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Ross, Diagnostic and repair technician
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Experience:  Licensed diagnostic and repair technician
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I have A vauxhall Zafira 1.7 diesel eco and the revs keep surging

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I have A vauxhall Zafira 1.7 diesel eco and the revs keep surging when drivind also when idling. the after a while the engine runs normaly, then it starts again.
Ther is no waring lights lit up.
Submitted: 2 years ago.
Category: Car
Expert:  Shantal-Mod replied 2 years ago.
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Customer: replied 2 years ago.

Please close question.

Expert:  Ross replied 1 year ago.
Hi I'm Ross, sorry for the delay in getting to your question! I am a diagnostic and repair technician and I look forward to working with you.When you say the revs are surging, do the revs bounce up and down, or does it just increase by its self and stay at a higher rpm? Also how high does it rev when it surges at idle? Thanks. Ross.
Customer: replied 1 year ago.

The revs bounce up and down and varies from aprox. 9,000 revs to 10,000 revs.

Then the engine may run smooth for a short while then the problem starts again. The problem period is now lasting longer and longer.

Expert:  Ross replied 1 year ago.
Ok, this sounds like a problem with the fuel system, before going further we need to find if there are fault codes stored on the engine management as this often pinpoints the fault.On these models you can find the fault codes your self using the "pedal test" methodSTEP 1: sitting in the drivers seat, press both the accelerate and brake pedal togetherSTEP 2: With both pedals pressed, put the key in the ignition and turn it to position 2, which is the ignition ON but not starting the engine. STEP 3:Once done, the spanner light will start flashingif it flashes 10 times it means the number is '0' and any other flashes corresponds to a number with a pause between each numberfor example code P0110the light will flash ten times then pause, flash once, (2sec pause) flash once, (2 sec pause) then flash ten times if you have more than one code it will stop for a break between each code.If there is a code stored in the system with the help of this code i can help further with a more accurate diagnosis, Unfortunately with modern diesels there are a lot of possibilities as to what may cause this problem and with the potential cost of some parts it's not economic to take a guess at this point and risk getting it wrong. Having no fault code also does eliminate a lot of sensors etc..
Customer: replied 1 year ago.

Thanks Ross,

After following your instructions, it was the engine management light that flashed and not the spanner key in this model.

The code it gave was 1625 and no other codes. I hope this helps with your diagnosis.

Thank you.

Expert:  Ross replied 1 year ago.
That's great thanks! I have looked into this fault and it would make sense that this is causing the problem. It is relating to the main ECU (Engine control unit) Holding voltage... This can have various causes but is usually the ECM Main relay, or the ECM It's self. The first step would be to check the relay which is in the relay box under the bonnet on the passenger side, 3rd relay down. Ideally substitute for a known working relay or swap with another identical relay from the car, However generally this fault will hold the engine in limp mode and as the revs bounce in your case I would also check the alternator output, I have seen these where the alternator gives an unstable voltage output which will cause the ECM To give this fault code with your symptoms. This is best done on a good multimeter or diagnostic scope which most good garages will have.The diagnostic steps for this fault would first be to rule out the relay, monitor alternator voltage, check voltage at the relay, and at the ECM, check wiring, and finally suspect ECM Failure. Although ECM Failure is highly unlikely due to your symptoms. If you plan to repair this your self a multimeter is a vital tool but otherwise the basic checks of the relay can be done and should be done first as a failing relay is relatively common. I hope I’ve provided the information you were seeking. If you need more help, please use the reply tab to continue our conversation. If you do not require further assistance, kindly rate my service. Thank you, Ross.
Ross, Diagnostic and repair technician
Category: Car
Satisfied Customers: 1180
Experience: Licensed diagnostic and repair technician
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Customer: replied 1 year ago.

Thanks Ross,

I will get this checked out by a local mechanic and will get back to you as soon as possible.


Expert:  Ross replied 1 year ago.
No problem, thanks for the update.

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