Diagnosing Hesitating/Misfiring X35i with No Codes

[andrewwynn]

Systemic issue implies power supply (Alternator) so watch real-time for volts fluctuation (which would explain the wot weirdness since weak Alternator often works fine at high RPM).

Have you run injector cleaner yet? Dirty injectors also much more likely to cause problem at low throttle vs. wide open

[ClutchKickChris]

Originally Posted by andrewwynn

Systemic issue implies power supply (Alternator) so watch real-time for volts fluctuation (which would explain the wot weirdness since weak Alternator often works fine at high RPM).

Have you run injector cleaner yet? Dirty injectors also much more likely to cause problem at low throttle vs. wide open

I have monitored the power supply and it is clean/stable. It charges the battery at idle. Also the stuttering/misfire issue was present months before any alternator codes later down the line.

No I haven't run injector cleaner, I read some threads saying direct injected engines don't requite it? Either way I'm willing to try it at this point, is there a recommended brand?

[andrewwynn]

Originally Posted by andrewwynn

Systemic issue implies power supply (Alternator) so watch real-time for volts fluctuation (which would explain the wot weirdness since weak Alternator often works fine at high RPM).

Have you run injector cleaner yet? Dirty injectors also much more likely to cause problem at low throttle vs. wide open

+1 on check the alternator. Having my 6 mo. since replacement fail and the warranty replacement failure within 20 min.

I used Bosch for the first two replacements, but since my valeo lasted 187,000 miles and the Bosch lasted six months then 20 minutes I asked if I could exchange the second Bosch for Valeo.

O'Reilly let me do it with $5 difference.

If you have a peak reading multimeter you can catch any blips in the voltage output.

[740iS]

Originally Posted by andrewwynn

+1 on check the alternator. Having my 6 mo. since replacement fail and the warranty replacement failure within 20 min.

I used Bosch for the first two replacements, but since my valeo lasted 187,000 miles and the Bosch lasted six months then 20 minutes I asked if I could exchange the second Bosch for Valeo.

O'Reilly let me do it with $5 difference.

If you have a peak reading multimeter you can catch any blips in the voltage output.

Were the Bosch rebuilds or new? I ask as I found that both O'Reilly and Autozone in this area are using the same rebuilder and just packaging them for the specific chain. Plus they are making mistakes with the rebuilds. Had O'Reilly also replace the alternator for my 318ti under warranty 6 times in the past year (they tried to blame the car but I proved it wasn't the problem) after having a rebuilt from them for 6 years without issue for the same car. Ended up buying a Valeo for the ti too. But they still refused to blame their rebuilder, eve though I've found a lot of people in the area that have had similar issues over the last two or three years.