Rev limiters and "limp mode" have almost nothing to do with each other.

All modern car engines have various mechanisms to prevent the engine from over-revving, but none have any mechanisms to object to the user demanding the maximum power the engine was designed to produce, which is typically produced pretty darn close to redline. Most cars sold in the USA do have speed limiters that will roll off power when you approach a designated maximum speed.

Most of the time, the transmission controller will force an upshift and the engine controller will gently roll off power for the shift if you are accelerating and rapidly approaching rpm "redline".

If you do manage to trick the transmission and engine controller into a "hard-hit" over-revving situation ( as can more easily happen in cars with manual transmissions or less intelligent ATs ), the engine controller will get more aggressive with cutting fuel and whatever else it takes to protect the engine from excessive rpm ( NOT excessive power ). This is called "bouncing off the rev limiter" because that's what it feels like. If you are silly enough to stay "on the gas" the engine will cut out until it drops below redline, surge forward again, and repeat until you get a clue and lift your right foot. It sounds and feels terrible, but the vast majority of the time the engine protects itself, no "codes" are thrown, and life goes on.

[ One situation the engine controller may not be able to control is an over-rev from engine braking down a descent. That's up to the transmission controller. And/or the idiot behind the steering wheel. ]

"Limp mode" should only be invoked when a "trouble code" has been generated by the engine controller, and that should NEVER HAPPEN in normal operation, including running the engine right up to redline. If codes are getting thrown from accelerating on the highway, something is wrong. If "limp mode" is being invoked, something is wrong. End of story.

Whether that "something wrong" is a messed up transmission controller that is allowing downshifts into an over-rev condition, is a relevant question. But so far, there has been no documentation of that.

 

 

Precision crafted performance (as long as you don't ever plan on driving over 70 mph). You gotta read the fine print on these things...lol

It's pretty hilarious that someone would actually try to defend a brand new car going into limp mode because you tried to accelerate and pass someone going 70 mph. Something is seriously wrong.

 

Hello. I have filed a formal complaint about this issue with NHTSA. Read it online in a couple of days. It was a very harrowing experience to say the least. Acura dealership was clueless, but I have been told by a little bird Acura is investigating albeit on the QT.

 

 

 

First time it happened it was 8-9 in the morning, in the seventies, clear. Second time it was ten at night, very humid, but that’s it.

 

 

 

 

 

This could be a totally different problem but the early Ford 3.5 Ecoboost motors were notorious for this issue. Ford had to make a modification to the intercooler to fix it.

3.5L GTDI - INTERMITTENT STUMBLE/MISFIRE ON ACCELERATION FROM HIGHWAY CRUISE IN HUMID OR DAMP CONDITIONS - BUILT ON OR BEFORE 12/16/2013
TSB 14-0017
FORD:

2013-2014 F-150
This article supersedes TSB 12-11-15 to update the vehicle model years, build date, Service Procedure and Parts List.

ISSUE

Some 2013-2014 F-150 vehicles equipped with a 3.5L gasoline turbocharged direct injection (GTDI) Ecoboost® engine, and built on or before 12/16/2013 may exhibit an intermittent stumble and/or misfire on hard acceleration after extended operation at highway speeds during high humidity or damp conditions. This may result in either a steady or flashing malfunction indicator lamp (MIL). Diagnostic trouble codes (DTCs) P0304, P0305, P0306, or P0430 may also be present. Evidence of misfire may be available in Misfire Freeze Frame Data even with no active DTCs.

 

^^^Interesting. Acura will probably tell us it's a safety feature to get us to drive slower in rainy weather.

 

 

 

I owned a Ford Flex that had an Ecoboost engine with the same problem...although it doesn't sound as severe as the RDX issues being reported. After countless trips to the Ford dealer, and countless times me bringing up the same F-150 recall issue you quoted, they always just told me they couldn't replicate it, and being that this was a Flex and that issue was with F-150s, they wouldn't even acknowledge the issues were related. I eventually sold the car for fear of my family's safety.

 

 

 

I opened a case last month. All Acura did was call my service manager to verify no codes, and left me a message saying they will make note of the issue. I called back to ask what would cause limp mode in general, I never got a response.

 

If all it takes is a momentary engine misfire to trigger a full "cripple mode" of the vehicle, it seems like Honda/Acura is being overly protective of their engines.

It could be something as simple as condensation on the inside of the air intake getting dislodged and sucked into the engine with the increased airflow of higher rpm operation. The engineers can examine their computer code all they want, they won't find that.

Back in the day, I drove my Dad's carburated International Harvester Scout Traveler ( look that one up, 4WD geeks! ) and that thing would stall nearly every time I punched the throttle to turn onto a 2-lane major truck route near my family's home. So then I'd be wrestling the thing onto the gravel shoulder at low speed without the benefit of power steering, as an 18-wheeler approached at about 75 mph. Good times. That was a problem with the completely analog fuel delivery and vaporization system.

With our 1st-gen MDX(s), when the oxygen sensors get a bit flakey with age, the things occasionally throw a code, illuminate the "Check Engine Light" and "VTM-4" light, and shut off the AWD system. Mr Murphy demands that this happen in a snow storm. The engine is running fine, it's just a potential emissions problem. There is no problem with the AWD system. So, WHY SHUT DOWN THE AWD?!!!! ( Pet Peeve )

 

 

Wow...

 

 

Is this an Acura thing? An RDX thing? Something else??

 

So, a little update. The dealership the car is at found codes stored in the computer. The same codes it threw the first time it happened. The last update I received was that they are waiting for someone to tell them how to fix it. Acura client relations and the dealership are actually being very helpful right now surprisingly.

 

 

I had a 2013 Hyundai Veloster Turbo and under certain high boost, high rev conditions it would go into limp mode. Many, many owners had the same issue. Hyundai eventually figured out that one of the rubber fuel lines was collapsing under the extreme draw of the high pressure fuel pump. starving the engine of fuel and causing the limp mode. They replaced the line on affected cars and implemented the new part into the new builds. Never had an issue again after that.

To those of you having this issue (or even other ones), a wise and cheap investment might be an OBD2 dongle and an app like Torque or Dash Command for data monitoring and logging info.

 

 

 

 

 

OTA updates are ONLY for the "audio system".

The ECM, TCM, or other modules CANNOT be updated via OTA.

 

My understanding (could be wrong, wouldn't be the first time) is that the OTA updates are for the infotainment system - programming updates for any of the vehicle control computers is done 'hands on'.

 

The more I hear about Acura client relationship the more I feel it is just a therapy call center, powerless and without real info. It is just human voice to tell you everything will be alright......

 

HAL 9000: "I'm sorry, Dave. I'm afraid I can't do that."

Spoiler: Everything wasn't alright...

 

This conversation can serve no purpose anymore. Goodbye.

 

"Acura Client Relations" is a frontline, level one support team in a call center full of dozens of agents - most of which will never own an Acura. Sort of like calling a garbage man a "sanitation engineer". We have access to the SAME information they do - it's called "the internet". These customer service numbers are primarily for people who don't know how or are too lazy to read their owner's manuals and don't understand how to call a different dealer if they're not satisfied with the one they tried to use.

 

Going to a different dealer isn't always trivial. In my mid-size and growing city there is one Acura dealer and two Honda dealers. The next closest Acura dealer would be about a 1.5 hour drive. After that, about 3 hours.

If you know of a dealer service department that will provide diagnostic consultations via telephone, please share!