BMW E87 116i Rubbish story and a question or two

[nick.lidgett]

Ok so last week my wife went to start the car and the engine management light started flashing , the whole car was vibrating like mad and sounded like a tractor.

I got home plugged in a borrowed laptop with diagnostic software and it came back as a misfire on cylinder 1.

I went to euro car parts and bought a new ignition coil, went home and fitted it, cleared the fault codes took it for a blast, at first it was a bit rough but I presume it was just unburnt fuel knocking about in there as after a few miles it cleared and it was driving and sounding fine so I took it home and dumped it back on the drive.

Now I have bashed this car in a few threads on here complaining of how slow it was, I would rather drive my van than the car. Now here is the thing, Saturday come round and the wife wants taking out and insists we use the BMW, begrudgingly I get in the drivers seat and we set off, after less than a minute I found myself actually enjoying the damn thing, I am certain that the car has more power, I feels much zippier and responsive.

Now I have a few questions;

1, Does the engine produce HP equally over the 4 cylinders for arguments sake would it be 100 / 4 = 25hp per cylinder?

2, If yes to the answer above, I could have been down a few HP for quite some time?

3, If no to the above am I just imagining it?

4, How broken does an ignition coil have to be for the ECU to pick it up?

5, As its such as cheap part £25~ is it worth changing the other 3 and the plugs in the hope of releasing a few more HP?


Cheers

 

[andy_mk3]

1, Does the engine produce HP equally over the 4 cylinders for arguments sake would it be 100 / 4 = 25hp per cylinder? +/- a bit yes but pretty much equal.

2, If yes to the answer above, I could have been down a few HP for quite some time? Possibly, impossible to say though. If it's had a misfire for a long time it would have damaged the CAT though.

3, If no to the above am I just imagining it? ..

4, How broken does an ignition coil have to be for the ECU to pick it up? Depends on the car, they all have different requirements to flag a misfire as a fault. Also depends on how the coil has failed, they don't always fail in a way that the ECU can pick up on it.

5, As its such as cheap part £25~ is it worth changing the other 3 and the plugs in the hope of releasing a few more HP? Not really, it's a case of they either work or they don't, on something like a 116i, a degraded coil that's not causing a misfire will show no noticeable loss in power really.

 

[nick.lidgett]

If it's had a misfire for a long time it would have damaged the CAT though.

The misfire was only noticeable that morning when she switched it on and there was no warning lights before, maybe we got lucky with it?

 

[Orionaut]

Ok so last week my wife went to start the car and the engine management light started flashing , the whole car was vibrating like mad and sounded like a tractor.

I got home plugged in a borrowed laptop with diagnostic software and it came back as a misfire on cylinder 1.

I went to euro car parts and bought a new ignition coil, went home and fitted it, cleared the fault codes took it for a blast, at first it was a bit rough but I presume it was just unburnt fuel knocking about in there as after a few miles it cleared and it was driving and sounding fine so I took it home and dumped it back on the drive.

Now I have bashed this car in a few threads on here complaining of how slow it was, I would rather drive my van than the car. Now here is the thing, Saturday come round and the wife wants taking out and insists we use the BMW, begrudgingly I get in the drivers seat and we set off, after less than a minute I found myself actually enjoying the damn thing, I am certain that the car has more power, I feels much zippier and responsive.

Now I have a few questions;

1, Does the engine produce HP equally over the 4 cylinders for arguments sake would it be 100 / 4 = 25hp per cylinder?

Yes, From a mechanical POV, if it doesn't there is something badly wrong.

2, If yes to the answer above, I could have been down a few HP for quite some time?

Possibly, though if the power loss was somewhat random, the ECU might not have picked it up as a notifiable fault (IE a failing coil might not necessarily generate a MIL on situation)

3, If no to the above am I just imagining it?

Quite possibly, Remember, You Too are only Human!

4, How broken does an ignition coil have to be for the ECU to pick it up?

Depends on the programming, but would probably have to be fairly consistent.

5, As its such as cheap part £25~ is it worth changing the other 3 and the plugs in the hope of releasing a few more HP?

Personally, I regard stuff like this like light bulbs, once one has gone, change the lot. They have a service life. once one has reached iot , the others will not be far off (And YES, change the plugs too. IME coil failures tend to coincide with very knackered plugs, even if they are within the, so called, recommended service intervals. For any modern car I would not advise leaving the plugs for more than 2 years/20,000 miles regardless of what it says in the book.)


Cheers

 

[Frozennova]

There'd actually be slightly more than a 25% power loss from "losing" a cylinder as you also have to account for frictional and pumping losses from the other cylinders picking up the slack so to speak