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Vipersilver Vipersilver is offline
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Default 30BB DME question - multiple misfires - 10-07-2018, 05:43 PM

The other night on the way home from work the air was cold and I had E30 in the tank, so I did a few pulls.

2008 e92 335i
Mods: JB4 Map 5, DCIs, FMIC, Phx charge pipe s/stock DVS.

I picked up a misfire on 6 that would not clear up. I went ahead and drove home on 5 cylinders since I had read that the computer will shut down the injector in a misfiring cylinder. When I was about 1 mile from home it started to run worse and seemed like a 2nd misfire.

My generic scanner showed misfires on 4,5 & 6, and multiple misfires. I cleared the codes and swapped the plugs and coils in 4-5-6 with known good parts just hoping for an improvement. Unfortunately it still ran just as bad.

JB4 Interface shows 30BB and nothing else. I assume I didn't let it run long enough to pick up the misfire codes.

I pulled the DME and tested the chips, only the mosfet for cyl 5 is bad.

Can a bad mosfet cause phantom issues with other cylinders?

Is there something else in the DME besides the injector mosfets that can cause misfires?

I didn't check compression, but I did put a scope in all the holes and didn't see any piston carnage. (could not see the valves.)

Since I need DME work, is there any reason to upgrade from MSD80 to MSD81?

I see there are places I can send mine in for repair, but I am concerned that there is more than just the bad mosfet 5 in there.

Sorry to load so many questions at once.

Thanks for your help!
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Dave @ BMS's Avatar
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Default 10-07-2018, 08:37 PM

Quote:
Originally Posted by Vipersilver
The other night on the way home from work the air was cold and I had E30 in the tank, so I did a few pulls.

2008 e92 335i
Mods: JB4 Map 5, DCIs, FMIC, Phx charge pipe s/stock DVS.

I picked up a misfire on 6 that would not clear up. I went ahead and drove home on 5 cylinders since I had read that the computer will shut down the injector in a misfiring cylinder. When I was about 1 mile from home it started to run worse and seemed like a 2nd misfire.

My generic scanner showed misfires on 4,5 & 6, and multiple misfires. I cleared the codes and swapped the plugs and coils in 4-5-6 with known good parts just hoping for an improvement. Unfortunately it still ran just as bad.

JB4 Interface shows 30BB and nothing else. I assume I didn't let it run long enough to pick up the misfire codes.

I pulled the DME and tested the chips, only the mosfet for cyl 5 is bad.

Can a bad mosfet cause phantom issues with other cylinders?

Is there something else in the DME besides the injector mosfets that can cause misfires?

I didn't check compression, but I did put a scope in all the holes and didn't see any piston carnage. (could not see the valves.)

Since I need DME work, is there any reason to upgrade from MSD80 to MSD81?

I see there are places I can send mine in for repair, but I am concerned that there is more than just the bad mosfet 5 in there.

Sorry to load so many questions at once.

Thanks for your help!
Replace Mofset & i should be ok.

You can upgrade if you want, but in general itís about a $20-$40 fix, any small appliance shop or PC repair shop can do it for you


Burger Motorsports
Home of the JB4 the worlds most popular turbocharged tuning system!

It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.
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Default 10-08-2018, 08:04 AM

Thanks Dave. I will look for someone local.

The main source of panic was - why are 4 & 6 misfiring if only the chip for 5 is bad.

I will have them all replaced anyway, so hopefully that fixes all.
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Default 10-08-2018, 10:03 AM

Quote:
Originally Posted by Vipersilver
Thanks Dave. I will look for someone local.

The main source of panic was - why are 4 & 6 misfiring if only the chip for 5 is bad.

I will have them all replaced anyway, so hopefully that fixes all.
Better safe than sorry- do it once & forget about it


Burger Motorsports
Home of the JB4 the worlds most popular turbocharged tuning system!

It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.
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Default 10-13-2018, 07:48 PM

Update:

I had all 6 mosfets replaced with Mouser part # 844-IRF644SPBF, Vishay N-Chan 250V 14 Amp.

A local electronics repair shop charged $140.00 to do the soldering - a little higher than what others have paid but I was happy to pay it.

#6 coil was toast. I dropped in a spare coil and it runs great now.

So the answer to the question "can 1 bad injector mosfet cause misfires on the whole bank?" - yes.

Thanks for your help.
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Default 10-14-2018, 07:39 PM

Quote:
Originally Posted by Vipersilver
Update:

I had all 6 mosfets replaced with Mouser part # 844-IRF644SPBF, Vishay N-Chan 250V 14 Amp.

A local electronics repair shop charged $140.00 to do the soldering - a little higher than what others have paid but I was happy to pay it.

#6 coil was toast. I dropped in a spare coil and it runs great now.

So the answer to the question "can 1 bad injector mosfet cause misfires on the whole bank?" - yes.

Thanks for your help.
Glad you are back on the road!


Burger Motorsports
Home of the JB4 the worlds most popular turbocharged tuning system!

It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please click here for more information on legal requirements related to use of BMS parts.
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