bad hesitation / lumpy acceleration

[brucelee]

Guys, can anyone help me? Checked the O2 sensors again and still neither one is oscillating at idle although they seem to respond and change voltage to throttle input - are they kaput?

I also cleaned both the VANOS solenoids swapped them around. The problem went away but has now come back with the opposite error code. I.e. before it was P1553, now it is P1554 - does this indicate that one of the solenoids is bad? Still also getting the knock sensor error code (P135B) but I'm wondering if this is as a result of one of the solenoids going bad.

 

[Nictrix]

I had a problem similar to this with our Mini last year.
It was like a missfire at low revs in every gear, it would eventually pull through it and be fine.
It was also less noticable if you thrashed it.
No fault codes showed up when a friend connected a reader to it.
I initially thought it was dodgy fuel as I had filled up at a different fuel station.
I also tried a fuel additive to try and clear it.
It was the plugs. Changed them for new ones and the problem vanished and has not came back.
When I removed the old plugs they were quite worn and the gaps were huge.

 

[brucelee]

Hmmm... I don't think its the spark plugs cos they were done less than a year ago during a service...

 

[brucelee]

Plus the hesitation only occurs now and then and not all the time

 

[Scooba_Steve]

If you've got a VANOS solenoid error code, which has moved bank when you've swapped them then it's a fair assumption is that one of them is bad. That's the investigative process BMW would use. You don't have to replace both - I didn't - they're about £80 new from Soper.

 

[brucelee]

Ok great, yeah I think I will do that first. I'm still a bit confused why my Torque OBD2 app won't show my O2 sensors oscillating though. I've read that they are wideband... could Torque be having issues reading their voltages?

Also, should I get OEM solenoids, like this: http://www.ebay.co.uk/itm/Genuine-BMW-Solenoid-with-Gaskets-for-Vanos-System-128i-135i-325i-328i-530i-Z4-/121783157337?hash=item1c5ad78259

Or... whatever these are, which are massively cheaper: http://www.ebay.co.uk/itm/New-Engine-Variable-Timing-Control-Valve-Solenoid-VVT-for-BMW-11367585425-917241-/171691768626?hash=item27f9a07b32

 

[Scooba_Steve]

Up to you as it's your car, like I said - OE from Soper were about £80 each. As for the O2 - I've got INPA which picked mine up.

 

[CrazyOneToo]

Scooba_steve what were the vanos issues you had? I've always had a slightly lumpy idle on my coupe, and recently the throttle has seemed a bit hesitant. Switching the AC on seemingly has quite a noticeable effect too - the throttle seems more laggy...

Just considering getting mine done now I've read the above!

My VANOS solenoid symptoms were a hesitation at steady speed and throttle setting, for a fraction of a second it was as if the car cut out.

I think I may be having the same issue now. Occasionally mine will cut out like something cut off the gas and spark for a split second. Also occasionally my throttle response is not very good. If you blip the throttle the RPMs go up rather slow and come back down rather slow. Just now I got the error code P1554.