Very lumpy idle and failed the MOT emissions test. Car is fine when above idle speed. Vanos replaced last year(Dr Vanos) and car ran perfectly for a number of months then the lumpy idle started and gradually got worse when engine hot. No starting problems from cold.
Garage bemused and cannot suggest a solution. No faults showing on the diagnostics. However cam is showing a 17 degree retard. They managed to adjust the cam to get it through the test but the idle problem continues and cam retard is still occuring. The mechanics are not happy they had a solution and over the last month have tried a number of things.
Cam sensors replaced. MAF checked and no air leaks in the system. Their only suggestion and also that of Chris Gant at Dr Vanos is a Vanos solenoid may be causing a problem in retarding the cam without showing a fault.
Anybody got any other suggestions I can relay on to the mechanics.
Very lumpy idle
Have you tried the ICV?
These are from other posts having searched for Engine Idle:
two days before M O T , typical, engine developed really bad idle also cutting out.suspected air getting in after airflow sensor after reading other posts,seemed probable as engine revs also slow to come down after revs.turnd out to be cranckcase breather pipe come adrift. lucky me , nice easy fix .pipe halfway along block under inlet manifold , awkward to get to but just a matter of reconnecting and tightening jubilee clip, engine now right as ninepence{that means okay}
http://www.zroadster.net/forum/viewtopi ... hlight=icv
Firstly you need to carry out a Vanos check using the Diagnostic machine, they just plug the Computer into the Diagnostic Port and run the test from the tests menu. It operates the solenoids and advances and retards both exhaust and inlet sides while the engine is ticking over. The readouts tell you if there is a fault but not what type of fault. It could be the inferior seals and O-rings which cause no noise but fail over time. It is usually the excessive play in the bearings which make the Vanos growl so you can have one without the other. With my car it was the ‘O’ rings which failed on the exhaust side. The main part of the Vanos is robust and the actual solenoids only occasionally fail.
These are from other posts having searched for Engine Idle:
two days before M O T , typical, engine developed really bad idle also cutting out.suspected air getting in after airflow sensor after reading other posts,seemed probable as engine revs also slow to come down after revs.turnd out to be cranckcase breather pipe come adrift. lucky me , nice easy fix .pipe halfway along block under inlet manifold , awkward to get to but just a matter of reconnecting and tightening jubilee clip, engine now right as ninepence{that means okay}
http://www.zroadster.net/forum/viewtopi ... hlight=icv
Firstly you need to carry out a Vanos check using the Diagnostic machine, they just plug the Computer into the Diagnostic Port and run the test from the tests menu. It operates the solenoids and advances and retards both exhaust and inlet sides while the engine is ticking over. The readouts tell you if there is a fault but not what type of fault. It could be the inferior seals and O-rings which cause no noise but fail over time. It is usually the excessive play in the bearings which make the Vanos growl so you can have one without the other. With my car it was the ‘O’ rings which failed on the exhaust side. The main part of the Vanos is robust and the actual solenoids only occasionally fail.
Saw this thread on Z3mCoupe re S50 rough idle so might be worth a read ?
http://www.z3mcoupe.com/forum/showthrea ... #post84667
http://www.z3mcoupe.com/forum/showthrea ... #post84667
Thanks Bugsy for the suggestions.
The ICV was one of the first things that came to mind and a new one fitted. Had absolutely no effect. The crank case breather pipe should have been checked but you never know. However, would tend to think that would cause more problems than just a lumpy idle. As to the Vanos, been there, done that and got the tea-shirt. The Vanos readout shows no fault whereas when the seals failed last year a fault code came up.
Jonttt thanks for the link.
A missing small runner T-Piece could easily be overlooked. As above I’ll get that looked at tomorrow.
It’s the cam retard that’s really baffling me. Take out the Vanos, MAF and Lambda sensors, not a lot left. Either way when we finally get it sorted I’ll post on the site to help those with similar problems in the future.
Thanks both of you for your help.
The ICV was one of the first things that came to mind and a new one fitted. Had absolutely no effect. The crank case breather pipe should have been checked but you never know. However, would tend to think that would cause more problems than just a lumpy idle. As to the Vanos, been there, done that and got the tea-shirt. The Vanos readout shows no fault whereas when the seals failed last year a fault code came up.
Jonttt thanks for the link.
A missing small runner T-Piece could easily be overlooked. As above I’ll get that looked at tomorrow.
It’s the cam retard that’s really baffling me. Take out the Vanos, MAF and Lambda sensors, not a lot left. Either way when we finally get it sorted I’ll post on the site to help those with similar problems in the future.
Thanks both of you for your help.
Problem solved.
The inner o-ring on the exhaust solenoid of the Vanos had split. Although the unit was recently replaced, Chris Gant from Dr Vanos was of the opinion was that one of the seals may have been damaged during the refitting of the Vanos. The seal was indeed damaged and fitting a new seal curred the problem.
Once again thanks to the members who provided some valuable help.
The inner o-ring on the exhaust solenoid of the Vanos had split. Although the unit was recently replaced, Chris Gant from Dr Vanos was of the opinion was that one of the seals may have been damaged during the refitting of the Vanos. The seal was indeed damaged and fitting a new seal curred the problem.
Once again thanks to the members who provided some valuable help.