W124 E280 variable intake system

[gasgas4]

For the past 5 months my E280 (W124) has not missed a beat, no fault codes. Perfect, except for one thing, it doesn’t have typical mid ranch punch that it should i.e. the surge at 3500 rpm. This car seems to pick up at about 4500 rpm, a 1000rpm later than it should. Personally, I’m convinced there is something wrong with the variable intake system or the . From what I have discovered by swapping bits from my other E280 and searching the internet, it’s a simple solenoid valve that opens a vacuum driven valve to open/close at approx. 3500rpm. To check the system I’ve wired in a bulb that indicates when the solenoid closes and sure enough when the bulb lights up you get the sudden increase in power (at 4500rpm). The problem that I have is that I can’t find any information that might explain why it operates so late in the rev range. Does anyone out there have any experience of this system or have any ideas.

 

[Niks]

I have a W124 E280 as well and I can confirm there definately is a mid-range power punch which kicks in at 3250rpm and then starts pulling from there on right till 6000rpm. If yours is kicking in at 4500rpm then there is something wrong.

 

[grober]

I have heard of a similar problem with a diesel engine. I'm not at all sure of this but was something to do with the OVP relay. If the solenoid valve is supplied with a constant 12v via the OVP and operated by earthing switched via the ECU then a faulty OVP might cause a problem but its a long shot . Might be worth checking the output from the OVP? The other possibility of course is that your car has variable camshaft timing on the inlet cam and this may not be operating correctly?

 

[gasgas4]

Already swapped the OVP today without success. Also swapped the static part of the variable inlet valve timing. Perhaps I should also swap the rotating parts just in case.

 

[kth286]

there are the two functions :

1. inlet manifold flap solenoid and

2. variable inlet cam solenoid.

I would have thought they would have thrown up a fault code if neither was faulty.

Test your code reader first.

Why not induce a fault code by unplugging (say) the inlet air temp sensor and checking that it is now registered as a fault code.

 

[grober]

there are the two functions :

1. inlet manifold flap solenoid and

2. variable inlet cam solenoid.

I would have thought they would have thrown up a fault code if neither was faulty.

Test your code reader first.

Why not induce a fault code by unplugging (say) the inlet air temp sensor and checking that it is now registered as a fault code.

I wonder if a purely mechanical fault on the camshaft variable valve timing mechanism would throw up a fault on these early cars ? Say if it was a bit clogged/sticky or the spring was broken but the solenoid coil was ok. Certainly worth checking tho.

 

[gasgas4]

Thought I try and kill two birds with one stone so I disconnected the cam solenoid. To be honest it was hard to tell the difference but it did give the correct fault code. The trouble is I'm not really sure how big an effect the cam advance has on the performance and it looks like a big job (cam chain etc).

I believe the cam advances at 1500 & then returns to normal at ~4500. It's a bit of a coincidence that I get a kick at 4500 when there should be no effect due to VVT.

The other thing that I didn't mention was that when I had the bulb connected to the intake flap solenoid it does flash at ~3250. So maybe it's not an on/off system. A small trigger maybe is enough to get the 3250 kick.

Thinking about it, I'm sure this car isn't as torquey as the old one which also points the the VVT.

 

[gasgas4]

check function of VVT soleniod and definated works as it should i.e. armature/plunger moving freely and returning on the spring. Of course this still doesn't mean it's actually working properly as the plunger just controls the oil feed to the positioning piston, see attached file for more info.