Missing a beat
I have a 2004 Vauxhall Signum 2.2 direct petrol auto with the Z22YH engine and 99,000 miles. Recently, it has felt as if the engine was occasionally missing a beat and the idle was a little lumpier than usual. Then the ‘spanner in a car’ symbol illuminated on the dash and, shortly afterwards, the engine lamp illuminated. The running became very poor, until the car would only judder along at 5mph. Turning the engine off and on restored normal operation, but the engine lamp remains on.
My £15 scanner showed no error codes, so I bought a Foxwell NT414, which has highlighted ‘P1191-52 – Fuel pressure system malfunction’ and ‘U2103-70 – Can-bus mode no communication’. This would seem to indicate a faulty fuel pressure sensor (is this the MAP sensor?), fuel regulator or high-pressure fuel pump.
It recommends checking the fuel pressure using Tech 2, but is this something I can check with my NT414? Also, should I replace the sensor first and see if that helps or do I need to get the fuel pressure checked? Incidentally, the fuel filter was replaced about six months ago. After clearing the codes, it took four attempts to start the car and then it ran quite roughly. In traffic, it would hardly pull at all, but putting it in neutral and revving the engine seemed to restore normal service. The ‘spanner’ symbol disappeared and just the engine light came on. When I got home, I checked the codes again and a third has appeared: ‘P0302-01 – Cylinder 2 misfire detected’. Rob Veltze The MAP sensor is a different component to the fuel pressure regulator. The MAP sensor detects manifold air pressure, while the fuel pressure sensor measures the fuel pressure in the fuel rail. The code ‘U2103-70 – Can-bus mode no communication’ may be an unrelated problem. It usually indicates a fault with the column integrated module (CIM) – this is a communication hub for the ECU and systems.
Given the fuel pressure codes and the misfire, there are three likely causes of the problem. The first is that the injector for number two cylinder is faulty. The second is that the fuel pump has failed. The third is that the pressure relief valve at the end of the fuel rail is stuck or broken, allowing loss of pressure.
Provided the sensor is working correctly, your NT414 should be able to read the fuel pressure from the live data. The fuel pressure should run at between 4.0-4.4 Bar, and if you are getting sufficient pressure and have eliminated the above possibilities, I would check the inlet system for any air leaks. If you are in doubt about the accuracy of the fuel pressure reading, it may be worth getting the pressure checked using a gauge.
Another possibility is that the EGR valve is faulty, but if this were the case I would expect to see a multiple misfire as opposed to the single-cylinder misfire that has been detected. UPDATE I received an email from Rob Veltze saying that, after having the fuel pump overhauled, the problems were rectified.