AFM lean/rich adjustment

[E30_Crazy]

I know, I know... The AFM is set from factory and should never be messed with, incase of a too-lean mixture and risk of damage, etc etc....

I had the car in for MOT the other day, and while doing the emissions test, it was coming up way too rich (not the car's mixture, the exhaust). The tester explained to me, that if the car's mixture is lean, then in doesn't burn efficiently, and gives a "rich" reading on emissions. He proceeded to stick a screwdriver/allen key/whatever tool to the AFM, and adjust it while running the emissions tester. He kept mentioning it was getting better, then said that it's at it max on the rich side! No more adjustment to be had from it. At this point, is was just passing, and this is on a non-cat model (Jan 87 on D reg). I know it's bad to run lean, but it shouldn't hurt to drive set rich should it? And according to his tester, it's not really running rich, just the AFM set rich to make it run normal-ish.

Could there be something wrong with the AFM? I expected it to be a little worse than a stock E30 on emissions but not outright fail so hard. It's got a 2.7 done on it, and a schrick 288 cam. It's a facelift engine still running facelift motronic 1.3 (supposed to have a chip tuned to the engine aswell).

If it sounds like the AFM gone bad, can I use the one left over from my pre-face high comp engine? Thinking about a MAF anyways, can this be grafted in on the motronic, or is this an upgrade only for those that are on standalone/piggyback?

Any suggestions, comments, advice is welcome and appreciated.

[Grrrmachine]

Absolutely no mention of the Blue Temp Sensor here, which is what's really responsible for the lean/rich mixture. Have you tested that?

http://www.e30zone.net/e30zonewiki/index.php/Blue_Plug

[DHFiS]

I havent heard that theory before. What emissions readings do you get?

[E30_Crazy]

I'll have a go at the sensor.

DHFiS, I'm not sure if I remember it for sure, but I think it was getting too many hydrocarbons? He said basically it was un-burnt fuel coming out that was giving the fail for emissions.

I'll head outside and give it a go for the cold ohms right now. Or at least soon. I just moved it a while ago. Only ran for a minute or so.

[daimlerman]

Blue sensor seems to fail in it's 'cold start' position....
Fitting a new one(less than £20)cured my 2.7 a couple of MoT's back.

[E30_Crazy]

Blue sensor seems to fail in it's 'cold start' position....
Fitting a new one(less than £20)cured my 2.7 a couple of MoT's back.

It was failing emissions cold then? Mine was full warmed up and failing.

[leeparkes]

Blue sensor seems to fail in it's 'cold start' position....
Fitting a new one(less than £20)cured my 2.7 a couple of MoT's back.

It was failing emissions cold then? Mine was full warmed up and failing.

The ECU 'thinks' the engine is cold when the sensor fails.

[Brianmoooore]

You will get high HC at the tailpipe if the mixture is rich, weak enough to cause a misfire, or if a cylinder isn't firing for some other reason.
Do you have the rest of the gas results?
The reason you shouldn't touch the AFM bypass is that, with a standard engine, if the gas results are out of spec., the reason is elsewhere, since the adjustment won't have moved itself, and efforts should be made to find the real fault, rather than masking the fault with another fault, which will then cause the engine to perform incorrectly if and when the original fault is discovered and cured, either accidentally or deliberately.
Your engine is far from standard, so there's no reason to suppose that the factory setting is the correct one, but again, if it was right before, don't touch the adjuster!
Check the blue temp sensor resistance at the ECU plug. Disconnect it, measure the resistance, reconnect it, reun the engine up to full temperature, disconnect the plug and measure it again.
Measure between pin 45 and earth.

[E30_Crazy]

Well, here's what I found...

Cold: Couldn't get a steady reading. It kept jumping around, giving me a number, then back to no continuity, to a number, to no cont. etc. The numbers were like 3000, 2200, 3400, random things like that.

Hot: Same as before with bouncing numbers and no cont. This time, numbers it spat out were like 98, 130, 110, back to 280 or so, etc.

So, my conclusion is that it must be the sensor. Are they the same on pre-facelift engines? If so, should I wait and do it when I can get back on the tester at the MOT place, so he can adjust the AFM back down? I don't want to plug in the new blue sensor, and then have it run so badly it breaks something else. Just spent 4+ months without being able to drive it

[E30_Crazy]

Exactly what I was thinking Brian, about covering it up with the AFM adjustment. Now, I don't want to swap the sensor, because then the adjustment on the AFM is so far out I don't know what will happen with a good blue sensor in it.

Just went and tested the ECU plug. Same sort of results. I get a low number (anywhere from 28 to 80's or 90's) then it jumps to no cont, then a higher number (120's to 190's) and then back to no cont, at which point I have to take one of the leads away, then back to the pin to get it to change again (which gives me two more numbers again)

[Brianmoooore]

The reading should be nice and steady, and on a hot engine, be around the 200 - 300 ohm region, slowly increasing as the engine cools. If you're sure the unsteady reason isn't coming from a faulty meter or leads (like some of my more well used examples!), then a new remp. sensor is in order.
Changing it now won't do any damage, although it might be a bit lumpy at idle. Screw the adjuster in yourself until it sounds right, but the final tweaking will need to be done on the gas meter.
Educate your MOT man that this is a BMW, not some mass market scrap yard dodger, and should be performing almost exactly as it did when it left the factory.

[E30_Crazy]

Pretty sure it's not the leads. I always test them against eachother before an ohms test anyways, making sure the meter is working, and the leads aren't acting up. It's almost a brand new meter and leads also.

I remember testing the one on my pre-facelift engine as well.... I think. Might have been the brown sensor. Either way, the blue one should be fine, as the old high comp was running fine before I dropped a nut down the spark plug hole

[Grrrmachine]

If you're getting shaky readings at the ECU, then test again at the sensor itself. If you get steady readings there, then there must be something up with the loom between the blue sensor and the ECU; probably at the plug under the inlet manifold.

[E30_Crazy]

If you're getting shaky readings at the ECU, then test again at the sensor itself. If you get steady readings there, then there must be something up with the loom between the blue sensor and the ECU; probably at the plug under the inlet manifold.

Nah, deffinitely at the sensor. Still getting bad readings there.

[e301988325i]

I had the car in for MOT the other day, and while doing the emissions test, it was coming up way too rich (not the car's mixture, the exhaust). The tester explained to me, that if the car's mixture is lean, then in doesn't burn efficiently, and gives a "rich" reading on emissions. He proceeded to stick a screwdriver/allen key/whatever tool to the AFM, and adjust it while running the emissions tester. He kept mentioning it was getting better, then said that it's at it max on the rich side! No more adjustment to be had from it. At this point, is was just passing, and this is on a non-cat model (Jan 87 on D reg). I know it's bad to run lean, but it shouldn't hurt to drive set rich should it? And according to his tester, it's not really running rich, just the AFM set rich to make it run normal-ish.

Could there be something wrong with the AFM? I expected it to be a little worse than a stock E30 on emissions but not outright fail so hard. It's got a 2.7 done on it, and a schrick 288 cam. It's a facelift engine still running facelift motronic 1.3 (supposed to have a chip tuned to the engine aswell).

If it sounds like the AFM gone bad, can I use the one left over from my pre-face high comp engine? Thinking about a MAF anyways, can this be grafted in on the motronic, or is this an upgrade only for those that are on standalone/piggyback?

Any suggestions, comments, advice is welcome and appreciated.

MAF can be grafted into standard motronic but needs lambda sensor fitted for motronic to adjust fueling. I've got a great link for a DIY M20 AFM to siemens MAF from a E36 328i, just needs live from the fuel pump relay and a bit of wiring cut and shut (read solder and heatshrink insulation).

Having messed a lot with AFM's I think your MOT man has been turning the adjustment the wrong way, your M20 will happily run lean at idle, rich readings on the CO2 means the car's running rich, aim for 1% CO2. However having the 288 fitted will increase your hydrocarbons at idle because the cam is not designed for a perfect idle but for power higher up the rev range. Increasing the idle (in the chip program) to 900rpm (stock 600rpm) will improve the hydrocarbons if they are causing an MOT fail. HTH

[E30_Crazy]

e301988325i: Idle seems to still be at around stock 600-700 rpm. But the first and foremost complication in the matter seems to be a faulty blue temp sensor, so I'm gonna look into replacing that first and "resetting" the AFM. Then, after getting it checked again on the emissions tester, if it still fails, I will look into getting a MAF/MAP and the chip idle raised a bit.

[Brianmoooore]

If needed, you can raise the idle speed a modest amount by permanently connecting the ECU's 'aircon' pin to 12 volts ignition live.

[E30_Crazy]

Would it still run as on an idle map then?

[kman82]

Somebody else much more informed than me can confirm or refute this but doesn't the 2.7 need a slightly different AFM?.. from the 2.5e? Would that explain why the adjustment screw is maxed out?

[e301988325i]

e301988325i: Idle seems to still be at around stock 600-700 rpm. But the first and foremost complication in the matter seems to be a faulty blue temp sensor, so I'm gonna look into replacing that first and "resetting" the AFM. Then, after getting it checked again on the emissions tester, if it still fails, I will look into getting a MAF/MAP and the chip idle raised a bit.

To me it doesn't sound like you blue sensor is faulty, much more likely a less than perfect connection from the prongs of your multi meter. The flashing numbers correspond around the correct levels for a working sensor. Can you test the resistance of someone else's blue sensor or another sensor i.e. CPS crank position (575ohms IIRC) to check your multi meter, prong to prong is always a good connection and will give good results?

If needed, you can raise the idle speed a modest amount by permanently connecting the ECU's 'aircon' pin to 12 volts ignition live.

Would it still run as on an idle map then?

Yes, as long as your TPS is registering idle correctly (which hasn't been discussed, have you checked it?) the idle is raised slightly to counter the extra load created by the air con pump.

[E30_Crazy]

I was getting a pretty good contact with the prongs of the sensor, and yes the multimeter works as advertised on anything else. I was getting the same readings through the ECU plug, but checking others things it read fine and steady.

I didn't think about the TPS, really. The throttle is set correctly, clicking just after movement, and always reliably returning to closed with another click. I haven't shot the TPS connectors/prongs yet though. That will be the next thing in order I guess. I've already started for a new blue sensor though. Won't hurt anything to have a new one.

[leeparkes]

I've got a great link for a DIY M20 AFM to siemens MAF from a E36 328i, just needs live from the fuel pump relay and a bit of wiring cut and shut (read solder and heatshrink insulation).

Post the link up then.

[E30_Crazy]

I've got a great link for a DIY M20 AFM to siemens MAF from a E36 328i, just needs live from the fuel pump relay and a bit of wiring cut and shut (read solder and heatshrink insulation).

Just a lambda wideband is all it needs? I just did a couple searches on it, and they all are using a piggyback/standalone like SMT6, Perfect Power etc. I imagine to get the most out of it, it's necessary, but I was just thinking more along the lines of just upgrading while replacing. Not a full change-over on management.

[e301988325i]

I was getting a pretty good contact with the prongs of the sensor, and yes the multimeter works as advertised on anything else. I was getting the same readings through the ECU plug, but checking others things it read fine and steady.

I didn't think about the TPS, really. The throttle is set correctly, clicking just after movement, and always reliably returning to closed with another click. I haven't shot the TPS connectors/prongs yet though. That will be the next thing in order I guess. I've already started for a new blue sensor though. Won't hurt anything to have a new one.

I've seen your job title in another thread, it's safe to say you can use a multimeter properly, definitely change the sensor. No not wideband, 0-1V for the motronic to adjust the fuel map. The other option is the plug in miller MAF but that's quite expensive. Definitely worth checking the TPS, when I got my car, neither the idle or WOT switches were making the circuit, fixing it cured the lumpy idle and set 10bhp free.

I've posted this about a dozen times over the past couple of years but here you go again. Ant @ A-tech now does the conversion, possibly with a chip instead of lambda fitment not sure.

http://www.e30clubsa.co.za/forum/index. ... -maf-swap/

Stubeedoo tried this conversion with an E36 320i siemens MAF which is a convenient 70mm dia, however it didn't work as planned, but there were a lot of variables involved all at once, LPG - MAF - WAR chip, and the thread states to use the 80mm 328i MAF and hose adaptors to suit this size.

Stubeedoo's - LPG - MAF - WAR chip thread

http://www.e30zone.net/modules.php?name ... c&start=75

edit - ANT is no longer trading

http://www.e30zone.net/modules.php?name ... highlight=

[E30_Crazy]

Yeah in the E30clubsa link, they are using piggybacks to be able to limit the output signal from the MAF to <5V since the motronic ECU shuts the engine down if the signal reaches 5V. IIRC the MAF usually reaches 12V max. Someone posted in the thread that some chips can have the MAF outputs mapped into the motronic 5V range. Haven't had my ECU apart yet, but supposed to have a custom chip made for the engine. I'll see about getting the MAF limits on it. I don't want to spend hundreds on piggyback stuff just to put a MAF on (just yet, anyways).

[Billwill]

My understanding of how the standard AFM works, from reading entries on the e30clubsa site, is that if you cannot get the O2 reading correct by means of the adjustment potentiometer then it is possible that someone has opened up the AFM and moved the spring clockwise or anti-clockwise.
I believe that moving the spring a notch or two clockwise makes the mixture leaner; anti-clockwise makes it richer. May be worth a try if or else fails...first mark the current position of the spring and re-seal the AFM with some silicon sealer.

[E30_Crazy]

Ok, blue sensor sorted, works basically as advertised. Also, the TPS and ICV both are reading good on ohms/continuity checks. I've looked for dry and cracked hoses (would mess with the idle, but don't think it would make it fail gas tester). I guess I could throw the old AFM on and see if it reads different the the current one (there's no differences in FL/pre-FL AFMs are there?) which would suggest the internal spring has been adjusted/come loose and rotated.

With as many 288 cams I've seen/read about being used, and not failing gas tests, it's kind of getting to me... The next step after the AFM would be the injectors I suppose? Double check the timing? Don't know if that would affect fueling enough (even with a 288) to make it so rich... hmmmm, any thoughts?

[kman82]

yes there is a difference in AFM's. (i think) you need the AFM off of a 325 e engine for a 2.7 conversion.

Edit: hang on i might be getting confused. The 325e has a different AFM, dont know if you need that or a standard 325i for the 2.7 conversion

2.5e part numbers are 0280202091 (bosch)= 13621710544 (BMW)

[Ajsingh]

^^ really?

I was told u have to use a 2.5 ecu and a 2.5 AFM with a custom chip

[kman82]

Edit to my post above

[e301988325i]

Copied from a post by the OP of the SA thread:

Don't forget that I had the 535i AFM on before, and the fuelling map was substantially tweaked... The values on the Perfect Power screen shot I posted earlier in this thread are off my engine and you can see how far the fuelling has been juiced up...

As far as I can tell, with my limited skills with a multimeter, the voltages put out by the 535i AFM and the Siemens MAF are almost the same... I was amazed too!

Andreas I will make a video.. Knowing how partial you are to lots of noise!

I'm telling you the noise gives the hairs on the back of your neck an instant erection!

0

[E30_Crazy]

And the 535i AFM didn't require any piggyback? Or did he have his piggyback with the 535i AFM. I'll have to read though it again.

[e301988325i]

You can put the 535i M30 AFM on PN eding 027 IIRC, but you need a lambda fitted and a tweak of the the black geared wheel inside the M30 AFM. I use one on my car now, I have the siemens MAF ready to go on just short of time at the moment.

Ps) A new rubber inlet elbow can be heated in water and stretched over the larger diameter M30 AFM.

[E30_Crazy]

Where exactly does the lambda need to be on the exhaust (if any one place is prefered)? And where does the signal get routed? I would go the MAF route before M30 AFM.

Even got a load of shrink tubing from work today to make the adapter harness. A sealed plastic bag with around probably 60-70 or more 6" pieces of all sizes. They have a "shelf life" and the stock supervisor said the only way to get new stuff is if all the old is used up (leaves the drawer open and walks away).

[HairyScreech]

the e36 sensor is right down at the end of the down pipes, right near the output of the gearbox, just for reference.

i think the e30 ones are about half way down the down pipes.