getting codes P0171 and P0174 (lean mixture) and P1342, P1344, and P1347 (misfire cylinders 1-3).
Very common. Very easy. Very hard. Depends on what it is.
I'm battling similar subtle (can't feel it) lean-mixture misfires myself:
- Does the order of the misfire OBDII DTCs diagnostic trouble codes actually matter (
1)
I'm starting with the vacuum hoses, since my plugs are new, and my CCV tests OK - yet my hoses are crumbly & my VCG is leaking on the passenger side & I have 100K miles on my fuel pump, fuel filter, and fuel injectors (which have only burned lousy Costco regular gas in the past 8 years and which are often driven on near empty):
- How to locate all the vacuum hoses in the E39 engine bay (
1) & where to get those vacuum hoses (
1) & what sizes to get for all the M54 engine vacuum hoses (
1) & correcting the F-connector errors in the realoem diagrams (
1).
bluebee said:
So far, the list of hoses to check seems to be the following:
Engine =>
Vacuum control =>
AIR PUMP F VACUUM CONTROL
- 04 VACUUM HOSE BLACK 3.3X1.8 11657803732 $16.43 (two pieces)
- 03 VACUUM PIPE 1 11727574490 $27.94 (one piece)
- 07 VACUUM HOSE BLACK 3.3X1.8 11657803732 $16.43 (two pieces)
- 09 VACUUM CAP (no part number shown)
Engine =>
Exhaust manifold =>
EMISSION CONTROL-AIR PUMP05 PRESSURE HOSE ASSY 1 11721435456 $22.73
Fuel Preparation System =>
Fuel Supply =>
Fuel filter, pressure regulator
- 13 VACUUM HOSE BLACK 3,5X1,8 11727545323 $14.82
- 11 Hose 1 13321437801 $24.87
Engine =>
Vacuum control =>
Vacuum control - engine
- 02 Hose elbow 1 11617503666 $8.17
- 03 Hose elbow 1 11617547582 $17.25
Fuel Preparation System =>
Fuel injection system =>
FUEL TANK BREATHER VALVE
- 03 fuel tank breather line 1 13907557924 $27.77
- 04 fuel tank breather line 1 13907504303 $27.77
Engine =>
Cylinder Head =>
Crankcase-Ventilation/oil separator
- 02 Vent pipe 1 11611432559 $25.73
- 03 Connecting line 1 11617504535 $33.87
- 04 Vent hose 1 11157532649 $15.37
- 06 VACUUM HOSE BLACK 3,5X1,8 ? 11727545323 $14.82 (not on all E39s)
- 07 Return pipe 1 11617504536 $33.87
Of those above, these smaller hoses seem to be most problematic:
- 04 VACUUM HOSE BLACK 3.3X1.8 11657803732 $16.43 (two pieces)
- 07 VACUUM HOSE BLACK 3.3X1.8 11657803732 $16.43 (two pieces)
- 09 VACUUM CAP (no part number shown)
- 13 VACUUM HOSE BLACK 3,5X1,8 11727545323 $14.82
- 06 VACUUM HOSE BLACK 3,5X1,8 ? 11727545323 $14.82 (not on all E39s)
And, these larger hoses are apparently problematic:
- 02 Hose elbow 1 11617503666 $8.17
- 03 Hose elbow 1 11617547582 $17.25
- 02 Vent pipe 1 11611432559 $25.7303 Connecting line 1 11617504535 $33.87
- 04 Vent hose 1 11157532649 $15.37
- 07 Return pipe 1 11617504536 $33.87
I was going to replace in this order: spark plugs, then coils, then ???
Neither of which will make a bit of difference on a lean-mixture situation; but replacing the plugs at 100K miles is a good thing.
- BMW spark plug application charts (
1) (
2) & the best plug to use (
1) (
2) & a deciphering key (
1) & keys to reading plugs (
1) & the truth about torque & anti-seize (
1) & the truth about gap (
1) (
2) & DIYs for replacing spark plugs (
1) (
2) (
3) (
4) (
5) (
6)
As for the coils, nobody sane replaces them willy nilly ... you test 'em first:
- How to test a BMW ignition coil (
1) (
2)
Should I change the plugs or do something else?
I'd go down this list:
- How to diagnose a BMW E39 engine misfire (
1) & how to battle E39 vacuum leaks (
1) (
2) (
3) & how to solve specific vacuum leak diagnostic trouble codes such as P0171, P0174, P0313 (
1) & P0170, P0173 (
1) & where to find all the vacuum hoses in the E39 (
1)
No rough idle (hardly, after replacing the DISA valve). I drove it about 50 miles yesterday, is this super dangerous?
Is the yellow SES blinking?
Tap your cats with a rubber mallet. If they rattle, they are probably due (overdue at that mileage) for replacement. A clogged cat will cause misfires.
Hmmm.... I don't think 'this' is in the misfire thread (I'll look, and add it if it's not there currently).
However, I'm curious ... HOW would a cat cause a misfire? (And, particularly a lean condition misfire?)
most likely failures are 1) a crankcase vent valve, 2) an intake leak (boot, vacuum line, etc), and/or 3) low fuel pressure.
I borrowed the free loaner (with deposit) Autozone CP9220A which I hope to learn from but I haven't yet used it since I'm first working on the vacuum system before I move on to the fuel system (I have 90 days):
- While replacing your spark plugs (
1), where is the fuel system pressure test Schrader valve for the I6 (
1) and for the V8 (
1) (
2) (
3)
BTW, this is a rarity, but nobody seems to know the answer to this vacuum hose question:
-
For all to benefit, WHERE are the ends of these hoses in our beloved E39s anyway?