Odd Misfire....

[MangoMan]

Hi chaps....

Just a quick one please.

My 2000 S500 (W220) has a random misfire.

A bit of background:

When I bought the car it had been more or less sitting idle for about 3 months.

Took it for quite a lengthy test drive before I bought and all was ok.

Anyway, got it home and after a couple of days, (waiting for Insurance and VED to clear) I decided to take it to the local Tesco Handwash, (used them before and they do a good job) then proceeded to put in some fuel as it was pretty much empty, and proceeded to go up to my local Sainsburys as they have a good Tyre Pump/Gauge.

It is about a mile up the motorway so gave it a bit of welly - nothing severe or high-revving - but when I stopped at the lights at the end of the offramp I noticed it was like lurching forward, as if I was releasing and applying the brakes all the time.
When I pulled away there was a definite misfire - could feel it! I thought, "very strange - never done that before"?

Anyway, parked up at the Air, switched off and checked my tyres - which weren't too bad really.

Got in and expecting it still to misfire - nothing! As sweet as a nut.... And has been ever since until today. (It has been about 13 days since I did the tyres by the way - behaved all that time).

Today it kept coming and going, usually going once switched off and then on again. Very strange.

So got home and I got one of those cheap Bluetooth OBDII Readers and did a Fault-Check.

It came back with a host of Codes, stupidly I did not take a note of them as I thought I had better clear them as they might be old Fault Codes in the ECU. Cleared the Codes and ran it again - NOTHING! No Codes at all....??? And no misfire.

Took it for a spin doing everything to try to bring the misfire back, (flooring it, kicking down, you name it) - nothing. Got home ran it for Codes again - Clear!

How can it misfire on one day then nothing for nearly 2 weeks then do it again...???

I'm lost here.... But I hear the MAF can cause this

Any ideas?

ps. By the way when I say misfire it feels like there are numerous pistons not firing, not just one.

Thanks in advance.

ps. Next time it happens I will remember to record the Codes.... Yes I know, stupid of me! No-one is more pissed off than me!

 

[BlackC55]

This is typical of an air mass sensor failure.

 

[MangoMan]

This is typical of an air mass sensor failure.

Thanks Ollie.

Please excuse my ignorance, but would that be the same as "MAF"? And would you recommending changing it out? I understand there are 2 types for this car? My E/N: is 113960 30 165699 What one would I need please? Thanks.

Just as a sidenote, drove around for over an hour this morning on motorways and A/B roads and nothing - sweet as you like! And No Fault Codes......??? Go figure!

 

[BlackC55]

Thanks Ollie.

Please excuse my ignorance, but would that be the same as "MAF"? And would you recommending changing it out? I understand there are 2 types for this car? My E/N: is 113960 30 165699 What one would I need please? Thanks.

Just as a sidenote, drove around for over an hour this morning on motorways and A/B roads and nothing - sweet as you like! And No Fault Codes......??? Go figure!

Olly has gone home poorly so this is Natacha replying! I believe it is the same thing yes!

 

[MangoMan]

Thanks Natacha..... I hope it is not this Flu bug doing the rounds - I hear it is really bad!
But when he gets back if you can just him about the other bits regarding the MAF please?
Thanks.
Take care.

 

[BlackC55]

Thanks Natacha..... I hope it is not this Flu bug doing the rounds - I hear it is really bad!
But when he gets back if you can just him about the other bits regarding the MAF please?
Thanks.
Take care.

It is the flu bug thing yes but please dont encourage him...there's been lots of sniffling and 'dying' this morning...Man Flu

Natacha

 

[MangoMan]

Hi.

Just a bit of follow-up.

Misfire still coming and going - worse in wet weather.

Anyway, I was told to check the connections on the O2 Sensor (Bank 2 Sensor 1) and found that the Sensor was loose by about 2-3 turns - tightened it and cleaned connection.

I am still getting these symptoms now.

1) Under normal driving condition - low to moderate throttle, no misfire.
2) Under hard acceleration the misfire happens and then persists after that even under low to moderate throttle.
3) Stop, turn off and restart - misfire gone.
4) Engine running but in Park it will rev freely and nicely up to 4000rpm. Go over 4000rpm and it starts behaving like you have hit the Rev-Limiter and it will not rev more than 4000-4200rpm. (Fluctuating. Like a Rev-Limiter). Redline is normally at 6500rpm.
5) Readout below on OBDII using Torque App:



I have cleaned the MAF Sensor and checked all the leads on Bank 2 - all look OK.

I'm confused because if you drive around sedately it will behave itself all the time, for days!! - even at motorway speeds! Just as long as you don't floor it or make it kick-down.

Any suggestions more than welcome as to be honest I've just about had enough!!

Thanks in advance.

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NB. Just to let you know that my other issue with the C/L and Soft-Close, it's seemed to have sorted itself out the same day it started...???

 

[MangoMan]

NB. I just thought I would mention that the strange thing is, is if I use the "Tiptronic", ie put it in 1st Gear and pull away and hold it, it will pull like a train and rev up to the redline, (or thereabouts) real sharpish. Then I change to 2nd and it still pulls cleanly. Then I have to back off because of speed issues. Then I just cluck it down to "D" and then all ok. No misfire.

But if I try the same thing just leaving it in "D" it'll rev up to around 4 grand and then it will stutter and misfire. And it will remain misfiring even if I try the "Tiptronic", it will change down but no acceleration.

If I stop, switch off - start, all's back to normal..... How weird is that???!!!

 

[MangoMan]

It is the flu bug thing yes but please dont encourage him...there's been lots of sniffling and 'dying' this morning...Man Flu

Natacha

Hi. Ollie/Natacha.

Would you guys have a "good" MAF that I could try out to see if it is actually the MAF Sensor please?

 

[Old spanners]

NB. I just thought I would mention that the strange thing is, is if I use the "Tiptronic", ie put it in 1st Gear and pull away and hold it, it will pull like a train and rev up to the redline, (or thereabouts) real sharpish. Then I change to 2nd and it still pulls cleanly. Then I have to back off because of speed issues. Then I just cluck it down to "D" and then all ok. No misfire.

But if I try the same thing just leaving it in "D" it'll rev up to around 4 grand and then it will stutter and misfire. And it will remain misfiring even if I try the "Tiptronic", it will change down but no acceleration.

If I stop, switch off - start, all's back to normal..... How weird is that???!!!

If it was the MAF I can't see how it would only effect the cylinders on one bank and not at all when you use the tiptronic. I would be looking more towards the ECU and perhaps a corroded connector.
You may need a more detailed reading of any fault codes.

 

[Bellow]

I'm confused because if you drive around sedately it will behave itself all the time, for days!! - even at motorway speeds! Just as long as you don't floor it or make it kick-down.

Classic symptom of failing ignition system - hasn't the energy to introduce the spark into the higher cylinder pressure that ensues from wider throttle opening.

Maybe MAF failure can do the same, but failing ignition absolutely will.

 

[MangoMan]

Classic symptom of failing ignition system - hasn't the energy to introduce the spark into the higher cylinder pressure that ensues from wider throttle opening.

Maybe MAF failure can do the same, but failing ignition absolutely will.

If it is the MAF how is it that only one bank of cylinders are effected?

Secondly, what would cause all 4 coil packs or 8 spark plugs, or both, to fail simultaneously?

 

[Old spanners]

If it is the MAF how is it that only one bank of cylinders are effected?

Secondly, what would cause all 4 coil packs or 8 spark plugs, or both, to fail simultaneously?

Just remembered you noted it was worse in wet weather, again this may point to a corroded connector. Are there any drains around the windscreen that may be partially blocked? I've no idea of the layout of where the various units are situated but may be worth a look especially as the faults are specific to one bank of cylinders.

 

[Bellow]

If it is the MAF how is it that only one bank of cylinders are effected?

No idea. I merely mentioned MAF as others say it's failure prone and for all I know, maybe is the culprit. However, what you describe as symptoms (ie, load) are signs of failing ignition.

Secondly, what would cause all 4 coil packs or 8 spark plugs, or both, to fail simultaneously?

Given the multitude of cylinders affected - I'd trace back to common source, eg, ECU.
HT side can fail (due to failing insulation most commonly) but LT side can also. Overheating of electronic components typical there. Higher load (ie, more throttle) stresses both HT and LT sides. Bad earths will also be tested under load.

 

[BlackC55]

Hi. Ollie/Natacha.

Would you guys have a "good" MAF that I could try out to see if it is actually the MAF Sensor please?

Unfortunately not the sort of thing we have laying around here

 

[MangoMan]

Unfortunately not the sort of thing we have laying around here

No problem - thanks anyway....