406oc.co.uk

Hi all

A couple of issues with my 407 that I am hoping to have some light shed on.

1) When changing gear, the car momentarily loses turbo boost, maybe for up to 1 second. Tends to happen when I want to accelerate briskly and only when I am changing gear. A very similar thing was happening on my previous 406 but only when I changed down and wanted to overtake. Is MAF a likely suspect or something else? The car is 9 years old with 80k on the clock.

2) When I am coasting along in gear and then press the gas pedal to get back on engine power, I often get a jolt as the car engages the wheels. A similar but less pronounced effect happens when coming off throttle and tends to be worse in lower gears. Sometimes it doesn't happen and I can come off and on throttle without any jolts but usually there's always something noticeable.

My first suspect is the knackered flywheel not providing any damping but could it be engine mounts or even some odd gremlin in the engine itself ...? Though doesn't really explain the jolt when coming off gas.

Any thoughts?

Maybe a sticky TPS?

Try looking at the live data as you operate the throttle, (ignition on, engine stopped), see if progresses smoothly from 0 - 99% as you press the pedal.

A knackered DMF will normally present as a wobble & squeaky noise on tickover.

Didn't think about tps. Might well be! Though once it's on boost, it stays there. Maybe just sticky at the top of the pedal travel...

Is yours the twin turbo Alex?

It is.

Sounds like you have a blockage or a split in a vacuum pipe - so the vacuum has to 'build' before the actuator, er, actuates...

Ah crap. I haven't the faintest clue on where to start looking for a vacuum leak on this engine. Will need to study Service Box diagrams to trace the tubes.... or even where the actuator is (is it likely to be the same sort of thing as we had on 406s with those solenoids on the bulkhead that you could swap over?)

Yes, but one solenoid is hard to get to.
If you use PP2000 it will say solenoid A or solenoid B, but in the meantime there is no harm in tracing eack pipe with your fingers to look for splits or cracked ends...

Richard is the one to speak too regarding this engine....

This looks like a nightmare....

This has been happening for ages but is not consistent. Sometimes it happens but mostly it's fine.

Where does the vacuum come from - the brake vacuum pump? Brakes are perfect* so I guess the pump itself is fine. Either the solenoid(s) or a split like you say. Hmmm, will have a gander to see what PP2K tells me.

Definitely worth going for a drive with the graphical parameter measurements running (note it doesn't show the graph until after you stop recording -- it doesn't appear in real time which sometimes makes people think that it's not working).

(1) Air flow meter
(2) Air cleaner
(3) Air mixer (air doser)
(4) air/air heat exchanger
(6) Inlet air temperature sensor
(7) Inlet manifold pressure sensor
(8) Turbocharger turbine isolation valve 2 (VT2)
(9) Body of the exhaust turbine of the turbocharger 1
(10) Pressure regulation valve "Waste Gate" (VT1)
(11) Proportional oxygen sensor 1
(12) pre-catalyst
(13) catalytic converter
(14) Exhaust gas high temperature sensor downstream of the catalytic converter
(15) Particle filter
(16) Differential pressure sensorParticle filter
(17) Body of the exhaust turbine of the turbocharger 2
(18) Turbocharger 2 (Vrec) compressor air recirculation valve
(19) Body of the inlet air compressor of the turbocharger 2
(20) Pressure sensor downstream of the turbocharger 2 compressor
(21) Turbocharger 2 (VC2) compressor isolation valve
(22) Body of the inlet air compressor of the turbocharger 1
(23) Electric EGR electrovalve

Hi Richard, what exact measurements should I be taking?

Last time I tried it, it just said please wait for a long time and never displayed the graphs is there some additional programme I need to install?

The jolting coming on/off the throttle sounds like engine mounts, classic symptoms and if left unchecked can start to pull on cables/hoses/exhaust flexi.

Yes, I thought so too but it doesn't happen every single time - surely a knackered mount would result in consistent jolting? Had look at the top one - seemed fine but I guess the culprit would be the bottom one, which, like in the 406, requires driveshaft removal.... And I know I already have a hole in flexi...

Regarding the super complicated vacuum system... I had a gander under the 'hood and managed to visually locate all of the solenoids. Three of them look easy to get to, fourth not so much but not a big pain either.

The vacuum pipes running to and behind the black hole that is the turbo are mainly made of aluminium, with only connection ends being rubber. Questions:

1) What is the difference between electrovalve (1) and solenoid valve (3) and which one would control the boost?
2) What are EGR vacuum pipes (20 and 21)? They seem to have some sort of erm.. thing at the end of it (like a flue cowl) but essentially don't go anywhere. Are they like relief valves or something?
3) How can I test any of these components?
4) Kelvin, did you ever get to the bottom of your vacuum leak?

Had it always happened? Since a remap? Do you still have your EGR in check?

Only asking because my Focus displays the exact occasional jolting you are getting and it's an EGR calibration issue.