carl0s

Hi.
Weird one.

If I raise "vvt minihub adaptation" above 0.5mm, i.e. I raise the minimum valve lift between 0.5mm and 0.8mm, so that throttle is used during the idle phase, then I encounter a problem during driving (after ten minutes or more) where the car drops into valvetronic failsafe, and the only recorded error is 27B8 differential pressure sensor implausibility. This is the MAP sensor on the back of the manifold. The freeze-frame data doesn't seem to show the MAP sensor data.. I'm not sure if I can alter what is recorded in the freeze frame data in INPA?

If I run the car in full valvetronic - i.e. 0.00mm minimum valve lift, and no vacuum in the manifold, or in fact anywhere below about 0.49mm minimum valve lift, then this does not happen.

I need the vacuum at idle so that my LPG autogas system works better.. otherwise the gases accumulate in the manifold when waiting at stop lights/traffic lights, and then there's a brief hesitation/hiccup during set-off. The vacuum at idle is helping to suck the LPG gas into the cylinders and gives a smooth drive all the time.

Any ideas?

We smoke tested the car last night - no problems.

My vent pipes (from valve covers to the manifold - the CCV pipes as some call them), I have botched them up with rubber hose. I wonder - is there supposed to be some kind of check valve in the pipe itself that I'm missing? They are expensive at £40/$60 each which makes me wonder. It is my understanding that the diaphragm flaps on the valve covers act as the check valves. - My CCV/PCV valves (the diaphragm flaps on the valve covers) are all perfect. I know there is a "cold weather country version" of the vent pipes that moves the PCV diaphragm valve into the middle of the vent pipe, but that is not of interest.

It is of course possible that the MAP sensor is faulty, although it reads OK most of the time.

DME and all other modules are up to date - I have an ICOM A2 and I updated them a bit ago.

I'm wondering if vacuum is sucking my botched-up vent pipes closed.. squeezing them. It's quite stiff rubber hose though. Hmmm.

carl0s

Actually it turns out that the car is doing this a lot of the time regardless of valve lift settings.

I have smoke tested and found no significant leaks (slight leak from valve cover gasket).

I have ordered: new MAP sensor, new vent hoses, new CCV diaphragms, and a replacement DME.

I am leaning towards a DME fault now, and if it turns out to be the case, then I'd like to try to identify the faulty passive component (resistor/diode) in question by comparing good with bad DME.

if it still misbehaves then I'll look at a replacement manifold i suppose!