Misfires

[Busterboo]

(Haven't put this on the Comprehensive problem list yet, but will.)

35iS. 73,000 miles. January 2021. Slight hesitation starting. Increased in a week to 'Call the AA'. 'Misfires on 4 & 5.'

Sytner's diagnosed injector failure and replaced all 6 under BMW Insured Warranty. Car ran very well and, for the first time, I fed it 99RON instead of 95RON (even thought the handbook says 95).

2,300 miles later. End of March. Starts normally, but misfires slightly under Sport acceleration. Warning light. Take it to BMW indy. 'Misfire on #2.' 'Needs new plugs and maybe one or more coil packs.' Told him to replace the lot, none of which it's had new in its life, I believe.

Will test tonight. Fingers crossed, because we're going on holiday on Friday.

(New plugs, coils and brake fluid change was £408.)

EDIT: Just tested. Fault still there. Misfire under acceleration.

[Pbondar]

Injectors, coils...have you had the waste gate rattles and HPFP for the full house on the engine ?

Seems it’s mostly a matter of when on the N54?

[Busterboo]

Injectors, coils...have you had the waste gate rattles and HPFP for the full house on the engine ?

Seems it’s mostly a matter of when on the N54?

Yes, had new injectors. But at 75,000 miles, that seems reasonable enough. Had new plugs & coils by choice, because the car was on its original sets, too. As for other common replacements on the 35iS, I'll bite the bullet (or, rather, the insured warranty will) if/when they come, because it's a great car.

As for the recent misfiring before & after new plugs & coils, it was a mystery to my BMW indy, who tested the car extensively, and would no doubt have been to the local AD. It has, however, stopped.

The reason? Well, is it possible that the car, having run all its life on 95RON, couldn't adapt to the Shell 99RON V-Power it was put on when the injectors were changed?

Back on Sainsbury's 95, it's running sweet as a nut.

[Pbondar]

I think, IMHO, if you go into N54 ownership with your eyes open and either tackle the issues as they arise and/or pre-emptively service those known issues and/or have a warranty, then for its prodigious performance it could seem a reasonable price to pay.

It’s the newbies, probably on an over committed budget that seems to be the ones most surprised...

Especially those who based reliability on those relatively faultless N52 engines.

I find it technically difficult to rationalise the change in octane rating (downwards) for sorting out a misfire..

Maybe a bit of condensation over the winter, fuel going off through standing?

[R.E92]

The problem will still be there. It's possible that bad fuel can cause misfires but unlikely. Too much of a coincidence that they happened after the injector replacement.

My money is on improper installation. An injector replacement is a simple task but it requires attention to detail that some people lack.

My Z4 had its injectors replaced about 5 years ago by a BMW dealer. It started to misfire occasionally, perhaps twice a week I would get a CEL and the car would go into limp mode. It turned out the mechanic had forgotten to install the decoupling rings and as a result the injectors weren't seated correctly thus causing the misfire.

Other common errors are missing teflon seals, upside-down bracket and incorrect injector coding.

That was one of many horror stories I have of dealers. I have since learnt to work on my own car almost purely out of a frustration with incompetent mechanics, I only ever visit the dealer to buy parts now. Unfortunately good BMW techs don't stay long at BMW as they move onto specialists or start their own shop so you're just left with monkeys and sales staff (just monkeys then).

If you live close to either Darren Wood in Stockport or Birds near Slough I would make the journey there and have them verify the install.

You can also take off your engine cover and take a load of photos around the injectors and I could spot any obvious errors. I've done the job myself recently on another car so have a good idea what it should look like. Can't verify the teflon seals or coding but the decouplers and brackets are visible.

[ronk]

The problem will still be there. It's possible that bad fuel can cause misfires but unlikely. Too much of a coincidence that they happened after the injector replacement.

My money is on improper installation. An injector replacement is a simple task but it requires attention to detail that some people lack.

My Z4 had its injectors replaced about 5 years ago by a BMW dealer. It started to misfire occasionally, perhaps twice a week I would get a CEL and the car would go into limp mode. It turned out the mechanic had forgotten to install the decoupling rings and as a result the injectors weren't seated correctly thus causing the misfire.

Other common errors are missing teflon seals, upside-down bracket and incorrect injector coding.

That was one of many horror stories I have of dealers. I have since learnt to work on my own car almost purely out of a frustration with incompetent mechanics, I only ever visit the dealer to buy parts now. Unfortunately good BMW techs don't stay long at BMW as they move onto specialists or start their own shop so you're just left with monkeys and sales staff (just monkeys then).

If you live close to either Darren Wood in Stockport or Birds near Slough I would make the journey there and have them verify the install. There's also another very good garage in Nuneaton called PMP cars that almost exclusively work on N54 engines, they are more rough and ready than the previously mentioned places but easily as competent and cheaper.

You can also take off your engine cover and take a load of photos around the injectors and I could spot any obvious errors. I've done the job myself recently on another car so have a good idea what it should look like. Can't verify the teflon seals or coding but the decouplers and brackets are visible.

Thats scarey when you consider what rates BMW main dealers charge for their labour rate!

[Nanu]

Had the same issues and if it was the injectors the state of the spark plugs will tell you. Mine were black on bank1. Replaced the 3 injectors on that side and like you, it ran fine for a while before doing the same again and the amber engine warning light came on. This time the plugs were fine. Try changing the oxy sensors. I did and the car feels like new again.

[Busterboo]

The problem will still be there. It's possible that bad fuel can cause misfires but unlikely. Too much of a coincidence that they happened after the injector replacement.
.....
My money is on improper installation. An injector replacement is a simple task but it requires attention to detail that some people lack.
.....
You can also take off your engine cover and take a load of photos around the injectors and I could spot any obvious errors. I've done the job myself recently on another car so have a good idea what it should look like. Can't verify the teflon seals or coding but the decouplers and brackets are visible.

First, R.E92, thank you very much for you kind offer at the end of your post and, before that, for the information in it.

Now, thanks to your advice, the most practical route for me is to ask my indy to check Sytner's installation of the injectors. Then, if he finds something, he can correct it and I can attack the AD, so I'll have a problem solved and some fun.

That said, the engine performance was excellent for 3 months after Sytner's work, so they may not be the culprits.

As for my comment about fuel in my last email above, it was to a degree tongue-in-cheek, but not entirely. So, I'll run the car until it misfires again before taking it to the indy, or not.

[Busterboo]

...
Try changing the oxy sensors. I did and the car feels like new again.

Thank you. Will tell the indy this, too.

[Busterboo]

Well, if it was the fuel, it took 3 tankfulls of 99RON Shell V-Power to start the misfires and has taken 3 of 95RON (not Shell) to clear them.

I filled the tank with 95 for the 4th time today and thrashed the car up hill and down dale for a 100 miles in Normal, Sport and Sport+, auto & manual, and it didn't miss a beat.

(Incidentally, the 35iS handbook approves the use of petrols between 91 and 98RON, not 99.)

[Busterboo]

Well, I did say if it was fuel ... but it wasn't. The misfires started again.

It seems that it was an oil leak contaminating two spark plugs.

Having put in new plugs & coil packs, my local indy, whom I trust, hadn't found this to be so and had recommended having the inlet valves cleaned. This would have been a nuisance, because the nearest walnut shell blaster who does E89s is 56 miles away.

Therefore, I took a deep breath and drove to my local AD, who kept the car for several days. Now, it's running sweet again. Quite what they did, I don't know, because, when the work was finished, all I just wanted to do was drive away.

[Pbondar]

So they didn't tell you what the fault was, how they fixed it and how much they charged you to do it?

[Busterboo]

So they didn't tell you what the fault was, how they fixed it and how much they charged you to do it?

As you no doubt know, some of the difficulties of using an AD are that you can rarely talk to the mechanics who work on your car and that information from them is often fed to you only as a bare item on the bill and/or through customer reception staff.

In this case, the receptionist said it was "an oil leak contaminating two spark plugs" (which is what I said in my previous post). From the items on the bill, the oil must have come from the failed rocker cover gasket. So, that's the 'what' and the 'how'.

As for the 'how much', however, the labour charge to replace the gasket also includes time spent testing the car to try to identify the misfires and their cause, so it's larger than just replacing the gasket.

The whole job included replacing the two front adaptive dampers at £567.27 each, new gearbox oil pan at £133.73 (and gearbox oil at £250) and the rocker cover gasket at £39.75. The parts total, including nuts & bolts, was £1,561.90 and labour was £891.67. The overall total was £2,679.28.

[Pbondar]

All noted thanks..

An unusual for an N54 reason for a misfire AFAIK, can add it to the repertoire of things to check in that event

You can see why people get anxiety attacks going to AD for anything but servicing.

My Volvo dealer wanted £1,500 to change front n rear discs n pads and wouldn’t release the car because at 5mm pad left it ‘wasn’t safe’

[Smartbear]

All noted thanks..

An unusual for an N54 reason for a misfire AFAIK, can add it to the repertoire of things to check in that event

You can see why people get anxiety attacks going to AD for anything but servicing.

My Volvo dealer wanted £1,500 to change front n rear discs n pads and wouldn’t release the car because at 5mm pad left it ‘wasn’t safe’

That almost sounds like blackmail, did you manage to persuade them to return it?
Rob