Miata with megasquirt problems

I am working on my 1990 Miata project. I swapped in an 04 Mazdaspeed Miata engine running on the CAS and 1.6L sensors. I have an Innovate MTX-L wideband. I finally got it to the point where I can start it. It starts and runs fine for 5-10 seconds then dies every time. It always runs for the same amount of time, it usually restarts right away. The MAP goes to 12kpa (from 81kpa while running) and the engine dies. After starting it a few times the MAP goes to the extreme end of the gauge (252 kpa) and the engine dies. After this it usually doesn't restart for a bit.

The wideband is wired into a switched 12v wire but it is not on while cranking.

I don't have a copy of the .msq file on this computer but it is the base 9093MSPNP file with the dwell settings for the coil changed to the MSM specs and req_fuel changed for the 1.8 and MSM injectors.

Any ideas of what to look for next?

The afterstart enrichment is giving that first 5 - 10 seconds of run time, then the engine goes lean and it dies. You need to adjust your warm up enrichment settings: http://www.megamanual.com/v22manual/mtune.htm#csenrich

If the engine starts and runs for a few seconds, then stalls, this is usually a sign that the afterstart enrichment isn't quite right. Leave everything else the same, and adjust the afterstart % and number of cycles. 20% to 30% and 200 cycles are reasonable starting points for most engines, but yours may run better with more or less. There should be a point at which it works without stalling. If the engine starts and runs for more than 20 seconds or so, then stalls, you need to adjust your warm-up enrichment bins. As you adjust your warm-up bins, you may need to re-adjust the afterstart, since these interact (i.e., a larger warm-up value may require a shorter or smaller afterstart enrichment).

Read the tuning part of the manual front to back - it helps a lot.

Hmm...I was thinking the afterstart enrichment lasted longer than that...let me see how that works out.

Nope, at least not for me - I just did this last week. I would get ~10 seconds of run time, then it would stall. I ended up doubling all the values in the warm up bins, warms up fine now, with no problems.

OR - it's not getting the keep-alive signal for the fuel pump once the car starts. Put a jumper in the diagnostic box between FP and GND to determine if that's the case.

Neither of those worked in the short time I tried it before my laptop battery died. I'll mess with it more later.

Since you are guessing, how about take some data. Turn on the WB sensor and record it. That will tell you a lot.

Record the engine, too- is it fuel, or spark, or something else that's turning the car off.

Record, record, record- then analize the data to see what is going wrong, and stop guessing.

I don't think the car is running long enough to let the wbo2 sensor actually display/log what's going on. I know my LC-1 takes a good 15-20 seconds before it starts doing anything.

I'm going with afterstart enrichment as well, but Alfa brings up good points. Log anything and everything you can, and post that stuff here if it doesn't make sense.

92CelicaHalfTrac wrote: I don't think the car is running long enough to let the wbo2 sensor actually display/log what's going on. I know my LC-1 takes a good 15-20 seconds before it starts doing anything. I'm going with afterstart enrichment as well, but Alfa brings up good points. Log anything and everything you can, and post that stuff here if it doesn't make sense.

Turn it on before hand, then. Since you are not in danger of actually drivng the car, use a second car to power the WB sensor. Or at least a second battery.

I can assure you that the sensor gives you correct information immediately if it's on. BTDT. Still BTDT on a daily basis.

alfadriver wrote:

92CelicaHalfTrac wrote: I don't think the car is running long enough to let the wbo2 sensor actually display/log what's going on. I know my LC-1 takes a good 15-20 seconds before it starts doing anything. I'm going with afterstart enrichment as well, but Alfa brings up good points. Log anything and everything you can, and post that stuff here if it doesn't make sense.

Turn it on before hand, then. Since you are not in danger of actually drivng the car, use a second car to power the WB sensor. Or at least a second battery. I can assure you that the sensor gives you correct information immediately if it's on. BTDT. Still BTDT on a daily basis.

2nd car... i wouldn't have thought of that.

But that's probably what it'll come down to unless he wants to re-wire it in his own car. When cranking, power is cut to the sensor, then it has to go through it's rigamarole again.

In reply to 92CelicaHalfTrac:

One thing I would tell the MS crowd is to come up with a simple set up that uses a cheap secondary battery to really go to town on the calibration. We use a pretty sophisticated second battery/charging system, which is vital to record the hardest part of the fuel cal to get right- the start.

That way, you are not really re-wiring the car- just isolating the instrumentation from the start.

Being that every single person who does a MS is working on a project, the odds of having a spare battery sit around is incredibly high. You don't need a very good one to run a WB sensor- and if you have a switchable charging set up, you can make sure it's in good enough shape.

The biggest red flag here is the MAP sensor giving seemingly impossible readings. As this drives a lot of the fueling, you probably won't sort out a fuel problem until you solve this. Could you post a data log of an attempted start and a copy of your MSQ?

In reply to alfadriver:

Sounds like a good time to put an inline disconnect into the power and ground side of the wideband wiring so it's easy to disconnect from the main car's harness and run it over to that 2nd battery or bench supply. Maybe even do both the power and 'data' side of the sensor system since you could then run the sensor output to a capture device as well as outboard supply for test & tune, then throw it back on the car's harness when done.

alfadriver wrote: then analize the data

I think you meant analyze...

Raze wrote:

alfadriver wrote: then analize the data

I think you meant analyze...

Well, i do believe he IS an engineer.

I definitely need to get the WBO2 powered while cranking. I think I may need to re-ground it as well. While it is in heating mode the O2 display on megatune is fluctuating wildly. Unless that is normal?

92CelicaHalfTrac wrote:

Raze wrote:

alfadriver wrote: then analize the data

I think you meant analyze...

Well, i do believe he IS an engineer.

I ususally go with that excuse.

A little more information:

With the ignition on and the engine not running the MAP reads 12kpa. If the ignition is left on for a minute or so the gauge goes up to 252kpa.

When it does run, the boost gauge reads normal vacuum until it shuts off.

EvanB wrote: I definitely need to get the WBO2 powered while cranking. I think I may need to re-ground it as well. While it is in heating mode the O2 display on megatune is fluctuating wildly. Unless that is normal?

I would guess that that would be normal since there's voltage going to the sensor itself in heating mode.

EvanB wrote: A little more information: With the ignition on and the engine not running the MAP reads 12kpa. If the ignition is left on for a minute or so the gauge goes up to 252kpa. When it does run, the boost gauge reads normal vacuum until it shuts off.

Do not ignore this. I'd like to see a data log of this and a copy of your tune file.

I uploaded the datalog and msq file on the MSefi forum since this forum doesn't allow attachments.

http://www.msefi.com/viewtopic.php?f=92&t=41133

When I change the afterstart enrichment settings under fixed MAP mode it will run until it returns to normal MAP mode. I changed the fixed MAP time period to 30 seconds at 80kpa and it ran until it that time period was up and then it dropped to 12kpa and died. It is idling around 9.8-10:1 according to the wideband.

Do you have a secondary measurement of MAP? 12kPa is WAY too low, and the drift impiles that something is wrong with the measurement- electrical or otherwise.

(oh, and you should idle much leaner than that- on a cold engine, you are pretty close to an a/f that will foul plugs...)

Yea, I need to lean out the idle, but it was running for 30 seconds and that is longer than it was before.

The boost/vac gauge reads normal until the fixed-MAP enrichment cycle is up and the MAP reading on the MS drops to 12kpa which kills the engine.

I am thinking maybe my MAP sensor is shot.

EvanB wrote: I am thinking maybe my MAP sensor is shot.

Good problem solving so far!

you may be right about the MAP sensor. Apart from a wiring issue, the only other thing I can think of is that the MAP sensor is mounted by screws - if the screws are too tight, maybe it's distorting the sensor?

Do you have a Megastim to check the sensor outputs when the Megasquirt is not wired to the car?