Lumpy idle - help please

UK forum for general and technical discussion about the Z3 roadster
Post Reply
Alan W
Joined: Thu 20 Jun, 2013 10:56
Posts: 670

  Z3 roadster 2.8
Location: Bexley, Kent UK

Lumpy idle - help please

Post by Alan W »

Car 2.8 auto - been driving like a dream until this afternoon.. now ticks over lumpy like it's running on 4 cylinders instead of 6.. drives perfect, smooth and fast.. but when ticking over its lumpy as hell.. ideas and suggestions welcome
1999 facelit Z3 Roadster 2.8 Auto in Cosmos Black aka 'Gloria'
Image
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Lumpy idle - help please

Post by Southernboy »

1. check all the rubber "hoses" from the MAF to the throttle - remove them and check for cracks where air can leak in.
2. Spark plugs.
3. injectors - use a short length of 8mm plastic hose / pipe and place next to each injector with the other end in your ear, and listen for rythmic "ticking" sound as they are opened / closed during idle. If you find an "oddity" - use an injector cleaner additive in the fuel as a first resort before going to a mechanic. If it doesn't sort it you may need to have the injectors professionally cleaned / serviced.
4.Check the CVV (Crankcase ventilation valve) that it's still operational - located below the intake manifold.
5. Possibly sticking valve lifters - Get a decent engine flush additive - follow the instructions on the product and do an oil change afterwards.
6. check the air filter element is still serviceable and air can pass through unrestricted.
7. could be one or more of the individual spark plug coils - use the same 8mm plastic pipe and listen for even firing at each plug - any misfire can be checked by changing the coil to another plug for confirmation of a faulty coil.
"Normal is overrated"
Image

Z3 Upgrades and Additions
Alan W
Joined: Thu 20 Jun, 2013 10:56
Posts: 670

  Z3 roadster 2.8
Location: Bexley, Kent UK

Re: Lumpy idle - help please

Post by Alan W »

Thanks Barry.. In that order?
1999 facelit Z3 Roadster 2.8 Auto in Cosmos Black aka 'Gloria'
Image
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Lumpy idle - help please

Post by Southernboy »

Not in any order, but useful to do the ones that don't cost anything first... :wink:
"Normal is overrated"
Image

Z3 Upgrades and Additions
Alan W
Joined: Thu 20 Jun, 2013 10:56
Posts: 670

  Z3 roadster 2.8
Location: Bexley, Kent UK

Re: Lumpy idle - help please

Post by Alan W »

Looks like l've found the culprit.. this little elbow on the air intake system.. could actually put my finger into the split..

Image
1999 facelit Z3 Roadster 2.8 Auto in Cosmos Black aka 'Gloria'
Image
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Lumpy idle - help please

Post by Southernboy »

There you go - tape it up and start the motor to check if it sorts the issue - then order a new part... :wink:
"Normal is overrated"
Image

Z3 Upgrades and Additions
Alan W
Joined: Thu 20 Jun, 2013 10:56
Posts: 670

  Z3 roadster 2.8
Location: Bexley, Kent UK

Re: Lumpy idle - help please

Post by Alan W »

Cheers Barry ☺
1999 facelit Z3 Roadster 2.8 Auto in Cosmos Black aka 'Gloria'
Image
User avatar
colb
Joined: Sat 05 May, 2012 22:46
Posts: 690

  Z3 roadster 1.8 TU
Location: Newport South Wales UK

Re: Lumpy idle - help please

Post by colb »

Looks like you found the culprit, noticed the list of things to check didn't include the idle control valve ICV, that may have been worth a check and clean if the hole wasn't the cause.
http://www.realoem.com/bmw/enUS/showpar ... 3411744713

Colb
Colb
1999 BMW 1.8 Z3
2003 BMW 2.5 Z4
1998 Honda Deauville NT650V
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Lumpy idle - help please

Post by Southernboy »

Good call on the ICV - Not as common a fault though.
"Normal is overrated"
Image

Z3 Upgrades and Additions
Post Reply