Hmm misfiring..

[ethanol-smart]

Right after a coldstart, my Smart is npt running on more than two cylinders.After some seconds, the third is coming slowly and then I can go.I assumed its becasue of my 100% E85 running even if its now summer (which is not so much varmer this year though...).

After I fixed an automated "cold start resistance", the problem is much less then before.But..two times now, I have had the misfiring coming back with also warm engine.Its a bit like also loss of power, and the first time, I thought it was because of low fuel level, since it was cured after filling up.Today it happened again though, with full tank.

Seems to start on a slight upphill and can go away if I take of the foot from the gaspedal.I stopped and restarted, and there was no problem again, however it came back one time, and then I activated a forced switch for running the fuel pump without relay.
Nothing happened first, but after some 5 seconds, the misfinrg went away for good, and I got home safely.Any of the times, I didnt push it like I sometimes do, and it was not very warm outside or in the engine compartment (highway in about 100 km/h on flat road)

Any ideas about the reasons? I have replaced the fuel filter and the fuel pump seems to work stable at least when on my direct switch.Is it the fuel pump anyway, or the relay?

It feels really a bit like too little fuel, just like after those coldstarts.Or just a ignition coil on its start to go?How do I find the misfiring one the easiest way?No check engine or other lamp lit.

[heinkeljb]

Re: Hmm misfiring..

If it is a "proper" misfire, then the ECU logs will show it and tell you which coil was at fault. If the misfire is due to an arc from one of the cable leads or a plug cap then it might not be logged.
Have you looked at the spark plugs since you got it running - just a thought, you have increased the compression and maybe the increase in heat and pressure have caused a fault in one of the plugs to show itself?

John

[madDan]

Re: Hmm misfiring..

Failing plug? lead/coil maybe injector?

Sounds a bit like Jorgens problem when he'd fitted an old damaged lead.

Misfires should throw an engine lamp if serious enough, the knock sensor should at least be logged.

To be honest though to many variables outside of the norm in your build it could be anything.

Intresting that forcing the pump on seems to cure it?

[ethanol-smart]

Re: Hmm misfiring..

TY for your input!
I dont know really.
Today nothing bad happened. Was warmer outside today than yesterday.
With a bad HT-lead, it should be worse when cold and moisty outside, this dont seem to be the case.
In rain, I still never had any problems.
I think it points to a bad coil.
I remeber now that on of them had one green (oxidized copper) HT-connection.
This I only saw one time before, it was on a Mercedes E220, and some 3 months later, that coil died totally.
(No misfiring what I know of before though)
Maybe its time to replace all three with something wiser, mounted in a cool and non vibrating environment.
I really hate this idea of putting the coils on the hottest spot of the motor and expect them to live long and happy...
I saw somewhere a three channel coil built togehter with 6 outlets, intended for Smart.
Anyway the HT-leads are **** too, so difficult to remove from the plugs that they only should be thrown away really..
Would be nice to replace them with long, nice ones to the body mounted coils, that dont give you any pain when working with them.

[ethanol-smart]

Re: Hmm misfiring..

Yesterday, the car went better than ever, I even scored a new low fuel consumption-record , with highway driving about 90-95 but anyway inspired on some wonderful winding roads, consumption was only 5.4l/10km, E85. It equals to 3,9l/10 km on gasoline with 5% ethanol mixed in (std in Sweden currently).
Not a single misfire,and quite warm outside too.

But, today, half day was running as a dream, strong and powerful, but on the way home, the misfiring started big time, I could stop and lock the car and re-start for beeing able to run some more km as usual, but then misfiring comes back on almost everything else than idle.
It turned out to be a trip of 40 km on maximum 55 km/h, also engine speed seems sensitive so I coulndt use 4th or 5th gear only either.
On that speed, if not a too high uphill, I managed to finally come home.
Now it doesnt help to force the fuel pump at all.
Must be one coil.
Car will be parked until I replaced the whole HT system of it, its any way due after 100000 km.
In the 70ths a HT system that broke down on you after only 100000 km woul dbe regarded as ****. Nowadays, nobody even question it...

Anybody mounted any other coils than the 3 std ones on this boiling hot engine?
I hate to put on proven **** details, new or used, which I know will soon fail again.
I prefer to find and use working stuff, and enjoy a normal working car for several 1000nds of kms.
I saw on many cars now the same problem, the coils dont survive the environment, and I dont blame the coil manufacturers, what other electrical component have to suffer the same hell?
Even without the HT aspect of things, I wouldnt ever in my life design a position for an electrical component in such a varm and vibrating position!

The solution is ofcourse longer HT-leads and body mounted ignition coils.
They exist for 1 to 6 channels, with one or two HT connections, since wasted spark is so common nowadays.
The Smart coil is in fact a normal wasted spark coil for a 4cyl std engine (I think?), so I guess a lot of different coils would fit.

For instance this:
http://www.ebay.de/itm/BERU-ZUNDSPUL...#ht_2612wt_987
a lot cheaper, 34 Eu each, than the original Smart stuff which often are some 100 Eu each...

[Thrumbleux]

Re: Hmm misfiring..

ES: In defence of engine mounting the coils is the more direct current paths for both the HT and the LT return to earth. (An additional earth strap between the head and chassis can only help here - easily done).
Almost certainly an ignition problem that your increased CR has uncovered.
I'd be careful using non smart coils - or I'd want to know that all HT pulses are correct polarity. Research Citroen 2CV wasted spark if you are unsure of what I am referring to.

[ethanol-smart]

Re: Hmm misfiring..

Yes, I see the point with the coil direct to the sparkplug, but if we think of it, in old day, when the coils where serving 4 or even eight spark plugs, the most usual problem was the HT-leads.
They are easy to fault search and cheap too.
Nowadays, in order to have no issues with bad HT-leads, we got coil issues before 100000km often...
I know what I prefer...
And with modern HT-leads, I can drive for 15 years without any problems, in old days, the leads where often due to replacement after some 80000km.

Its all about money in my eyes, the leads means a cost that can be eliminated when building the car, and the customer will have to pay instead, by randomly stopping cars, and high repair, hopefully after the end of the guarantee period...
If there was a real benefit to put the coil directly onto the plug, I dont think we would see so many tuners and racing people moving them away from the engine....

From what I have heard, most modern coils show the same primary and secondary resistance and the only thing that can make a real difference is if its a CDI-system (which is very rare on cars, mostly on small engines like lawnmowers and chain saws), and iff there is a built in amplification stage (a smart or a dumb coil).
The Smart car have a dumb coil, without any amplification stage, right?
About the Citroen 2CV, this is the big exception, I was informed, the 2CV have a totally different, higher inductance, than other coils on the market.
Will stay away from them...

What about this alternative..?
http://www.diyautotune.com/catalog/i...ack-p-430.html

[Thrumbleux]

Re: Hmm misfiring..

I didn't realise the 2CV coil was such an exception - but for sure, you wouldn't want a plug firing from the side electrode.

As to other (aftermarket) coils - I wouldn't know where to start! The ECU on a smart seems capable of causing problems over anything and everything it doesn't recognise or approve of. One day it will prevent a car from starting because its driver parted his hair on the wrong side. Finnicky then...

[ethanol-smart]

Re: Hmm misfiring..

I didn't realise the 2CV coil was such an exception - but for sure, you wouldn't want a plug firing from the side electrode.

As to other (aftermarket) coils - I wouldn't know where to start! The ECU on a smart seems capable of causing problems over anything and everything it doesn't recognise or approve of. One day it will prevent a car from starting because its driver parted his hair on the wrong side. Finnicky then...

I hope not!!

[Thrumbleux]

Re: Hmm misfiring..

Somehow - don't ask me how! - the ECU can read a misfire and identify the cylinder affected.
Is that through reading data from the coils (ionisation?), or from some other parameter(s), such as cyclical speed variations (the CDI is sensitive enough on this to permit deletion of a cam position sensor and rely on the crank one only and its ability to detect which cylinder is being hefted over compression TDC).
If it's from the coils though....

[madDan]

Re: Hmm misfiring..

The Knock sensor detects a misfire, the ECU knows which cylinder is supposedly firing you know that timing ring thingy on the flywheel (quite handy that it does I guess )

[ethanol-smart]

Re: Hmm misfiring..

Are you sure that the knock sensor is involved?
Isnt it enough to look at the crank variantions to see wich one is misfiring?
Posssibly in combination with that a too rich mixture is detected by the lambda sensor, (which in fact also can smell from which cylinder it comes), that can relate the smell to a cyclic variation and the ECU can shut off the injector in order to save the catalyst form being flooded with unburned fuel.

[Thrumbleux]

Re: Hmm misfiring..

Post #12. Suspect you have it covered there ES. For the knock sensor to detect a 'miss' it would have to be detecting regular combustion - and then still it would have to be able to detect abnormal combustion, ie knock. That's treble the capability compared to knock detection alone, and knock detection itself is (well, judging by the price of aftermarket electronics to run knock sensors) a tricky task.
The Diesels monitor the variations of crank speed - for starting at least, via one crank sensor. Possibly the petrols can detect a miss.
Good spot on the Lambda - and cylinder shut-down. If you are wrong - then smart are wrong for not configuring it that way!
Definitely though - combustion monitoring via the plug electrodes re ionisation, is or has been used by some. Pioneered by Saab IIRC on their Trionic(?) system. Careful with coil selection ES!

[ethanol-smart]

Re: Hmm misfiring..

I know about the pioneers at SAAB (RIP)..
They are as far as I know, the only example so far of ionisation detection.
Im thinking now of simply using Merc own twin spark coils. They should have no issues giving 2 good blasts simultanously in one compresssed cylinder, apart from a normal waste spark coil, which might have lower power.

Will make some measurements of the primary and secondary resistance of the coils in the Smart and try to get the correct figure of the Merc twinspark coils. Hopefully they are not too far away from each other, both being Bosch units.

If it works, at least the horrible engine degrade Merc made 1995, when going from 24v straight 6 DOHC-VVT, to a 18v (90!) deg V6 with single OHC twin spark, could mean some progress for man kind.....

[Thrumbleux]

Re: Hmm misfiring..

to a 18v (90!) deg V6 with single OHC twin spark, could mean some progress for man kind.....

Not a fan of the V6 then...
I'd forgotten Merc had gone twin spark with that engine.
Are you aware of the Swissauto and smart connection - from where the turbo and twin plug concepts apparently originate?