hi fellas,,,searched for hours,on the site,just need a bit of imput about maf...jerky; bad at around 2000 rpm steady throttle,,serges,rich fuel,,,,no vac.leaks,replaced o2 twice,throttle pos. sensor ,temp.sensor,,took off all connectors I could find and cleaned them,,,cleaned the maf,no diff. : when I unplug the maf, it starts ok, runs about the same as if plugged in,,,good at wot, but slow acceleration, or steady throttle it is very jerky, and at a steady rythm, about every 2-3 seconds,,,the maf as you know is a nasty price,,in canada, 1600.dollars,,,and find out it didn,t fix the problem,,,youch,,,,I don,t have that kind of loot,,in some posts,I read it also might be a faulty chip?? and to check the maf with a volt meter, is that difinitive?? the post said, measure pin 1 or 5 on maf,,sorry for being so stupi,,,,the maf is connected? bare the wires? probe to 1 or 5 to ground unplugged, or between 1+5,,,the post wasn,t clear,,,,farrell helped quite a bit,,,followed his suggestions, and came to the maf,,,but the pluged and unpluged ,with the same ,,almost,,,the same symptoms,,,,occured ,,I am a bit concerned it may not be the maf,,,,and the $ issue,,,,what do you think??? does it indicate it might not be the maf?? 4 nights till I fall asleep on the computor, my boys,,,at that,,,I may have missed something on the posts,,,thanks a bunch,,,,,,bryon,,,p.s. just want to make sure before spending the$ havent yet paid for the car, its just discouraging,,,the car is 93 e34 m5 3.8 ltr. with 78,000km.,,,just a little less than 80,000 miles,,,,thanks guys,,,,,especially ferrell, for his long suffering with guys like me,,,,I am more used to coils and points,,,carburaters , how ever you spell it......hope you can help....bryon, canada,,,,the nearest dealership is 3 hours away, and they did nothing when I brought it to them,,,the other, 6 hours, away, said there is nothing wrong,,,,+ 340.oo bill, and 6 hours back,,jerking and serging ,,,,,,,
thanks alan, I have changed the fuel filter,,and put injector cleaner through it, and the coil packs,, there is no hesitation when passing someone what so ever, wide open throttle no misses at all,,,,I wonder still if there could be somewhere a vac leak,,,couldn,t find one though,,,,the diagnostics at the 2 dealerships , showed all the sensors were working fine, and the maf,,,,but no faults,,,,,farrell said it would have to be really bad to have a fault come up,,,,thanks,,,if you think of something else,,let me know,,,,,thanks again,,,bryon
I was wondering, if it could be a part in the computer that isn,t working,,,,? in the early start up about a minute of opperation,,,it runs just fine,,,,then jery, surging,,,as one other member put it fishbite effect,,,,which reminds me I have got to go fishing soon,,,,anyway,,,,he fixed his when he put a chip into the car,,,,,,a unichip,,,,which the usa unichip said had no application for a 3.8 ltr. m5,,,,,,,......
Have you done any measurements (voltage) on the MAF or lambda sonde? You could measure the voltage of the MAF during idle, 2k rpm, 3k rpm and a full load run to see how high it gets.
There might be a member who could do the same to compare your values (if lower -> Defective MAF or (noticeble) vacuum leak). If you disconnect the MAF the engine management can get in to some kind of limp mode/ alterative mode. Instead of using the MAF signal for main load it can use the TPS signal for main load. But like nepbor said, you should notice a real difference.
There might be a simple way to know if your MAF is working propperly. The OBC computer on your M5 has the capability to see the fuel consumption real time. You can search the forum to see how you can do that. Use the function, do a full load run (example in 3rd or 4th gear were there is enough time) and compare with other members. This is a known manner to test the MAF's on E39 M5.
The MAf is one of the biggest factors on fuel time injection. The engine managements sends the injection time in a voltage to the OBC/instrument cluster. If your MAF is faulty you could see some differences, but again you need other members to do this "test" to with their E34 3.8 M5.
In your first post you told us that you replaced the O2 sensor twice. Why did you replaced it twice?
__________________ To///Mba
The Following User Says Thank You to Tomba For This Useful Post:
I changed it twice, because I had a 525i that surged just like this one, though it didn,t buck or wasn,t jerky, fish-bite effect, and the o2 sensor cleared the problem with surging,,,,and the person I asked to put the first one in was a beginner mechanic and she said she had trouble with it, so I didn,t want to take any chances, thinking that possibly a wire or bad connection may have resulted from her having a hard time putting it in,,,,I tried to voltage check the maf from the explanation on the site for another model, and the wires were diff. colors and I didn,t get any voltage,,,,so if anyone can tell me how to check the voltage,,,appreciate it,,,,I can check it tomorrow before I order another one....thanks
,,,,bryon
I was wondering, if it could be a part in the computer that isn,t working,,,,? in the early start up about a minute of opperation,,,it runs just fine,,,,then jery, surging,,,as one other member put it fishbite effect,,,,which reminds me I have got to go fishing soon,,,,anyway,,,,he fixed his when he put a chip into the car,,,,,,a unichip,,,,which the usa unichip said had no application for a 3.8 ltr. m5,,,,,,,......
I highly doubt "part" of the computer has failed. That's almost always and "all or nothing" thing... Fuel and timing maps don't spontaneously change.
I'm not 100% sure how the M5 fuel injection parameters are set up, but typical fuel injection setups will ignore the 02 sensor for the first few minutes of operation (until it is warm enough to give accurate readings) and rely on the MAF sensor to adjust the fuel mix. I would strongly suspect the O2 sensor in your case if, as you say, it runs fine for the first couple of minutes and poorly thereafter..
I just had a MAF go on one of my cars and it exhibited very poor performance in the first 2 minutes - then would run well - but lean. Never got a "bad MAF" code - only got a "lean condition" code (and some bad pinging under load of course).
Shouldn't be too tough to check that the voltages from the O2 sensor are in spec.
I highly doubt "part" of the computer has failed. That's almost always and "all or nothing" thing... Fuel and timing maps don't spontaneously change.
I'm not 100% sure how the M5 fuel injection parameters are set up, but typical fuel injection setups will ignore the 02 sensor for the first few minutes of operation (until it is warm enough to give accurate readings) and rely on the MAF sensor to adjust the fuel mix. I would strongly suspect the O2 sensor in your case if, as you say, it runs fine for the first couple of minutes and poorly thereafter..
I just had a MAF go on one of my cars and it exhibited very poor performance in the first 2 minutes - then would run well - but lean. Never got a "bad MAF" code - only got a "lean condition" code (and some bad pinging under load of course).
Shouldn't be too tough to check that the voltages from the O2 sensor are in spec.
Cheers.
Disconnect the O2 sensor, start the car, let it run a while and see if there's any difference.
My 535i did this once and it turned out to be the O2 sensor......totally screwed up the running of the car. I took real time readings from the OBC to monitor the fuel consumption....typical idle values with a.c. off are 2.4 - 2.7L/h on the ( my ) M5....535i was alomst identical.
Once the O2 sensor was plugged in it ran up to 4.5L/h....culprit identified !
Remember that if the ECU is not receiving the O2 signal it may NOT be the sensor itself - it could be that the plug or wiring has corroded, or has been wired up wrong.
Most O2 sensors are different - they need wired in correctly!
Lets hope you get this fixed soon - it can't be nice
To///Mba
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