broken mx5

[biff]

hi Geoff,
Ask here : miata-bounces@realbig.com , and pay a visit here
http://www.miata.net/garage/
Keith Tanner is your man.
Hope it helps
Biff


_____

From: e-admin@mx5club.org.nz [mailto:e-admin@mx5club.org.nz] On Behalf Of
geoff cotton
Sent: 19 February 2006 07:21
To: mx5list@mx5club.org.nz
Subject: broken mx5


Hello people! I have recently bought a 1.8, '94 mx5. It stopped on me. No
spark. But before this happened the car has been having moments of power
loss, like a retarded spark. plugs & leads are new. It was not missing, just
gutless.Then a small cut-out; then when I stopped the engine it would not
restart. It has had problems before, because it has evidence of new coils,
crank sensor, lots of probe holes in the wiring, and the E.C.U. has been
removed. Tests so far are negative; Has anyone had this fault with their mx?
I am an 'A' grade mechanic, so I know how finicky electronics can be. I am
conversant with EFI, so dont be afraid to talk technical! This may be a
common fault; I can only ask... Cheers Geoff cotton. (Nelson)

[geoff cotton]

Hello people! I have recently bought a 1.8, '94 mx5. It stopped on me. No
spark. But before this happened the car has been having moments of power loss,
like a retarded spark. plugs & leads are new. It was not missing, just
gutless.Then a small cut-out; then when I stopped the engine it would not
restart. It has had problems before, because it has evidence of new coils,
crank sensor, lots of probe holes in the wiring, and the E.C.U. has been
removed. Tests so far are negative; Has anyone had this fault with their mx? I
am an 'A' grade mechanic, so I know how finicky electronics can be. I am
conversant with EFI, so dont be afraid to talk technical! This may be a common
fault; I can only ask... Cheers Geoff cotton. (Nelson)

[geoff cotton]

Hello people! I have recently bought a 1.8, '94 mx5. It stopped on me. No
spark. But before this happened the car has been having moments of power loss,
like a retarded spark. plugs & leads are new. It was not missing, just
gutless.Then a small cut-out; then when I stopped the engine it would not
restart. It has had problems before, because it has evidence of new coils,
crank sensor, lots of probe holes in the wiring, and the E.C.U. has been
removed. Tests so far are negative; Has anyone had this fault with their mx? I
am an 'A' grade mechanic, so I know how finicky electronics can be. I am
conversant with EFI, so dont be afraid to talk technical! This may be a common
fault; I can only ask... Cheers Geoff cotton. (Nelson)

[Grant]

Geoff, please let us all know the outcome.
For those others on this list, my experience of a failed to operate 1.8
engine has been passed on to Geoff. In my case, all diagnostic tests were ok
with no error codes etc. All sensors tested ok. The only problem was the
engine would not go.
After replacing coil pack, removing and testing of the ECU with no faults
found, replacing the fuel pump relay as the fuel pump would not run. The ECU
commands the fuel pump off if a sensor signal error is found so making
diagnosis difficult.
After many frustrating hours, the mechanic started removing sensors for a
close physical inspection. He discovered a small crack in the cam angle
sensor which meant the sensor was not positioned accurately so the output
from the sensor to the ECU would go out of tolerance (probably too low a
level to be correctly detected) so the ECU would shut off the fuel pump.
A replacement sensor cured the problem immediately.
I assume the test of the sensor is purely a test of the coil resistance and
this of course passed. If it was possible to check the output pulses on an
oscilloscope would probably show it up immediately. Don't know if that's
possible but as I'm an electronics tech, that's what I would do! Could be
why I'm no mechanic!
Before mine stopped completely, it occasionally would misfire at high revs
as if the engine was switched off very briefly. I now know this was probably
the fuel pump being switched off. It now runs very well and with more power
than before as well. Probably always had a slight misfire that I didn't
detect.
Grant in Blenheim.

[Grant]

Geoff, please let us all know the outcome.
For those others on this list, my experience of a failed to operate 1.8
engine has been passed on to Geoff. In my case, all diagnostic tests were ok
with no error codes etc. All sensors tested ok. The only problem was the
engine would not go.
After replacing coil pack, removing and testing of the ECU with no faults
found, replacing the fuel pump relay as the fuel pump would not run. The ECU
commands the fuel pump off if a sensor signal error is found so making
diagnosis difficult.
After many frustrating hours, the mechanic started removing sensors for a
close physical inspection. He discovered a small crack in the cam angle
sensor which meant the sensor was not positioned accurately so the output
from the sensor to the ECU would go out of tolerance (probably too low a
level to be correctly detected) so the ECU would shut off the fuel pump.
A replacement sensor cured the problem immediately.
I assume the test of the sensor is purely a test of the coil resistance and
this of course passed. If it was possible to check the output pulses on an
oscilloscope would probably show it up immediately. Don't know if that's
possible but as I'm an electronics tech, that's what I would do! Could be
why I'm no mechanic!
Before mine stopped completely, it occasionally would misfire at high revs
as if the engine was switched off very briefly. I now know this was probably
the fuel pump being switched off. It now runs very well and with more power
than before as well. Probably always had a slight misfire that I didn't
detect.
Grant in Blenheim.