Mi16 - New Transplant Misfiring On 2 & 4

[DrSarty 90 1 Cars]

Attempt at uploading images - plugs and Mi16 (dirty though) inlcuded.

 

Hope it works

 

 

Dr S

[DrSarty 90 1 Cars]

Going berserk now - 4 is the misfire (cam belt end). I've tried a brand new plug with both of the NEW leads I have, and when running (lumpy stylee as it would when missing), pulling off HT lead 4 makes no difference.

 

As the compression test went well, (unless another injector has failed all of a sudden) to me there's only another new dizzy cap to try - then I'm all outa ideas.

 

Why oh why me????

[DrSarty 90 1 Cars]

AAAARRRRRRGGGGGHHHHHHH!!!!!

 

Now, after changing everthing (new Dizzy cap tonight) cyl 4 is still misfiring - in so much as when it's ticking over, it's still lumpy and whipping off number 4 makes sod all difference.

 

PugRallye (is local to me) and has proved a real star offering realtime help, but now this is getting silly. We currently think perhaps it's something totally stupid like the HT lead not 'clamping' on the plug, but I can't push it down any further although I will try a plier pinch before the next fitting/running attempt.

 

So what do you do when:

 

all 4 injectors firing what looks to be equal amounts of fuel

 

plug on lead out of head appears to spark blue (but I suppose it still could be weak?)

 

you have new leads/plugs/amp/coil/rotor arm & now dizzy cap and...

 

cyl still won't fire??????????????????????

 

Totally, totally baffled

 

Dr (mucho confused) S

 

P.S. My dad once said 'life is like a sh%t sandwich - the more bread you've got the less sh%t you've gotta taste'.

Well it would appear my bread bin's truly empty.

 

Help anyone - a visit maybe??

Edited September 12, 2006 by DrSarty

[DrSarty 90 1 Cars]

Ok, at whit's end. If you've followed this thread you'll know everything in ignition line seems to check out. Injector on 4 is firing when rail clear of head and compression test showed a good and even read with the others.

 

Current suggestion is a broken valve spring - probably exhaust. Any agreement out there? And can I check or replace in car?

 

Dr S

Edited September 13, 2006 by DrSarty

[pugrallye 0]

broken valve srping?? jesus well quickest way to check would be remove rocker cover and look see

[DrSarty 90 1 Cars]

broken valve srping?? jesus well quickest way to check would be remove rocker cover and look see

 

Exactly, Jesus! BUT, I phoned the chap who helped me refurb the head (I did 50% of it with him) and whilst we did find 1 broken spring back then [a] the engine ran fine anyway and we ordered one in and replaced it anyway! So it seems the least likely option.

 

Next plan is to swap injector 4 purely to eliminate fuelling as the cause. Then to swap plugs 3 and 4 just on the almost unimaginable possibility that it could be two duff plugs on the trot. Then all 4 plugs out on their leads to visually inspect comparitive strength of spark.

 

Only then can I contemplate lifting rocker cover off and (I've been told) push down with a screw driver onto the cam followers on 4 to check for one easier to open valve than the others. PR: I thought I wouldn't be able to see the springs?

 

Anyway - I'm still convinced it MUST be something silly but I'm bucked fackwards if I can figure it. Can you spare an hour tonight between now and Sunday to work your local majic - or anyone else for that matter???

 

Dr S

Edited September 14, 2006 by DrSarty

[DrSarty 90 1 Cars]

Don't wanna get myself too excited but MAY have found the problem. One of forum's very kind & helpful followers suggested measuring fuel output from injectors.

 

With the aid of 4 of my baby boy's plastic (identical) cups, and 10secs of turning engine over, it appears around 50% of the fuel amount was delivered by 4 in comparison with the others. I did this twice, very diligently and both 'tests' delivered the same result.

 

With 3 spare injectors that wouldn't fire when tested soaking in meths overnight (thanks Pugrallye), and the possibility of one test/keep one from Anthony (thanks in advance), we could be rocking in the next 48hours.

 

Alternatively this could be another dead end.

 

Here's panicking...I mean confidently anticipating

 

Dr S

[nick 3]

Just out of interest (and going off in a completely different direction) which way up have you mounted the AFM?

 

Nick

[DrSarty 90 1 Cars]

Nick: This project has been a long time coming, one reason is I did lots of research on how to do it, making sure I saw as many Mi16 installs as possible. There are loads of old wives' tales out there , but one I DID pay attention to was that the AFM should be mounted as per standard, i.e. flat.

 

Mine (which was from a BX16v, which means it has the longer rubber air hose AFM to plenum) is mounted as it was in the BX, i.e. not turned or tilted. I said old wives' tales because I've seen loads where to make it all fit back in, people tip it on its side - I've even seen one upside down, and they all seem to work!!

 

The upside of me keeping it 'right side up (RSU)' is that I could rule it out as a reason for probs in the future. The downside is RSU plus longer hose = really f%^king tight squeeze.

 

Does anyone know whether the AFM thing is an urban myth?

 

Dr S

[nick 3]

Not an urban myth, thats why I asked.

 

I had loads of trouble getting mine to run right (similar situation to you, chugging on tickover like it was running on 2) I had the AFM mounted on it's side so that the flap was hinged at the bottom. I turned it round 180 degrees which cured all the problems instantly. I assume that the weight of the flap was holding itself open slightly at tickover destabilizing the mixture.

 

Nick

[VisaGTi16v 1]

Interesting. Never heard of that with the AFM. I have mine pointing down so the wiring plugs on the top. Does that mean the flap is hinged at the top or the bottom, I forget? It is running a bit worse under 2k than it used to but then ive just put a bbr starchip in to test it out so I presumed it was that. Maybe I will put the standard one back in to compare as it could be the AFM flap at low revs

Edited September 15, 2006 by VisaGTi16v

[jackherer 543]

I've never had a problem with the angle of the AFM, and I've worked on a LOT of them now. I would say your AFM must be a bit worn or something.

[nick 3]

Agreed, but it's just something else to rule out. On mine you could literally spin it round and it would splutter and chug, spin it over again and it would run perfect. Maybe someone had loosened the spring off a notch or two to richen the mixture up a bit?!!?

 

If I remember correctly, with the plug to the top, the flap is hinging from the top also so it should be closing fine.

 

Nick

[DrSarty 90 1 Cars]

!!! Yay Yay Yay

 

Misfire RECTIFIED!!! Thanks to all - the answer was in replies posted to this thread, BUT...it seems that once again, expert advice is often the common sense that others fail to see. A big learning experience for me.

 

In summary - my misfire was caused by cyl 4's injector delivering insufficient fuel. The jar firing test and comparing levels showed this to be the case. In fact one of the injectors from a breakers yard that initially didn't fire at all, but then (thanks to Jon - Pugrallye) spent a night in a jam jar full of meths, fitted to rail fired first time. Jar level test produced much better results, hence smooth running once tested properly. The proverbial pig in sheizer.

 

Experts e.g. pitcrew etc may quite rightly pick holes in some inaccuracies I'm about to state, but for the benfefit of any other novice stuck in a frustrating misfire situation like me, here's my advice.

 

1) Get the kettle on, sit down and think it through

2) Internal (petrol) combustion engines follow the suck - squeeze - bang - blow principle so, please consider using this guide:

 

* if decent air is getting in (I believe the cooler the better) to the combustion chamber

* and arriving in the combustion chamber is also SUFFICIENT fuel (enough millilitres) that is/will mix nicely with the aforementioned air

* and the combustion chamber is sufficiently air tight because the valves have closed properly as the piston is rising to the top

* and SUFFICIENT (a big enough) spark (ignition source) arrives at just the right time to ignite the mixture because the ignition system (which could comprise many often bewildering components such as ECU, ign amp, coil, rotor arm, distributor cap & many wires, leads and spark plugs)

* then providing all other mechanicals are in order then you WILL get a power stroke from that cylinder

* multiply that by number of cylinders doing that IN THE CORRECT ORDER

* and the valves also opening again to allow the exhaust gases (waste) to be removed from the engine via the exhaust system (through the turbo in turn if applicable) THEN....

 

Your engine WILL run

 

3) Like the 'fire triangle', which means lose one of three components - fuel/air/heat - and the fire goes out, anyone of the guide's points being either missing or insufficient (**the problem with my Mi16 lump**), and you will have a problem.

 

4) Trace it through, calmly with your lurvely cup o' tea in your mit and you'll find it.

 

I've written this because had I NOT given the ignition system such a bad rep and feared it because it was complicated unlike the fuel system and plonked the blame on it, and instead thought it through simply - is there ENOUGH fuel and spark in an engine I'm confident is mechanically sound, I would have slept easier and been happier sooner.

 

This is not meant to be a lesson, just a reminder to those who flap like me that a cuppa tea and a sensible think through will probably fix most things.

 

A happy ending. THANKYOU THANKYOU THANKYOU!

 

Dr S

Edited September 15, 2006 by DrSarty

[pugrallye 0]

well said rich