Troubleshooting help needed: High rpm, full load miss
04-09-2008, 10:07 AM
#1
AudiWorld Super User
Thread Starter
Troubleshooting help needed: High rpm, full load miss
2007 RS4. Here's the symptoms:
In 3rd (or higher) gear, full throttle, I can feel the engine missing from about 7000-8200rpm. It only happens under full load, full throttle, very high rpm.
No CEL, no autoscan VAG-COM faults, only a very few and random misfire in VAG-COM, usually none, but still misses even when zero misfires are logged.
I would like to narrow the problem down prior to bringing it into the dealer, because reproducing the problem requires speeds above 90 mph - which could be dangerous for the Tech during business hours. I do my testing late at night with no traffic on a divided freeway. But the car needs to get fixed so I can drag race it this Spring.
Seems almost like a fuel starvation issue to me (fuel pump, fuel pressure regulation, fuel filter, injectors). Any ideas what I should be logging to narrow down (or nail) the problem?
THANKS!
In 3rd (or higher) gear, full throttle, I can feel the engine missing from about 7000-8200rpm. It only happens under full load, full throttle, very high rpm.
No CEL, no autoscan VAG-COM faults, only a very few and random misfire in VAG-COM, usually none, but still misses even when zero misfires are logged.
I would like to narrow the problem down prior to bringing it into the dealer, because reproducing the problem requires speeds above 90 mph - which could be dangerous for the Tech during business hours. I do my testing late at night with no traffic on a divided freeway. But the car needs to get fixed so I can drag race it this Spring.
Seems almost like a fuel starvation issue to me (fuel pump, fuel pressure regulation, fuel filter, injectors). Any ideas what I should be logging to narrow down (or nail) the problem?
THANKS!
04-09-2008, 06:39 PM
#3
AudiWorld Super User
Thread Starter
How do you check the vacuum system, other than visual
Seriously, I have plenty of vacuum gauges - static and differential - but what should I be lookin for? Or are you speaking of checking the vacuum system (somewhere) in VAG-COM? I've not seen a vacuum problem cause problems at high rpm - other than a vacuum leak to a vacuum controlled fuel pressure regulator. Are you asking me for the ECU part number and software version? What's the connection?
04-12-2008, 09:22 AM
#4
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Apply vacuum to the system using a hand vaccum pump with gauge and see if it keeps it.
The 4.2l FSI intake flaps as well as the tumble flaps are vacuum system operated, if this is not operating correctly the engine will indeed loose power. Since you de-flapped it, you may want to check your sealing there first...
In terms of ECU part number and software version, based on our experience especially with US models they are usually less up to date than for example German models. Newer software versions sometimes come with updated fault detection which makes it easier to find problems. We have also seen cases where subjective power loss has been fixed by software updates as well as the normal bug fixes like cold start issues, jerking and similar things.
In terms of ECU part number and software version, based on our experience especially with US models they are usually less up to date than for example German models. Newer software versions sometimes come with updated fault detection which makes it easier to find problems. We have also seen cases where subjective power loss has been fixed by software updates as well as the normal bug fixes like cold start issues, jerking and similar things.
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