Rough Idle and Misfire

[Z4JB]

All,

Apologies for starting a thread on something many people have had, but I’m wanting to try and narrow the issue down before throwing more money at the problem.

I have recently got my hands on a brilliant looking and great condition 2004 3.0i. I have however been battling with an issue, the elusive misfire. No codes (typical) and is only really noticeable under acceleration, in 2nd and 3rd predominantly although I have noticed it through all 6 gears (the car is manual). The car has just had a major service at an Indy before I purchased it.

To try and resolve the misfire, I replaced all 6 ignition coils with 6 brand new ones. The car now runs and sounds much better, the misfires are now less common, however the rough idle (which always happens but sometimes is worse than others) comes and goes as it did before the coils were replaced. My concern is clearly, something is still causing a misfire.

Attached is a video, of a concerning noise when lightly revving the throttle, almost like a choked noise, like the car is wheezing at those low RPM’s (coming seemingly from inside the intake manifold). This to me, doesn’t sound brilliant and leads me to wonder if before replacing all kinds of weird and wonderful sensors, whether this might be the issue and if so - what is it?

Thank you for any direction and help!

[youtube] https://youtube.com/shorts/CffJKpm8WGY?feature=share[/youtube]

 

[bigwinn]

Evening

Good thread!

My instant go to would have been coils as that’s my past experiences.

Can’t remember where you are based but I would get it on inpa to see if a certain cylinder is underperforming and diagnose from there

Happy to help if I can

Stuart

 

[bigwinn]

Assume you have checked the intake boot

The noise you describe is fairly common

However it does sound more tappy than usual have you checked your DISA?

 

[Z4JB]

Assume you have checked the intake boot

The noise you describe is fairly common

However it does sound more tappy than usual have you checked your DISA?

I haven't checked the DISA but I have checked the boot and all seems well there. I have noticed however that under hard acceleration there is at times a lack of power particularly where you'd expect DISA to kick in around 4000rpm (having experienced a couple of misfires around 2/3000), so you could be spot on. If the DISA has failed and is still in one piece at least, how could you tell it has failed?

 

[bigwinn]

Get the DISA off

Simple job 2x t40 bolts and see if any play in the vane or the pivot pin

It’s a rattle you’ll hear if it’s starting to fail and I’m sure I’m hearing something like that on your video

If I’m wrong at least it’s checked

 

[enuff_zed]

Stuart beat me to it with the Disa.
If not that then:
Recently discovered my Autophix 5900 reader will show a live feed of the vanos cam angles. If you can find something similar then its worth a check.
The 53-plate 3.0i I'm currently resurrecting shows no movement whatsoever at any rev range, so the vanos is fubar'd.

 

[Z4JB]

Evening

Good thread!

My instant go to would have been coils as that’s my past experiences.

Can’t remember where you are based but I would get it on inpa to see if a certain cylinder is underperforming and diagnose from there

Happy to help if I can

Stuart

I really appreciate the advice Stuart, thank you! That's a great idea, I have had this done at an Indy close to me before for a previous car so would be good for me to return with the Z4 and see what the outcome would be, I'll give them a ring tomorrow. For your above comment on the DISA removal, I'll do this in the morning to check the state of play. Could the valve not opening correctly cause misfires? (I can see how it would certainly cause a lack of power). I am assuming there should be 0 play in the vane or pivot pin?

 

[bigwinn]

Evening

Good thread!

My instant go to would have been coils as that’s my past experiences.

Can’t remember where you are based but I would get it on inpa to see if a certain cylinder is underperforming and diagnose from there

Happy to help if I can

Stuart

I really appreciate the advice Stuart, thank you! That's a great idea, I have had this done at an Indy close to me before for a previous car so would be good for me to return with the Z4 and see what the outcome would be, I'll give them a ring tomorrow. For your above comment on the DISA removal, I'll do this in the morning to check the state of play. Could the valve not opening correctly cause misfires? (I can see how it would certainly cause a lack of power). I am assuming there should be 0 play in the vane or pivot pin?

Very possible.

On mine there was a definite sticking at 4K revs which prompted me to go looking

Good luck keep us posted

 

[Z4JB]

Thank you both, I'll see what state the DISA is in and if there is play I'll look to replace - hopefully I'm not dealing with a VANOS issue, MPG is still reasonable on motorways (34mpg) and I wouldn't say there is any throttle hesitation, just subtle misfires, slight rough idling and a lack of power higher up the rev range although all 3 of those issues could be VANOS related The things we do for the ones we love eh, someone has to fix em or they'll end up lost in the automotive ether.

 

[enuff_zed]

Thank you both, I'll see what state the DISA is in and if there is play I'll look to replace - hopefully I'm not dealing with a VANOS issue, MPG is still reasonable on motorways (34mpg) and I wouldn't say there is any throttle hesitation, just subtle misfires, slight rough idling and a lack of power higher up the rev range although all 3 of those issues could be VANOS related The things we do for the ones we love eh, someone has to fix em or they'll end up lost in the automotive ether.

If it does turn out to be vanos, and you're not confident to take it on, then head straight to bigwinn.

 

[Z4JB]

UPDATE:

So today I have made 'some' progress, however good or bad I am not sure yet and would appreciate your thoughts.

1.) Removed the DISA valve, checked for play in the valve and pin, there is no play in the pin (it doesn't move in any direction it shouldn't) however the valve itself has around 5-7mm of play before engaging. Could this be enough play to cause noticeable issues? I have ordered a new DISA for the sake of it.

2.) Having replaced the 6 ignition coils in the week (4 were original, 1 was Delphi and 1 was Bosch) with 6 new Bosch coils (Part No 413110187) I thought I might as well replace the spark plugs as well (even though they have just been replaced on a service before I bought the car about 1000 miles ago) - why not eh! The plugs that were in there were NGK R's (BKR6EQUP) and as you'll see below in the images, 5 of the plugs were either dry or had a tiny bit of what I am hoping is fuel on the thread, but cylinder 4's plug was wet and I mean, wet. This is seen best in the image where I placed them into the cardboard sleeves the new plugs came in. It didn't feel viscous enough to be oil, nor did it smell like much, quite a thin liquid with a slight petrol smell. Surely if this was a rocker cover gasket issue I'd be seeing all 6 plugs saturated? Replaced all 6 plugs with Bosch Platinum (FGR7DQP+) and torqued to 28nm.

Replacing the plugs, the car now sounds smoother and in terms of cranking, previously it would crank 6x before chugging into life, now it only takes 4x. Took it for a good drive and when up to temp revved out in 2nd and didn't notice any misfiring (something that would normally happen). The only time there was any hesitation on acceleration I am putting down to the traction control kicking in.

Plan for tomorrow morning is to remove the new plugs after having had a drive since they've been in and see whether there is any liquid on them (at least to the same extent as the old ones). This car had better start shooting up in value is all I'll say.

2004 3.0i with 75,000mi on the clock.

 

[enuff_zed]

Don't forget that the plug holes are surrounded by separate gaskets. One that does the front three and one that does the back three.
It is entirely possible to have a leak into just one plug recess. You should be able to see that by looking down the bore when you take the plug out. So check that and see if you have a leak.
If so get yourself a kit which includes all the top cover gaskets and refresh them.
Like this:
https://www.amazon.co.uk/gp/product/B006DHV0PS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Z4JB]

Don't forget that the plug holes are surrounded by separate gaskets. One that does the front three and one that does the back three.
It is entirely possible to have a leak into just one plug recess. You should be able to see that by looking down the bore when you take the plug out. So check that and see if you have a leak.
If so get yourself a kit which includes all the top cover gaskets and refresh them.
Like this:
https://www.amazon.co.uk/gp/product/B006DHV0PS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Thanks for this, I've just ordered it from your link. In terms of work required, any specific precautions to be aware of/other kit needed for the job?

 

[enuff_zed]

Each of the bolts holding the top cover on has a seal around it. Double check those to make sure they are reusable. If not you may need to order new ones.
It's fairly straightforward to change the seals. Remove the strut brace to make life easier, then note how the cables clip in down the bottom edge and pop them out.
You'll need to disconnect all the coil leads and remove the cable carrier: again, have a look and you'll see quite easily how it clips into place.
Word of caution: when you disconnect the earth wires from the coils loom it is very easy to spin the whole bolt assembly which will twist and break the wires. You may need an open-ended spanner on the bolt underneath to hold it still while you undo the earth wire screws.
It sounds complicated but really once you have eyes on it you'll see it's all logical and straightforward.
You've already swapped the coils, so you know how they come out.

When you come to fit the main cover gasket you'll see it has 'half moon' sections at the front and rear. Where these meet the main flat edge there is quite a sharp angle which the seal struggles to fill. A small blob of gasket sealant in each of those angled corners will prevent future leaks.

 

[enuff_zed]

Here's the bolt seals.
https://www.amazon.co.uk/KIMISS-Gasket-Engine-11121726537-11121437395/dp/B07M9YPCBH/ref=sr_1_3?adgrpid=1175378829982499&hvadid=73461375307109&hvbmt=be&hvdev=c&hvlocphy=41548&hvnetw=o&hvqmt=e&hvtargid=kwd-73461317327244%3Aloc-188&hydadcr=6815_1858113&keywords=11121437395&qid=1661015252&sr=8-3
Very sorry, but if you hadn't been so damn quick on the click you could probably have picked up a kit with those in as well.

 

[Z4JB]

Here's the bolt seals.
https://www.amazon.co.uk/KIMISS-Gasket-Engine-11121726537-11121437395/dp/B07M9YPCBH/ref=sr_1_3?adgrpid=1175378829982499&hvadid=73461375307109&hvbmt=be&hvdev=c&hvlocphy=41548&hvnetw=o&hvqmt=e&hvtargid=kwd-73461317327244%3Aloc-188&hydadcr=6815_1858113&keywords=11121437395&qid=1661015252&sr=8-3
Very sorry, but if you hadn't been so damn quick on the click you could probably have picked up a kit with those in as well.

Haha, thanks for all of the above. I ordered new seals for the bolts too along with the order I'll see what difference this makes then. Long term, if oil has been leaking into the cylinders, how bad will this be to the longevity of the engine?

 

[enuff_zed]

Here's the bolt seals.
https://www.amazon.co.uk/KIMISS-Gasket-Engine-11121726537-11121437395/dp/B07M9YPCBH/ref=sr_1_3?adgrpid=1175378829982499&hvadid=73461375307109&hvbmt=be&hvdev=c&hvlocphy=41548&hvnetw=o&hvqmt=e&hvtargid=kwd-73461317327244%3Aloc-188&hydadcr=6815_1858113&keywords=11121437395&qid=1661015252&sr=8-3
Very sorry, but if you hadn't been so damn quick on the click you could probably have picked up a kit with those in as well.

Haha, thanks for all of the above. I ordered new seals for the bolts too along with the order I'll see what difference this makes then. Long term, if oil has been leaking into the cylinders, how bad will this be to the longevity of the engine?

It'll be a seep at best. It burns off in seconds. Not as if it' flooding in there.
Only issue is when you leave it a while the oil saturates the plug and you get a misfire until it burns off.

I used to run old Fords. The Pinto engine was notorious for this. Big cloud of smoke on start up, but then ran fine. Never had an issue with an engine due to this.

 

[Z4JB]

Well that's a bit of a relief, seems like an inexpensive fix as well so well worth me doing even if that isn't the issue. In terms of the 5mm worth of play in the DISA, is this worth fixing? I do have the new one on the way but I didn't know how much play there should be really.

 

[Z4JB]

UPDATE 2:

So over the last couple of days, I replaced both the DISA and the MAF. Both of these replacements seem to have solved the misfire. The car now drives really smooth and the power seems consistent and linear across the rev range.

However I am still getting on a cold start of a morning, the moment you turn the engine on the idle will start at 1100RPM, hunt up and down a little between 1100-1300 then consistently drop slowly in the same manner i.e hunt between 800-1000 then sit happily at 750RPM solid as you like for the rest of the day. This whole initial hunting goes on for about 30 seconds. Something more sinister? Or just a big engine chugging into life?

 

[enuff_zed]

Have you cleaned the Idle Control Valve?
Sits behind the Disa so that'll have to come off again.
Electrical connector on the front and the small hose from the inlet pipe goes to one side of it.
The other side is a push fit into seal. So just be careful when you put it back in.
Take it out and see if the valve moves as you twist it around. If not, a hefty dose of cleaner and make sure it comes loose and rattles about.