Smoking & stuttering
I have a 2002 Peugeot 806 2.0 HDI with 153,000 miles on the clock. About 18 months ago, I noticed an increasing amount of exhaust smoke. When I took it to a diesel specialist, they bypassed the EGR valve and this stopped all the smoke, albeit at the expense of bypassing the EGR valve. The car has been running very well since then, has six-monthly oil and filter changes and an annual air filter change. However, over the past two to three months, I have noticed occasional stuttering in the power delivery from the engine.
It is as if the car has gone into ‘limp-home’ mode (a problem I had on a previous Ford Galaxy). However, the power always returns almost immediately, without switching off the ignition and resetting the ECU (as I had to do with the Galaxy). The frequency of these episodes is increasing and their duration is now lasting for about 20-30 seconds. It seems to happen more on an incline or when I accelerate as if to overtake. The power always returns, which makes me suspect it is a fault with the turbo rather than the engine, or perhaps with the hoses/intercooler/sensors, but I’m not sure where to begin looking. If the hoses were leaking, would it not be a permanent problem?
Aside from these episodes, the car runs beautifully and will easily sit at high speeds on the motorway. I do all my own servicing and maintenance, and would feel comfortable trying to source the problem if I was guided in the right direction. I also wonder if bypassing the EGR valve last year might have something to do with it? Would you have any advice on where to begin looking or could you direct me to any website that shows the layout, etc, of the turbo system, if this is where the fault is likely to lie? Colin Askew When you say the EGR valve was bypassed, I am assuming that it has been blanked off. I would much rather see the EGR problem rectified than blanking off the system, but this is a personal preference and should not be the cause of your problems.
You have mentioned the frequency of the oil and air filter changes, but not the fuel filter. If this has not been done for some time, replacing the fuel filter would be my first move. I would then check for any leaks (however minor) around the injection and leak-off pipes. Ingress of air is a cause of many diesel problems.
You may also have a failing in-tank fuel pump. If the electric pump in the fuel tank is not putting out sufficient flow, it can cause a short term fuel shortage to the high pressure pump. Reading any fault codes retained in the vehicle's ECU may help pinpoint the problem.
As you correctly say, if it was one of the turbo intercooler pipes, the fault would be more constant. Check around the pipes – any signs of a leak will be indicated by an oily patch on the hose or connection.
Oddly, one other component that is often responsible for random loss of power is the brake light switch. The switch is normally linked to the ECU to cut the fuel supply when braking. Sometimes a faulty switch can cut the fuel supply intermittently.
Finally, I would check the vacuum hose to the turbo wastegate actuator, to ensure this is operating correctly, and also the plug to the injection relay, to confirm this is clean and secure.