Misfiring Mi

[Miles 331 1 Cars]

Some how I missed this, But you can check the teeth on the flywheel to see if there is any damage, Just look down the CAS hole or the gap above the starter depending on the age of gearbox,

But I've never come across this before in all my years !!!!

Even interferance in the loom is very unlikly, But I have come across a intermitent break in the CAS wire in the loom before which you would never see unless you un tape it all

[DrSeuss 0]

pacey, try out this

 

http://polly.phys.msu.su/~zeld/oscill.html

 

is it temperature related at all? If its something like an ignition component breaking down, it will only get worse as it gets hot.

[GtiMad 1]

This misfire was present in the donor BX, Pace has replaced everything else that was transfered over from it, two auto-electric/diag guys have said the CAS is not giving a clean signal, the cas has been replaced, twice, and so has the loom.

 

Can it be anything apart from the sigal that is being read from the flywheel? Cos I cant think of anything, hence the Curleywurley's.

[pacey205 2]

Well guess what boys and girls I ve just spent however long bashing and scratching myself up swapping the flywheel for another one and it made absolutely f*** all difference to anything. Its till misfiring between 3-4.5K and I still havent got a f***ing clue why.

 

Im really not in a good mood now, this bastard thing has been a non-working drain on my finances for christ knows how long and Im still not getting any benefits out of it.

 

f*** knows what Im going to do now either, I'm really not amused with this.

 

Michael

[DrSeuss 0]

Fancy a megasquirt

[pug_ham 240 3 Cars]

Have you tried all new(or known working) componenents that plug into the loom? (coil, igniton module, CAS etc) if you have then it leads me to think its a wiring problem, all the more fun.

 

Graham.

[pacey205 2]

Yes, everything that can be swapped has been swapped for new or spare if new not available (i.e. AFM, ECU).

 

I was thinking about this last night and the signal from the CAS was not right when AB's diagnostics guy tested it so now the flywheel has been eliminated it must be something electrical. Interference or something I guess but christ knows how Im going to track it down, I suck at electricals

 

Michael

[maxi 36 1 Cars]

Yes, everything that can be swapped has been swapped for new or spare if new not available (i.e. AFM, ECU).

 

I was thinking about this last night and the signal from the CAS was not right when AB's diagnostics guy tested it so now the flywheel has been eliminated it must be something electrical. Interference or something I guess but christ knows how Im going to track it down, I suck at electricals

 

Michael

 

 

Have you got a whole new loom you can try??? Cant believe its not the flywheel, that was the last thing left.

 

Maxi

[pacey205 2]

Maxi I know, I was so dissapointed when I got it done and fired it up this weekend, properly loosing the patience and the faith in it now

 

Ive already tried a second loom, but Ive got the one that I shortened spare that I could try again I suppose.

 

Michael

[Anthony 1,000]

If you really get stuck, then I've got a complete BX 16v ML4.1 management (loom, ECU, AFM, etc) sat here that definately worked perfectly if you want to try swapping bits over to locate the problem (or atleast definately rule out bits as being the cause).

[elrikos 0]

know this is quite possibly a silly question but have you measured the distance between the cas and the flywheel? i believe they came in 2 heights and in some appliucations a spacer shim is required. this would definitely give a dirty signal if you've got the cas with the larger gap and the gearbox with the mount already built up.

just a thought but may well be an option.

easy to check too. simply align the cas hole so that its looking at a flat spot rather than a valley as it were.

then take a blob of blu tack and put it on the end of the cas. then bolt the cas into the hole. then unbolt it and measure the thickness of the blu tack. you may find its outside spec (think the spec distance is 1.5mm iirc but haynes will reveal all!)

 

hope it helps matey

good luck.

rich

[pacey205 2]

Cant say I have actually measure the gap between the sensor and the flywheel but there wasnt a spacer when I stripped the engine down although I am now using the box off my 205 1.9 but I cant imagine there would be a difference there seeing as they are essentially the same box.

 

Anthony: Thanks for the offer I may have to take you up on that at some point.

 

Michael

[nick 3]

It's funny you mention interference, Dave Walker mentioned something about that in his column in last months PPC and I'm sure he was talking about a Motronic set-up.

IIRC he was saying that you should use good quality suppressed ignition leads to stop them interfering with the signal from the CAS.

 

Nick

Edited January 16, 2006 by nick

[C_W 3 1 Cars]

Just to add what I'm experiencing with mine at the moment; it has had this low speed mis-fire since November when it mysteriously decided not to start at all on the morning of a Cadwell park trackday. Eventually got it going but ever since then it had this misfire below 2000rpm when it was hot.

 

Last week I took it for a run and it died completely and tonight, after messing about changing lots of bits found it was the coil (I had a spare luckily) and it started up fine. Great I thought, thats what it was; the coil was breaking down and eventually broke altogether. Took it out for a run and its the same low speed misfire when hot so the same as before. Tried a different CAS sensor (thanks Graham!) and ignition amp and no difference. The plugs and HT leads and cap are all new.

 

Think these kind of things are more annoying than a total non-starter!

Edited January 17, 2006 by C_W

[pacey205 2]

Nick: Leads are brand new ones from neat (brand escapes me at the moment) but I know they are a decent brand.

 

Id definately agree with you there chris, Id much prefer a bonefide problem than this impossible to track down fault as at least I could get it sorted then and run it in, get it MOT'd etc.

 

One thing that I forgot to mention is that when running the switched live direct from the battery the car actually seems to run worse albeit with the same basic problem :S

 

Now this to me would indicate that there may be something there but I dont have enough knowledge to determine what that might be, any gems ?

 

Michael

[jackherer 543]

One thing that I forgot to mention is that when running the switched live direct from the battery the car actually seems to run worse albeit with the same basic problem :S

 

have you measured the battery voltage both with and without the engine running? I'm thinking that the alternator may be overcharging or causing interference maybe... that could easily be rpm specific too, might be worth checking the voltage at the rpm the misfire happens at, or just temporarily removing the alternator belt.

[pacey205 2]

Alternator belt has been removed (dad did it the other night) and the misfire was the same. Havent measured the voltage across the battery at misfire revs but its reasonably new and seems to be holding its charge well although it did require a charge after being sat for a couple of months lol.

 

Michael

[Guest Michael MRK]

umm.., its hard but u tried to check for the cam gear ?? that one that rotate the distributor arm ??, i know its very hard to give spark and cuts it at certain rpm, but anyway, its something u need to check it..!!

i dunno about the mi16 engines, but if there is a vacuum lin connected to the spark advancing unit, u'll need to check this one also, it might be the spark advancing unit (something wrong with the diphragm)

 

i dunno what else but 'll check..

[Anthony 1,000]

umm.., its hard but u tried to check for the cam gear ?? that one that rotate the distributor arm ??, i know its very hard to give spark and cuts it at certain rpm, but anyway, its something u need to check it..!!

i dunno about the mi16 engines, but if there is a vacuum lin connected to the spark advancing unit, u'll need to check this one also, it might be the spark advancing unit (something wrong with the diphragm)

There's no distributor or mechanical/vacuum advance on an Mi16 - the ignition side of things is all ECU controlled, but still uses a dizzy cap/arm to send the coil output to the correct cylinder.

[Guest Michael MRK]

oh okay, didn't know that, so its motronic engine..., first time to know, okay, then for the 1st possibilty the cam gear..!!

[pug_ham 240 3 Cars]

Micheal & Chris, I've been thinking about this a few times recently & I wondered about whether a relay dying could cause these symptoms.

 

Reading this topic by taffycrook, I could be onto something.

 

Worth a try after everything else you've done anyway.

 

Graham.

[Anthony 1,000]

No harm in swapping it out to prove it, but I really can't see that a dying relay would cause a regular misfire in a very specific rev range

[pacey205 2]

Two brand new ones in mine so its unlikely.

 

Michael

[pug_ham 240 3 Cars]

Two brand new ones in mine so its unlikely.

Ok, was worth suggesting though after finding taffy's post along the same lines as my thoughts.

 

Your problem looks deeper & its time to try a different loom. You've tried everything else so it must be the wires connecting them all up.

 

Grahan,

[hman205 1]

have you got an Earth running From the Gearbox to the Neg - Battery?

 

might be worth checking it / moving to a differrent Earth point

 

also The ignition amp how is it mounted? have heard if they arn't on there Correct backing plate and correctly mounted they can produce very starange results

 

Also What plugs are you using and is the Engine Standard of Raised compresson?