Evening All,

I would appreciate some expert guidance on this vehicle.

This car has had a misfire for approx 3 months and has gradually got worse over time. The vehicle drives well in 1st and 2nd gear and will rev to 5000rpm with no problem. However, in 3rd gear onwards from about 2500rpm the vehicle misfires (and pops) and has distinct lack of power. The problem is progressively worse with the higher gears selected.

Customer has fitted new plugs and leads plus ignition module which has not improved the situation.

My checks are as follows:

Emissions good. Natural idle: CO 0%, HC 140ppm, CO2 16.1%, o2 0.4% Fast Idle: CO 0%, HC 60ppm, O2 0.2%, CO2 16%, Lambda 1.01

MAF is showing 12.8 KG/H (idle) and 41.6 KG/H (fast idle).

Injection duration appears low for a multi-point system at 0.5ms.

All other sensors appear to be in range.

Now here is the big clue. Manifiold vacuum is low at 12"HG rising to 17"HG at max revs in neutral. The engine sounds ok at idle and high revs I have ruled out air leak based on 02 readings and blocked exhaust on vacuum readings. This thing does not have hydraulic tappets.

So my suspicions at the moment is on the waste-gate. I cannot reach the actuating lever nor apply vacuum to test it. Not having any expertise on turbos, I wonder if this could be the problem.

I would be grateful for any sort of input.

Regards

Pete M