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Mistery to be solved - Vaccum Solenoid Valve - Turbo actuator

sciroccopt

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Accord 2.2 CTDI
Hi all,

Does any one knows exactly how the Vacuum Solenoid Valve works in the turbodiesel models? In this specific case I'm referring to the one that connect directly to the turbo actuator. The valve contains 2 connections, one to turbo and other one to Vacuum Solenoid Valve located in the front of the engine, plus one connection that have small air filter, why this connection with air filter is necessary?

I'm going to explain the background behind this question and what is the mystery to be solved.

Around 320Ks Km I begin to feel a lack of power between 2.000 and 2.500 rpm, but it only in recoverings after a slowdown, per example, I was riding at 3.000rpm, if I took the foot from throttle till it reach down 2.000 rpm, when I press it again there was no response from turbo, or at least a very faint one. This symptom only happen in this situation, didn't happen with straight acceleration from idle rpm. When happen, the way to recover power was pushing clutch without taking foot from throttle making the rpm go high and take the foot again from clutch or tapping several times with the foot in the throttle, first technique always work, second some times not.

I ignored this symptom for some time, at 370ks Km, the turbo failed, I thought that probably the described symptom was related to an already starting to fail turbo, I exchange turbo and to my surprise, the symptom was still there with exactly the same behaviour.

I decided to try to make something about it, and after some threads ****ysed in several forums, I decide to have a go in cleaning and eventually replacing the EGR valve, I've done both things and no result, the behaviour was the same.

At 390Ks km, I had an gas smell inside the car, it was the exhaust manifold that had a crack, it was repaired and for my surprise... the lack of power symptom disappeared....

Happily I drove the car for more 10 - 15ks km and for my dismay, the problem returned...

Ok, this can't be turbo, can't be EGR, well, I decide to ignore it again and I drove the car without giving it a though till recently reached 500Ks km, to be honest I was waiting to have a very expensive failure in the car sooner or later so I was already thinking what car I was buying next, but since the car reached this nice Kms qty, I decide to have again a serious look at this problem.

If turbo and EGR was ok, maybe was something about the mechanism that control turbo actuator, like vacuum lines or Solenoid itself, so I began taking it out and then I notice the the little air filter that the solenoid should have was not there, in attach you can find two pictures taken from internet, with and without the filter exactly like mine was.

Well, I began to think that maybe some dirt had enter the solenoid or vacuum lines and was creating a bad behaviour somewhere creating the described symptom. I cleaned all lines, the solenoid and put it together again in the car, looking at the solenoid, I decided to put a screw in the open hole of the solenoid, the one lacking the filter (don't ask me why), I tested the car and... no lack of power symptom, well, I decided to take out the screw and the symptom returned back, I put the screw again and the symptom disappear again!!!!

Well, to be honest, I have to test the car in a more intensive environment, only next week I will drive the car for some hundred miles wit a lot of de-aceleration and acceleration, that will be the real test to check if the symptom completely disappear with the screw put on.

I've try to find on the net an explanation how the vacuum control acts on the turbo actuator and why is necessary this air input in the solenoid valve and now I return to the question in the beginning of this post, how this system works?

Have in mind that all the explained din't create any ECU error.

Best regards,
114709_With_filter.jpg
114710_Without_Filter.jpg
 
The 2 Turbo Actuator EVR solenoids (Part #: 36180-RBD-E01 - for my '06 Accord anyway) control the vacuum that is used to open and close the Variable Nozzle Turbine (VNT) vanes in the Turbo itself. If the actuator isn't getting the right vacuum from that system the vanes won't operate correctly and the power delivery will be seriously affected. That sounds like what is happening with your car from what you've said.

The filter part of the EVR is there to allow air to be drawn into the system to negate the existing vacuum as required. The filter just stops any crud being drawn in with it and, I suspect, also seals the EVR so it can maintain vacuum in the first place. If you are able to regain performance by blocking the filter port, then that, to me, suggests that EVR is broken and can't maintain vacuum - hence the system won't act correctly until you block that flow of air into it with a screw.

In short, I'd try and swap it with another EVR solenoid to see if that works (I would be surprised if that didn't solve your problem). If that works then I'd replace the duff one with a new EVR, as a used one will probably be tired anyway.
 
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