CLK 320 V6 Engine 'Lumpy' at idle
05-15-2008, 08:25 AM
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CLK 320 (W209)
CLK 320 V6 Engine 'Lumpy' at idle
Can anyone help me, I have a w209 v6 320 and it has developed a fault at idle.
The engine will surge or hunt with a wobble at idle revs, and make the car judder if in Drive. I have taken it to the dealer and diagnostics is not showing a fault. They replaced the air mass meter and enriched the fuel input to all the cylinders. They claimed this would scale itself down with a few hundred miles and auto adjust. So far it has not.
I then decided to get a second opinion and the MB specialist I took it suspected an air leak on the manifold, so he tested for this and could not find anything, and even conducted further diagnostics for a couple of hours (more thorough than the dealer themselves and did not charge me £130 for the privilage).
He also checked the fuel pressure, and this was normal.
One thing he did notice was that at idle the pressure in all the cylinders was fluctuating, cant quite remember the test, but is showed anywhere between -1 m/s to +5m/s
All other aspects are fine, acceleration, auto gear change is smooth, their is no loss in power at any revs/gear change. Just when it is at idle.
The engine rev counter does NOT fluctuate when it is at idle if this helps?
Any ideas?
The engine will surge or hunt with a wobble at idle revs, and make the car judder if in Drive. I have taken it to the dealer and diagnostics is not showing a fault. They replaced the air mass meter and enriched the fuel input to all the cylinders. They claimed this would scale itself down with a few hundred miles and auto adjust. So far it has not.
I then decided to get a second opinion and the MB specialist I took it suspected an air leak on the manifold, so he tested for this and could not find anything, and even conducted further diagnostics for a couple of hours (more thorough than the dealer themselves and did not charge me £130 for the privilage).
He also checked the fuel pressure, and this was normal.
One thing he did notice was that at idle the pressure in all the cylinders was fluctuating, cant quite remember the test, but is showed anywhere between -1 m/s to +5m/s
All other aspects are fine, acceleration, auto gear change is smooth, their is no loss in power at any revs/gear change. Just when it is at idle.
The engine rev counter does NOT fluctuate when it is at idle if this helps?
Any ideas?
05-27-2008, 04:07 AM
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2006 CLK 350 Fog City, CA, USA
one test showed " One thing he did notice was that at idle the pressure in all the cylinders was fluctuating, cant quite remember the test, but is showed anywhere between -1 m/s to +5m/s".
Do you mean the cylinders compression (psi) were fluctuating??? If so, how did he measure that with the engine running?
Did they put on engine analyzer (oscilloscope) on to the #1 ignition wire and measure the spark parameters (ie. High Voltage and firing time interval)?
If the analyzer shows the high voltage was fluctuating, then the High voltage module or cables is bad for that cylinder. If the firing interval is varying between -1 Milliseconds to +5 Milliseconds, then still could be a bad electronics in the ignition module or distributor/rotar is worn/dirty.
Good Luck
Do you mean the cylinders compression (psi) were fluctuating??? If so, how did he measure that with the engine running?
Did they put on engine analyzer (oscilloscope) on to the #1 ignition wire and measure the spark parameters (ie. High Voltage and firing time interval)?
If the analyzer shows the high voltage was fluctuating, then the High voltage module or cables is bad for that cylinder. If the firing interval is varying between -1 Milliseconds to +5 Milliseconds, then still could be a bad electronics in the ignition module or distributor/rotar is worn/dirty.
Good Luck
