Injector Correction Values.... - Alfa Romeo Forum
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(Post Link) post #1 of 11 Old 17-10-12 Thread Starter
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Help Injector Correction Values....

I've been struggling with poor power and lumpy running at low revs. (2010 2.0 JTDm in a 159)

It's been back to the Alfa dealers a couple of times - No P code so they won't do anything.

It was in for a service at Autolusso B'mth this pm and they showed me the injector correction values - Cyl 2 and 3 were 0.6 and 1.4 while 1 and 4 were 0.2 ish at idle.

Is this bad? What do these numbers mean - Please help....
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I'd like to know as well. Mine vary from minus 1 to plus 1 or something.
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'Tis all very clever stuff/way too complicated/black magic*

The car uis stil under warranty and went back to the dealers yesterday and I was very pleased at their attitude. The ran a diagnostic check and confirmed the values that AutoLosso had shown. I went inot the workshop and chatted at length with Ian (the technician actually doing the work!) which was very useful. He showed me the Alfa tech manual (on a scren - of course) which showed alllowabel raneg for the correction values. As long as the values or +/-2 they are OK.

While this was very interesting, it didn't get any closer fixing the problem.

DPF regens seem to be the current suspect at the moment. The ECU readout shows the car has done 304 regens in 36000 miles. On average this is about every 120 miles, which seems to be a lot more frequent than exected. Last regen was ~60 miles back.

So - Injector correction values look OK. Regen history looks suspect....

* delete as appropriate
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This a response on the ECU Tuning Forum; so I can't vouch for it's accuracy, but "OdinEidolon" is from Italy so I guess that's OK He does run a Peugeot 406 btw It does seem to confirm that readings between -2 and +2 are normal.


"Re: Fuel injector problems

Postby OdinEidolon Mon Jul 23, 2012 10:55 pm
Hi there! There are very accurate sensors that measure the vibrations caused by the fuel exploding in the cylinders one at a time. Based on this and more data, the ECU calculates the correction to apply to every injector (4 injectors, 4 cylinders). The correction is calculated in mm^3/stroke, because it is the correction to the IQ - Injected quantity (called injected flow set point in that picture), that is the amount of fuel each injector squeezes in the combustion chamber at every cycle.

So if the |correction| is very big that means the injector has something bad, a value above 2 already is a hint, above 3 a proof, 4 is a certainty. Injectors should be removed (this can be a pain - I speak from experience) and cleaned professionally (with ultrasonic waves), or worn parts replaced. This is expensive. At least 60€/injector.

In your case if the corrections go to 0 at load that's a good thing. However it'd be nice to have a video of this during various stages of driving, that is as if you were driving normally. To do this grab a program that records the screen (like Autoscreenrecorder Free) and start it up, then go for a short trip.

Also specify if this happens from cold or hot more frequently, and if your revs go up and down..

My corrections too are very big (~4 numbers) just after I turn the engine on, then after a couple of seconds it settles down to ~1. Also strange, you have a very low idle. Mine idles at 750rpms without AC and 803 with AC on. I prefer a higher idle because the oil pump comes into play earlier, but that's not a huge difference. That can be changed via a remap by the way."

Brilliant Blue 156 GTA SportWagon

2011 Ghiaccio Bianco 159 2.0 ltr JTDm Lusso SportWagon
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Hi Toc1c

Thanks for x-posting this. Sounds very reasonable, and consistent with what I have picked up elsewhere.

But....a knowledgeable chap from italy driving ad 406...??? I hope he has a ferrari in the garage, or at least a picture of a ferrari on his garage wall

BTW I see you have done some suspension upgrades - Antiroll bars and springs. Do they Make much difference on the road? Have you lowered the ride height too? I'm in danger fo going the same route once the car comes out of warranty
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The springs lowered the car a "bit" not sure because it was already on stock Veloce springs which are 25-30mm lower than standard, I would estimate the dropped it another 10mm or so. Take a look at my images, the silver wheels are standard while the shot at Ickworth is with the lowered set-up.

The ARB kit made a huge difference to the handling; it was a big step up from the standard 156 set up. 26mm front / 18mm rear. Even with the Pro-Kit springs and FSD shocks the 20v still wallowed like a stranded whale, while when on a previous 16v diesel it was OK. I guess this was to be accepted considering the heavy lump and gearbox.

The biggest gain was the stability when exiting bends, the transition from roll into the straight is now very smooth whereas before it lurched. I would go as far to say that if I had only limited funds I would disregard replacing spings and shocks for the ARB. In addition to it stopping roll, it also stopped the rear bottoming out and hitting the tyres on dips when travelling at speed (I have 225/45 x 17 fitted).

The car handles great now just as Alfa intended (but failed to deliver).

Take your point why would you drive a Pug 406 anyway? I had an early 1.9 oil burner and it was pathetic - spent most of it's time being fixed. Mind you it was only 90 bhp!

Last edited by TOX1C; 22-10-12 at 12:15.
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Thanks - good info and lots to think about.
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hello,

I have a the following "problem":

Had a scan and the following values came out:

0.6, 0.9, 0.9, -2.4

I want to mention that the car is running perfectly, I have a smooth idle, everything is great. Still, the -2.4 got me worried. What does that mean? Why the correction is negative?

And one more thing: This is ONLY at idle. When accelerating, the values are something like 0.2, 0.1, 0.1, 0.2.

Thank you!
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IMO the best test is to check injection correction values at around 2000rpm in 5th or 5th gear... driving at constant speed for longer period. If corrections stay below +-1.5 in that conditions then everything is OK...

Negative values usually mean that injector is over fueling.
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Thank you!
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Ps: any other input will be much appreciated!
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