Cold Start Misfires - Injectors?

B6/7 S4/RS4
#1

I’ve been trying to get to the root cause of some cold start misfires I’ve been having, and I think it’s the injectors.

On cold starts, the car consistently misfires on cylinders 4 and 7 while idling. I have tried moving the coils and plugs around, but the misfires do not move, leading me to believe it could be the injectors. I do get misfires occasionally on the others at higher rpms (something else I need to troubleshoot eventually), but on cold starts it’s constantly 4 and 7.

Do you guys recommend changing out all the injectors while I’m in there? or just the problematic ones?

I was looking over injector prices and they seem to vary quite a bit. I can pick them up locally for 178 CAD at the dealership. But then I found them on a few sites for cheaper…

Mfg is CTS turbo but they’re described as “OEM”? They’re 87.50 USD each (!)
http://www.ctsturbo.com/cart/products/RS4_Fuel_Injector_Set_of_4-346-111.html

Some OES ones for 99.95 USD each
http://www.ecstuning.com/Audi-B7_RS4--V8/Search/SiteSearch/Fuel_Injector/ES2081134/

Which ones would you guys recommend? Also, are doing the seals (part 06E-998-907) recommended too? They’re $11 CAD each at the dealership.

EDIT: just to add, the plugs are somewhat recent - about 1.5 years and I think 15-20k kms. Fuel filter was also changed pretty recently. Coils were never changed but are the non problematic revision.

#2

email V8

with respect to purchasing what did Neil B say?

#3

Neil quoted $178 + tax each. And $11 + tax each for the seal kits.

#4

wonder what he’d quote me lol

#5

The CTS ones are oem. CTS doesn’t make injectors must just be a typo

#6

Would be great if you could give it a shot if you have time.

I just posted in the AZ Owasco Parts thread for the prices

#7

Cool thanks. If they’re actually OEM then it seems like the best choice.

#8

Before you replace them move them first. You already kjow carbon will cause missifres at low and moderate rpm… I would not spend a d8me till you know its the injectors…you moved the coils try the plaugs…also pulling out the iniectors and moving thrm might g8ve you a chance to zpot some issie with them

#9

That’s a good point. I keep thinking I did a carbon cleaning recently but it’s actually been around 15-20k miles and over a year since I did it. I had been planning to replace the injectors when I do a cleaning this fall, but moving the injectors around might be a good idea.

So I guess my next question would be whether the seals need to be replaced for just moving them around as well. Are they one time use kinda seals?

#10

Cold start misfires automatically means carbon build up to me. I would pull the intake manifold and do a good cleaning to start off with.

If that doesn’t fix it then start swapping fuel injectors. As long as you lube the blue top fuel injector seals really well with silicone then you will be fine.

#11

He just had it cleaned like 10,000 kms ago (6200 miles)

edit: mistro it was 20k miles!!!

wtf. You had it done last August I guess. Didn’t realise you drove that much. I have put 17,000 kms on since then.

#12

I’m assuming it is. I’m at work so I can’t check the exact kms but I recall I had somewhere around 50-55k miles on it when we did the testing at the strip last year. I’m past 70k now.

This is exactly why carbon didn’t cross my mind either lol. It felt like it was just done a few months and a few thousand miles back.

Edit: yeah seems like I had it done around the 50k mark
http://audirevolution.net/forum/index.php?topic=1077.msg25174#msg25174

#13

You might also want to look into having the injectors cleaned before just buying new ones right away. The smallest amount of varnish/carbon buildup can really mess up the spray pattern and atomization.

#14

^his car is FSI.

Otherwise BG 44K works wonders for cleaning fuel injectors.

#15

If anyone is looking for injectors I can get you better pricing then what’s listed :wink:

#16

Yeah, I thought I knew a show that worked on FSI injectors but apparently their equipment isn’t quite finished.