Autosport Labs

Hi,

Ive had to miss my first race this season after a misfire & random communication issues between my v3.3.1 mjlj and the edis.
It all ran fine with a good map before winter - but now misfires and won't drive above 2500rpm. She starts and idles fine, but I noticed the misfire when in the garage, revving slowly up through 2500rpm.

I adjusted the map about 5 times with no difference, making me think only edis is firing in limp home mode. When I attach the laptop, all is fine until I start the car when the realtime graph (and the dials on the laptop) freezes. My seperate in car rev counter works okay all the time.

This makes me think my mjlj / pip saw problem. Ive done the voltage checks as suggested at the bottom of the v4 page (pip - 12v when not running / 5,5v running + saw - 0v / 0.2v). Im happy the wiring is good for pip & saw.

The only issue Ive had to affect things is a big short a week back that melted an earth wire when I put ignition on. It wrecked my race battery, but the mjlj circuit board visually seems okay & everything works before I push the starter!

Sort of tempted to by a new mjlj, but its a different version so will require more work to fit!

Im supposed to be racing again next week - at this rate, I could've bought a new mjlj with saved entry fees!

One thing to add...

I reinstalled all the firmware to the mjlj using the hc08sprg etc etc, and when power goes on and you should get...

Waiting for HC08 reset ACK...received 0xfc (good).

I don't get 'good', I get something else - it was 11pm and 12 hours into it, so I can't remember what it was. *%$£ !

errr off- something...

*%$£ again.

First thing you should do is run the engine with the Megajolt disconnected. You want to verify if the misfire is still there with the engine only running on EDIS. If so, you will need to check the trigger wheel / sensor installation.

We've seen very few if any misfire conditions related to the megajolt itself. Usually it's related to the EDIS module losing sync with the trigger wheel wheel.

Let us know what you find out!

Hi brent,

Ive disconnected the mjlj and it runs the same.

Im thinking this means the car is just running with 10 deg fixed advance, which the car doesnt like around 2500?

When I rev the car in the garage, it only seems to pop & faulter at 2500ish - before and above that, all seems okay (as much you can tell from in a garage!)

Hi brent,

Ive disconnected the mjlj and it runs the same.

Im thinking this means the car is just running with 10 deg fixed advance, which the car doesnt like around 2500?

When I rev the car in the garage, it only seems to pop & faulter at 2500ish - before and above that, all seems okay (as much you can tell from in a garage!)

Is your crank sensor bracket loose or anything?

Dudes,

Thanks for the replies! Been running over this in my head all day at work.
I did think over the crank sensor maybe getting some vibration around that 2500rpm mark - its solid on there & doesnt seem to resonate when I blip the carb with the bonnet off.
Not sure if the crank sensor would cause the loss of data feed to my laptop, but I can see where youre coming from!

I have the car back in the garage now - needed 4 people to push it up my 12.5% driveway!

Dudes...

Had some time tonight to look into this little drama. I went back over the Vr sensor as suggested.

The gap between the head and the wheel is 0.2mm - too close?

The sensor mount was solid - so I went onto the shielding - I had the vr shielding going into pin 7 on the edis alone, with the pip/saw shielding from the mjlj going straight to main edis earth on pin 9. That can't help. Goes to show how knackered I was trying to get this ready to race - fresh pair of eyes etc etc.

Can't run the car until tomorrow - probably made too many enemies trying to run the car up and down the street trying to cure this snag, so I won't push it!

BB

Just ran her in the garage - didn't seem to hesitate or pop around the 2500 mark after the earth wire changes.

Should be able to drive her in the next day or so, & hopefully get racing on Sunday!

BB

Drove the car again - still there after sorting the edis/vr earth thing.

Completely lost now.

Okay...

So I replaced the coil - still idles and revs freely, but won't drive past sbout 2500rpm (bogs down) + configurator freezes

Ive replaced the edis - no change

My vr sensor is good and advance changes when I rev.


Sooooooo lost.

I'm looking over your past comments carefully. Can you elaborate more on how you felt you fixed it after inspecting/fixing the wiring for the VR sensor? did it run correctly for a period of time? was that just revving it in place, or with actual driving?

Did you change the ground configuration since you started troubleshooting it? All grounds (megajolt, wiring shields, etc) should go to the EDIS module ground, and then to a good grounding point on the chassis.

Also, with the Megajolt disconnected, it should still rev smootly through the power band, not suddenly falter at 2500 RPMs.

More: is your engine's 12v power smooth and reliable throughout the RPM range? Sometimes failing alternators inject a huge amount of noise into the system.

Even more: how are your plug wires? new? somewhat old? old? What do your plugs look like?

Hi

thanks for the reply - nothing really with the shield earth fix. She still exhibits the same issue.

the plugs and leads are good - I get resistances of between 4 & 6 on a 20k ohm scale, plus plugs are not coked up or burned out.
I've been through the weber as well. All seems normal with no blocked jets or filters. After this, I spoke to my (very reputable) engine builder & he reckons defo electrical sooo,

Im going scrap the first half of this season and strip & rebuild the system from scratch. Quite a few of the race organisers have kindly returned fees, so I have some cash to put in to solving this.

Does anyone think the configurator freezing on startup is a clue towards the fault?

BB