Having posted about how pleased I was after the Vanos seals had been done on my 3.0 Z4 the other week, I’ve noticed that even though it revs well to the red line and feels I think better at the top end, the bottom end power seems very poor, and idle is lumpy (thinking both related), wondering if anyone had any suggestions as where to start. I know cam cover vent pipe had a split which was taped up and needs a new pipe which I’ll do this weekend, but wonder if garage has messed something up, or if having the Vanos seals done is just highlighting an already underlying issue? Any pointers folks?
Post Vanos rebuild - poor bottom end performance
- Thread starter Oxtobyd
- Start date
I had a lumpy idle after doing my first one.
Code reader said inlet cam stiff.
On inspection I found that the shuttle valve inside the vanos unit, that the solenoid moves to let oil in, was sticking in it's bore.
I whipped it out, rubbed it with some fine wet'n'dry and popped it back in. Problem solved.
So, I would suggest a code reader if you have one.
If not, remove the solenoids and you'll see (or feel, given the access) the end of a shuttle valve in the recess. Push it in with your finger. It should move in smoothly and pop back out when you let go. If not, clean it up. It's a very close tolerance fit and only takes a little oil varnish to make it stick.
Code reader said inlet cam stiff.
On inspection I found that the shuttle valve inside the vanos unit, that the solenoid moves to let oil in, was sticking in it's bore.
I whipped it out, rubbed it with some fine wet'n'dry and popped it back in. Problem solved.
So, I would suggest a code reader if you have one.
If not, remove the solenoids and you'll see (or feel, given the access) the end of a shuttle valve in the recess. Push it in with your finger. It should move in smoothly and pop back out when you let go. If not, clean it up. It's a very close tolerance fit and only takes a little oil varnish to make it stick.
bigwinn said:
Why does every job require tiny hands and eyeballs on the end of your fingers….
Managed to get the exhaust cam sensor out and give it a clean, also cleaned the sensor connector with contact cleaner just in case, and the connector for the exhaust solenoid, but no luck still rough idle, so next task would be trying to get the exhaust solenoid out, but looks like I need a deep 30mm socket to get it turned.
Before I go down that rabbit hole, what do people think is most likely, sensor or sticky piston in the solenoid, one is a lot easier to tackle?
Cheers
thought i'd offer an update.... having waited and waited for a deep, very deep, 32mm socket to arrive (btw anyone buying a 32mm deep socket it needs to be in total lenght 85mm, and not the usual 70mm one, and i think the following will work fine, but i can't confirm yet. Neilson CT4561), and it's still not come, i dediced to make my own 'special' tool, see pic.
basically a chopped down 32mm box wrench, with an eye ring screwed in, then a bolt screwed through the eye-ring, then an o2-sensor socket around that, and yay it worked. what a faff!
thankfully having extracted the exhaust solenoid there was no movement in the piston when given the shake test, so swapped out with a known working one, and also swapped out the cam position sensor with a new one that did arrive, and the results seem to be a lot better, but i'll know better when i get chance to give it a proper run out and the roads are dry again.
basically a chopped down 32mm box wrench, with an eye ring screwed in, then a bolt screwed through the eye-ring, then an o2-sensor socket around that, and yay it worked. what a faff!
thankfully having extracted the exhaust solenoid there was no movement in the piston when given the shake test, so swapped out with a known working one, and also swapped out the cam position sensor with a new one that did arrive, and the results seem to be a lot better, but i'll know better when i get chance to give it a proper run out and the roads are dry again.
In the hope updating this thread is helpful for others in the future who find this.... having still got some rough idle problems and not the low-end power i'd hoped (having taken it for a run the other day), I decided to swap over the intake/exhaust vanos solenoid/pistons. (mainly to see if things improved and the error code changed, but also I was fed up of lacerating my arm reaching to get the exhaust solenoid off!)
Swapping things around interestingly did improve the rough idle (though still not perfect), and the power did seem a little better (but I was driving in the heavy rain, so seeing the traction control kicking in, meant I was taking it a little steady), but I was still throwing a P0015 code in ISTA. I figured i'd check the DISA and that's all fine, (moved well, returns back to default when released, and hold open when vacuum closed). I then swapped a few injector coils around having watched the rough idle settings in INPA, and this helped a little with some of the cylinders, yet still not right. (also did an oil and spark plug change just as a matter of course).
next thing I'm trying is a set of new Febi Solenoids and Gates Camshaft adjustment valves, since I did notice how noisy the vanos solenoids were from start (especially what was the exhaust solenoid before swapping in to the intake), i.e. i could hear them inside the car, and I know it was them since when pressing a finger against them, the noise was in time with the movement I felt inside them. The noise did settle down, but leads me to think something is not 100%. Here's hoping the swapped solenoids and valves will finally sort things.
Swapping things around interestingly did improve the rough idle (though still not perfect), and the power did seem a little better (but I was driving in the heavy rain, so seeing the traction control kicking in, meant I was taking it a little steady), but I was still throwing a P0015 code in ISTA. I figured i'd check the DISA and that's all fine, (moved well, returns back to default when released, and hold open when vacuum closed). I then swapped a few injector coils around having watched the rough idle settings in INPA, and this helped a little with some of the cylinders, yet still not right. (also did an oil and spark plug change just as a matter of course).
next thing I'm trying is a set of new Febi Solenoids and Gates Camshaft adjustment valves, since I did notice how noisy the vanos solenoids were from start (especially what was the exhaust solenoid before swapping in to the intake), i.e. i could hear them inside the car, and I know it was them since when pressing a finger against them, the noise was in time with the movement I felt inside them. The noise did settle down, but leads me to think something is not 100%. Here's hoping the swapped solenoids and valves will finally sort things.
Oxtobyd said:
That seems a little odd to me.
I always thought the solenoid was simply on or off, like a mechanical switch. You imply that yours are rattling to and fro?
Does this mean they are not latching properly, or that the signal to them is intermittent?
But as Stuart says, you seem to be getting closer at least.
