Mike_k

Hey all. 2007 FSI 4.2, just had a bunch of work done on it including new injectors, carbon cleaning, high pressure fuel pump, etc. Car has been trouble free for a month until today when I get these two codes.

Codes are for implausible signal for each of the two intake flap position sensors. I can clear them and they come back right away.

Physically the top actuator connected towards the upper center of the intake manifold moves freely and switches position with the engine on and returns once it's off. So that one is working. The arms connected to both position sensors however are not moving when the engine is on but I can move them by hand. When I move them by hand they don't feel as if there is any natural position they want to return to though.

So my questions:

1. What is the purpose of the two lower arms connected to the position sensors compared to the arm on the upper motor connected to the upper center of the intake manifold?

2. Do the motors go bad?

3. Should these lower arms be moving when I turn the engine on?

Does anyone have a diagram of the variable intake runner system on the 4.2 FSI?

Thanks in advance.

Mike_k

Disregard. There's a TSB out for this. The potentiometers (position sensors) get stuck because of a deformed oil seal and then they throw this code because neither can move if one can't.

Sometimes hitting them with wd40 works. Otherwise you need to remove them, ideally replace the oil seals, lube them with wd40 and reinstall. If neither of these fix the problem then you need to replace the motor.

The motor is known to fail so the TSB officially says to replace that first and then if the codes persist to address the sensors but none of us are under warranty any longer so the smart move is to address the sensors first and the motor only if necessary.

Mine seem to be freeing up and the motor now moves them but not fully so I'll probably remove the sensors and clean those since I can feel each sensor snagging at the point where the motor stops pushing them.

If you have this problem and would like access to the TSB just send me a PM and I'll send you screenshots.

mishar

Thanks. Good to know. I would just use some better lubricant than WD40.

Mike_k

Actually WD40 is what the TSB calls for.

Mike_k

Update on this. Codes came back… I took a closer look and the arms broke off at the motor so when the motor turns it's pushing the post that holds the arms out of it.

I'm thinking this actually happened because of the stuck potentiometers. Anyhow, I ordered the revised pump which includes new arms as well and appears to be a pretty simply swap.

For anyone else that ventures down this road the part number for the revised motor is 079129086B.

I'll report back on whether or not this is the fix but I'm 99.9% certain it is.

MP4.2+6.0

I'm not familiar w/ this system with whatever the drive for it is. My 2000 4.2 had a vacuum based valve system with some electrically driven switches to activate the vacuum diaphragms involved. Regardless, the question I have and really couldn't follow from your original post is whether the intake flap shafts themselves are free to move. That is, is the whole point of the system--the flaps that control the intake runner length switching--moving or not? My own experience is the broken arm stuff is frequently a symptom of stuck parts, at least on the older set up, rather than a root problem.

jakematic

#'s 18 and 19. Not the intake manifold runner - I was thinking the same thing and got rather confused.

Implausible signal typically means electrical issues Mike.
Check the harness as well, especially and grounding points/tracks.

Mike_k

Nah it's the motor itself. The car pops up with the exact codes of the TSB and I can physically replicate the problem. I'll report back for closure in a few days when I replace it but I'm 99.9999999999999998175% sure it's the motor. So I guess there's a chance it's not!

jakematic

I think it is too, but never hurts to check.
Fairly inexpensive part anyway so I'd just change it as well

baconballs

Hello!

I'm new here, but was reading this thread as I have newly experienced these messages on my 2006 RS4 4.2L saloon. I have a question though. My car only seems to have one potentiometer fitted, with the orifice blanked off. I have attached a couple of pictures and would welcome any comments.





Potentiometer present (RHS )





No potentiometer... just a small silver blank seen here edge on.