95 E320 brake pressed engine revs
 

My wife's 95 E320 wagon has been giving her some problems. She tells me when she pushed the brake today, the engine started to rev (all the way up to 3K). She claims her foot was not on the gas and has been mentioning it seems to surge when she's in parking lots but never like it did today. She said when it happened and it finally slowed, all the dash lights on the bottom came on. Not sure if that was because it died or she panicked and shut it down or what. Just repeating what she tells me. The car has 150K on it roughly. Wiring is original. Is this a wiring problem, sensor, vac anyone have any ideas?

OK, read the DM codes. Got 4, 5, 10, 16, 19.

DM = 4,5,10,16,19

Pin 8 = 4, 13

Pin 14 = 11 blinks.

a bit more data to add. When I sit in the car at idle, in park I push the gas peddle and the car sort of delays in response. Rev's maybe from 600 to 1K then drops back to 600RPM. Add more pressure, increases a little to maybe 12-1500RPM and drops back again, all the time keeping steady pressure on the foot feed. When it gets up to 1500-2K, then it holds the RPMS great at the higher end.

Also, my wife tells me that last couple tanks that the mileage has gone to crap. Usually gets 23-27 mpg, now getting 17 mpg. Does this add to anyone's thoughts on the underlying problems?

Sounds like wiring harness to me.

In total speculation mode: the only connection between brake and engine is the vacuum line to the intake manifold, though I don't see a direct reason for the big jump in rpms. Given the throttle problems, I would check on MAF and throttle body.

I had the same thing happen to me once this summer with my 95 E320, pulling into a parking spot. It flustered me a bit until I realized, while braking my foot was also pressing the gas pedal.

Historically - and this is speaking from what I know about the Audi problem in the 80s, after the problem finished splashing on the headlines - the problem is psychological. It is incredibly difficult for the driver to believe he is making an error with the pedals when his brain is telling him that his foot is standing on the brake pedal. That's why there were so many people who steadfastly insisted there was something wrong with the car. This problem extends to other models and incidents as well.

I offer that your wife may not realize she is touching the gas pedal while braking, especially if her foot is on an angle, as mine is while driving. Stories by 'witnesses' can be notoriously unreliable. Can you replicate the problem?

I understand today's vehicles are designed so there is about a two inch separation between the brake and gas pedals, and the brake pedal is two inches higher than the gas pedal. Perhaps the brake pedal has too much travel from air in the lines.

I'd love to blame this on my wife, but I think it's an actual problem of some kind. See my 3rd post on some idling data. That isn't normal for the car. The brake booster leaking has been suggested as well as the bloody harness may be raising it's head too.

That's okay. I'm just brainstorming. Try clearing the codes and see what reappears.

The problem may indeed be a bad engine wiring harness or bad throttle body wiring. You wouldn't be wasting money by replacing both. I replaced them in my car without waiting for problems to occur. The throttle body wiring and engine wiring harness looked everything like the pictures posted on this site. Replacement of the trottle body wiring was a no-cost DIY, once I got the wires.

Do you have any links or pics on the throttle body wire replacement? I didn't realize this was able to be done as a DIY and replacing wires. I thought it was a fairly expensive change out. Any info would be appreciated.

^You have to replace the entire throttle body.

There was an article online that illustrated the electronic throttle actuator rewire procedure, but I see that it's now pay-for-information.

Rewiring the Right Side Electronic Throttle Actuator (ETA) | V12 Uber Alles

The tricky part is to dissect the connector in a fashion that it can be glued back together. I made copious notes and drawings to keep things straight so I wouldn't cross wires.

Here's a link: http://www.restoreyourmercedes.com/Mercedes%20throttle%20body%20rewire.html

I found something from my computer that may help.