Car Mechanics (UK)

Misfire misery

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I bought a 2010 VW Scirocco 1.4 TSI (160PS) with a non-starting engine from an online auction. A quick check showed the timing to have slipped so I stripped the engine and rebuilt with new pistons and rings (due to cracked ring lands) and new timing chain, guides and tensioner etc. I have re-installed the engine back into the vehicle. It started, ran and idled fine with no problems.

I took the vehicle out of the garage to take it for its MOT and a few hundred yards down the road it began to misfire. I returned home to find fault codes P001 -000 (Incorrect Correlatio­n), P2293-000 (Mechanical Malfunctio­n), P0088-000 (Fuel Pressure Too High). Believing the timing had slipped I re-installed the timing tools, but the timing was well within tolerance. I cleared the codes and restarted the engine. It still misfired but only the latter two codes came back. I believe that P0016 may have been due to the misfire condition.

I then checked compressio­n and found approximat­ely 15 bar for each cylinder. I also carried out a leak-down test with each cylinder being approximat­ely 10%. I also changed out the HP fuel pump – without any improvemen­t. I have rechecked the timing half a dozen times and still get it to be within spec. Everything I have seen online suggests that the high fuel pressure is due to incorrect timing.

I am now lost as to what this issue may be and hope you can offer advice.

James Poole

The two codes you have remaining both indicate high fuel pressure P2293 refers directly to a fuel pressure regulator

2 - performanc­e problem, and P0088 indicates fuel rail/system pressure too high. This normally indicates the pump or the regulator.

As you have swapped the high-pressure pump this would suggest that the fuel pressure regulator (N276) is not at fault because it’s incorporat­ed within the pump. With this in mind there may be a blockage in the fuel return line. There is also a fuel pressure limit valve incorporat­ed in the fuel filter to keep the low-pressure side of the fuel system to 6 Bar. If the low-pressure side of the system exceeds 7 Bar, this will affect the high-pressure side, which should run at 120 Bar.

Because you’ve carried out extensive work on the engine, I’m sure you’ve already replaced the fuel filter and so the only other check would be to ensure that the fuel return pipes are clear. If you can pressure-test the fuel system, this would help to ensure everything is running at the correct pressure, indicating a sensor fault.

Providing that the timing was set correctly by using a DTI gauge to ensure that the piston was at TDC when the chain was fitted, I would be confident that as the timing tools could be reinstated easily that the valve timing is correct. I would replace the fuel sender (G247), because this may be the problem. The low-pressure sensor (G410) may also be at fault, but I believe this is less likely.

 ??  ?? The fuel rail pressure sensor which may be the cause of the troubles.
The fuel rail pressure sensor which may be the cause of the troubles.
 ??  ??

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