engine problems

UK forum for general and technical discussion about the Z3 roadster

Moderator: Gazza

Post Reply
wizard4
Joined: Sun 12 Oct, 2014 13:40
Posts: 42

  Z3 roadster 1.9

engine problems

Post by wizard4 » Sat 08 Nov, 2014 21:33

Ok a new development has started today, when I switch off the engine, it carries on running for a few seconds. Any ideas as to the problem, fingers crossed it aint going to be expensive to fix. :(

User avatar
Topperz
Joined: Tue 20 Nov, 2012 20:08
Posts: 89

  Z3 roadster 2.0

Re: engine problems

Post by Topperz » Sat 08 Nov, 2014 21:50

My wife has that problem when I try and turn her off

She's expensive

If I remember correct year ago it used to be called pre-ignition

Sure someone will be along shortly to chip in
The only bad thing about owning a Z3 is bedtime .......boing!! time for bed said zebedee

Z3 cosmos black individual 2.0

X1 /MSport XDrive 2.0d mineral white

wizard4
Joined: Sun 12 Oct, 2014 13:40
Posts: 42

  Z3 roadster 1.9

Re: engine problems

Post by wizard4 » Sat 08 Nov, 2014 22:17

Brilliant toppez im still laughing sweet dreams buddy. lol :lol:

Mike Fishwick
Joined: Fri 19 Jun, 2009 11:27
Posts: 1991

  Z3 roadster 2.8
Location: Daglan, France

Re: engine problems

Post by Mike Fishwick » Sun 09 Nov, 2014 13:14

Give us more details - after switching off, does the engine run smoothly, or roughly? If roughly, then it could be due to an accumulation of carbon in the combustion chambers, indicating a need for a good thrash to blow it away. Do you use 95 octane fuel? If so this is a prime cause of carbon accumulation.

Having said that, at switch off the fuel supply should be turned off, but you could also have a leaking injector of two - again, use decent fuel as amtter of course, as 95 will cause build ups of resin etc on the nozzles. A decent injector cleaner would be a good idea anyway.

If the engine continues to idle normally, the answer could be a simple electrical fault which is maintaining power to the engine management system, such as a faulty ignition switch, a sticky contacts in the DME relay. Do the headlamps go out when you turn the ignition off and the engine continues to run?
A Z3 is not just for Christmas - it's for life!

wizard4
Joined: Sun 12 Oct, 2014 13:40
Posts: 42

  Z3 roadster 1.9

Re: engine problems

Post by wizard4 » Sun 09 Nov, 2014 22:45

Thanks for the reply mike, well where do I start, 95 octane is all I can get here, running smoothly well its rough on idling, it appears to run at 600rpm, with an occasional misfire. Sometimes when I turn the ignition on the key stops before I can do a full turn, so I have to take the key out and start again then its fine. Today the engine stopped as soon as it was switched off, so seems to be intermittent, as for the rpm what should it be, I have only had the car about 6 weeks, In that time I replaced the cat as it disintegrated inside, then I had to replace the exhaust system from the cat back, as the wrong one had been fitted, and was falling off, so not a great start, the mileage is currently 134,859.
Cheers :roll:

Rafolian
Joined: Wed 27 Feb, 2013 08:41
Posts: 547

  Z3 roadster 2.8

Re: engine problems

Post by Rafolian » Mon 10 Nov, 2014 07:11

If your have been having intermittent problems with the ignition switch, this could be where the problem lies.

User avatar
Southernboy
Joined: Thu 07 Oct, 2010 13:39
Posts: 6312

  Z3 roadster 3.0i
Location: Johannesburg

Re: engine problems

Post by Southernboy » Mon 10 Nov, 2014 09:35

.my 10cents worth.....
1. 600rpm at idle is about right...could be closer to 700rpm and that would be very right..
2. the odd misfire can be caused by a sticky valve lifter.. the cure is somewhat aggressive... Take the car out onto a road where you can accelerate up to around 140 Kph in 5th...then drop it down to 4th and let the clutch out so that the rpm jumps up...llet the car use the gear to slow to around 100 Kph, then go back up to 140 and repeat several times... this often will "flood" the upper cylinder and head with oil and clear the sticky...If it persists, it is recommended you get a good engine flush to add to the oil and do the same as described above. The engine flush will / should clean out any muck... you will be in for an oil change though...
3. add a can of injector cleaner to your fuel at next fill up
4. add a can of "valve ease" to your fuel

The continued running after turning off the ignition is called "pre-ignition" as described previously. It is generally caused by carbon deposits on the tip of the spark plugs or carbon deposits on the exhaust valves.. in which case it could be described as "detonation".. these deposits get extremely hot and glow acting as a heat source to continue igniting fuel. When you turn off the ignition, there is normally a continued flow of fuel to allow for the next start up, and this is what feeds the motor in your case at switch off... I would recommend you get the plugs out and check them for contamination. If it's being caused by deposits on the exhaust valves, there's nothing for it but to get the cylinder head off and have it cleaned and those valves checked for burning / pitting etc.
Here is a link to understanding the issue...http://www.brownsmarina.com/tech-preign.html

All the above are methods I used on my 2.8 which had a similar issue and were recommended to me by a BMW mechanic. It did cure the problem - eventually. Which specific treatment was responsible I can't say as I used them all. In fact I did the engine flush thing 3 times, the injector cleaner as many times at least and the valve ease at least twice...
Hope this helps..
Re the key issue, I would say you have a mechanical problem in the ignition barrel of the lock and perhaps a small squirt of WD40 into the keyhole may suffice to sort something like that...
"Normal is overrated"
Image

Z3 Upgrades and Additions

Jonco
Joined: Sat 04 Jun, 2011 08:24
Posts: 382

  Z3 roadster 1.9
Location: Cheshire

Re: engine problems

Post by Jonco » Mon 10 Nov, 2014 09:49

wizard4 wrote:......... Sometimes when I turn the ignition on the key stops before I can do a full turn, so I have to take the key out and start again then its fine. Today the engine stopped as soon as it was switched off, so seems to be intermittent, ...........
There may be two separate problems. The engine possibilities have been covered above but the key problem may be the start of a ignition barrel problem. Mine failed early this year http://www.zroadster.net/forum/viewtopi ... =5&t=39608 but has been Ok since ( tempting fate) after re-engaging bottom connector.

Rafolian
Joined: Wed 27 Feb, 2013 08:41
Posts: 547

  Z3 roadster 2.8

Re: engine problems

Post by Rafolian » Mon 10 Nov, 2014 11:08

If it is intermittent, ie sometimes switches off right away that would rule out pre-ignition/carbon build up as it would happen all the time if that was the case surely? I would look at the ignition switch before I started pulling the head off.

User avatar
Southernboy
Joined: Thu 07 Oct, 2010 13:39
Posts: 6312

  Z3 roadster 3.0i
Location: Johannesburg

Re: engine problems

Post by Southernboy » Mon 10 Nov, 2014 11:12

Carbon build up could be the problem since it will depend on the running temp at the time of switch off... if you have been driving hard at high speed or even low speed in traffic, the motor will be hotter than on a short slow run... so there is no hard and fast rule to say it should happen every time or intermittently.
"Normal is overrated"
Image

Z3 Upgrades and Additions

Mike Fishwick
Joined: Fri 19 Jun, 2009 11:27
Posts: 1991

  Z3 roadster 2.8
Location: Daglan, France

Re: engine problems

Post by Mike Fishwick » Mon 10 Nov, 2014 13:32

From your desription the ignition switch sounds as if it is the culprit. If you want tobe sure, remove the lower part of the column shround behind the steering wheel to expose the connectors on the switch. Next time the problem occurs, pull the thick red wire off the switch - this will kill the supply to the switch, and will stop the engine.


However, if the key does not turn off all the way you can be sure that the key or the lock is the problem. If you have a spare key, give it a try, and in any case lubricate the lock by injecting WD40 into it, using the small tube which comes with the aerosol, followed by a little engine oil. Like any other mechanism, lock to not like to be operated dry.
A Z3 is not just for Christmas - it's for life!

Post Reply

Who is online

Users browsing this forum: No registered users and 10 guests