Ignition fault, megajolt related
Turbo Mini Forums

I,m about to set fire to the A35 !!

After going so well last weekend and even running fine this morning it is now driving me crazy.

As soon as I approach 4000 rpm and any real boost it cuts dead,the rev counter goes to zero(its takes its signal from the MJ) and the AFR gauge goes to a row of dashes(Usually a sign its off scale , either too rich or too weak to register).
As the revs drop it cuts back in again and the rev counter and AFR gauge revert to normal. There is a large embarassing bang from the exhaust as the unburned fuel ignites.

It did this once before and a change of EDIS seemed to fix it.

This time, changing the EDIS has not helped.

Any ideas anyone (I have my own box of matches, thank you )

I had this, turned out my sensor bracket was flexing at a certain rev range (for you 4000 rpm) due to a harmonic or something. This causes the mj to lose signal before regaining it and the unburnt fuel ignites in the exhaust.

sesnor bracket (as above)

power feed to edis intermittant (splice a small bulb to the edis power wires right at the edis module and have the bulb in the cab or where it can be observed .. again this is "controlled" by engine vibration.
lack of supporssion on coil +ve wire
noisy alternator messing up power to EDIS or messing up the VR sensor wires..

p.s. rather annoyed i missed your car at avon :( looks awesome

Edited by evolotion on 17th Jul, 2010.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

What air gap have you got the sensor set at?

Alex

AlexF

Thanks for the ideas.The sensor bracket is a welded up item, never given a problem before.Air gap may be a little karger than necessary, but again, has worked so far. Will re-check both these aspects, but I am favouring the VR sensor wiring being affected by external; noise, so will re -route that too.Maybe the bolt securing the sensor to my bracket has loosened ?

Will let you know what works in due course.

Evolution -Not too difficult to spot me I would have thought ? I am booked in at MITP for your second chance and the organisers are letting me run on Sunday.

Check your earths as well I had a similar problem in the past.

Ron

had similar check the earth's and the wire to the VR sensor is well shielded.

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

i would have spotted you if i was there, i packed up and left on saterday night due to a cracked liner!

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

Well, it turned out to be dodgy wiring -I think.

I checked the sensor and bracket and all seemed OK. The sheilded wire from the sensor was still clipped up out of the way so still OK.

Looking at the wiring around the Edis is could see some stray filaments of the sheild on the sheilding wire where I had tee,d the rev counter wire into the PIP line and I think one of those was intermittently touching a tiny part of the exposed PIP line where I had strained it all trying to tuck it all out of sight.Tidied up and re wrapped the whole area and it was happy at 90 down the M40 on my way to Uxbridge show today so fingers crossed.

Thanks again for the pointers - I must remember the condenser trick -maybe I should put one on anyway ?

Apologies Denis - I still dont know all the characters on this forum so I did not twig that you had left before I got there.Commiserations on the engine - will you be able to get to Santa Pod next month ?.