So my car started stuttering under load last Friday. In the morning the car was fine, also drove fine when I went out to lunch, but symptoms suddenly appeared in the afternoon on the drive home. Basically it hesitates very badly if I try to accelerate, but starts, idles, and cruises normally seemingly without issue. Car is 1999 540i 6-speed with about 161,000 on the odometer.
Some diagnostic info I was able to get with a generic OBDII scanner:
-Only two codes stored: P0170 and P0173, but did not trigger check engine light
-Long term fuel trims on both banks are around 24%
-Short term fuel trims stay around 0% at idle, but go as high as 25% when trying to accelerate normally
-MAF reading 0.69lb/min at idle, increases with rpm/load
-Post-cat O2 sensors holding relatively steady around 0.78V, pre-cat O2's seem within normal range
-Test#7 in secret menu shows 1.7L/19.4L/21.1L with a little over 1/4 tank
-Test#14 shows the following codes stored: C7, F5, 44, BF, D7
Right now I'm leaning towards dying fuel pump, but would like to get a second opinion. I would rather not drop $300+ on a new fuel pump only to find out it's something else. Thanks in advance.
Some diagnostic info I was able to get with a generic OBDII scanner:
-Only two codes stored: P0170 and P0173, but did not trigger check engine light
-Long term fuel trims on both banks are around 24%
-Short term fuel trims stay around 0% at idle, but go as high as 25% when trying to accelerate normally
-MAF reading 0.69lb/min at idle, increases with rpm/load
-Post-cat O2 sensors holding relatively steady around 0.78V, pre-cat O2's seem within normal range
-Test#7 in secret menu shows 1.7L/19.4L/21.1L with a little over 1/4 tank
-Test#14 shows the following codes stored: C7, F5, 44, BF, D7
Right now I'm leaning towards dying fuel pump, but would like to get a second opinion. I would rather not drop $300+ on a new fuel pump only to find out it's something else. Thanks in advance.
E39 540i Stuttering Under Load
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