I have a megajolt installed on my crossflow powered car and have had no problems until recently in 3000 miles but the car has recently developed a missfire under load as when pulling away or revving hard in neutral. When it occurs the shift lights flash even though the engine is only running at 2000 or 3000 rpm.it seems to get worse when the engine is hot as in traffic and sometimes clears once moving faster and cooler or under less load.I have also seen the run time screen flick up on the rpms when ticking over at 1000 rpm but only occasionally.
I suspected the crank sensor or its connections but have replaced the sensor and connector plug and adjusted the clearance to 1mm, I also have changed the Edis module and plug leads with no success.I then decided that it must be the megajolt but have run it on a test rig and heated it up with a hairdrier but cannot replicate the fault.
I dont think it is an installation fault as i have had no problems at all since installing it until now, all my wiring is shielded and earthed at the edis unit only and i am running resistor plugs.
I am driving my megasquirt from the tacho output so cant try the car with the megajolt disconnected.The only thing I havent been able to change yet is the coil but am unsure if that would cause the fault as it appears as if the input to the edis is sensing to high a rpm. I have put a scope on it and it looks a smooth waveform with no obvious spikes on it.
It is a v2 unit with the discreet transistors on the outputs.
Paul
Missfire under load, on installation after 3000 miles.
Moderators: JeffC, rdoherty, stieg, brentp
Do you get a misfire when
Do you get a misfire when you disconnect the MJLJ and run it off of the default timing? For the test you can run the megasquirt tach input off of the PIP line from the EDIS module.
The shift light flashing and the uptick in the RPM you're seeing is caused by additional pulses the MJLJ is seeing on the PIP line- If it receives what it thinks are extra PIP pulses it will read this as blips in the RPM. These extra pulses could be caused by noise on that wire.
it would be good to put an oscilloscope on the PIP line to see how clean that signal is.
Brent
The shift light flashing and the uptick in the RPM you're seeing is caused by additional pulses the MJLJ is seeing on the PIP line- If it receives what it thinks are extra PIP pulses it will read this as blips in the RPM. These extra pulses could be caused by noise on that wire.
it would be good to put an oscilloscope on the PIP line to see how clean that signal is.
Brent
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Oliver Sedlacek
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Sounds like spikes to me
As it used to work, something must have changed (I know I'm stating the bleeding obvious). I would check the earth connections, as the symptoms are that you are picking up spikes.
I will try it with just the
I will try it with just the Edis connected , I didnt think of using the pip signal to trigger the megasquirt.Will have to wait until the weekend now until i can get time to put it back together and test it during the daytime.I suspect it is a dirty trigger signal but dont understand why it would suddenly occur after a number of trouble free miles and suspect it must be a component fault and really only have the coil left to try.
Paul
Paul
Now fixed. It turned out to
Now fixed.
It turned out to be the wiring for the rev counter, I had used the diode circuit and installed the components in the loom near the coil connections and heat shrinked them together.I removed the parts and found that the zener diode had broken at one end and the lead was making intermittent contact, it was one of the small glass type diodes. I dont fully understand how it was affecting the unit but was obviously causing some spikes in the coil wiring etc.
I removed it and tried the edis output and the megajolt output but neither would drive my tacho, however i found that if i connected it to the pip connection on the megajolt it works perfectly. Im not sure if it is a good idea to leave it connected here though as it may cause further interference but seems fine at present.
Paul.
It turned out to be the wiring for the rev counter, I had used the diode circuit and installed the components in the loom near the coil connections and heat shrinked them together.I removed the parts and found that the zener diode had broken at one end and the lead was making intermittent contact, it was one of the small glass type diodes. I dont fully understand how it was affecting the unit but was obviously causing some spikes in the coil wiring etc.
I removed it and tried the edis output and the megajolt output but neither would drive my tacho, however i found that if i connected it to the pip connection on the megajolt it works perfectly. Im not sure if it is a good idea to leave it connected here though as it may cause further interference but seems fine at present.
Paul.