Missfire

Tomf · Post by **Tomf** » Tue May 11, 2010 11:16 pm

Ok well i had some problems with my megajolt unit (it wasnt alive), but thanks to NITROPIXIE thats all fixed now.

But im having some problems with some pretty bad missfires, not all the time and there not constant to load and RPM... For example driving along at 60mph around 3200rpm i got a light missfire, so i lifted off a little, went to put the power back on, missfired worse, then lost power badly, so took out of gear after a second i put it back in gear, a slight missfire, then it cleared and reved freely and as usual.

In a 30 minute drive this happened about 6 times... sometimes at say 20mph some 70mph so no real link there.

I would also like to add that for one day i ran the car on just EDIS4 whilst NITROPIXIE was fixing my megajolt unit and i experienced these same problems, so i dont believe this issue to be linked to megajolt itself.

Also when i ran the engine for one day on distributor and i didnt experience any of these problems so its definitely electrically related and not fuel...

My Edis 4 is earthed to the shell and iv also added an earth strap, the signal from the VR sensor is using the standard cable as removed from whatever ford i removed the VR sensor from...

I have also tried two different coil packs and a different set of plugs/leads, iv not changed the VR sensor yet though...

If anyone has any ideas what my problem could be i would really appreciate some help.

Post by **brentp** » Wed May 12, 2010 2:47 am

If this hasn't been covered before, then perhaps review the design of your VR sensor bracket? If the bracket is not rigid it may vibrate around mid RPM range, and this manifests itself as hesitation / misfire. Does it happen under load, or when freely revving? only in a particular RPM range and not above or below?

Tomf · Post by **Tomf** » Wed May 12, 2010 9:55 am

Hi unfortunately, it have experienced the missfire under load, i dont think i have from freely reving though.

I will defonately double check my mount, though, bit when i made it i did think i over engineer it...

NITROPIXIE · Post by **NITROPIXIE** » Wed May 12, 2010 5:59 pm

Are you running resistive plugs????

Tomf · Post by **Tomf** » Wed May 12, 2010 8:12 pm

Yep iv tried two different plug sets, both resistive, well i presume they are as they ha the R in the part no...

NITROPIXIE · Post by **NITROPIXIE** » Wed May 12, 2010 8:53 pm

Miss fire underload points to the coil pack in my book.

Some fords don't have shielded wires to the vr sensor. Might be worth getting some shielded wire or make sure the vr sensor wire is not near any ht leads.

What connection do you have supplying power to the edis and coil pack? Do they always have a solid 12v and there is no chance of it breaking contact?

Then there is the vr sensor like Brent said. Any chance of a pic of it?

Tomf · Post by **Tomf** » Wed May 12, 2010 9:59 pm

The power feeds are both ignition live feeds and all the wires are soldered together with no connectors such as spade connectors, etc..

Heres a picture of my bracket.

BRUCEROE · Post by **BRUCEROE** » Thu May 13, 2010 2:21 am

It sounds to me, like a weak spark system. You already swapped the coils & wires, but the coil drivers in the EDIS4 could be weak. Another experiment would be to try the VR gap at .030" and .060", no difference in problem implies the issue is elsewhere. Bruce Roe

Tomf · Post by **Tomf** » Thu May 13, 2010 9:31 am

Hi Bruce,

ill have a play with spacing my vr sensor in and out to see it it has any effect. Iv not tired a different EDIS4, will the gap test tell me if the EDIS 4 is failing?

BRUCEROE · Post by **BRUCEROE** » Thu May 13, 2010 5:07 pm

The gap test, is just to see if VR noise pickup or vibration are a problem. If the gap (and induced signal level) have no effect on the problems, they are likely not the source of the problem. Bruce

NITROPIXIE · Post by **NITROPIXIE** » Thu May 13, 2010 6:33 pm

Bruce it certainly does sound like its low powered or similar.

Tom you haven't used a resistive wire to power the coil pack?? like some ballasted ignition systems have.

And do your earths have good contact with the body??

Also some older wires can get corroded internally causing a resistance if you have reused them. Check to see if your getting a full battery voltage at the EDIS and coil pack with a multimeter. You could also try measuring the resistance of the ground and 12v at the coil pack and edis unit to the respective battery lead.

Hope this helps with some more possibilities.

Keep it up fella

BRUCEROE · Post by **BRUCEROE** » Thu May 13, 2010 9:52 pm

Good power & ground are critical. But if those are OK, the random failure nature sounds like a failing transistor (an EDIS4 coil driver).
Regarding grounds, any nut & bolt through plastic will come loose when the plastic yields to pressure a tiny bit. So to secure these I use 2 nuts tightened together to keep things in place, or a locking style nut. In one case I nut & bolted a ground directly to steel. Then I put the plastic part on the long bolt, and put a double nut over that. Bruce

andyroo75 · Post by **andyroo75** » Tue May 18, 2010 4:54 pm

Out of interest are resistive plugs a requirement??

I have been using the standard spec ones for the engine which arent resistored and they keep failing.
Happened twice ran three days then plug in No 3 went bad. Swapped it and next day plug 2 went.

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