Ford 1.8 TDCi turbo/boost problem

b318isp

My wife's car is hesitating under load. The effect is like hitting the rev limiter on a petrol car - a momentary hesitation, followed by the engine running again, back to a momentary hesitiation, etc.

It doesn't happen under part or light load.

Running Torque OBD, the following can be gleamed:

- Car runs fine under steady state conditions, no noise or unexpected behaviours on sensors
- No fault codes at any stage
- MAF seems to work fine
- When the turbo spools up, the psi climbs normally and then peaks. This peak is the held at a constant for a short period of ~0.5 to 1 seconds (I assume this is the wastegate opening, preventing over boost and holding maximum pressure)
- Shortly after the turbo pressure peaks (the 0.5-1 sec), the fuel rail pressure drops to 0 (or close to it) and the engine load % drops to 0 (or close to it)
- Once the turbo boost pressure decays, the engine load and fuel rail pressure recovers
- The cycle starts again
- When the engine is coasting in gear, the Engine Load drops to 0 but the fuel pressure drops to maybe 20% of its peak.

So, it seems that there is some safeguard in the engine that is cutting fuel when the boost pressure is high.

The question is, what is causing this?

My suspicion is that the wastegate is not operating fast enough, or at slightly too high a pressure. Over the weekend, I'll check the hose feeding it.

Anyone able to concur or point out something different on this?

Thanks.

b318isp

Anyone?

George Dalton

What model and year is it?

b318isp

Ford Galaxy, Oct 2007, QYWA engine 125bhp 1.8...

George Dalton

The first thing to do (if it hasn't been done already) is replace the fuel filter. Those 1.8tdci engines are very prone to running issues caused by a dirty fuel filter.

b318isp

OK, I know it wasn't changed on the last service. Would it cause the behaviour described though?

George Dalton

Yes definitely. Have seen it happen to loads of them.

b318isp

OK, great - thanks a lot.

b318isp

For completion sake - in case anyone searches for this fault, it was indeed the filter. Thanks George.