Low rev hesitation/judder

**jmejamie** · 24-12-2017,08:31 AM

Yeah I will certainly read the blocks when I get VCDS back and then report back here for the results of that. Then I will look at getting down the dealership and grabbing a loom!

Either way will update you guys here.

Merry Christmas to you both 😁

Jamie

**fishybusiness** · 24-12-2017,11:47 AM

Would second the injector loom.

Mine was noticeably worse when the engine was cold, and always seemed to give trouble below 2000rpm.

Started about 170k, was at 175k and getting worse when I changed it. Problem went away immediately.

**rowdy-999** · 24-12-2017,01:28 PM

A faulty loom wont always show up on VCDS.

**mrcheesbrough** · 24-12-2017,01:40 PM

Originally Posted by rowdy-999

A faulty loom wont always show up on VCDS.

If there’s no Fault Code recorded then using Measuring Blocks will show if there’s a larger compensation discrepancy between the injector with a loom fault and those without. How much that needs to be before throwing a fault I don’t know but the available maximum is +3 or -3. Our Alhambra has roughly only +/-0.2 difference between each injector with a fresh loom. Before that one was running around +1.75 above the others and probably on occasion upto +3. This had a Fault Code in the memory.

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**rowdy-999** · 24-12-2017,01:44 PM

Originally Posted by mrcheesbrough

If there’s no Fault Code recorded then using Measuring Blocks will show if there’s a larger compensation discrepancy between the injector with a loom fault and those without. How much that needs to be before throwing a fault I don’t know but the available maximum is +3 or -3. Our Alhambra has roughly only +/-0.2 difference between each injector with a fresh loom. Before that one was running around +1.75 above the others and probably on occasion upto +3. This had a Fault Code in the memory.

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Being intermittent it may not always show up.

**mrcheesbrough** · 24-12-2017,01:48 PM

Originally Posted by rowdy-999

Being intermittent it may not always show up.

Indeed. It took three years for us to actually change the loom as I waited for the Fault to develop in the hope it would become more definite/obvious. Wish I’d done it sooner. It’s a different car now.

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**jmejamie** · 25-12-2017,03:12 PM

So i've got VCDS today and managed to get the logs on the injector group. I did logs in different situations like idle and then holding a set RPM. I did notice the values don't seem to sit still and when i first started the car up one of the injectors just randomly started climbing and then came back down on its own again?

I Should probably note that all these tests were done at a stand still, i did not actually drive the car.

I have attached the files in case any of you can tell me what you think?

car injector logs.zip

Thanks for the help so far guys!

Merry Christmas

Jamie

**mrcheesbrough** · 25-12-2017,05:19 PM

Originally Posted by jmejamie

So i've got VCDS today and managed to get the logs on the injector group. I did logs in different situations like idle and then holding a set RPM. I did notice the values don't seem to sit still and when i first started the car up one of the injectors just randomly started climbing and then came back down on its own again?

I Should probably note that all these tests were done at a stand still, i did not actually drive the car.

I have attached the files in case any of you can tell me what you think?

car injector logs.zip

Thanks for the help so far guys!

Merry Christmas

Jamie

Probably not best analysed with a stomach full of red wine and turkey but at a glance Cylinder 2 injector seems a bit ‘lazy’ - there are periods where it makes no compensation when I’d expect it to float a little. Cylinder 1 injector spends a lot of time in high negative compensation figures. I would expect this to be a lot more in line with the other injector figures really. Worth noting that although it’s in high negative compensation, it’s still within tolerance so probably won’t throw a Fault Code. However if you’ve more than one injector effected by a faulty loom the combined effect would be quite dramatic. A loom change is relatively simple and cheap compared to any of the other parts you might change to identify further possible causes of the fault.

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**jmejamie** · 26-12-2017,09:58 AM

Thanks for taking the time to look at those logs for me Mrcheesbrough! Hope you enjoyed your Christmas dinner!

I am now waiting for the dealership to open tomorrow so i can give them a call and get a wiring loom ordered.

Will keep this post updated. Fingers crossed this is going to be my fix!

I looked at the log files after you said about injector 2 being lazy and i can see what you mean. 2 seems to do very little changing under most the scenarios i created for it and injector 1 seems to just be in a world of its own compared to injector 3&4.

Thanks again

Jamie

**jmejamie** · 29-12-2017,11:39 PM

Right so the new loom came today! Snapped the old one in half to remove it because it was a pain in the *** on my engine compared to others where the engine isn't inline and they can slide it out with easy access. I did make sure any pinging plastic bits were kept away from the internals. I had a fight with the new one but got it fitted now and not really had a chance to drive it properly yet. I did get some more logs of both idle and 1200 RPM in case someone can take a look and determine if it is looking any healthier?

New loom logs.zip

Just curious to ask... i have put a fair amount of injector cleaner through the car in its time and had a carbon clean done. Given that there is a chance this injector was being lazy what are the chances that i might need to give it more of a clean if it hasn't been running optimally?

Thanks guys
Jamie