206 1.6HDi 110 Boost Issue

[tyresmoke]

I have boost hesitation when driving heavy footed through the gears, more prevalent in 3rd, 4th, 5th . Tends to happen around 2700rpm then goes flat for a second to 3200rpm before picking up again. Could this be the VAC solenoid and is there anyway to test it? I notice looking at the turbo when idling that the actuator rod is short, turn the engine off and it slowly (3 seconds) extends to max length. Start the engine it sucks it short again. Is this normal or should it hold the vacuum?

[PeterW76]

Based on my understanding that actuator behaviour is normal. Also watch the actuator while getting someone else to rev the engine. As revs rise the actuator should extend. Look for juddery movement - possibly the variable vane mechanisim is sticking due to carbon build up.

EGR valve can also be a common cause of flat spots/hesitation.

[tyresmoke]

Thanks, I have purchased a new VAC solenoid to fit this weekend, the turbo is new but will look for the juddery movement and ask for a replacement under warranty if need be.

[davidireland]

Get a diagnostic check done. Pay attention to air flow in relation to reference in the parameter measurements..

[tyresmoke]

Fitted new VAC solenoid Saturday, was a later design black and not brown but same part code. First thing I noticed was turbo actuator was not being sucked to the shortest length when idling (about 7mm off). Took for a drive and the boost was way down. Hooked up planet for a live data run, missing about 0.5 of boost. Tested all the VAC pipes for correct sealing / leaks could not find any faults. Refitted old VAC solenoid and car returned to how it was before.... full boost but with the hesitations. Refitted new solenoid and still 0.5 bar down on boost. Triple checked all pipe work and still the same.

Left the battery disconnected for 30mins to hopefully reset the ECU just in case it needs to re-learn there’s a new part fitted. Drove round all weekend and still the same 0.5 bar missing. Could this be a faulty part or does it need some sort of jiggery pokery performed on the ECU?

[davidireland]

The vac solenoid is not the problem.
What are the fault codes?
How much loaded is the particle filter? % ??

[tyresmoke]

No fault codes, everything working as it should except the turbo hesitation. I will see what the loading is on the DPF, need to reboot computer in to XP. brb

[davidireland]

Is there any play in the shaft of the turbo?

[tyresmoke]

Hi David, DPF loading is 6%. Interestingly I checked the turbo from the intake end the other day and to my horror there was up & down movement, but no in and out movement. I since understand that up & down is normal as the bearings run on a bed of oil. The play does seem excessive to me approx 1mm but this is a new recon turbo which has done about 2,000 miles. What sort of tolerance are we talking I can try measure it?

On the VAC solenoid issue, my old brown one was giving -0.6bar of vacuum on the turbo actuator at idle, the new one only -0.2bar

[tyresmoke]

I have now done the following:

1. Replaced Mass Air Flow sensor with new Peugeot item
2. Replaced faulty new VAC solenoid with second-hand brown type from breakers
3. Disconnected electrical ports of the Air Doser butterfly’s (part of the EGR system) the purpose of this is to direct compressed air through the intercooler or bypass intercooler for warmer air, or a mixture of both. Just in case the butterfly valves were sticking I have disconnected these in the fully intercooled position for testing.

The boost issue has returned to how it was before by changing the VAC solenoid, strong but with hesitation. I still have no fault codes and the boost dips low of the reference points between 2700-3200rpm and the turbo stalls sometimes after a gear change. The new MAF meter and Air Doser disconnect made no difference.

I have now replaced the Air Doser inc the replacement of air temp sensor & air pressure sensor (boost) these were included as a whole unit, with no effect still the same!

I have measured the radial play on the turbo shaft from the intake end with a digital micrometer and its 0.64mm when warm. Is this too much? It does seem excessive to the eye.