What is limp mode
#2
Limp mode means that your engine threw a code that is more dangerous than your average code that throws your check engine light. I would never think this could happen on a car without boost as it is usually only caused by over boost issues.
#3
To be a little more specific than golfkid777's post, limp mode is generally triggered anytime you get a CEL depending on how the vehicle manufacturer sets up their ECU. When a vehicle is in limp mode, many things can change to prevent further damage and/or protect the engine from further damage. These things can include:reduced rev limit, different shift points, and retarded ignition timing which really is the most noticeable that I have experienced in past vehicles. This does not only apply to boosted vehicles however, all vehicles can experience limp mode.
#4
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Limp mode is found on I'd say the majority of vehicle motors these days and most often is caused by overheating or serious detonation issues, etc. It often times involves one of your cylinder banks shutting down (cut down to half the cylinders), spark timing retarded as conservatively as possible, etc...
#5
Yeah, I am new to the japanese scene and the NA scene. I just sold my Audi S4 and the only thing that could make that car go into "limp mode" was overboost. Some of my friends with A4s that had the NA V6's had major problems at times and their cars still had all the power and ability. When you had detonation or significant misfires the ECU just ran the car slightly richer to be safe but never threw it into limp mode.
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#8
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As I recently stated in another thread, a simple problem could also throw a GS in limp mode. I had the air intake piping come loose at the throttle body and sure enough, limp mode went into effect. I thought the car was starting to seize up or something, no power, would hardly shift, all kinds of lights on. Once I got it home and popped the hood, I found the intake piping about half way off at the throttle body. Buttoned it up and no problems since.
#9
Limp mode is when the MIL is illuminated for any code, the computer places in generic parameters for the suspected sensor, allowing the vehicle to still operate. It is referred as limp mode because the performance and fuel economy may be reduced. It doesn't have anything to do with boost or none boosted engines, or overheating. If there is the possibility of damage to the engine or catalytic system the MIL will flash warning the operator to shut down the vehicle and bring it in for service immediately, preferably by towing. One example is a misfire, raw fuel is being dumped into the exhaust and cat system and can cause the cats to melt down, the light will flash. If you have a faulty O2 or Air Fuel Ratio sensor the light may come on solid and generic parameters are used to try and keep the vehicle running as best as possible.
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