Jump to content
Sign in to follow this  
Statek

M44B19 misfire at idle

Recommended Posts

Hi guys,

I've got a 1998 Z3 which has a weird misfire at idle. It feels absolutely fine while driving, but it vibrates at idle. It's been slowly getting worse, or at least more noticeable. 
The revs at idle are at around 650rpm, which seems ok. If you stand by the exhaust pipe, you can hear it misfiring maybe once every few seconds though.

What I've done so far:
- New spark plugs
- New PCV valve
- Cleaned throttle body
- Cleaned IAC valve
- Visually checked for vacuum leaks - all hoses are like new, the car has <60,000kms
- Replaced the coil with one from another car

Cleaning the throttle seemed to help a little, but definitely still has the intermittent miss.

My 318ti has a similar issue, but that car is a 'race-car-in-progress' so (A) the shaking doesn't bother me there, and (B) it doesn't tend to sit on idle for much of its life.

Any pointers as to what to look for?

Cheers, Kris.

p.s. Not sure if related, but it tends to get around 10L/100km (or 10km/L if you prefer), which seems a bit high for a 1.9 which doesn't get driven all that hard.

Edited by Statek

Share this post


Link to post
Share on other sites

I was gonna say pcv , but I see I have done it ,

there are vac hoses attached to the injectors , check those for splits,

remove top half of the manifold to get to them.

also the hose going to the PCV perish with oil going through them and split .

try spraying some engine start or brake cleaner , wd40 around the the intake system see if the idle picks up.

could be a bad MAF.  can scan for you if you bring it around.

bad engine mounts can cause vibrations on these.

fuel economy sucks on automatic m44 m43 m42 engines

as they use a 4speed GM box (like a holden trimatic with a overdrive)

5spd manuals will use far less fuel , more like 7-8l per 100km

 

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for the leads Brent, I'll check those things and see what I find. 
If nothing comes of it, then I'll get in touch to arrange a scan.

Cheers!

Share this post


Link to post
Share on other sites

Does it misfire when cold and hot? DISA valves can leak and act up

Nothing beats a smoke machine for finding vac leaks

 

  • Like 1

Share this post


Link to post
Share on other sites
2 hours ago, Eagle said:

Does it misfire when cold and hot? DISA valves can leak and act up

Nothing beats a smoke machine for finding vac leaks

 

Yes, both cold and hot, although it is more noticeable when it warms up and the revs drop further. I'll look into that.

Yeah, the more BMWs I acquire, the more I think i'll have to look at making a smoke machine for myself :lol:

Share this post


Link to post
Share on other sites

Further checked:
- PCV hose
- Injector hoses
- Cleaned MAF (no change), swapped MAF with 2 spares (no difference)
- Checked DISA valve while manifold is off - looks ok, closes and opens when applying vacuum as expected

I'm not ruling out worn engine mounts for some of the vibration, but the engine definitely has a misfire at idle.

While the manifold is off, I've noticed the number 3 and 4 injectors have wet spots around the top. I'm pretty sure that leaking injectors could cause this misfire, although I'm not sure why it's only affected at idle. Thinking about it, it would also be increasing fuel consumption... Hmm..

Looks like I'm going to need some new o-rings, and continue tracking this down afterwards (although fingers crossed this might be the cause).

All.thumb.jpg.050f4d28e544397e606937b6e2c2327f.jpg

Share this post


Link to post
Share on other sites

Super common to have cam timing doing this, the gears are adjustable and fairly easy to fix 

I have a timing tool cut for these for this reason 

  • Like 1

Share this post


Link to post
Share on other sites
38 minutes ago, dirtydoogle said:

Super common to have cam timing doing this, the gears are adjustable and fairly easy to fix 

Hmm... didn't think something like this would develop before the engine even hit 60,000kms. Good to know it's common though. I'll look into it, thanks!

Share this post


Link to post
Share on other sites

The cam timing is set differently to different markets from what I can tell. Mostly a compromise with noise/vibration vs throttle response 

However eliminate everything else is always a good idea 

Share this post


Link to post
Share on other sites

While waiting for the o-rings to arrive, I've been thinking (dangerous!). I was still very suspicious of the DISA valve so I pulled it out - easy enough.

Checked visually - it has a little play on where the lever holds the flap, but nothing terrible. Applying vacuum to (read: sucking) the little hole under the solenoid closes the flap. However, manually closing the flap and looking through the hole at the diaphragm I noticed that only around 3/4 of the rubber diaphragm move with the lever, and the rest remains attached to the housing. Looks like I may have found the problem.

I can't seem to find a rebuild kit for the M44 DISA valve... anyone have any leads?

I might pop up to pick-a-part on the weekend and pull them until I find a good one, as I don't really want to spend $400 on one just to find out it doesn't fix the issue.

DISA.jpg

Edited by Statek

Share this post


Link to post
Share on other sites
1 hour ago, Statek said:

While waiting for the o-rings to arrive, I've been thinking (dangerous!). I was still very suspicious of the DISA valve so I pulled it out - easy enough.

Checked visually - it has a little play on where the lever holds the flap, but nothing terrible. Applying vacuum to (read: sucking) the little hole under the solenoid closes the flap. However, manually closing the flap and looking through the hole at the diaphragm I noticed that only around 3/4 of the rubber diaphragm move with the lever, and the rest remains attached to the housing. Looks like I may have found the problem.

I can't seem to find a rebuild kit for the M44 DISA valve... anyone have any leads?

I might pop up to pick-a-part on the weekend and pull them until I find a good one, as I don't really want to spend $400 on one just to find out it doesn't fix the issue.

DISA.jpg

got good ones in stock

 

Share this post


Link to post
Share on other sites

Just replaced the parents one (again) which had the same issue, it was creating a small vacuum leak out the rear pipe fitting and the shitty flap was rattling as well. 

DISA prices keep increasing in price it seems, the last one years ago was $350 NZD, this one was over $600 with shipping and GST added.

Edited by Eagle

Share this post


Link to post
Share on other sites

Could just rip the flap out and be done with it. You wont notice any lack of torque or reduced response from a M44, will you? :lol:

Share this post


Link to post
Share on other sites
14 hours ago, Eagle said:

Just replaced the parents one (again) which had the same issue, it was creating a small vacuum leak out the rear pipe fitting and the shitty flap was rattling as well. 

DISA prices keep increasing in price it seems, the last one years ago was $350 NZD, this one was over $600 with shipping and GST added.

Try www.partsouq.com for parts next time. I've ordered quite a few bits from them, some genuine and some aftermarket, almost always cheapest on the market. The genuine BMW DISA valve from these guys, including shipping would end up around $380.

Share this post


Link to post
Share on other sites
11 hours ago, Young Thrash Driver said:

Could just rip the flap out and be done with it. You wont notice any lack of torque or reduced response from a M44, will you? :lol:

It's an idea. The automatic gearbox will compensate for the lack of torque... B)

Share this post


Link to post
Share on other sites
9 hours ago, Statek said:

Try www.partsouq.com for parts next time. I've ordered quite a few bits from them, some genuine and some aftermarket, almost always cheapest on the market. The genuine BMW DISA valve from these guys, including shipping would end up around $380.

Yeah i found a few places in Europe that had it for around that but shipping times were 2-3 weeks and i needed it asap. The GST was the big hit as the valve its self was just over $400

Share this post


Link to post
Share on other sites

Kept trying to sort the issue out.

- Scanned ECU - no codes, diagnostics didn't show anything interesting
- Replaced DISA
- Swapped cam sensor with one from another vehicle
- Unplugging the O2 sensor didn't change anything, so replaced the O2 sensor with a new Denso sensor (only around $40US, so worth a shot)

I've had several friends use the car, and nobody noticed anything wrong, so I'm beginning to think I'm being overly sensitive.
If it keeps bothering me, I'll attempt the timing, but I'm overly busy at work recently and don't really have time/desire to mess around with it.

Edited by Statek

Share this post


Link to post
Share on other sites

Have you tried swapping the cam position sensor?

Share this post


Link to post
Share on other sites
30 minutes ago, gjm said:

Have you tried swapping the cam position sensor?

Yes :)

Sorry, I've done quite a few things in the last few months and no longer remember them all. I'll add that to my previous post.

  • Like 1

Share this post


Link to post
Share on other sites

You're certainly it's a miss and not broken down engine mounts? The 4 cyl mounts are fluid filled

Share this post


Link to post
Share on other sites
12 hours ago, dirtydoogle said:

You're certainly it's a miss and not broken down engine mounts? The 4 cyl mounts are fluid filled

Yep, replaced those too :) 

¯\_(ツ)_/¯

Share this post


Link to post
Share on other sites

The M44 had an inherent rough idle issue which could be overcome in most instances by a  mod to camshaft timing. Have a look...just google : " E36 BMW M44 camshaft timing modification"

Share this post


Link to post
Share on other sites
2 hours ago, B.M.W Ltd said:

The M44 had an inherent rough idle issue which could be overcome in most instances by a  mod to camshaft timing. Have a look...just google : " E36 BMW M44 camshaft timing modification"

Thanks Glenn, I have read quite a few posts about this mod. It's an option, I was a bit iffy about doing anything to the timing due to the cars low mileage - surely it hasn't been like this from factory? 

In a couple of weeks, once I've replaced the blower fan on my friends Mini and clutch on my sister's Corolla, I might attempt adjusting the timing. My 318ti has a similar feeling idle, but it's done 260kms and the idle doesn't bother me since it lives near the redline when it's being driven. Might experiment with this car first.

Edited by Statek

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×