Mis-fire

[gsx600]

Apart from plugs (just changed) and leads (on order) what else is likely to be causing a misfire.

Seems to happen under light load about 2 - 3 k rpm, but if I accelerate hard it seems to run ok

I'm thinking it's electrical and hopefully the new 10mm leads will help it, but does fuelling cause misfire, as I recently adusted CO down to 3% (from 7%) and raised fuel pressure as well

any other normal ideas

[pwd95]

I was getting this with the 400, very annoying. Have you checked for an air leak.

[chunder]

Definitely fuelling could cause it - specially as that seems to be the last thing altered. Could be 101 other things as well of course !

I have found overfuelling in this range causes a misfire - I have been unable to get fuelling right on mine for a long time, just able to move the under or over fuelling up and down the rev range - resorted to fitting an o2 sensor and controller and currently replacing the ECU with an aftermarket programmable thingy !

[gsx600]

chunder said:

Definitely fuelling could cause it - specially as that seems to be the last thing altered. Could be 101 other things as well of course !

I have found overfuelling in this range causes a misfire - I have been unable to get fuelling right on mine for a long time, just able to move the under or over fuelling up and down the rev range - resorted to fitting an o2 sensor and controller and currently replacing the ECU with an aftermarket programmable thingy !

It's the way I'm going at the end of the year hopefully with full MS n spark setup, but was hoping to eliminate other things first

[leorest]

gsx600 said:

...hopefully with full MS n spark setup...

Has anyone done this to a Wedge already? This is another one on the long wish list though by the time I get round to it UMS will probably be long in the tooth

[numbnuts]

wait for the leads, it sounds like one is breaking down under load to me.

[gsx600]

Got the leads today, and they look far too nice too be spoilt by my engine bay (10 mm red pro race set - from a very nice man with a lovely Chim), thicker than my arm they is. Look a lot better than the old blue set begining with an M (that 2 have already come apart in 2 years )

If it does not cure the misfire I could use them to tow the car to the scrappy

Edited by gsx600 on Wednesday 6th September 18:16

[v8 racing]

Have you got a proper rotor arm?

[gsx600]

What do you mean by proper, it's not a lucas but was replaced about 4 months ago.

Are you asking for the 10mm leads needing / using more power or the misfire ?

[v8 racing]

take your rotor arm set fire to it and then throw it as far as you can, go to ebay i am selling genuine lucas ones for a tenner, and before anybody jumps on my back that this is advertising its not i am just trying to help guys/girls out with the correct parts! I WOULD NOT FIT ANYTHING THAN A GENUINE LUCAS ONE!

[campbell]

Hi Paul

What fuel pressure are you runing at?
If it is rather high with out the vac on, say over 45 pounds your car will proberly idle and run at constant revs rought, try setting it to stock pressure 36 pounds, also get a Lucas rotor arm and cap, any thing else are crap.
Take the vac off the advanced, retard on the dizy, if the car dosnt back fire on constant revs dizy is fooked and dont bother with lucas to sort it, they are realy crap at fixing things like that and cost a lot of money.
If you can check all of your valve springs, just in case any are broken like mine were grrrrrrr.....
do you use any injector cleaner, or do you know how good they are, a good sonic bath and flush will sort out many things and also check to see if the injectors weep inder high pressure..
Check the throtle pot is set at 0.32 to 0.34 volts but no higher than 0.38v
Cheers

Campbell

[gsx600]

I'll try a few of those things again once the leads are fitted. Ordered some spares - nudge nudge so hopefully they will arrive soon.

I agree with you on the dissy which is one of the reasons it is being binned along with all engine wiring, and injection system for either the omex or mega suirt depending on what funds allow after the house buy, kidney sell etc

There seems to be so much on these 20 year old engine ancillarys that seem to go wrong more frequently that we are probably all going through the same situation in trying to keep them alive a bit at a time, but I think we need to come to a point and say SKIP and start afresh with a bit of modern techie, never know might get that 300 hp oneday Yet more visions of seeing the rear end in the mirrors as a pile of rust on the road as I drag down the local blacktop, dont worry I'll brake, uur where did they go ?

[infinity]

the 400SE who was previously owned by Cantus, thereafter by Gun Metal and is now in the possession of the Hardy-clan suffered from the same. It turned out to be a lousy condensator on the ignition. For details PM Cantus.

[TVR 3X]

If you scrap the dissie how are you going to drive the oil pump?

Russ

[gsx600]

TVR 3X said:

If you scrap the dissie how are you going to drive the oil pump?

Russ

You can take out all the internalls for spark and just leave the dissy body, and I think I have seen the top section cut off, so the shaft is still there to drive oil.

I have a spare one and looking to see what could be done, as well as using the shaft and body as a crank sensor /trigger sensor as I'm thinking the dissy must move in relation to the crank ?

[GreenV8S]

gsx600 said:

TVR 3X said:

If you scrap the dissie how are you going to drive the oil pump?

Russ

You can take out all the internalls for spark and just leave the dissy body, and I think I have seen the top section cut off, so the shaft is still there to drive oil.

I have a spare one and looking to see what could be done, as well as using the shaft and body as a crank sensor /trigger sensor as I'm thinking the dissy must move in relation to the crank ?

Dizzy doesn't make a particularly good crank position sensor because it goes twice as fast as the crank (you can only get the position +/- 180 degrees), although that's enough for semi-sequential fuel + wasted spark, also the dizzy tends to suffer from backlash (one of the reasons to stop using it) so the reading won't be particularly accurate. The dizzy does make a damned fine crank phase sensor though if you're going for fully sequential fuel or coil-per-plug ignition.

[leorest]

gsx600 said:

[quote=TVR 3X]You can take out all the internalls for spark and just leave the dissy body, and I think I have seen the top section cut off, so the shaft is still there to drive oil.
I have a spare one and looking to see what could be done, as well as using the shaft and body as a crank sensor /trigger sensor as I'm thinking the dissy must move in relation to the crank ?

Yeh but no but yeh but anyway... I think the dizzy runs at half the crank speed otherwise you'd get a spark at every top dead centre (think four stroke) so best place for crank sensor is directly on the crank.... or somint or nuffing

[gsx600]

GreenV8S said:

The dizzy does make a damned fine crank phase sensor though if you're going for fully sequential fuel or coil-per-plug ignition.

Knew I'd want it for something else, so is the dissy in phase with the cam ?

Edited by gsx600 on Thursday 7th September 14:50

[chassis 33]

If you lock up all the advance mechanisms!!!

Regards
Iain

[jchase]

The lobes on my dissy aren't very accurate - as the timing difference between same phase cylinders is over 4 degrees.(Thats about 0.1mm lobe error) With a big toothed wheel on the crank, you can have the teeth out by as much as 1mm, and it will still be way under a degree off.