'94 E420 stumbles nearly stalls when cold - PeachParts Mercedes-Benz Forum

Larry Delor · #1 02-18-2007, 10:16 PM

I've notice lately that, when cold, the E420 just doesn't want to go - I feel safer stomping on the accel pedal on the 300D when it is cold, than with the 420....at least I know the 300D won't stall.

OK....When cold, I step on the "gas" to get into traffic, and not much happens....either it brumbles* and then finally catches itself, or it nearly stalls (I had it stall once) and I let of the gas quickly, so it won't stall - then try it again.
If this thing had a carb, I'd say the accelerator pump is shot.

O2 sensor?

Thank you for your thoughts!

-Larry

*"brumble": a low rumble ...the kind you hear when a motor is bogging - Secondaries are open, but it just kinda goes baaaaaaaah.

mbdoc · #2 02-19-2007, 08:10 AM

More like a bad mass air flow sensor.... ALSO the distributor caps could be gummed-up.

Larry Delor · #3 02-19-2007, 04:15 PM

Thanks for the reply Doc,
The air mass sensor was replaced within the 6 months or so. I will check the caps for wear. (is that what you mean by "gummed up" - wear & carbon streaks?)

thanks!

-Larry

PS: If it's the air mass sensor, why would this manifest itself only when cold? - because the wire isn't getting hot fast enough?

mbdoc · #4 02-20-2007, 07:53 AM

corrosion better known as the "greed gook"

Larry Delor · #5 02-21-2007, 05:53 PM

Here are pics of the caps and one of the rotor. They show some wear/corrosion, but I don't think it's the worst anybody has ever seen. I did note small hairline cracks near two of the posts on the pass. side cap.

For the longest time, I had the CEL on for a mundane code (something about module box being too warm) - naturally, if the light is already on, you're not going to see any "new" codes. Well, sure as S, I had codes 10 & 17.

Rassinfrassinfrikkinfrakken

I've reset the codes, and will see which one pops up first.

Something I noticed: When accelerating moderately, once I get past a certain RPM range, the car suddenly finds an extra set of balls, and really gets going.

vtabenz · #6 02-21-2007, 11:52 PM

I know when my 190e was doing that exact same thing, only when cold, I changed the altitude sensor and that was all it needed.

DRICHFL · #7 02-22-2007, 01:40 PM

Larry,

Does your E420 surge up and down then almost stalls while you are accelerating? Do you notice the RPMs surges up and down as if the engine can not find an idle? If so I suggest you check your Ignition coils, it could be possible that one of the coils are going out. Worse case is the Ignition Module is starting to fail

. If possible try to swap a good Ignition Module with someone to see if that is your problem. On my E420 the Ignition Module finally put me down and I had spent months trying to solve that problem. I at first thought it was my Electronic Throttle Actuator "ETA" (M16/1). There is not an exact code to say the Ignition Module is going out, that is why I suggest trying to swap out with a friend to see if that is the problem.

You can also try to see if you can scan the Ignition Module to get it to produce some type of codes. My Ignition Module did not produce any codes that would lead me to any error because it was cool and it only gave me a good reading. It was not until I tried to start the engine over and over again and the Ignition Module heated up and finally gave me false reading. Since your engine still starts up and run, allow your module to get heated up then scan the codes and see if you get any false codes.

I hope this helps.

Check JimF's site
http://pages.prodigy.net/jforgione/MB_DI.html
http://pages.prodigy.net/jforgione/MB_EA.html

Larry Delor · #8 02-22-2007, 04:09 PM

DRich,

Thanks for the reply.
When accelerating, it doesn't really surge per se, it just seems to take a long time to decide what mixture it wants/needs, and then hauls butt.
The ignition module is only 2 years old, as is at least 1 coil (don't remember if both were replaced).
The majority of the trouble is when the car is cold - once it is warm, there is just a minor hesitation most of the time.

It idles fine hot or cold. It is more difficult to start cold - longer cranking time - like I wrote in an earlier post, if it had a carb, I'd say the accelerator pump was shot. *sigh*

Larry Delor · #9 02-24-2007, 09:13 AM

Code 10 popped up first, yesterday.

I don't know if it's me or not, but it seems to run better when the codes are re-set. Must be some kind of placebo effect.

Larry Delor · #10 02-26-2007, 06:07 PM

So, I did some investigating, and using a home made code reader tool, I found the following:

Pin 5 gives me Code 10 (CTP (idle) recognition from EA/CC/ISC control module (N4/1), short circuit) (from JimF's site)
Pin 6 gives me Code 13 & 30 (Stop Lamp switch & CAN data line to EA/CC/ISC module (N4/1) (from JimF's site) - Note: the stop lamp switch was replaced a couple of years ago - is this a leftover code?

Pin 7 gives me Code 6 (Starter lock-out/backup lamp switch (S16/3)) (from JimF's site) is a back out lamp broken? wouldn't the dash lamp indicate this?

Pin 17 gives me Code 8 Haven't the foggiest what this means.

What I am wondering is, is it one item that is malfunctioning and causing a cascade effect?

Thanks!!

-Larry