Over the last couple of days I transcribed notes from my race car "diary" into electronic form and posted them on Bf.c this morning in response to a thread about cutouts. On the chance that this might help someone, I'm posting it here.
What follows is a long tale of chasing and ultimately solving a cutout problem. At the least it may be entertaining and at best it may help someone with a similar problem.
10/09/2007
The car is an early production (06/87) 325is. I replaced the 153 DME
with a 173 well before this started happening and it ran fine for a
couple of track weekends. When the problem first surfaced it might
happen once in a while. But with time it has progressed to happening all
the time.
Around 5400-5800rpm the engine experiences a sudden and complete loss of
power. It seems to occur at higher rpm at the beginning of a track
session, when the engine is relatively cool, and at lower rpm once
everything is good and hot. From the driver's seat it feels as if the
ignition was briefly switched off and there's no stumbling, misfires, or
loss of power prior to the event. If I persist through the cut-off(s)
the engine will pick back up and run to the redline.
I have noticed that the CEL will come on just before the event and when
it happens the tach will drop a lot more would be appropriate for the
loss of speed from coasting. On occasion I've seen it briefly go to
zero. The CEL is so consistent with the loss of power that it can be
used as a shift light. And the CEL will extinguish as soon engine rpm is
reduced by an upshift or by accelerating through the cut-off region. It
doesn't appear to matter whether the critical rpm is reached at WOT or
at partial throttle. Having to short-shift at 5200-5300rpm on the track
is a major irritant...
In an attempt to solve this problem (and fix other problems) I've:
1) Replaced the O2 sensor (new OE part)
2) Swapped in a known good AFM
3) Swapped in a known good 173 DME
4) Replaced the injectors (new OE parts)
5) Replaced the crank position sensor (new OE part)
6) Replaced the TPS (new OE part)
7) Replaced the main & fuel pump relays (new OE parts)
8) Replaced the coil (new OE part)
9) Replaced ignition wires, cap, & rotor (new wires & OE parts)
10) Cleaned all grounds and primary power connections
11) Replaced intake manifold gaskets & all hoses
12) Verified proper operation of the ECT sensor (and swapped sensors)
13) Proved there are no leaks in the brake booster
14) Replaced the oil filler cap and dipstick o-rings
15) Eliminated the evaporative control system
16) Acid cleaned & sealed the tank & replaced both pumps (new OE parts)
17) Replaced FPR (new OE part)
18) Checked C101 for corrosion
19) As of 10/28, replaced the alternator
With all of that done and other routine maintenance (timing belt,
filters, valves adjusted, plugs, etc), the engine runs better than it
probably has in quite some time. And I now have a nifty collection of
good spares. But nothing I've done has had any affect on the problem.
I have proved that the used AFM and DME are good by installing them in
another E30 and they behaved perfectly there.
The fault codes stored in the DME are 1251 and/or 1261. 1251 is an injector
fault and 1261 is a fuel pump relay fault. The only thing I can think of to
do at this point is to ohm out the wiring in the harness.
10/20/2007
I've ohmed out all power and ground connections to the DME, coil, and
injectors. Nothing remarkable there. But in checking power connections I
did find that there's about 4.5ohms of resistance to the hot side of the
coil, which means the ignition switch isn't quite healthy. Just for
grins, I bypassed the ignition switch to feed power directly to the coil
and DME "Start" input, to no affect.
Now I'm thinking that the prime problem may be 1251 (injector fault). If that
fault, and only that fault, happens after a single event I'm inclined to
figure out a way to bypass that part of the harness (even though it ohms out)
to see if that fixes it.
10/21/2007
Now I know what it is. The car is possessed by demons. To fix it I need
a young priest, an old priest, and a large jug of Bavarian Holy Water...
In trying to see if the injector fault code was repeatable I did several
runs where I cleared the codes, duplicated the problem, and scanned the
DME. The reported fault codes were completely random and different each
time. Maybe the alternator is noisy?
As a next step I'm going to rig something up to allow in-car disconnect
of the alternator and see if that changes anything.
10/28/2007
Since I had an alternator that just needed new brushes, I swapped
alternators after fixing the spare. That didn't eliminate the problem,
but it may have moved the event higher in the rpm band. It was happening
at about 6k and the CEL would come on a couple of hundred rpm below the
event. More testing is going to be needed to see if it really has moved
higher.
Now I only getting a 1262, which is an idle speed control fault and may be
related to the CEL that occasionally comes on while the engine is idling or
during a long down hill closed throttle run. But that code can also be set by
a stall above 600rpm. So it might be related to this problem.
I'm running out of the possibilities. The only thing I can think of to
do now is to ohm out all of the wires in the engine harness. But I don't
understand why a problem there would be rpm sensitive and not also cause
cause problems at other engine speeds.
11/16/2007
I found the spec for the CPS air gap (1mm or.040") and discovered the CPS was
a lot closer to the crank wheel than the spec calls for. I adjusted the gap,
but that made the problem slightly worse. So it is looking more and more like
a problem with the wiring harness and specifically the CPS signal
wires. Perhaps there's some damage to that circuit or the CPS connector that
is attenuating the signal. That would be consistent with it only occurring at
high rpm and with the problem being worse when the air gap was opened up. I'll
have to catch up on work around the house before I can dive into diagnostics
on the wiring harness.
I know the head needs freshening, but before I pull it I want to run a
compression test and see if more engine work is warranted. If I haven't found
and fixed this problem by then I'm inclined to replace the engine harness
while the head is off and it is easier to get to the harness where it runs
under the intake (for grand problems, grand solutions).
03/13/2008
I found other information that says that the air gap can be .012-.028. I
re-adjusted the CPS, which made no difference at all. I am seeing a pair of
fairly consistent codes after an event (misfire on cyl 7 and injector failure
on both banks). The first would be a coil or coil interface problem and the
latter could be a wiring or injector interface issue. But then, both could be
caused by a CPS or power fault. For grins, I tried disconnecting the cylinder
ID connector and saw that the DME did register that failure. It had no affect
on the problem, so it would appear that the signal is valid. Likewise for the
engine temp input to the DME.
I've pulled the boots on "interesting connectors" to look for corrosion, but
haven't found anything suspicious. I noticed that when one of these events
occur that the MPG gage drives to 40mpg concurrent with the tach drop. That
may imply that the DME is not supplying injector pulse width info to the
cluster.
I think I need to find out whether the CPS signal is going away, or whether
power to the DME is being interrupted. I think the check needs to be done at
the DME.
03/23/2008
Power to the DME is good. I probed to wire from the code relay (ignition on
signal) and the wire from the main relay (DME power) and saw normal system
voltage at each. I monitored each wire with a test light while driving the car
to repeat the problem. The light never flickered or dimmed during an
event. Therefore I'd say power to the DME isn't an issue.
03/24/2008
I think I saw a DC level appear on the CPS signal during an event. That could
be as a result of chaffed wires in engine harness. It seems a stretch that
both DME's would have that fault, so the harness is now my prime suspect.
03/25/2008
I found what should be a good harness, still wrapped around a 80k mile engine
that was running great before the car it is in was rear ended. So I'm
summoning the young priest, old priest, and a large jug of Bavarian holy water
and swapping engines and the harness. I'm tired of screwing with this and I
want to race the car at Roebling. The fresher engine should mean that I can
defer the head rebuild and such and I suspect it'll make a bit more power. It
will almost certainly burn less oil (a track weekend is 2-3 quarts).
I'll pick up the engine sometime next week...
04/12/2008
Work has gotten in the way of picking up the engine and harness... But I know
one more item that isn't the cause. I pulled the harmonic balancer to see if
its rubber mount had failed. That could cause the problem, but the harmonic
balancer looks fine. No signs of cracking or separation.
Continued in the next post...
What follows is a long tale of chasing and ultimately solving a cutout problem. At the least it may be entertaining and at best it may help someone with a similar problem.
10/09/2007
The car is an early production (06/87) 325is. I replaced the 153 DME
with a 173 well before this started happening and it ran fine for a
couple of track weekends. When the problem first surfaced it might
happen once in a while. But with time it has progressed to happening all
the time.
Around 5400-5800rpm the engine experiences a sudden and complete loss of
power. It seems to occur at higher rpm at the beginning of a track
session, when the engine is relatively cool, and at lower rpm once
everything is good and hot. From the driver's seat it feels as if the
ignition was briefly switched off and there's no stumbling, misfires, or
loss of power prior to the event. If I persist through the cut-off(s)
the engine will pick back up and run to the redline.
I have noticed that the CEL will come on just before the event and when
it happens the tach will drop a lot more would be appropriate for the
loss of speed from coasting. On occasion I've seen it briefly go to
zero. The CEL is so consistent with the loss of power that it can be
used as a shift light. And the CEL will extinguish as soon engine rpm is
reduced by an upshift or by accelerating through the cut-off region. It
doesn't appear to matter whether the critical rpm is reached at WOT or
at partial throttle. Having to short-shift at 5200-5300rpm on the track
is a major irritant...
In an attempt to solve this problem (and fix other problems) I've:
1) Replaced the O2 sensor (new OE part)
2) Swapped in a known good AFM
3) Swapped in a known good 173 DME
4) Replaced the injectors (new OE parts)
5) Replaced the crank position sensor (new OE part)
6) Replaced the TPS (new OE part)
7) Replaced the main & fuel pump relays (new OE parts)
8) Replaced the coil (new OE part)
9) Replaced ignition wires, cap, & rotor (new wires & OE parts)
10) Cleaned all grounds and primary power connections
11) Replaced intake manifold gaskets & all hoses
12) Verified proper operation of the ECT sensor (and swapped sensors)
13) Proved there are no leaks in the brake booster
14) Replaced the oil filler cap and dipstick o-rings
15) Eliminated the evaporative control system
16) Acid cleaned & sealed the tank & replaced both pumps (new OE parts)
17) Replaced FPR (new OE part)
18) Checked C101 for corrosion
19) As of 10/28, replaced the alternator
With all of that done and other routine maintenance (timing belt,
filters, valves adjusted, plugs, etc), the engine runs better than it
probably has in quite some time. And I now have a nifty collection of
good spares. But nothing I've done has had any affect on the problem.
I have proved that the used AFM and DME are good by installing them in
another E30 and they behaved perfectly there.
The fault codes stored in the DME are 1251 and/or 1261. 1251 is an injector
fault and 1261 is a fuel pump relay fault. The only thing I can think of to
do at this point is to ohm out the wiring in the harness.
10/20/2007
I've ohmed out all power and ground connections to the DME, coil, and
injectors. Nothing remarkable there. But in checking power connections I
did find that there's about 4.5ohms of resistance to the hot side of the
coil, which means the ignition switch isn't quite healthy. Just for
grins, I bypassed the ignition switch to feed power directly to the coil
and DME "Start" input, to no affect.
Now I'm thinking that the prime problem may be 1251 (injector fault). If that
fault, and only that fault, happens after a single event I'm inclined to
figure out a way to bypass that part of the harness (even though it ohms out)
to see if that fixes it.
10/21/2007
Now I know what it is. The car is possessed by demons. To fix it I need
a young priest, an old priest, and a large jug of Bavarian Holy Water...
In trying to see if the injector fault code was repeatable I did several
runs where I cleared the codes, duplicated the problem, and scanned the
DME. The reported fault codes were completely random and different each
time. Maybe the alternator is noisy?
As a next step I'm going to rig something up to allow in-car disconnect
of the alternator and see if that changes anything.
10/28/2007
Since I had an alternator that just needed new brushes, I swapped
alternators after fixing the spare. That didn't eliminate the problem,
but it may have moved the event higher in the rpm band. It was happening
at about 6k and the CEL would come on a couple of hundred rpm below the
event. More testing is going to be needed to see if it really has moved
higher.
Now I only getting a 1262, which is an idle speed control fault and may be
related to the CEL that occasionally comes on while the engine is idling or
during a long down hill closed throttle run. But that code can also be set by
a stall above 600rpm. So it might be related to this problem.
I'm running out of the possibilities. The only thing I can think of to
do now is to ohm out all of the wires in the engine harness. But I don't
understand why a problem there would be rpm sensitive and not also cause
cause problems at other engine speeds.
11/16/2007
I found the spec for the CPS air gap (1mm or.040") and discovered the CPS was
a lot closer to the crank wheel than the spec calls for. I adjusted the gap,
but that made the problem slightly worse. So it is looking more and more like
a problem with the wiring harness and specifically the CPS signal
wires. Perhaps there's some damage to that circuit or the CPS connector that
is attenuating the signal. That would be consistent with it only occurring at
high rpm and with the problem being worse when the air gap was opened up. I'll
have to catch up on work around the house before I can dive into diagnostics
on the wiring harness.
I know the head needs freshening, but before I pull it I want to run a
compression test and see if more engine work is warranted. If I haven't found
and fixed this problem by then I'm inclined to replace the engine harness
while the head is off and it is easier to get to the harness where it runs
under the intake (for grand problems, grand solutions).
03/13/2008
I found other information that says that the air gap can be .012-.028. I
re-adjusted the CPS, which made no difference at all. I am seeing a pair of
fairly consistent codes after an event (misfire on cyl 7 and injector failure
on both banks). The first would be a coil or coil interface problem and the
latter could be a wiring or injector interface issue. But then, both could be
caused by a CPS or power fault. For grins, I tried disconnecting the cylinder
ID connector and saw that the DME did register that failure. It had no affect
on the problem, so it would appear that the signal is valid. Likewise for the
engine temp input to the DME.
I've pulled the boots on "interesting connectors" to look for corrosion, but
haven't found anything suspicious. I noticed that when one of these events
occur that the MPG gage drives to 40mpg concurrent with the tach drop. That
may imply that the DME is not supplying injector pulse width info to the
cluster.
I think I need to find out whether the CPS signal is going away, or whether
power to the DME is being interrupted. I think the check needs to be done at
the DME.
03/23/2008
Power to the DME is good. I probed to wire from the code relay (ignition on
signal) and the wire from the main relay (DME power) and saw normal system
voltage at each. I monitored each wire with a test light while driving the car
to repeat the problem. The light never flickered or dimmed during an
event. Therefore I'd say power to the DME isn't an issue.
03/24/2008
I think I saw a DC level appear on the CPS signal during an event. That could
be as a result of chaffed wires in engine harness. It seems a stretch that
both DME's would have that fault, so the harness is now my prime suspect.
03/25/2008
I found what should be a good harness, still wrapped around a 80k mile engine
that was running great before the car it is in was rear ended. So I'm
summoning the young priest, old priest, and a large jug of Bavarian holy water
and swapping engines and the harness. I'm tired of screwing with this and I
want to race the car at Roebling. The fresher engine should mean that I can
defer the head rebuild and such and I suspect it'll make a bit more power. It
will almost certainly burn less oil (a track weekend is 2-3 quarts).
I'll pick up the engine sometime next week...
04/12/2008
Work has gotten in the way of picking up the engine and harness... But I know
one more item that isn't the cause. I pulled the harmonic balancer to see if
its rubber mount had failed. That could cause the problem, but the harmonic
balancer looks fine. No signs of cracking or separation.
Continued in the next post...
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