Hi all,

After some advice on why my Ford Fiesta 1.6 TDCi is intermittently losing boost. (It's 2006 model with 90bhp engine. Same engine as loads of Peugeot, Citroen, Volvo etc cars - DV6. I'm 99% sure this is a pre-dpf model.)

 

Symptoms:

The engine intermittently decides whether it fancies giving any boost or pretending to be a naturally aspirated engine. Speed, engine speed, gear, temperature... nothing seems to have an overriding impact. Sometimes when I push the throttle it gives me boost, other times it doesn't.

 

 

What I've done so far:

The problem started at the same time as an EGR fault. The EGR fault was "valve sticking". I cleaned the valve out, although it really wasn't sticking or particularly dirty. The motor on the EGR valve is non-responsive so it's the motor itself not the valve that is stuck. In the interest of not letting loads of EGR through needlessly I've blocked the EGR valve with a blanking plate.

The turbo issue itself seems linked to the vacuum system that controls the wastegate actuator. I've check all of the pipes in the vacuum system and there are no leaks. I've checked the vacuum pressure made by the vacuum pump and it's making a very stable 700mbar vacuum. The system has a solenoid valve which controls how much of this vacuum goes to the actuator. I've checked the vacuum between the solenoid and the actuator and it seems to be an unsteady vacuum when idling. It intermittently holds about 600mbar vacuum (which holds the wastegate solidly shut) or drops to much lower levels. I believe this is the cause of the boost issues. I've tried 2 solenoid valves with no luck - one which worked perfectly on a different car. I've measured the voltage on both of the pins on the solenoid valve. One provides a stable 14V signal (presumably positive supply from battery) and the other seems to intermittently float around in a similar fashion to the vacuum pressure. I suspect this intermittent signal is the issue... but what would cause the voltage supply to be intermittent?

 

Could this intermittent voltage be caused by the car going into "limp home mode" because the EGR valve is "stuck"?

 

Any thoughts or suggestions are hugely appreciated!

Thanks.

This is exactly what is hapening to my car. Can not find any more info on this. Did you get to the back of it??

Hey Mat I have the exact same engine and year fiesta as you. When the fault came with the Egr did the engine management light come on? I had an issue a few months ago where the engine light came on and from using a diagnostic unit found it was due to the Egr valve (something about a high current) which I think might mean it was stuck closed as back then the car was just moved in and out the garage for 2 months. Got the code deleted and since then it hasn't popped up again. I haven't had any turbo boost problems with it. Have you checked the turbo veins (if these turbos have any) that they aren't sticking. On my dad's previous car the turbo would sometimes not provide boost or not spin up and he used I think it was Mr muscle oven cleaner on the veins. After that never had a problem. 

Im just curious but what blanking plate did you use? Was it one with or without a hole as I'm planning on buying one for mine and just don't want to engine light to come on. 

I’m having this problem on a 2007 facelift 1.6 tdci and I can’t figure it out! Is the boost control solenoid suppose to make a noise or not? Or go on and off? As mines done both

I have the same problem just can’t get the car to boost over 10 psi I found a hole in the pipe work sorted that went to work the next day made 17 18 psi of boost on the way to work then made just 10 psi on the way home ???? If I unplug my mass air flow sensor the boost comes back but the sensor is there for a reason I’ve put a new one on and still I’m only getting 10 psi I’ve even done a boost leak test the car is so sluggish please help