Running rough

Rufley

Newbie
British Zeds
Joined
Apr 10, 2023
Points
3
Location
Sheffield
Model of Z
3 1.8L
My 1997 Z3 1.8l is sporadically running rough and 'conking out' (will restart by dropping into 2nd going downhill). Was doing this before its recent service at Quarry Motors Sheffield (~35k on the clock) but disappointingly continues to do it now. No clear pattern, it happens whether hot or cold, perhaps associated with coasting down hill (flooding?). It's clearly only firing on one or two cylinders and I can usually clear it by running the revs up. Any suggestions appreciated, thanks.
 

t-tony

Zorg Expert (II)
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British Zeds
#ZedShed
Joined
Dec 31, 2013
Points
226
Location
Torksey Lock,Lincoln, England
Model of Z
E89 Z4 23i Auto
Get a code reader and check for fault codes. I suspect cam position sensor failing.

Tony.
 

colb

Zorg Guru (V)
British Zeds
Joined
Nov 25, 2012
Points
178
Location
Newport, South Wales,UK
Model of Z
Z3 M43 1.8 (1999) and Z4 E85 2.5 (2003)
First thing would be to put a code reader on it to see if any codes have been set which may point you in the right direction to fix this issue.
Sounds like its loosing spark, could be the ignition coil breaking down, replacing it with a known good unit might be the way to go paticulaly so if you have misfire codes when its scanned for codes. Check the condition of the plugs, a set of new ones would do no harm and rule them out as a cause of the issues you have. Plug leads should be examined for any damage, replace any that look iffy you could do a resistance check on them using a voltmeter. Leads don't last forever and the age of them now may well be a cause as they breakdown. If it was serviced, what did they replace already?
@t-tony makes a good suggestion re the camshaft sensor, when code read if its iffy then I would expect it to have set a code. Replace with an OEM brand, dont fit cheap ones.
 

NZ00Z3

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New Zealand Zeds
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Dec 9, 2014
Points
158
Location
Timaru, New Zealand
Model of Z
3.0L, 2.8L, 2.0L Z3 Roadsters
While you have the code reader plugged in, go to the "Live Data" section and check the fuel trims. Any >10% indicate a vacuum leak.
 

Andyboy

Zorg Guru (II)
Joined
Jun 2, 2019
Points
119
Location
SHEFFIELD
My 1997 Z3 1.8l is sporadically running rough and 'conking out' (will restart by dropping into 2nd going downhill). Was doing this before its recent service at Quarry Motors Sheffield (~35k on the clock) but disappointingly continues to do it now. No clear pattern, it happens whether hot or cold, perhaps associated with coasting down hill (flooding?). It's clearly only firing on one or two cylinders and I can usually clear it by running the revs up. Any suggestions appreciated, thanks.
I'm in Sheff and have the old BMW dealer code reader - you're welcome to bring it over.
 

Andyboy

Zorg Guru (II)
Joined
Jun 2, 2019
Points
119
Location
SHEFFIELD
That problem can also be the idle control solenoid on the front of the inlet manifold - this little b*****d.
 

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colb

Zorg Guru (V)
British Zeds
Joined
Nov 25, 2012
Points
178
Location
Newport, South Wales,UK
Model of Z
Z3 M43 1.8 (1999) and Z4 E85 2.5 (2003)
@Andyboy makes a good point regarding the idle control valve, whip it off and give it a good clean with carb cleaner spray so the internal flap moves freely when its given a shake. The do get gummed up and stick, easy enough to take it off but take care with the gasket when taking it off.
@NZ00Z3 also makes a good point re checking the fuel trims in live data, high readings will point to vaccum air leaks across the system, split or holed rubber pipes, intake boot, and blanking plugs at the rear of the intake manifold that split and fall off.
Smoke test is probably the best way of finding any leaks.
 

Zephyr

Zorg Guru (III)
Supporter
Joined
Aug 10, 2022
Points
136
There is a video in youtube about the idle valve and he pries it open. Do not do this.
He clearly destroys the valve.
Just clean with carb spray and blow with air.
but whatever you do, do not open it. (235€ for a new one I paid and I still feel an idiot for doing this although I knew it was wrong).
 
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