running without mass air flow sensor

[93bmw325is]

ok you guys will find this very intresting
my car is runnning horriball has no power, spits ,spudders, bogs, can barly get iot up to highway speed.
so i thought to myslef maybe its the mass air flow sensor so i started the car and unplugged it to see if there was a change in the performance. to my amaze ment once i unplugged it the idle smoothed out and the car ran great and became drive able
so i got used mass air flow sensor from some one today swapped it but it still ran like shit so once agein i disconnecte dthe MAF and it runs great , is it bad that im driving my car around with the MAF disconnected?also has anyone heard of such a thing before this is very odd to me
thanks ,mike
MERRY CHRISTMAS

[Balthazarr]

You need to give it time to adjust to new HFM.
If no improvement, maybe the used one you bought is dead also.

W/o the sensor signal A/F is going to be incorrect.
Perhaps your O2 sensor needs replacing?

[tomas3314]

Long sory short....Happened to me before, yes car will run better unplugged IF your MAS is bad. Figured that out the long, expensive way. I also got a bad 2nd "used" MAS from a reputable seller of used parts SO you need to make sure you get one that works.

[93bmw325is]

Long sory short....Happened to me before, yes car will run better unplugged IF your MAS is bad. Figured that out the long, expensive way. I also got a bad 2nd "used" MAS from a reputable seller of used parts SO you need to make sure you get one that works.

i unplugged my battery and installed the one i picked up today and then reconnected the battery after a few hours and the car runs great!!!!!!!!!!!!!

[hc1001]

glad ur car is running normal again...

[93bmw325is]

thank you! i am also it was very troubleing with this problem.
HAPPY HOLIDAYS

[93bmw325is]

i guess i spoke to soon , i got in my car tonight and i drove abot 5 minutes car ran great. so i stop at the gas station and talk to a freind and i go back over to my car and i hear the funny idle . so im like shit its doing it agein. so i get in i drive it and it took like 3 minutes to go one block so i pull over disconnect the mass air flow sensor and drive home with in riunning smooth with the sensor disconnected,so unplugging the battery and reconnecting it mad it run good for a day. iguess i just have to un hok my battery every day and teh car will run good? lol, this is an odd thing

[martialartsblac]

i guess i spoke to soon , i got in my car tonight and i drove abot 5 minutes car ran great. so i stop at the gas station and talk to a freind and i go back over to my car and i hear the funny idle . so im like shit its doing it agein. so i get in i drive it and it took like 3 minutes to go one block so i pull over disconnect the mass air flow sensor and drive home with in riunning smooth with the sensor disconnected,so unplugging the battery and reconnecting it mad it run good for a day. iguess i just have to un hok my battery every day and teh car will run good? lol, this is an odd thing

so did you ever get that worked out? i too am running w/o my mass air flow sensor

[amancuso]

Yeah, read post #4

[martialartsblac]

Yeah, read post #4

yeah i read that i must have zoned out between that post and the last ones. at least im not at work zoning out

[joshe36316i]

why don't you calibrate it?

[taseal]

i'm having the same problem.... we broke the maf cleaning it, then I got a new one from a member here which happened not to work... (does exactly what you said) and when you unplug it, it will drive perfectly fine (good perf, good mileage etc) I'm not sure on bimmers, but on camaro/fbodies if you disconect the battery and reconnect it, the ecu (PCM) will go into learning mode and for about 50 miles it will learn about the new sensors, changes.... its a good thing to do everytime you install a mod...

i'll unplug mine and see what happens, i'll let you know what happens

[martialartsblac]

well last night as i started the car to go home the car ran horable. breaked didnt work and it was smoaking like it was on fire. so i run the scan tool and it gave me the Od code. so im picking up an o2 sensor tomarrow. weel see then

[TeXJ]

Im having this same issue with a swapped e30 running obd1, m52b28. I'm on my second new MAF. I disconnect it and all works fine.

Any update to this post?

[M3AN]

Vacuum leak or faulty MAF.

If the amount of air in the system does not match what the MAF is reading you'll get erratic performance. Unplugging the MAF forces the engine to run on default maps which can obscure any symptoms.

If you've eliminated the MAF (cleaned/replaced/etc) as the cause then it will most likely be a vacuum leak, get the car smoke tested, shouldn't cost much at all. That will identify which lines/hoses need to be replaced (a visual inspection may suffice but it's not really foolproof).

[shogun]

Limited Operating Strategy (LOS)
In the event of a serious fault in one or more of the sensors or their wiring circuits, Motronic will substitute a fixed default value in place of the defective sensor. This procedure is often termed limp home. A serious fault occurs when the signal from the sensor is outside of its normal operating parameters. When operating in LOS the engine may actually run quite well with failure of one or more minor sensors. Since the substituted values are those of a hot engine, cold starting and running during the warm-up period may be less than satisfactory. Also, failure of a major sensor, ie the AFS, will tend to make driving conditions less easy. Once the fault has cleared, Motronic will once more accept the live signal from the sensor. The following LOS measures are taken in the event of a failure

Component..............................Action
AFS........................substitute values are calculated from the TS position. The load signal is fixed to 6.0 ms and the ignition timing to 20° BTDC once the TS contact is open.

ATS........................substitute value of 50° C . A code will not be set, and LOS will not commence until a minimum of 3 minutes after engine start and the engine idling for a minimum of 30 seconds.

CID sensor.............injectors are pulsed simultaneously

CO pot..................substitute value of 2.77 volts

CTS...................substitute value of 80° C if ATS value is greater than 20° .
if ATS value is less than 20° , substitute value of ATS value for first three minutes after engine start-up.

OS.....................substitute value, open loop control

TS.....................substitute values, restricted engine operation

[M3AN]

I don't think there's a limp mode on e36's is there?

Either way, disconnecting the MAF does not trigger it. You can run MAF-less with practically full power for extended periods if you want to, it's just not efficient for fuel or components.

[TeXJ]

I've checked for vacuum leaks and then had 3 other mechanics check as well. I don't think mine is a vacuum or MAF issue. I'm thinking mine is a signal to DME issue. I think..

[shogun]

I don't think there's a limp mode on e36's is there?

well, they call it like that because:" Motronic will substitute a fixed default value in place of the defective sensor. This procedure is often termed limp home."
That is not as severe as on my E32 750 with the EML, there a REAL limp home mode can switch off even 6 cylinders, throttle valves only open partially and RPM goes to abt. 2500 only and the auto trans is set in 3rd gear. Even when the throttle valves are out of sync by more than 2%: limpmode. Or as they call it there: Emergency “Failsafe” operation in the event of component failures https://www.europeantransmissions.co...MW/EML-BMW.pdf

[B320i]

I don't think there's a limp mode on e36's is there?

There's DEFINITELY one on my 320i (this has the Siemens MS40.1 DME, not the Bosch Motronic). I presume the programming is similar.

A bad knock sensor will cause it - from just after startup, will basically go batch-fire the injectors, running very rich, very boggy acceleration until 2000rpm (even then it still isn't great).

At the moment having a problem where it goes into limp mode once warmed up. Runs fine, then, it's like a light switch being flipped. But not quite as restricted/boggy-feeling as when I had the bad knock sensor. Given I've never truly been able to resolve a pinging issue, my suspicion is a CTS.

Disconnecting the MAF doesn't trigger it for me, only makes the return to idle and throttle response a bit peculiar.