Engine Cuts out On Track
 

Put my car on track first time yesterday. Have had car for 1 year. Did mostly suspension and chassis work. Cleaned and sealed motor - timing belt/water pump etc, otherwise no work by me on motor.

Here's some info.
94R package car - 100k motor - never opened.
Have a Turbo from a 300Z factory turbo set up.
Manual boost control running about 10psi.
Intercooler.
MiataLink piggyback (at least I think that's what it's called) with a "tethered" hand programming unit attached to my ECU behind passenger seat.
I've never touched any of the engine management stuff except for the manual boost adjuster.
Wrapped exhaust manifold and down pipe but not the turbo itself.
On track yesterday at 90 degree+ ambient temperature (TGPR in Alabama).

Car ran great for 3 - 4 laps - pulled strong up to about 6000 where I was shifting. Then it would just shut off for 1/2 second or maybe 1 full second. Then come back on for 2 seconds to 4 seconds.

Tried a new fuel filter as most simple fix - but of course no help.
Ran with hood off the car for a session to mitigate underhood heat, but same result.

Anybody have a similar experience?

I don't have much experience with turbo motors or aftermarket engine management, so I'm looking for any suggestions anybody may have. Any help would be greatly appreciated.

You lost me at the Link. I don't know squat about them. How much fuel was in the tank?

Is it something like this?



Mine started doing that a few days ago. It's really intermittent, can happen once or a dozen times in a few seconds, then not come back for hours. Or in a few minutes. Really odd. Ground issue maybe?

I had the same problem. Turned out to be a broken CAM sensor.

How would I confirm a Cam Sensor problem?
The link is to a YouTube video showing the misfire right at the end of the video. You can see my helmet jerking forward as the car loses power for about 1 second at a time. Tach does not drop during these losses of power. Is this similar to the Cam Sensor problem you encountered?

The Link piggyback doesn't do much -- I had one for 4 or 5 years. Basically it looks at RPM and MAP and drives a set of aux injectors (either 2 or 4), an ignition retard circuit (intercepts the signal going to the coils, I think) and a boost control solenoid. Sounds like the boost control logic (which blows chunks) isn't in use here.

It's unlikely the Link piggy is causing the cutting out because it just doesn't have that much control. Does it happen repeatedly? Always at 6K? Does it happen over bumps?

--Ian

Youtube says the video is private.

--Ian

Changed setting - video should be available now.

Thanks for comments on Link Codrus - will need to learn more about it. Problem is not sensitive to bumps. Recently went through all grounds I could find, including the one near firewall in front of driver with several grounds on common screw - cleaned that and scraped and cleaned and then refastened. Not RPM sensitive - once it happens it will happen at any RPM until it "rests" for a while. When the problem is happening it is throttle sensitive. I can put very light throttle (<25%) in and it runs - then as I squeeze more throttle it cuts out. It will do that till I allow it to cool down - or drive it slowly for a while. Also happened once when I was running steady on highway in 95 degree weather at close to 90mph. I needed to pull over and let it rest for 5 minutes then drive 75 mph no problem. On track it pulls fine up to 6k - 7k rpm for about 5 minutes, then starts doing its missing thing.

And correct - using a manual boost control. Electronic boost is wired but not plumbed into the wastegate circuit. I have the boost adjust knob located inside the center armrest console via an adjusting cable - easily accessible while driving. Been running 9 - 10 psi on track.

CAM Sensor:
Sorry- it was actually the Crank Angle Sensor. And diagnosis was wriggling hard on the cables with the engine running makes the engine stop.

About the link: Funny enough I had the CAS problem when I was also running the link piggyback. And the Link intercepts the ignition signal and modifies it. So any problem with the link or the wiring to it WOULD cause your engine to stall. In order to troubleshoot that I would remove the Link from the ignition circuit and drive the car. Of course now you don't have the timing retard from the link under boost, so I would DEFINITELY wire the WG open too.

Temps?
 

What are your engine temps looking like during this? The Link has a built in temp protection and if you try to get into boost while your engine is running hot it will cut out on you. You should also be able to pull up your coolant temp on the link to see if it is receiving the correct signal from your coolant sensor.

The old Link piggyback (old FMII for '99) I had is not hooked up to the water temperature. I think his is essentially the same, so I don;t think that's it.