Please help
 

Hi all, I have an '01 Miata, completely stock at the moment. A few days ago when driving the check engine light came on and the engine would feel like it was hitting the rev limiter hard (as in cutting out completely). I checked the code and it said "P1345 Cylinder Discrimination signal" (that's what the code reader read). Did some research and replaced the cam angle sensor. Cleared the code and it was great for awhile, today the same thing started happening again.

When I got home from work I checked the sensor wiring well back into the main harness. I can't find a problem with the wires. Oh, and if I unplug it the engine will not start.

One thing that I find odd is that the rpm that the engine cuts out at varies, one time it will be 5k, then 3.5k, then 6K etc. it idles perfectly in case that matters.

Do you think my replacement cam sensor is bad or is it maybe the crank position sensor, according to Mazda they are both crank position sensors, an upper (the cam sensor) and lower (the crank sensor). Or is it something completely different?

Any advice greatly appreciated.

Jim

How many miles on your engine?

Have you replaced the timing belt?

More info required.

Does it restart immediately?
RPM varies but under acceleration, cruise, coast?
Any gauge indication, temp, oil (aka idiot light)?

P1345 for Mazda is no CMP or SGC Signal. Any chance of incorrect install?

starts and idles perfectly. Accelerates fine, but will suddenly act like the injectors are shut off (ie cam angle sensor as per cel code P1345), back off the throttle it runs fine. The engine does not quit, it feels like either the injectors are shut off (which would make sense with a bad cmp) or the ignition quits (can't say for sure which because it starts and idles perfectly and will rev with no load), but as soon as you back off the throttle it's fine, I can cruise all day long if I short shift and keep the revs down. I can set the cruise at 110 kph in 6th gear and drive all day long. The car has 117,000 km on it. Timing belt was supposedly changed at 90,000, at least according to the service records. Oil pressure and water temp are fine according to the guages.

What really confuses me is that the rpm that it cuts out at varies. One minute you can red line, the next it cuts out at 3.5k, or 4k, or 5k rpm, the rpm it cuts out at is always different.

I don't know how you could install the CMP sensor incorrectly, it's one bolt and a plug in connector.

Does anyone know if the crank angle sensor will throw the same error code?

Afm/vaf... (+,-)

In english please

I reread my original post, what I should have said is that the engine cuts in and out, it doesn't die.

I drove it to work today, no cel when I started it, ran great on the 25km drive in, halfway home it started cutting out again, this time it happened to be right around 2800 rpm, so I had to kind of limp home (about 100km/hr in 6th @2500 rpm), the cel did not come on this time.

Any suggestions?

Sounds like fuel delivery issue. Maybe check your fuel pump and filter.

Brand new fuel pump, put it in last Saturday.

now change the fuel filter....

Have you checked all your ground wires?

Check your injector connectors too.

I had a problem with my fuel filter and my engine would go lean but it would not cut off. I think he has another issue.

just throwing it out there.


one of my old cars would cut out like that (wasnt a miata), i changed the fuel filter and problem was solved....

Thanks for the suggestion won ton, the filter was supposedly changed by the dealer just before I bought it.

What I think is happening is the cam sensor is sending a bad signal, which tells the ecu to cut the fuel flow to the injesctors, which causes the cutting out. According to my local Mazda dealer the cam position sensor tells the ECU which cylinder is @tdc so it knows which injector to fire.

What I don't get is why it is so intermittent/unpredictable. I am wondering about a bad ground, does anybody know where the ground wire for the cam sensor is grounded?

RAFA, I will check the injector connectors, any suggestions on where to check for bad grounds, I don't currently have either a shop manual or wiring diagram, I guess I need to pick one up. Does anyone think it's possible that it might be a bad signal from the crank position sensor?

Did this problem happen after the new fuel pump or was it before?

it started before, and continued after, as far as I can tell changing the fuel pump had no affect at all.

I only have the 2000 wiring but it shows the ground for both cam sensor, crank sensor and Mass Airflow at ground number 5 which is on the inlet manifold.

It could be a bad crank sensor. Check the gap between the sensor and the crank plate. Check that all four lugs are in place and undamaged on the plate. Check the wiring has not been compromised by a belt. Check the connector, I think it's up in front of the cam cover.

If you suspect wiring, get that manual and check for continuity back to the ECU etc.

Have you been monkeying with the lower crank pulley at all? have you checked that the sensor is spaced the right distance from the teeth on the trigger wheel?

the gap should be 0.5—1.5 mm {0.020—0.059 in}. if it's too far, it could act flaky. also may want to check the wiring on that sensor too.

I haven't touched the crank/crank sensor at all. Right now I have my wiring harnes apart to check it all.

I do have a question. Do both the cam and crank sensor have 3 wires ( i believe they do). Which one is the +12v wire, is it the white/red one? I see that the cam crank and MAF sensors all have a white/red wire. I am going out to check the crank sensor now.

On the 2000 the +12V is White/red for crank, cam and maf.