Throttle Surging issues E320 PLEASE HELP!
 

I just bought a gorgeous 94 E320. Super low miles and obviously very well taken care of. I do have a wierd problem however that is stumping the mechanics.

This has happened three times - never the first start of the day, but usually after I run the car 30 or 40 miles... leave it for 90 minutes or more, and get back in the car.

The car starts and idles perfectly. As soon as I give it some throttle, the car surges like crazy, like you're cutting power to the ignition or something. It has also happened while I'm going along at 65 mph. It feels like the motor just quits. I look at the tack and can see that the motor is actually still running, but no power whatsoever. I limped it into a parking lot, and it sits and idles perfectly. Try to move the car... and it jumps around, surging continously.

Two independent shops tell me the Wiring harnesses go bad in these cars, and when they do, it causes all kinds of wierd codes and happenings. "Replace the wiring harness and most of these elusive "short" type problems disappear"... so they tell me.

Well, I picked the car up today after the wiring harness replacement, and it ran great for 40 miles. Got it home and parked it. Got into the car 2 hours later... same deal.

The first time this happen (pre-harness replacement) the code read: "182 Safety Fuel cut-off switch signal for LH/HFM N/34"

This last time, there were no codes even though I was disabled with the car for over 40 minutes.

Any ideas?

I have more or less the same car and the same problem. It´s been like this for six years now, but only on hot days or if I am in slow traffic for too long.

The limp mode is what causes the stumbling but nobody knows what causes the limp mode. I just ventilate the engine bay for 5-15 minutes depending on outside temp and the car runs fine again. It has nothing to do with engine overheating, but some part, like the crank sensor or another sensor or connection seems to be sensitive to ambient heat. But impossible to diagnose so far....

Do a search on "OVP relay"....

I have left off the bottom, under engine shroud to get more air flow through the engine compartment.

I've spent 2 hours reading about OVP relays, and haven't seen a problem that sounds just like mine. My car starts and idles perfectly. Something seems to be kicking it into Limp Mode occasionally. Turning the car on and off several times usually solves the problem... until the next time.

I also gather that the OVP can trigger a lot of different symptoms, so I'll look into it further. The shop that did the wiring harness a few days ago has the car again.

I saw one posting where a guy had a similar problem and it usually reared it's ugly head after he drove for a while and then parked it. He thinks the heat buildup in the engine compartment contributes to the problem... that's why when he gets in the car an hour later, the problem shows up.

Is that the thought behind removing the bottom engine cover?

In my case, I have got a new OVP and the same problem remained, I have also removed the bottom cover with little or no difference. It is mainly the heat that builds up under the hood when parked or in slow traffic that causes the bad signal. i have also looked into the throttle linkage and reprogrammed the CPU without success. It leaves no fault codes at all....

Btw, if I can build up the limp home speed enough to engage the cruise control, it will override the limp setting and usually the car cools down enough to work normal again pretty soon...

Second check would be Heat Soak of the crank position sensor..fairly common.
Do not over-look the OVP , specially if it still has the OLD part#.
It can cause your problem.

OK, I give up......What is the "OVP" :confused: I need to learn more about the quirks on the gassers as until we bought our '94 E 320 wagon, we only had diesel Mercedes.

Already found out the head gasket is leaking oil!!

Over Voltage Protection device..

It basically is just a smart fuse and it's purpose is to protect the ECU form voltage spikes , preventing ECU damage.
They are known for causing ECU related faults as they interrupt feed power to ignition and fuel suppy.[ along with abs]
The late 124 chassis IL-6 had so much trouble with them, that they came out with a modified part, so any time one is seen with the original part # , it is recommended that it be changed before blaming part failure on ECU and other electrical parts before hand...

Do a search on OVP and you will have enough reding for a week...

Today I put in a new Crankshaft Position Sensor, it is a hot day, and I then drove it for fifteen minutes. Parked and returned 45 min later and the car was again in Limp Home Mode, (so was I) and I opened the hood for five minutes to ventilate. Then it started and worked normal again.

Drove home on a narrow road and just when I was overtaking two cars, it turned into limp mode again, very fun to get out of that situation...

Stopped, ventilated for five minutes and got home safe.

I´ve been to three different MB service centers without any result so far...

Hi Vulpro,

Any success that you can share??

94 e320 surging
 

two observations concerning this car.first limp home mode does'nt cause the surging that has been described.second if my memory serves me the 94's had an electronic accelerator[original style].part of the wiring harness that you had replaced is a large plug that goes in under the front of the intake to the pigtail harness for the electronic accelerator[bracketed to the intake by 2 10mm.nuts]you need to take this loose and slit open the cable to see if this pigtail harness to the e.l.a.has suffered the same fate as the other wiring harness.experience has shown that it has.if you are lucky and all is still good tape up the slit and proceed to the computer that runs it located in passenger floor under a panel.find a used one of these at a salvage yard and it should fix problem. david poole owner european performance dallas tx

Thanks for your reply. The surging we refer to is actually caused by the limp home mode, since if you try to accellerate, the engine shuts off at 1500 revs and then comes back to shut off again, and again. This is the surging.

On harness problems, they exist, but in my case the car has had this problem only on hot days and since it got just 12.000 km. And as the other with the same problem, it goes away by ventilating the engine bay, I don´t even have to shut it down meanwhile...

After new OVP and CPS (reference sensor) the problem remained the same.

My car can get into this mode also when driving fast if the ambient temp is 25 °C or above, but also if I let it idle in subzero temps for 30 minutes or so. Then it goes away by just opening and closing the hood...

So there is something that must be pretty open in the engine bay since just a little fresh air helps? Or?

Could it be that the multirib belt slipping becuse the AC got the protection fuel saftey shut off otherwise look into the klima relay and try to heat it up with hot air to se if the problems occur when the car is not warmed up if there is some soldering is in bad shape, in the relay is the fuel shut off function.

On my car this can happen with or without the AC working. Where is this relay located and can it shut off the fuel without the AC engaged?

If so, maybe it would be easier to put some ice on it when the LHM appears next time? Or just check and resolder anyway...

It`s in back of the battery behind the plastic cover it's a black relay 6zyl/klima stands on the top of the relay when the relay is the problem the car stop completly but check it out anyway sometimes things can happen that should not happen,

do you got the cruise control?(tempomat) what are the rpm on the tachometer when this thing happens if the rpm are 1500 it could be the cruise control Idle speed control acutator

Yes I have cruise control. The limp mode can start at any speed, often after just idling at a traffic light, or as I described, when overtaking at high revs.

Today I was lucky, driving 650 km nonstop in 28°C with no problems, but if I go out and start the car now after an hours rest it will most likely be in limp mode again...

To find out if the cruise control is a part of this, can I remove a fuse or what?

Edit: I did just that, restarted the car, it was in limp mode now, removed the fuse, no success...

We're still working on this car.

Agreeing with AMG, the "throttle surging" is probably actually the "cutoff" that we experience when attempting to accelerate. It feels like throttle surging when the power comes on and off rapidly. The limp-mode cuts power at 1500 rpm and then allows power again at about 1200, so, with your foot on the gas, it bucks around on and off and feels like surging.

We've done a lot of other research. We're thinking it's the Throttle actuator and the throttle actuator wiring harness. Harness is ordered from Germany (about $100)

We're going to send the unit to Beckman. They will test the Actuator for $80... which they will apply to rebuild cost if it's bad. (rebuild is about $1000 compared to a new MB unit at $2000+)

Incidently, mine occurred several times on 90 degree days, but happened most recently when it was only 75 outside. Raised the hood for 5 minutes, and it started right up again -- no problem.

Thanks for the update. You may be on the right track, hope you´ll find the exact problem since it must be just a minor thing in reality. Although it can be expensive nevertheless!

I gave up and bought myself a G500 and will take care of the CE later...

Please continue to post on your progress!

If you go to www.4mercedes.com a rebuilt will cost you $400.00. Thats where I got mine and its been great ever since!!

Chris

Considering you're going to send your throttle body out for check up and maybe reman, you might want to check 1 maybe 2 vacuum hoses.

One is about 1" long and connects the two parts of the flap housing.
When you remove the plastic intake to the throttle body you'll see this pik

http://www.peachparts.com/shopforum/attachment.php?attachmentid=32996&d=1146490401

The flap housing is to the right. 4 bolts (2 under the plastic caps and 2 more further to the right.) Wiggle and the flap assembly will come off.

I'm a little vague on the following, because I was so excited to instal my remaned throttle body. ... I think there is another hose that comes off the (lower rear passenger side) of the throttle body (sorry I don't remember where it goes).

Obviously, if either hose is dried out or cracked, a bad vacuum could affect the performance.

Bob
PS I also had a reman done by 4Mercedes.com.
PPS Don't forget to disconnect the 3" link (ball on each end) from the throttle body and yes, the throttle body does come out between the 3 and 4 intake tubes, but it takes a bit of twisting.

E320 if FIXED!!!
 

Well, I am finally enjoying my "new" E320. A 94 with 24,000 original miles was giving me fits with it's surging and "limp" mode.

Did a complete wiring harness... which the car absolutely needed, but unfortunately that repair did NOT fix the problem I was having.

Anyway, the bottom-line is that I did a lot of studying. My mechanic talked to a lot of other shops that work on older cars like these, and ended up talking with a couple of real "experts" (!) Anyway, everyone's first guess was that the car needed a throttle actuator rebuild which we ended up doing.

Sent it out to Beckman Technologies and for right around $1100, they sent us a rebuilt unit (compare to $2000+ for a new MB part.) As you know, other guys rebuild them for about $500, but Beckman has the reputation for doing the best and most complete rebuild. One shop in Florida told my mechanic that he has 55 gallon drums in the back of his shop FILLED with throttle actuators from E320's and he has a pile of wiring harnesses 10 feet tall behind the shop. He said this is the problem 99% of the time.

Incidentally, my guy cut a slit in the wiring harness that comes off the throttle actuator and opened it up just for grins. He couldn't believe the condition of those wires! He told me they were all cracked and split exposing bare wire. There were black carbon-like deposits inside and it looked like it was caused by possible sparking, arching and so on. I was tempted to do a manual wire replacement job... one by one, but decided that I just wanted the problem to be over so we did the rebuild. (all this on a perfect car with an engine compartment you could eat off of) Amazing... the deterioration of the wiring...

Hope this helps with others struggling. It was a serious pain in the A**, but the car is a perfect specimen and a joy to drive. Between the harness, the Throttle Actuator, OVP Relay and a few other things we did, it cost me about $3000 to get the car right, with only 24,000 ,iles, I'm hoping to get many years out of this car.