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Mk3 2.0tdci 163ps juddering at 1500 rpm


Daves99
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I had a problem with diesel smoke from the exhaust at idle when warm. I had my injectors tested and 2 failed the test, these have been replaced and coded in but I now have a rough spot at 1500 that wasn't there before. Any ideas?

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I suspect that possibly the wrong number injectors have been coded, a common mistake.

The cylinder number order, the firing order, and the injector number is nearly always in a different order.

Use FORScan to monitor the injectors and disconnect one at a time to check which number they are. Then recode them if there are any that are wrong.

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I was told by someone that I should replace all 4 injectors but I didn't know if this was necessary due to 2 of them testing ok

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On 8/11/2022 at 10:25 PM, Daves99 said:

I was told by someone that I should replace all 4 injectors but I didn't know if this was necessary due to 2 of them testing ok


The 2 fuel injectors that tested OK may still be within tolerance but do no longer match their original calibration code. Before changing the injectors this was not a problem since the PCM adapted itself to the injector wear through the Years.

By programming 1 or more calibration codes the adaptation is reset. You now have 2 new fuel injectors that perfectly match the calibration code. The 2 existing fuel injectors however do no longer match the calibration code and cause the engine to run rough.

The actual calibration code of the existing fuel injectors should be calculated during the injection tests. The obtained calibration code is used to program the PCM instead of the code that is printed on the fuel injectors itself. However very few diesel specialists do actually have the test equipment to calculate calibration codes. This is why many specialists recommend to have all 4 fuel injectors replaced simultaneously.


If the existing fuel injectors are still pretty close to the original calibration code you can be lucky. The PCM will adapt itself to the fuel injectors within time. However you should be prepared that the 2 existing fuel injectors will also fail soon.

 

 

 

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2 hours ago, JW1982 said:


The 2 fuel injectors that tested OK may still be within tolerance but do no longer match their original calibration code. Before changing the injectors this was not a problem since the PCM adapted itself to the injector wear through the Years.

By programming 1 or more calibration codes the adaptation is reset. You now have 2 new fuel injectors that perfectly match the calibration code. The 2 existing fuel injectors however do no longer match the calibration code and cause the engine to run rough.

The actual calibration code of the existing fuel injectors should be calculated during the injection tests. The obtained calibration code is used to program the PCM instead of the code that is printed on the fuel injectors itself. However very few diesel specialists do actually have the test equipment to calculate calibration codes. This is why many specialists recommend to have all 4 fuel injectors replaced simultaneously.


If the existing fuel injectors are still pretty close to the original calibration code you can be lucky. The PCM will adapt itself to the fuel injectors within time. However you should be prepared that the 2 existing fuel injectors will also fail soon.

 

 

 

Thank you. I thought it might be something like this and have ordered 2 more injectors.

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I have now replaced all the injectors and the car is running worse and smokes heavily under load.  They have been coded in. 

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I have reset the pilot injector values and taking the car for a drive, the car is suffering from a knocking noise that wasn't there before changing the injectors. Does anyone have any ideas on what could be causing this? 

Thank you

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On 8/19/2022 at 2:10 PM, Daves99 said:

I have reset the pilot injector values and taking the car for a drive, the car is suffering from a knocking noise that wasn't there before changing the injectors. Does anyone have any ideas on what could be causing this? 

Thank you

Anyone? It's still showing no fault codes 

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I have sent the injectors back to be checked and have been informed that they are all sowing signs of damage from possible the pump falling. Has anyone come across this before

 

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Dont see how they can be damaged, i think they are trying to con you, did you perform the injector relearn process properly after resetting the pilot injection values? I have started a similair thread but i still have the clatter after the process has been completed, there is no smoke in my instance. I dont think there is many people on here who can help us unfortunately. See my thread.

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18 minutes ago, TomsFocus said:

Pump failure can send metal shards into the injectors which causes damage.

I assume that cleaning out all the fuel lines and replacing the pump/damaged injector should solve this, 

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1 minute ago, Daves99 said:

I assume that cleaning out all the fuel lines and replacing the pump/damaged injector should solve this, 

Yes, but the cleaning does need to be incredibly thorough to make sure all traces are removed from the HP side. 

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3 minutes ago, TomsFocus said:

Yes, but the cleaning does need to be incredibly thorough to make sure all traces are removed from the HP side. 

Thank you. I was a bit surprised by them saying that the pump had broken down because it ran fine apart from the odd bit of smoke at idle.

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33 minutes ago, Daves99 said:

Thank you. I was a bit surprised by them saying that the pump had broken down because it ran fine apart from the odd bit of smoke at idle.

They are having you on IMO, did you perform the relearn procedure after resetting injector values?

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31 minutes ago, RSpilla said:

They are having you on IMO, did you perform the relearn procedure after resetting injector values?

The relearn was performed 

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8 hours ago, RSpilla said:

They are having you on IMO, did you perform the relearn procedure after resetting injector values?

I'm thinking the same

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