Mi16 - New Transplant Misfiring On 2 & 4

[DrSarty 90 1 Cars]

Hi (still new to forum)

Have fired up Mi16 (from BX16v) in 1.6GTi and it worked first time, if a little lumpy. We (kit car builder for 30+years) and I feel it's a misfire on cylinders 2 & 4.

 

Reason for confusion (can't test 'til weekend) is that it has new plugs, dizzy cap, rotor arm & leads and was from perfectly running BX16v. It COULD just be the leads (? why though I don't know), as when we bodged 2 older leads together it started to smooth out, so the leads will be the first thing to swap. It ticks over quite comfortably, so it seems as though it isn;t only running on 2 of 4 if that makes sense. Whipping off 2 and/or 4 leads makes no difference????

 

I have a new coil and rotor arm to check if needed, and have had suggetsted that TDC sensor could need a clean. The plugs on 2 & 4 were slightly darkened on checking and I got mega jolts of both HT leads when removing them, so it seems a spark and fuel are getting there.

 

Has anyone come across this before or can offer an alternative fix IF the extra parts I fit don't cure it please?

 

Dr S

 

P.S. I was wondering whether it just needs to really build up oil pressure and is simply just not opening the valves correctly?

[kyepan 291]

I managed to put the leads on in the wrong order once and it popped banged and ran terribly on two cylinders..

[jackherer 543]

unplug the four injectors and look into the plugs to check the pins haven't been pushed back. the injectors all fire simultaneously so you would still potentially have sooty plugs but way too little fuel.

 

if its not that I would use a jumplead to earth all four spark plugs out of the engine then turn it over to see if all four spark, then I'd take off the fuel rail and see what the injectors do when aimed into a bucket. if the fuel and spark look ok then its compression test time I'm afraid

[DrSarty 90 1 Cars]

thanks u guys, anymore ideas?

[Jonmurgie 2]

We had this EXACT issue on my jenvey install... turned out that on one of the injector wire pairs a little spike of wire had stuck through to the other wire and was causing it to short out. Although they fire together it isn't until the plug fires that the issue becomes apparent.

 

So, I'd carefully check the injector wiring and look for any tiny point of contact... and when I say tiny I mean tiny as mine was like the smallest of small things and it's a testament to the work of PowerStation that they found it so quickly

[DrSarty 90 1 Cars]

We had this EXACT issue on my jenvey install... turned out that on one of the injector wire pairs a little spike of wire had stuck through to the other wire and was causing it to short out. Although they fire together it isn't until the plug fires that the issue becomes apparent.

 

So, I'd carefully check the injector wiring and look for any tiny point of contact... and when I say tiny I mean tiny as mine was like the smallest of small things and it's a testament to the work of PowerStation that they found it so quickly

 

WOW - Thanks, that could - if everything else doesn't work - could be the problem. Another chap suggested checking the injectors so, if moving through the simplest things first:

-leads

-coil

-rotor arm

-cleaning TDC sensor

I could then check the injector pins/plugs & wires one by one.

 

In fact, even though I don't want it to be the case, I have a sneaking suspiscion that that is what it is, because logically if I got zapped by the HT lead then there must be a good spark. New everything kinda restricts faulty components in the ignition chain, so, I'll keep ya posted.

 

Again, what a forum - top help.

[Powers 13]

Ignition amplifier. I bet you a pint of the finest, as i had almost exactly the same problem with mine and it is always my first point of call with any ignition problems on a Mi16.

[DrSarty 90 1 Cars]

Ignition amplifier. I bet you a pint of the finest, as i had almost exactly the same problem with mine and it is always my first point of call with any ignition problems on a Mi16.

 

Hmmm, the plot thickens (and P.S. I'll take you up on that bet).

 

Don't wanna sound dumb, but is the ignition amplifier that ali heat sink with the Bosch blue placky thing on it? I've heard they cost a kidney to replace! Or is it the thing I know as a stubby coil that is usually bolted to the inlet manifold and takes the king HT lead and a 3/4 pin multi plug?

[pugrallye 0]

its your blue thing on a heatsink, and they arent that expensive anymore

[DrSarty 90 1 Cars]

its your blue thing on a heatsink, and they arent that expensive anymore

 

Thanks. This weekend, due to the recommendations I'm goona try the amp first. I have an 8v BX GTi as well and I've been told the amp's the same, so I'll swap 'em and see if (FINGERS CROSSED) it cures the misfire.

 

Only if not will I move on through HT leads, coil, rotor arm, TDC sensor and finally....gulp...the possibility of a short in the injector plugs/wires.

 

Incidentally, I found this page via a google search which clearly states that a 2 cylinder misfire can and is often caused by a failing/failed amp on pre 1992 frog lumps aka citroen/pug.

 

<http://www.carelect.demon.co.uk/mot1.html>

 

Hope it fixes my prob and helps others. I may owe matey a pint by the looks of things - hope so, £2.50 to fix is a bargain.

 

Dr S

[pugrallye 0]

what ignition setup you running? igniton amp from a 205 gti is different to an mi one

[jackherer 543]

what ignition setup you running? igniton amp from a 205 gti is different to an mi one

 

I've never had a problem using 205 8v amps on Mi16s.

[pugrallye 0]

god i had loads on my first one, put two or three different ones in it and ended up stumping up for an mi one (when they were expensive) and all was well and happy with the world, trying to remember (was a long time ago) im sure one had seven pins and the other had six or something similar

[DrSarty 90 1 Cars]

Thanks to more people joining this one. Just to explain, I had & drove the original donor BX16v, hence a) knowing it works(ed) and had everything, ECU, engine, loom, IGNITION AMP etc.

 

Somehow in the build I lost the ally heatsink, but I made a new one and bolted it to the o/s inner wing. There is a possibility that somehow I swapped it with the 1.6GTi donor Pug one, but never mind, I've been advised that 8v ones are the same, and one of you has said you've had no probs.

 

I've found a Magnetti Marelli replacement for £24, but the original is a Bosch. Does this pose a problem? Does anyone know a better/cheaper supplier?

 

Also, as per the link I left it does say a failing amp can cause the 2 cyl misfire I have - but does anyone know why?

 

As for fitting, is it right that I wire brushed and bared the metal on the inner wing - greased the ali plate and bolts (in lieu of heat paste) and led an earth braid from one of the bolts to a spare gearbox bolt hole for extra earthing grunt?

 

Anymore for anymore??

 

Dr S

[jackherer 543]

you need to use proper thermal transfer paste really. I've fixed ignition amp problems by cleaning them up and applying new paste, its important that they dissipate heat well.

[Dream Weaver 2]

You have to use heat transfer paste, not grease, from what i've read.

 

Try it and see what happens

[pugrallye 0]

I dont know why on a single ignition amp system it causes a misfire on two cylinders, as it only recieves an AC signal from the reluctor which switches same transistors on and off for any cylinder!?

[DrSarty 90 1 Cars]

I dont know why on a single ignition amp system it causes a misfire on two cylinders, as it only recieves an AC signal from the reluctor which switches same transistors on and off for any cylinder!?

 

 

Perhaps we'll never know. Either way, Friday evening I can go through the fault finding process on mine and see if (hopefully) just swapping in a new amp fixes the misfire.

 

Regards & standby standby

 

Dr S

[DrSarty 90 1 Cars]

Perhaps we'll never know. Either way, Friday evening I can go through the fault finding process on mine and see if (hopefully) just swapping in a new amp fixes the misfire.

 

OK OK, update time - progress made but fault not fixed, but a new idea forms. Your opinions pls.

 

Now swapped in term all ignition components less dizzy cap (which was new anyway). Started checking connections, cleaning plugs and looking for mistakes - none. New ignition amp, same lumpiness. Continued to new HT leads, then coil, then rotor arm...no change (bugger!!!! )

 

Then, to buy time I got connecting the dash loom to the BX16v senders as I have forum print outs and ploughed through the Haynes wiring diagrams consuming about 200gallons of tea. Revs, temp, charging, reverse lights and dials all working, but oil gauges not playing the game. An idea spawns.

 

Jonmurgie did suggest injector wire short, and sparks and fuel and compression will be checked in the morning, but I'm confident all but one are good, and that's compression. My kit car guru and I are wondering that as I am failing to get an oil pressure reading then perhaps I simply haven't obtained one because the oil pump has a vapour lock through sitting idle for 2 years. Haynes says a new oil pump should be primed. Although I haven't fitted one, we think that time has drained it and perhaps the engine genuinely hasn't built up enough oil pressure to open the valves properly giving poor compression hence lumpy running?????

 

As the rev counter's working, we can see it revs smoothly and ticks over quite happily at about 950rpm, but is just simply lumpy, as if running on 2-3 cylinders. WHAT DO YOU GUYS THINK?

 

Dr S

[pugrallye 0]

you either have an injector problem, best way to test injector wiring is with noid lights (unplug injector and plug in noid light) or a compression misfire, simplest way is to run it up then whip out all the plugs and inspect them

[DrSarty 90 1 Cars]

First off I was a d!ck...the misfire was on 1 & 3 - numbered from wrong end. HERE'S AN UPDATE - unfortunately not over yet.

 

After changing all the ignition components, nothing changed, still lumpy. Compression test went well and surprsingly even, reading green 13.25 (bar I think) on tester across the board.

 

Then took of fuel rail and watched 3 injectors fire into a plastic tub. SHOULD HAVE DONE THIS EARLY DAYS...never mind. Number 2 wasn't firing at all. Most annoyed because paid £90 to have injectors cleaned and flow tested, all passing. Logically, this would explain that the fuel under pressure, as it couldn't exit through 2 found the easiest route via 1 & 3 in the process over fuelling (is this a logical deduction?).

 

Anyway, mad dash at 4pm on a sunday to a breakers and got a complete Citroen fuel rail with Bosch yellows for £15 . Really excited that fix found...chose one, cleaned it...naff all (again)...chose another and bingo - 4 firing injectors.

 

BUT my friends, whilst it was definately better it's still lumpy - you can strill see it shaking just like a mild misfire and you can hear it burbling too. THE CAR IS NOW HOWEVER DOWN HERE IN BEACONSFIELD, BUCKS. ***Pugrallye are you reading this??? Please say you are and can come over & goose at it***** and I can now work on it every night to get it right.

 

We think it's overfueling but don't know why. I'd like to post a picture of the plugs which I'll take out tonight as this should tell a/the story, but I don't know how to post a picture - it always asks for a URL and I'm not that clever

 

Anyone available with ideas? Was a perfectly working BX16 lump. Could it just be that 1.6 fuel pump supplying too much??? Could the big brass screw in the AFM which is uncovered have an effect (I wish a quick turn on that would do it!), or because of sitting around for 18months the ECU gone screwy?? If anyone (Pugrallye) has a spare brain that could be a simple swap test.

 

This is fixable I know, and probably quite simple, but it is frustrating. HEEEEELLLLPPPP!!!

[DrSarty 90 1 Cars]

More info - if someone will show me how to post piccies I can show you my plugs (ooer missus )

 

Whipped them out tonight and 1-3 are all text book, light brown deposits. BUT 4 (cam belt end) was dark, wet and sooty.

 

This smacks of a bad/no spark! This MUST be either a s*itty lead or, (and I can't believe I'm saying this) a bad NGK???

 

This would mean I've had 2 probs all along, which is the worst scenario when fault finding. I.E I found the w*nk injector but it still wasn't completely cured.

 

ANY COMMENTS PLEASE - I'll try tomorrow same dark plug in 4 with 1 x exchanged lead (to eliminate one option) then buy one plug and try in 4 with both leads if necessary. At that point if not fixed there's only the option of (again, can't believe this) another new dizzy cap.

 

IDEAS....

 

Dr S

[Powers 13]

I guess i owe you that drink!

I very much doubt its the fuel pump as all the gti ones are all the same.

Here is what i would check/try/test:

Check the lead and spark plug, change if necessary.

Follow the 3 wires coming out of the coil ( on the intake manifold) all the way to the ignition amp, usually they go into a brown connector which is usually knackered and can cause problems. Thats if it hasnt been changed already!

Change the AFM

 

Hope that helps. If i think of any more i will be in touch!

[pugrallye 0]

sounds like you have an iffy HT lead, either not clamping or arcing off to the engine, will have a look tomorrow/ weds if you like possible dizzy cap is cracked too

Edited September 11, 2006 by pugrallye

[DrSarty 90 1 Cars]

sounds like you have an iffy HT lead, either not clamping or arcing off to the engine, will have a look tomorrow/ weds if you like possible dizzy cap is cracked too

 

 

Pugrallye: I'll bell ya re Wednesday, sounds like a good chance to meet and get your advice. As for HT lead, which I'll swap/check tonight, when we did the 'in the dark' check there was no sign of arcing, but I'll try it anyway. To me it's leaning towards an iffy plug, because the dizzy cap is new too - but I'll try anything twice. Regards all and stay tuned.

 

Dr S