Rough idle - Page 2 - Vauxhall Antara Forums
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post #11 of 14 (permalink) Old 3rd November 2020, 11:26
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Yesterday, 21:53 Richy
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OK Victor, I'm clearly wrong in my assumptions. Thanks for the advise

Presumably you need to take the car to Vauxhall to get the leak off test carried out ?
Do you have any idea why it doesn't do this when the engine is cold or is it just how it is.


You weren’t completely wrong in your diagnosis, you were very close to the mark when you said “the hunting sound I think is the engine ECU continually adjusting the injectors to try to meet some setting which it is unable to do”. I’m not saying what’s definitely wrong with your car, I’ve never even heard it first hand, just going by that clip you posted.

The reason why it doesn’t do it when it’s cold is because Pilot Learning only takes place once the engine is up to temperature (~ 80 deg F).

Surging /uneven idle can be caused by a faulty suction control valve (SCV) on the injection pump but a faulty SCV usually also causes poor starting which I don’t think you have.

I’ve never experienced this with my own vehicle but I’ve noticed a couple of things as reported on the Antara and Captiva forums:

It tends to happen to engines where a diesel tuning chip has been used.
It tends to happen more with automatics.
Surging /uneven idle can be caused by a faulty fuel filter.
Any other cause of fluctuating fuel pressure (faulty pump, leaking connections, faulty common rail pressure switch etc)

2015 Antara Exclusiv 2.2 163ps Manual 2WD
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post #12 of 14 (permalink) Old 3rd November 2020, 16:25
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Thanks Victor, Understand now about pilot learning being about 80 degrees. At the moment the knock seems intermittent, it can be doing it then all of a sudden stop. This makes trying to diagnose even more difficult. One thing I will do is change the fuel filter as I don't know if this has previously been changed. The other items like oils and air/oil filter etc have all been changed regularly since I have owned the car.

The car starts well and really runs very smoothly except when the diesel knock happens, if your stationary you can feel a very slight vibration but it is slight.

I will also try some forte diesel additive and keep an eye on and see what happens. It is difficult being a DIY mechanic especially with modern engine ECU's as its not easy to gain access to all the programming criteria, this is where help from people like yourself is so important and welcome. The other thing I meant to mention earlier was no engine light, so whatever this is, is hopefully quite minor. I have also noticed that for the first few miles my engine RPM runs slightly higher than normal around 1000rpm whereas when hot its about 750rpm. I think this is normal as the car replaces its charge, I found a receipt so I know that at 30k my inlet throttle body was cleaned out, but I don't think this is connected. My car to my knowledge has never been chipped and is manual.

Cheers Richy
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post #13 of 14 (permalink) Old Yesterday, 18:35
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Update: just got my antra back after 2 months at the dealers, they sent the injectors off for testing and cleaning. They said they drove the car for an hour so they think that they have fixed the problem. 20mins drive home.... the knocking is back again, unless a computer tells them whatís wrong they havenít got a clue! Back she goes in the morning.
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post #14 of 14 (permalink) Old Today, 07:51
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As my earlier note I replaced my fuel filters, (2) which were black as the ace of spades, I don't think they have ever been changed, they are easily forgotten when they are on the underneath of the car. The car now is running a lot smoother as Victor suggested however due to my current discharge/battery issues I have not had the chance to give the car a long run but since changing the filters I have not heard the noise.

For those DIY'ers out there the job is quite straight, i put the front of the car on ramps to improve access, put bowl under the filter, undo the phillips screw and drain casing into bowl, with 27mm socket loosen both filters and drain excess into bowl, lubricate the o-ring seals on new filters, fit new filters torque to number on case, refit phillips screw then I turned the ignition on about 10 times to bleed the filter before starting the car.

Be wary in 2012 they swapped filter type so best remove one of the filters and measure length and diameter before ordering. I bought the wrong ones initially which were pleated, the right ones for my car have a smooth filter media. Richy
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