True or false?

[BoSNiaN]

Hey guys, been getting an intermittent CEL since yesterday and since I don't have my laptop setup with vagcom yet, I went to a local Audi shop I am good with and they scanned it for me. Few misfires that he went on to explain but I want to make sure he knows what he is talking about before I try to figure out the cause.

1)Our cars are not able to pinpoint an exact cylinder misfire especially at high RPMs. When a misfire happens, multiple codes get spewed for "random" misfires. This would mean you couldn't switch out a single coil pack by knowing which one is bad.

2)Flashing CEL always means a misfire, and it is logged, but only temporary (stops flashing on the dash once the misfires stop occurring).

3)Generic OBDII readers will not even output basic codes (I tried this today with mine and it just said "E" for error I think, so this might be already confirmed).

4)Turbo only spools during acceleration/load, so I could rev to 7000K RPM in neutral and my turbo would never be activated.

[Ed Gein]

4)Turbo only spools during acceleration/load, so I could rev to 7000K RPM in neutral and my turbo would never be activated.

Really dude? Do you even know how a turbo works? As long as your engine is running your turbo is spinning, or "activated" as you like to say. Exhaust gasses spin one side of the turbo which spins the other side at the same time forcing air into your engine. Hence the term "forced induction". You dont get boost or "activation" until the engine spins the turbo fast enough to force air in.

[Fourplay]

Really dude? Do you even know how a turbo works? As long as your engine is running your turbo is spinning, or "activated" as you like to say. Exhaust gasses spin one side of the turbo which spins the other side at the same time forcing air into your engine. Hence the term "forced induction". You dont get boost or "activation" until the engine spins the turbo fast enough to force air in.

Do you even know how a turbo works? Because there isn't enough engine loading in neutral to continuously spool a turbo, regardless of how high you rev it. The only way you can get enough load to spool in neutral is a launch control system (2-step, etc.) or an anti-lag system, both of which create enough engine load to spool the turbo in neutral.

OP, you may be able to get 3-4 psi by blipping the throttle in neutral, but you cannot sustain it with just throttle blips. No load = no spool.

[Ed Gein]

The way he worded it I didnt even think he knew what a turbo was so I explained the basics. I know you dont get boost unless the engine has a load on it just like it wont make power/torque unless it has a load.

[STONER]

1) Extremely easy to diagnose a misfire. Yes the scan tools are very good you just have to know how to read the info. They have a misfire counter. So say your driving and it starts flashing, which is indication of a misfire taking place, hook up scan tool drive it watch what cyclinder is misfiring the most. Say its cyclinder 1. Take spark plug move it to cyclinder 2 and coil to 3. drive again, watch the counts. if the counts go to 3 then you know its a coil issue. same with 2 except plug. now if it stays at 1 then dig deeper. could be injector, which is associated with decent amount of smoke. You could have compression issues, but thats another story.

[DRAKLORE]

Ok everyone calm down... Let's not give misinformation...
Fourplay is correct, and just because your creating exhaust gasses doesn't mean they are flowing over the turbine, the wastegate bypasses the turbo when there is no load, I'm pretty sure it's because it would be bad for the turbo if it were to build boost as well while the rpms rise and fall so fast under no load... But that portion is purely speculation on my part, and Sprode could tell you exactly the reasons.

I'm going to say that most modern engines are fairly capable of determining what cylinder is missfiring. In my experience with several different cars there is a missfire counter and also a monitor which allows you to ^see which cylinders are misfiring the most.. Which includes an exact number of times each cylinder has misfired. Now I'm sure if Astros vans and neon coupes use obd2 in this fashion... That the audi is also as capable.
As far as generic code readers, I have a 35$ reader that tells me the codes and brief description.
Flashing CEL doesn't necessarily mean misfire, it actually means pull the fuck over their is a catastrophic condition occurring, the ecu categorizes codes into specific classes and determines when and how to set the engine light, this is linear accross
All makes and models using obdii. Flashing CEL usually means that what's occurring will either damage the catalyst or motor.
Most of the time this condition is a misfire though.
So one two and three are completely false
Four is false but you are close :-)

[Sprode]

Hey guys, been getting an intermittent CEL since yesterday and since I don't have my laptop setup with vagcom yet, I went to a local Audi shop I am good with and they scanned it for me. Few misfires that he went on to explain but I want to make sure he knows what he is talking about before I try to figure out the cause.

1)Our cars are not able to pinpoint an exact cylinder misfire especially at high RPMs. When a misfire happens, multiple codes get spewed for "random" misfires. This would mean you couldn't switch out a single coil pack by knowing which one is bad.

2)Flashing CEL always means a misfire, and it is logged, but only temporary (stops flashing on the dash once the misfires stop occurring).

3)Generic OBDII readers will not even output basic codes (I tried this today with mine and it just said "E" for error I think, so this might be already confirmed).

4)Turbo only spools during acceleration/load, so I could rev to 7000K RPM in neutral and my turbo would never be activated.

Jesus guys.

1) I don't know how well the car self-diagnoses misfires. If it is only happening at high rpm, it may take you 4 tries to figure out which is which. If you are asking if you can buy a single coil pack yourself to test it yourself, you can certainly use the swap method. I have an extra coil for testing my supra as well.

2) Flashing CEL can mean many things. It just happens to most often mean a misfire. It is ALWAYS potentially catastrophic for your engine.

3) OBDII is not going to give you the codes you need to VAGCOM for, no.

4)



Compressors have a minimum rpm where they will begin to build pressure based on blading design/curvature and aero concerns. If you look at the compressor map above, the horizontal lines across the map are constant speed lines. Admitted, that isn't our turbo (it is bigger than ours) so the speeds aren't correct (ours will spin faster). But there is a minimum shaft RPM that must be achieved before the compressor will produce pressure.

Anyone who's stared at the boost gauge knows, especially in high gear and low rpm, as soon as you punch it, the boost gauge will show just about 0 for a bit, then take a little while before it will start producing positive pressure. This threshold is caused by the shaft accelerating below and up to said threshold. The load on the turbo/engine, just like weight transfer in the drag suspension thread, allows more TIME for the conditions to affect the state of the system. It is also why you boost lower in first gear.

Shane: Wastegate bypasses when there is too much load, not too little. Gasses are always going thru the turbine. And the bypass/blowoff valve keeps your turbo from surging when you rev in neutral. Surge under load is really the only thing that is really bad for your turbo.

[BoSNiaN]

Ok, thanks for the reply guys. If 1 cylinder will misfire more than the others, that is helpful to know but still more work than it telling us "cylinder #1 misfire" and not spewing out #2-4 as "random" misfires as well. Also, will misfires ever cause the CEL light to stay on solid, even if they have stopped? 2 days ago, I caused misfires twice and both times it flashed for 10-20 seconds and the CEL went away, yesterday I caused it, it first flashed, but now is solid on my dash


@Shane, what OBDII reader do you have? Other people seem to think it wouldn't work either

[BoSNiaN]

Also, do any mechanical parts we buy from the dealership come with a warranty? Example: bought 4 new coils from the dealership yesterday, if they crap out in 30 days or under a year, can I bring em back and get a new set if I still have the receipt?

[abhisabs_86]

i totally agree with sprode in terms of the turbo behavior...i work on turbos(very large ones) as my profession...the compressor map shown by sprode is the approximate size i work on...wastegate is a failsafe device which activates when certain conditions are met inorder to avoid damage(mostly at very high load and never at low loads)....and yes exhaust gases are always passing over the turbine wheel and once the compressor wheel reaches a minimum required rpm it will start producing enough positive pressure..hence we see a turbo lag....

[abhisabs_86]

hey bosnian....did you say you bought the coils....as far as i remember ignition coils are a recall item and are prone to failure ....and since you have misfires and CEL on they should have replaced it for free...even if they did not you should be able to return it and get a replacement if they go bad

[Sprode]

i totally agree with sprode in terms of the turbo behavior...i work on turbos(very large ones) as my profession...the compressor map shown by sprode is the approximate size i work on...wastegate is a failsafe device which activates when certain conditions are met inorder to avoid damage(mostly at very high load and never at low loads)....and yes exhaust gases are always passing over the turbine wheel and once the compressor wheel reaches a minimum required rpm it will start producing enough positive pressure..hence we see a turbo lag....

You consider 60mm to be a very large turbo? Have I got some stories for you then....

[abhisabs_86]

i meant larger...my bad....i work with CAT though

[BoSNiaN]

hey bosnian....did you say you bought the coils....as far as i remember ignition coils are a recall item and are prone to failure ....and since you have misfires and CEL on they should have replaced it for free...even if they did not you should be able to return it and get a replacement if they go bad

They were already replaced once after the recall, and I don't think theres any outstanding "extended warranty" on them from the factory, even if I am getting misfires and a CEL...I was more asking about the new coils I bought, if they come with any from the dealership.

[DRAKLORE]

A coil isn't exactly a mechanical device but I think it depends on how cool the parts guys are which determines whether they are willing to sit on the money waiting to get paid back by audi for the "faulty" part... Because it's them who would eat the money if audi decides the coil failed under normal conditions.
And I feel sort of like a jack ass for saying "no misinformation" then speak out pm anus a little bit about the turbo behavior lmao

Anyways the obdii reader I have I got at autozone, it's orange and gives codes and emissions parameters. I'll check the exact model later

Obdii was enacted in 1996 to create a format for engine diagnostics. So every make and manufacturer must comply.
Previous to that every auto manufacturer had different connectors and programs that they used to read their own codes and diagnostic parameters.
This made it very expensive to be a mechanic because of the multitude of computers and cables needed to diagnose the vehicles that came through the shop. So a fault, coding system was devised that would allow easier and universal diagnostic of every car. So a p0301 on every car was a misfire of cylinder 1 no matter what car. And tools like a "genisys" can be hooked up and used on every car without having multiple connectors.
Typically every car is regulated to have certain parameters and codes that these "generic code readers" can access and monitor. But the obdii connector has multiple empty pins which allows for manufacturers to "add" data monitoring or programming features unique to their own computer based software and pin layouts.
So essentially there are still things like "VAG-COM" for VW/Audi or "IDS" (integrated diagnostic software) for ford and so on.
Those programs allow you deeper Access to modules that the "generic" programs do not have access to, which allows for programming and exclusivity to manufacturing dealerships.
Like Ross-tech you can still purchase the hardware/software to access those modules, but it will cost you$$$
People say Ross-tech is expensive!
IDS access for ford requires a 750$ cable and a yearly fee of 500$... And you have to be ford certified...
The genisys is a generic reader that is alot lot like the 20$ vag com cable and Ross tech lite yet it's a self contained unit and universal across most all platforms.
.02 worth of info.