and balance controls on sterio equipment. Spray the cleaner on the strip, and move the vane through its range. To re-seal the unit, use a non-corrosive sealant. I used high temp gasket making sealant. DO NOT use silicone sealant with acetic acid!

Of course, there are other failures that can cause rough acceleration at part throttle, injectors, ignition, etc..
Good Luck,

>
> Hi guys, got a weird problem on the way to work today. Under part
throttle, I get a kind of hesitation and then uneven acceleration. Seems to be ok under full throttle, more pronounced at lower RPM's. Doesn't seem to be related to boost. More like a spark or fuel thing. This is brand new, car was running great yesterday. Havent' had a chance to check spark plugs or
anything. Any ideas?
> 89-951

Mark Parker

Adding to what Luis has posted. I read through, and now can't remember where, a procedure for adjusting the contact points attached to the vane so that they sweep across a previously unused portion of the resitance strip. That being the most wear prone part of the unit, it would give new life to a 20 year old part at no expense except a little time. Is anyone familiar with the article I'm talking about?

Operator

i keep posting stuff about the afm but no replies

according to an old post.. opening the afm kinda ruins it becuase its pressurized from the factory?

im having an idle drop problem (let off the gas - shift to neut - idle drops too low) and i was thinking its the afm but.. hey.. who knows right?

david fracolli

One other thing you will need to check is the output of the AFM. As the AFM ages the thin film resistor will change resistance. This will effect the output signal to the DME. While measuring resistance will tell you if the thin film resistor is linear it will not tell you if it is putting out the correct signal.
At idle the output voltage should be about .8 volts and at full throttle it should be greater than 4.8 volts.
I had the same problem with my N/A and while the resistance test showed perfect linearity when I measured the output I was only getting 3.6 volts at full throttle. Replacing the thin film resistor fixed the problem.
Not sure who started the notion that removing the black cover will ruin the AFM but this is not true. The only thing you have to be concerned about is making sure that you reseal the cover so no moisture gets inside.

emilysgranny

Raceit ; the afm is the same as the 944S and I have a spare.And the Brain.And the box

triscadek

http://frwilk.com/944dme/afm.htm < air flow meter link.

Raceit

Oh my! That is great! Thanks for posting that little jewel.



If I'm not able to rebuild it I may take you up on your offer emilysgranny.