1997 E320, suddenly looses acceleration

[Bigdaddybenz]

This happened twice......Driving along, suddenly gas pedal does not accelerate the engine when applied, tach stays at idle, engine runs smooth, no check engine light, car coast to a stop.....

Pull over, restart engine and vehicle accelerates correctly as if something was "rebooted"

This happened twice today, I suspect that it will get worst, please any advice would be greatly appreciated!

Thanks, in advance!

[Arthur Dalton]

Car is going into Limp mode ...have it scanned for codes

Also, does it do it right after brake application?

[Bigdaddybenz]

Scanned for CAN codes?????............I would think that limp mode would cause the check engine light to come on.......I experienced the infamous misfire problem because of a defective spark plug connector last year and the engine management system apparently cut off the fuel injector in an attempt to save the converter.......I was under the impression that this was considered "limp mode" as I was still able to operate the vehicle in a diminished capacity.

I am certainly not questioning your advice, I simply wish to better understand the concept.

[Bigdaddybenz]

ps, no check engine light activated during this episode........Check engine lamp works as it briefly turns on (tests) during the normal engine start up procedure.

[Arthur Dalton]

A limp activation can come from traction system , EA , or CC fault and that is why I asked about the brake.

So, again, did you notice the problem after using the brake pedal????????

Is yes , then change the infamous brake lamp switch.

[Bigdaddybenz]

Actually, this happens during my commute at highway speeds between 50-70 mph, without brake application.....Had several episodes of this today in the 40 mph range without touching the brake pedal........If I were to describe the "feel" of the gas pedal when this happens, I would say that it feels "airy" and it is completely unresponsive, no matter how many times I step on the gas pedal, the engine remains at idle speed and will not throttle up!.....If you look at the tach, it remains in the 800 rpm (idle range) as aI coast to a stop, at which point I remove the key and restart the engine then proceed to drive as if nothing happened at all until the next episode.....

If this were not a Mercedes, I would best equate this to a broken throttle cable that somehow repairs itself once I restart the car.......ps, at no time does the engine stumble or misfire during these episodes, it jus simply drops down to idle speed, remains SMOOTH running and will not respond to the gas pedal being depressed.

You mentioned "limp mode" earlier, but wouldn't limp mode allow you to move the vehicle, to some degree????? When this happens, my car just coasts and will not accelerate at all......Just for the sake of diagnostics, I pulled over, put the tranny in park then shifted into gear, I could feel the trans kick in but when attempting to accelerate I get ZERO response and the car will not move..................Once I restart it, BAM! Everything's normal.........Today the frequency of episodes is increasing and I'm clocking them by miles, it is occuring about every 20 miles driven, or so.

Hope the helps, please reply and thanks for th email!~

[Arthur Dalton]

Scan for codes ..I think you will find a conductor plate output sensor code..

[Bigdaddybenz]

Arthur!!! I scanned for codes using my OBD II, one code emerged "PO455" "EVAP Emission Control System Leak" (LARGE).......I erased the code and restarted the vehicle.....

Would a "PO455" cause the problems that I am experiencing or is it incidental to my recent troubles????

Thanks in advance

[Bigdaddybenz]

ps, forum archives come up with a basic description for 2 forms of "limp mode"

E420 Transmission Control Problems

When my problem occurs the engine drops to idle speed and pressing the gas pedal does absolutely nothing, the car will not move at all!

[Bigdaddybenz]

Ok, I'm finally catching on.......I need an SDS scan of the transmission, correct?

[Arthur Dalton]

PO355 is am emmissions code and that will light the CE
A trans speed sensor code can cause your problem and not light a CE .
So, yes ,I would scan the trans .

No other codes with your scanner???

[Bigdaddybenz]

No other codes, just the PO455" "EVAP Emission Control System Leak" (LARGE)

just a shot but just checked my trans fluid level and it is low, barely shows on the dipstick tool.......would low fluid level force the trans into limp mode???

[Arthur Dalton]

I sure would start there ..certainly something to consider/try before getting into anything.

[Bigdaddybenz]

Ok, I'll take your advice.......Let me ask, as my symptoms do not appear to match any description of limp home mode........How excatly is it that you suspect my car is going into limp home mode as when this occurs my car will not move under any circumstance until I restart the engine????

I'm REALLY confused about this and would really love to understand the concept.

Once again, thanks in advance!!!!!

[Arthur Dalton]

I only suspect your car is getting a signal to limp ..that can be many things and a scan should tell you what direction to go.. that's all. The ECU resets until it gets the limp causing signal again.
Is it a pressue sensor from low fuid?? I don't know that, but I would start with the correct fluid level before I went chasing around..

Again, there has to be a stored code..you expect a CE lamp with the code... but there are many codes that do not bring on a CE lamp b/c the problem is not effecting/related to emmissions .
I am not a electronic trans tech., but it is possible that codes would be a help in diagnosis the next step..