Engine Trouble

[STH212]

So after trying to drive our car this weekend, we ran into a problem of having it idle perfectly but as soon as you open up the throttle, the engine (YFZ450)misfires, sputters and dies. We had the engine on the dyno and when we tuned it and it ran fine without any problems. We spent the better part of the day trouble-shooting and came up with nothing. Here's more details:
Engine: Yamaha YFZ 450
ECU: Microsquirt
Checked coil, injector, (observed signal from ECU with oscilloscope), crank sensor, MAP sensor, changed coils, injectors to known good ones, verified fuel pressure, checked fuel lines for any blockages, pulled valve cover (all seems normal) and everything seems fine. Any thoughts?

[STH212]

So after trying to drive our car this weekend, we ran into a problem of having it idle perfectly but as soon as you open up the throttle, the engine (YFZ450)misfires, sputters and dies. We had the engine on the dyno and when we tuned it and it ran fine without any problems. We spent the better part of the day trouble-shooting and came up with nothing. Here's more details:
Engine: Yamaha YFZ 450
ECU: Microsquirt
Checked coil, injector, (observed signal from ECU with oscilloscope), crank sensor, MAP sensor, changed coils, injectors to known good ones, verified fuel pressure, checked fuel lines for any blockages, pulled valve cover (all seems normal) and everything seems fine. Any thoughts?

[Dash]

Bad battery?

We have had problems with our car from last year ( F4i) killing the battery. If it goes bad, it won't let you rev up at all.

[Boffin]

All your earth's check out fine?

Or what is battery voltage in the car when it is running compared to the dyno?
A difference there will cause it.

[Jay Lawrence]

I'm assuming you've checked your fuel/ign map and there's nothing strange going on above idle? Forgive me for being a douche, but "have you got the right map in?"

[wweissin]

Check ALL of your sensors. Make sure they are reading correctly. Crank/Cam, pressures, temps. Make sure that your engine is syncing at idle. If I had to guess I would look at the TPS sensor.

[B Lewis @ PE Engine Management]

Does the Megasquirt have the capacity to detect "Crank Errors"? Sometimes when moving from the dyno to the car, the wiring (or routing of wires) changes such that you induce electrical noise on the crank signal. That noise sometimes can cause problems at specific frequencies or engine speeds.

[ibanezplayer]

"open up the throttle"

If by open up the throttle you mean jumping on the pedal and the car not responding look at your acceleration enrichment.

Can you provide some more details as to what exactly is going on? is the car moving?

[Mbirt]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by B Lewis @ PE Engine Management:
Does the Megasquirt have the capacity to detect "Crank Errors"? Sometimes when moving from the dyno to the car, the wiring (or routing of wires) changes such that you induce electrical noise on the crank signal. That noise sometimes can cause problems at specific frequencies or engine speeds. </div></BLOCKQUOTE>

Brian's spot-on. My money says it's electrical. Make a .msl datalog of what is happening and then, in Megalogviewer, display RPM, TP, and Sync Loss Reason on the same graph. From my experience, it's sync loss reason 2 if you're running wasted spark and sync loss reason 11 or 17 if you're running a cam sensor.

Sync loss reasons and some remedies: w w w . msextra . c o m / doc / ms3 / syncloss . h t m l

Did you remember your resistor in the VR circuit?

[STH212]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by ibanezplayer:
"open up the throttle"

If by open up the throttle you mean jumping on the pedal and the car not responding look at your acceleration enrichment.

Can you provide some more details as to what exactly is going on? is the car moving? </div></BLOCKQUOTE>

By open up the throttle I mean slowly open the throttle body, not jamming down on the pedal, it makes no difference whether it's stationary or driving. Also, I forgot to mention that it drove well for about 30 seconds before this started occuring. Also, battery voltage was checked, it's a pretty constant ~12.5 volts. As for syncing, microsquirt has a lost sync counter and nothing was counted, but thank you for the link Mbirt.

[STH212]

Forgot to mention but yes, both fuel and ignition maps have been verified as the ones that it was tuned for on the dyno.

[Tim.Wright]

I will also suggest the problem may be electrical. Or fuel pressure.

The fact that the problem only appears as flow increases (flow of both fuel to the injectors and current to the ignition system) suggests it might be a bad earth, dead batery or a dying fuel pump.

We had a dying fuel pump a few years ago which gave the exact same symptoms. An easy check is to pull off the high presure line and stick your thumb over the pipe to see if its bulding up pressure. FSAE pumps tend to have a hard life, being run dry every so often - so a dead pump is always a possibility.

Tim

[Jay Lawrence]

As for fuel, also check your pressure reg. We had one that started not holding pressure for some reason (didn't bother investigating, just changed it for another we knew worked).

[nms553]

I second the Fuel Pump concern; we've had numerous issues with pumps (including debris in filter)
1. check map
2. check fuel press and spark
3. check all sensor readings
4. verify ref sync connection is correct

-if all looks good
inspect/swap fuel pump
swap ignition boxes
bad/dirty gas?
swap ECUs

[Mbirt]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by STH212:
By open up the throttle I mean slowly open the throttle body, not jamming down on the pedal, it makes no difference whether it's stationary or driving. Also, I forgot to mention that it drove well for about 30 seconds before this started occuring. Also, battery voltage was checked, it's a pretty constant ~12.5 volts. As for syncing, microsquirt has a lost sync counter and nothing was counted, but thank you for the link Mbirt. </div></BLOCKQUOTE>If you're cool with emailing me a log which captures the phenomenon, I'd be more than happy to take a look at it. A megasquirt team's gotta look out for another, right?

The guys at the msextra forums are also extremely helpful and it's easy to get a knowledgable response from a big-shot like James Murray (jsmcortina) in as little as an hour. Just be sure to post your .msq and .msl, maybe even a .csv composite log when you create your thread.

[Rex Chan]

Our engine (CBR600RR03-06) displayed the same symptoms on the dyno when we put in too much accel enrichment. As soon as you blip the throttle, the engine would stumble, and lose revs to below idle (&lt;3500 RPM), before recovering to idle.

However, there are probably a few differences between your case and ours: we run a MoTeC M48 with our main fuel table using MAP (not TPS), and using Delta MAP for accel enrichment; our dyno is a steady-state Heenen Froude eddy current dyno, so we only tune at SS, therefore our dyno tune does not represent driving conditions.

In 2009, they had issues with the ignition system wiring affecting the sync & ref signals.

Last thing, how did you get the car moving without opening the throttle? Don't you have to open the throttle to get the car moving?