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B7 RS4 misfires at high RPM

 
Old 07-29-2015, 08:47 AM
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Default B7 RS4 misfires at high RPM

So I'm having a new issue with my '07 RS4. The car runs like new, full power, very happy, until I bring the revs up much over 5k, say around 5,500 or 6,000, I get misfires on cyl. 1. The issue is consistent whether at full load or bringing the engine up to speed slowly, hot or cold. The interesting thing to me on this is that once I create that environment where cyl 1 starts misfiring, it does not stop misfiring until the ignition is turned off. This can be simply pulling into a parking lot, key off for 5 seconds, restart, problem gone. I've already swapped coil packs and spark plugs from cyl 1 to cyl 2, but the problem doesn't follow those parts. Within a few thousand miles ago, the car was in for manual carbon cleaning, got new spark plugs at that time, and at 112,000miles seems faster than I ever remember. Very healthy and still operates full power and without issue as long as revs do not get too high. Which is annoying only having a couple months of new clutch, super clean with tubi rear silencers before this started. Any ideas on what could cause this?
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Old 07-29-2015, 10:52 AM
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Mmmmmmmm Tubi!

Well that sux High pressure injector or injector harness perhaps? It's a royal pain to swap them to see if the issue follows though. You might check the output of the pre-cat O2 sensor on that bank to see it's reading when it misfires. For example, if it goes lean, the #1 injector might not be delivering adequate fuel. If it goes rich, then perhaps it's losing spark on #1. You'll have to get a baseline when it's running good to compare. Just curious, are the ECU's flashed?

In the mean time, it wouldn't hurt to run some good injector cleaner. I buy RLI Bio-Plus™ Injector Cleaner Gas Conditioner by the gallon and run it in every tank of fuel for at least 5-6 years now. At $42.85, that turns out to be about $0.33 per tank. You can double the dose for super-cleaning too, but I just do the "maintenance" dose of about an ounce per tank. Disclaimer: I have NO affiliation with that company whatsoever.

Bio-Plus? Fuel Injector Cleaner (1 gallon jug)



Hope you can get it sorted.

Last edited by ELEVENS; 07-29-2015 at 10:54 AM.
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Old 08-13-2015, 11:07 AM
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Yeah the standard tubi, in my opinion, must be the perfect exhaust for this car. It does everything you'd want and all but disappears from inside the cabin at constant rpm. I now drive with the windows down and no music 95% of the time. I do have an AWE tune that I've been running for four years. Curious why they still don't have it as an available tune for sale on their website though. That gives a little concern, but car has been good with it so far so whatevs. Where do you buy the BioPlus?
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Old 08-13-2015, 07:01 PM
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Originally Posted by Wombat1482 View Post
Yeah the standard tubi, in my opinion, must be the perfect exhaust for this car. It does everything you'd want and all but disappears from inside the cabin at constant rpm. I now drive with the windows down and no music 95% of the time. I do have an AWE tune that I've been running for four years. Curious why they still don't have it as an available tune for sale on their website though. That gives a little concern, but car has been good with it so far so whatevs. Where do you buy the BioPlus?
You need to go back to oem flash
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Old 08-14-2015, 05:21 AM
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Originally Posted by Wombat1482 View Post
<clip>
Where do you buy the BioPlus?
Directly from the RLI website. The link is in my previous post.
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Old 08-14-2015, 01:40 PM
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Okay thanks, I ended up getting it off of amazon, but wasn't sure if it was available in-store. I'll post on any findings. Has anyone out there posted any good pictures of wiring schematics, fuel schematic, or just a layout of the engine bay to identify things to give me a bit of a head start? And I may be dated on this, but do these cars still use ignition control modules? Basically I'd like to know where the voltage to the ignition coils originates from so I can check harnesses. And trying to get a heads up on procedure to pull injectors.
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