FSI Fuel Injector Maintenance

[komseh]

I'm mirroring this post from another forum since not everyone goes there and I feel this information needs to be shared as widely as possible. There's scarce sources of information about fuel injectors affecting performance and driveability on these motors.

I'll start with my recent symptoms and the diagnosis that led me to cleaning the fuel injectors.

Symptoms:
Surging idle - Idle was constantly fluctuating
Rough cold start - The cold start cycle was extremely rough with RPMs approaching 2000

Other possible symptoms:
Engine misfire
Performance loss
Increased Fuel consumption
Engine damage - Possible in the event of a fully clogged or leaking injector. There have been a few documented cases of this.

Causes
In our cars the fuel injector heads are exposed to the combustion chamber so they can get carbon on/in them just like our intake valves. Fortunately the buildup is not near as dramatic as the on intake valves. However, when you have a tolerance of 1 micron any amount of carbon buildup can affect the injector flow in a big way.

When I had my injectors cleaned, the guy said he found sludge inside the injector filter baskets. I'm still not sure on the cause of that or if it should be expected on our injectors.

Diagnosis
Fuel trim data is a good place to start if you think your injectors might be clogged. Look at VCDS measuring block 032, which shows your long term fuel trims at idle and load. Short term fuel trim can be monitored in block 033.

A clogged fuel injector will inhibit optimal fueling in the motor. The ECU will see this lack of fuel over time using the O2 sensors and call for a permanent fuel trim correction. Looking at measuring block 032, a clogged fuel injector will cause a positive number to show up in the Partial field(Partial means at load). In my case it was showing between +5% and +6%. While these numbers are in spec, we really don't want to be running lean. Lean conditions are bad for engine performance and safety.

If you have positive long term fuel trim at load(block 032 Partial field), you can be fairly certain your fuel injectors are not flowing optimally if your car meets the following conditions:
Good O2 sensors - Bad O2 sensors can cause inaccurate fuel trim readings
Good fuel pressure on both banks - Check measuring blocks 103, 106, 140
No vacuum leaks - Check the Idle field in block 032, it should be slightly negative in a good condition.
Normal short term fuel trims - Your short term fuel trims need to be within +/- 10%.

Solutions
Clean your damn injectors! Like with soap and water dummy. I wish it was that easy.
You'll need to either:
Buy a new set of injectors, OEM part number 079906036D or Hitachi part number FIJ0008
Send your injectors off for cleaning, should be around $200 + shipping. Look for someone with an ASNU machine. I used https://www.racecityinjector.com/ but it's best to find one in your region to minimize shipping time.
If you opt to buy a new set you will minimize down time and have the option of reselling the old ones after having them cleaned.
If you want to optimize your fueling you could buy a batch of injectors and have them flow matched by the cleaning company. I think buying 12-16 of the Hitachi injectors from Rockauto and selling the unused ones would be the most economical way. Flow matching injectors just involves testing a set of them until you find 8 with flow rates within 2% of each other.

Here's a data sheet showing injector flow results before/after cleaning. Two of the injectors were pretty bad off. I'm guessing those were both in bank 1 in my case which is why my LTFT@load was at +6%.


Conclusions
Please share data. I would like to see long term fuel trim snapshots from other RS4 owners - it only takes one minute to check. If you have any of the symptoms listed above, you should consider servicing or changing your fuel injectors during your next carbon clean. If you have a positive LTFT >10% on either bank you might not want to wait that long.

In my opinion, fuel injector maintenance should be integrated into the maintenance schedule for our cars. I think once every 40k miles or 2 carbon cleanings is more than sufficient, but I'll be monitoring my fuel trims to see at what point they start to degrade.

[komseh]

Reserved

[alexj87]

I recently had my injectors replaced while hunting down a misfire.

FWIW - FCP Euro seemed to have the lowest price on Injectors

and if you are in the northeast Marren Labs is one known place for injector testing/cleaning https://www.injector.com/

[komseh]

I recently had my injectors replaced while hunting down a misfire.

FWIW - FCP Euro seemed to have the lowest price on Injectors

and if you are in the northeast Marren Labs is one known place for injector testing/cleaning https://www.injector.com/

Did you buy the Hitachi or OEM from them?

[WinterRunner]

I don't think I"ve ever had this done, and after 86K miles, and 4 carbon cleans, I ought to look into it next go around...

[alexj87]

079906036D - OE Part #
079906036D - Hitachi Part #

I went with Hitachi, didnt feel like paying another 100 bucks for a box that says Audi

[komseh]

Did you buy the Hitachi or OEM from them?

Ah okay, well the Hitachis can be gotten for $57 per injector from Rockauto.

[komseh]

I don't think I"ve ever had this done, and after 86K miles, and 4 carbon cleans, I ought to look into it next go around...

Would you mind checking out your fuel trim numbers in VCSD and posting them here?

[alexj87]

Ah okay, well the Hitachis can be gotten for $57 per injector from Rockauto.

Son of a bitch! hahaha i guess this is what the forums are for, good on you!

[WinterRunner]

Would you mind checking out your fuel trim numbers in VCSD and posting them here?

If you give me a quick how to/write up on doing so, I'd be glad to. I don't even come close to utilizing the capabilities of vagcom, I'm ashamed to say....

[komseh]

No problem:

Ignition on, Engine off

1. From main screen, click "Select Control Module"




2. Select tab "Drivetrain" then "01-Engine"




3. Select "Meas. Blocks - 08"




4. Select the first Group field, enter 032 and click Go. The highlighted field labeled "Adaptation (Partial)" is the number we are concerned with, but go ahead and provide both numbers. The idle fuel trim is useful as well.




5. Go back to step 2, select "11-Engine II", and repeat steps 3 and 4 to get the reading from Bank 2. You can also view both banks at the same time by selecting controller "31-Engine other"

[ven0m]

Causes
In our cars the fuel injector heads are exposed to the combustion chamber so they can get carbon on/in them just like our intake valves. Fortunately the buildup is not near as dramatic as the on intake valves. However, when you have a tolerance of 1 micron any amount of carbon buildup can affect the injector flow in a big way.

Question

Wouldn't this be the result of normal wear over time and not carbon build-up?
How would the carbon come into an injector that is constantly under pressure and if it did, wouldn't the fuel that is going out of the injector push the carbon out again?

I understand that the seals etc. wear out over time, it is a normal wear and tare item, but blaming that on carbon build-up in our FSI's is a bit vague.


Just my 0,02$


ps: I'm going to a tuner for some dyno runs next week and to disable the vmax digital limiter. I'll ask him to also check the values for the injectors, I'm curious about the values and I'll compare them with the posted ones so I have a reference what good values are.

[nross33]

Would you mind checking out your fuel trim numbers in VCSD and posting them here?

Oops

[komseh]

Question

Wouldn't this be the result of normal wear over time and not carbon build-up?
How would the carbon come into an injector that is constantly under pressure and if it did, wouldn't the fuel that is going out of the injector push the carbon out again?

I understand that the seals etc. wear out over time, it is a normal wear and tare item, but blaming that on carbon build-up in our FSI's is a bit vague.


Just my 0,02$

You're correct. The primary buildup happens on the surface of the injector tip. This happens to all fuel injectors over time, but ours is accelerated because the injector tips are exposed to the heat and carbon of the combustion chamber.

As far as carbon buildup INSIDE of the injectors, that was more of a guess on my part. The person who cleaned my injectors said there was sludge inside of them and that this was unusual in his experience. Perhaps I ran into a bad tank of fuel or two, but I would be surprised if the fuel was dirty enough to cause sludge buildup. Then again, the car had 60k on it before I got it so who knows what the PO put in the fuel tank.

[WinterRunner]

I will do so, thanks for the rundown, should have results tomorrow.

[WinterRunner]

Would you mind checking out your fuel trim numbers in VCSD and posting them here?

So here is the consensus:

Bank 1: -2.0%, -1.2% Bank 2: -1.4%, -2.0%

Not entirely sure what these mean, but they seem pretty consistent among the 2 banks.... Please comment and enlighten me ;)

[komseh]

So here is the consensus:

Bank 1: -2.0%, -1.2% Bank 2: -1.4%, -2.0%

Not entirely sure what these mean, but they seem pretty consistent among the 2 banks.... Please comment and enlighten me ;)

Those numbers mean your motor is running slightly rich at idle and load on both banks. You couldn't ask for better fuel trim numbers imo.

I don't think you would benefit much from cleaning or replacing your injectors. Keep an occasional eye on the numbers though and let me know if any of them get near -/+ 5%.

[Flying Tomatoes]

A buddy of mine just did this a few months back on his car. He's around 110k miles. The before and after cleaning flow numbers were pretty astonishing.

[komseh]

Those numbers mean your motor is running slightly rich at idle and load on both banks. You couldn't ask for better fuel trim numbers imo.

I don't think you would benefit much from cleaning or replacing your injectors. Keep an occasional eye on the numbers though and let me know if any of them get near -/+ 5%.

WinterRunner, just wanted to add there's nothing wrong with preventative maintenance. It would be good to see before/after flow rates on injectors that aren't showing symptoms too.

[WinterRunner]

Thanks komseh, I'm glad they look good. Regarding preventative maintenance, other than cleaning or replacing, what is there to do for the injectors?

[komseh]

You could run some fuel system cleaner, but there is little benefit to that kind of product if you run a fuel with detergents like chevron or shell.

[WinterRunner]

I run the Audi FSI additive once every 4-5000 miles, and only use Shell, maybe that's why they look so good at my mileage...

[Quattrors4]

injectors can be replace for cheap now ,they are like 67$ a piece ,i just replace all off them for under 600$

[Jason@Addict]

Have been doing a lot of these lately - with good luck from just cleaning them as opposed to buying all new. The main thing is actually the spray quality in addition to the flow differences. I suspect it's mainly a result of carbon build up. Usually manifest itself in idle misfires that start to affect partial throttle and cruise. Easy enough fix and makes a big difference in start up roughness and overall smooth running at low loads. Can improve peak power as well depending on how bad they are.

[CoreyRS]

Have been doing a lot of these lately - with good luck from just cleaning them as opposed to buying all new. The main thing is actually the spray quality in addition to the flow differences. I suspect it's mainly a result of carbon build up. Usually manifest itself in idle misfires that start to affect partial throttle and cruise. Easy enough fix and makes a big difference in start up roughness and overall smooth running at low loads. Can improve peak power as well depending on how bad they are.

Jason, did you take any pictures? Im curious to see what they look like...but currently my laziness > curiosity :-)

[komseh]

Visually they will just have a thin layer of brown carbon on the tips.

[komseh]

I don't run them, but I believe Hitachi is the manufacturer for all of the injectors that fit the RS4. I'm not sure if the OEM branded ones go through any additional quality control, but that could be the difference. Or it could just be Audi pulling their normal pricing premium bullshit. I think several members run the Hitachis including alexj87 who posted earlier in this thread.

[FWP!]

There was somebody who started a thread about this very topic about a year ago, I can't find it. But he had charts provided to him by the company who reconditioned his OEM injectors, and they showed before/after differences and it was pretty nice looking. They were able to get them all matched within 2% IIRC. I've been searching and I can't find the thread, I was going to send mine in to the same shop he sent his the next time I do a carbon cleaning.

[komseh]

There was somebody who started a thread about this very topic about a year ago, I can't find it. But he had charts provided to him by the company who reconditioned his OEM injectors, and they showed before/after differences and it was pretty nice looking. They were able to get them all matched within 2% IIRC. I've been searching and I can't find the thread, I was going to send mine in to the same shop he sent his the next time I do a carbon cleaning.

Anyone with an ASNU machine should be able to generate those reports accurately . I added a picture of my report to the OP.

[RS4POWER]

There was somebody who started a thread about this very topic about a year ago, I can't find it. But he had charts provided to him by the company who reconditioned his OEM injectors, and they showed before/after differences and it was pretty nice looking. They were able to get them all matched within 2% IIRC. I've been searching and I can't find the thread, I was going to send mine in to the same shop he sent his the next time I do a carbon cleaning.

That thread was started on QW.

Here you are: (Car had ~105k miles, several injector cleaners introduced and italian tune-ups aplenty)

[highPSI-S4]

Having an issue with the car now and don't want to throw money, was thinking injectors but it might be a combination of things. this is a rough summary of todays events.



1. Replaced Rear 02 Sensors with (2) new Bosch units for Emissions testings.
2. Drove around a lot so the car could adapt since I didn't know or could not find anything related to setting readiness on RS4's
3. 1 hr later car is ready for emissions testings
4. Car is backed up onto emission service station ramps and within seconds falls on its face
5. Tried starting the car, once car was level again and CEL popped on, pulled codes and got a code for N276 Malfunction.
6. After car started we cleared the codes and drove it, no issues.
7. Because of the codes we were going to have to drive around again to set readiness, but decided to Contact ROSS Tech instead with assistance on setting readiness manually.
8. ROSS Tech on the phone guiding me through the steps for setting readiness, everything going well. Basic Setting (Value 71) Emission Reduction = PASS
9. Next, Basic settings Value block (34) Lambda Control, with foot on the brake pedal, use other foot and press the accel pedal until 2K RPM and hold. (this is where the car acted up)
10. Car is stuttering and misfiring while trying to set readiness with a flashing CEL, so we back off the throttle.
11. Contacted Jimmy Bones for better VAGCOM assistance, and we were able to monitor misfires at idle and load.
12. Don't remember the block values but I was seeing constant misfires on cyl 5, 7, 8 with a count of like 300+ each cyl.
13. Initial thinking is injectors, Jimmy performed a Carbon clean on my car 5k miles ago with new plugs, and other parts. (Fuel Filter was replaced 1 1/2 wks ago)
14. thoughts?

[OscarMeyer]

Did you check the fuel pressure on the hp and lp pumps? Are you meeting requested values? If you are, then I would say it's your injectors.

[highPSI-S4]

Did you check the fuel pressure on the hp and lp pumps? Are you meeting requested values? If you are, then I would say it's your injectors.

Ahh, I thought I missed something. Thank you for that!

We did check the HP, LP, pumps and requested vs actual values. At idle requested vs actual was the same, with load applied Actual values and Requested value still matched.

[highPSI-S4]

So I went into the garage today to start the car, rough misfire during the cold start but no CEL. took out the VAGCOM to log and drove down the street still no misfires. once car was warmed up CEL started flashing and I counted 300+ misfires on CYL 5, 7, 8.



Here's my results from logging.

[Quattrors4]

So I went into the garage today to start the car, rough misfire during the cold start but no CEL. took out the VAGCOM to log and drove down the street still no misfires. once car was warmed up CEL started flashing and I counted 300+ misfires on CYL 5, 7, 8.



Here's my results from logging.

go to engine other and check idle and long term fuel trims and post it, block 32

[highPSI-S4]

I though maybe I didn't get a good screen shot, but looking again no values for Bank 2. I assume its a bad o2 on bank 2?

[Quattrors4]

how many miles since you cleared r reset the ecus?

[highPSI-S4]

How many miles? No clue, codes are cleared every Time I use the Vagcom. So 5/6 times.


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[Quattrors4]

How many miles? No clue, codes are cleared every Time I use the Vagcom. So 5/6 times.


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well you need to drive the car for a few miles 25 at least if its running of course and then check block 32
ecus needs time to adapt

[highPSI-S4]

Yeah, is running but I'm not gonna drive it.
Started the process of removing the injectors and sending them off to get cleaned and flow matched, also going to swap the coil packs to see if misfires follow to rule them out.

Also will add, it's be roughly 4k miles since carbon cleaning and the valves already have black gook all over them. I assumed it would be a little bit cleaner.

I'll post those pics later.

FYI, pulling the injectors was a pita, anyone have a good procedure for injector removal? I pried mine but didn't feel comfortable applying so much force?





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