1997 E420 surging idle

#1 10-29-2002, 10:20 AM

I'm a new MB owner. I recently purchased a 1997 E420 w/47k miles. I've moved "up" to a nice family sedan and had to give-up my 1988 Supra which just past 250k Original Owner Miles. I've really enjoyed the car for the 10+days of ownership but now seem to have a small problem.

At idle the RPM's tend to bounce 50/60 rpm. I've done a search on the list and found similar posts but mostly on older models and not the newer w210's / M119's . Is it the "same" throttle actuator / wire harness problem from the older cars or is this something peculiar to the w210's? Looks like almost everything is electronic (as compared to vacuum) .... It doesn't seem to be throwing any codes as I don not get any check-engine lights. I notice the symptoms whether I have any ACC on or off.

A couple of other observations:

- I notice that the engine temps seem to vary a bit from just under 80c in highway driving to 90c/95c in stop 'N go traffic. Thes temps are perfectly normal but is this normal behavior? My old Supra was rock-steady under all load conditions until my BHG .

I have previousely done alot of my own work on my Supra but may be resigned to having to find a good MB tech for this vehicle. What's the concensus on std consummables like oil, oil filter, air filter etc? MB or aftermarket?

Looking forward to hitting the 300k mark with this vehicle!!!

Thanks in advance!

Bob
1997 E420 - Kensington, Md.

G-Benz · #2 10-29-2002, 12:48 PM

Unfortunately, the "surge" problems could be caused by many things...my W124 has the problem, and I just live with it, as I haven't found time to pinpoint the problem...and I can't afford to just "throw parts" at the problem.

As far as your temp indicator...MB temp sensors are dynamic, so you will notice the gauge needle rise and fall as you change speeds, ambient temps, driving environments, etc. A lot of other manufacturers deliberately set their gauges up to stay at a "midpoint", and will hold that postion until a serious overheating problem results.

Personally, I like the MB versions better. I know what "normal" readings look like, and when something is amiss, I will deal with far sooner than AFTER I blow a head gasket or something!

You can do searches here and find varying opinions on what to use for normal maintenance. I personally stick with OEM filters and brake pads. My ML is on the synthetic oil program, while my other MBs go the "dino" route. For coolant, I use the pink MB coolant on ALL of mine.

#3 10-30-2002, 08:26 AM

G-Benz

>> Unfortunately, the "surge" problems could be caused by many things...my W124 has the problem, and I just live with it, <<

hmmmm It's not too annoying so I'll forgoe too much investigation until the next service interval at 60k.

>> MB temp sensors are dynamic, so you will notice the gauge needle rise and fall as you change speeds, ambient temps, driving environments, etc. <<

That was simple. That eases my mind on that front.

Thanks!

Bob
1997 E420 - Kensington, Md.

robaincltnc · #4 11-23-2002, 08:24 PM

Diveguy,
Are you still happy with the e420? I will be in the market for one very soon unless I hear to many horror stories. I have only heard good things so far. Let me know what you think about your 97?
Thanks,
rob

#5 11-23-2002, 09:03 PM

Your temperature gauge will move alot between 80 and 95 C; if it starts going up to 100 and above, definately have a tech take a look. Many people will tell you that it is "normal", but generally you don't see temps above 100 unless something is functioning correctly or if the ambient temperature is above 95 F. A coolant flush might be a good idea.

As you come to a stop, the idle will generally fall from 600/700 RPM range to 500/550 range. This takes several seconds and is normal. Once it has fallen to the 500/550 mark, it should not oscillate (or bounce up and down as you described). The idle is a function of sensor inputs & various electronics, so most people see an idle between 500/550. My E420 generally idles just a micron above 500 RPMs regardless of AC or electric load.

If your idle is continuously oscillating, there are a number of possible causes. See if you can narrow down what triggers it or if there is a way to change how it behaves:

- Is it different with teh A/C on or off?
- Is it different with varying electrical loads?
- Does the car misfire?
- Does the car hesitate under acceleration?

As far as I know, the wiring harness along applies through '9x-'95 models. Your car is a '97, so a wiring harness wouldn't be as likely. I'm not a tech, but I'm guessing vacuum pressure. If there is a misfire or any subtle misses, try a bottle of Chevron's Techron. It's pretty mild, but has helped some.

The engine requires Premium Unleaded (92/93 octane). I purchased my E in Dallas, TX and have since relocated to Seattle. It's not terribly fond of the gas up here. In Texas, Premium is 93 octane; in Washinton it's 92 Octane. I can't scientifically provie it, but I think it has made a difference in my car (and not for the better...)

Gilly · #6 11-23-2002, 10:05 PM

I like the 210 chassis E420 alot, really great driving car.

The surging very well could be the throttle actuator (lots of different names for the same part, so don't be confused. I usually refer to it as the throttle motor). I have replaced a few of these on 119 engines, not unheard of. Not to worry about the harness, that is mainly on about 93 to 95 6 cylinder egines.

On the temp fluctuation, the dual fans are often overlooked on these cars. It actually uses a single motor, the one on the drivers side with the big hub. Try spinning the hub on that side, see if the other fan moves as well, they are connected by a thin belt. You can't see the belt, it is hidden by the fan support bracket, but the 2 fans should turn in unison. You of course will notice if the fan spins freely, not binding. Finally you can idle the engine with the AC on and should eventually see the fans run, if not you may have a bad fan motor or fan control module.

Gilly

robaincltnc · #7 11-23-2002, 10:43 PM

Gilly,
Thanks for your thoughts on E420.

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