Very Bad Running 300E
 

Hey guys I have been through the site a lot in the past week looking for what could be wrong with this car.

I have a 1988 300E with 167k. Car was given to me by father in law. It ran great and had MB service the entire time he owned the car. Now on to the good stuff.

Wife had been driving it and said that the blower wasn't working anymore. No issue for me as the car is still cold when I arrive at work 3 min drive. I took the car from her filled it with 87....I know. Anyways the car started to drive really bad. It felt like it had a bad miss. So I pulled the plugs and changed them. while I was changing them I looked at the rotor and cap. Did not look good but thought is this fixes it then I will change that a little later. Again got to #5 broke the wire. Went and got new wires. Replaced all of them and it was still running bad. Then on the way home i looked down and remembered oh **** it needs premium fuel. So i went and bought some lucas oil octane booster and filled it up. No change. Drove it a few more days with the bad miss but fine idle. Then it got worse so I replaced the rotor and cap. No change. Tested the coil. Got a MSD coil to replace it with but have not changed it since I do not believe that is the problem. This weekend I seen that it was at a half tank so I filled it back up with 93 octane. Ran great after the fill up. Went to drive it in the morning and it was running ****y again. Just drove it to the store to get cigs and it is really running badly. It will not idle or drive unless I FLOOR it. You can shut the engine off then start it again and it will idle for about 15 secs fine then starts to pitter and putter. Floor it it will idle again in the same sequence. ANY IDEAS........ I am quite familiar with cars besides mercedes. I have owned many race cars but am at my self with this one. PLEASE HELP.

I am thinking that maybe the fuel pumps but am really unsure. Car has always been driven never sat around

You should have let the tank empty out before adding the fresh gas, epecially if you aren't buying quality gas (toptiergas.com).

My MB had about 8 gallons of 'bad' gas in it (from sitting) which I put in my '00 Sierra. Truck ran like crap, hard start, stumble, etc... basically the driveability you're describing and only got slightly better when I added 10 gallons of premium (only requires 87).

This time I ran the tank almost dry before refilling, and full tank of 87 had it back to normal.

Still, it wouldn't be a bad idea to check and see if your pumps are running, how they sound & what kind of current they're drawing.

If you haven't changed the fuel filter(s) lately, that might be something else to look at.

I only use sunoco and BP. I just can not imagine that this gas would be causing this problem with the octane booster and the 10 gallons of 93 octane. How can I check these fuel pumps. I here there are two? Where are the filters located.........Any other ideas?

I am unfamiliar with Mercedes engineering so if you offer advise can you please offer guidance with it. Thanks

300E
 

Check the DIY links for info on the pumps and filter. It is easy to change the filter. It might be clogged or contaminated.........................

I dont see anything that describes the location of the filters in a 300e. Lots of information on the diesels though

Fuel filter and fuel pump is inboard and in front of the right rear tire/wheel ... accessible from underneath the car. There should be a black plastic cover over the fuel pump and filter to protect them from road grime. Three 10mm plastic nuts hold the cover in place.

I had this exact same problem with my 560SEC. Turned out that the fuel filter had become clogged, and was causing fuel pressure to drop drastically. Changed the fuel filter, and it ran great!

Shortly after that, my fuel pumps both died, my mechanic said it was because of the strain that the clogged fuel filter had put on them. So they worked for a while after that, but they sounded really bad, and were on their way out.

Fuel Pump
 

My 1989 300E had difficulty starting up hot or cold. It would start and die or would take several attempts to get it going. I had to change the rubber fuel line from the fuel filter to the metal line due to a leak earlier this year. I changed the fuel filter since I was down there too. After changing the filter, the old gal fired up right away, hot or cold without hesistation about 95%+ to this day. The old filter must have been clogged or contaminated...........

As suggested above do replace the fuel filter and the adjacent fuel accumulator .
Next would be to clean the tank filter/ strainer. with this end clean most fuel starvation and hot starts (accumulator caused ) will be sorted.
mak

Thanks All. This sounds much easier to change out then my 04 cobra. Gotta drop the entire IRS Subframe to get to it...I will try this and report back tomorrow night

where can I find the accumulator at????

Here :)

To purchase

This website would be a good place to purchase new parts.

Get new pumps, filter, accumulator and fuel tank vent valve on Friday. Figure just change it all since I am there already.

Same problem
 

I have the same problem and it's been driving me nuts. I replaced the spark plugs, cap, rotor, OVP, fuel distributor (had a couple of spares) and finally, the fuel filter. Had some improvements now reading this I have to go replace the fuel accumulator.maybe the fuel pump. Hopefully my catalytic converter is not clogged.
Vehicle- 190E 2.6 Sportline

I replaced both fuel pumps and the fuel accumulator, The catalytic converter was good still the problem was there.....I replaced the fuel injectors and the car ran much better after that.

Alright,
Got the new pumps, filter, and accumulator. Full Tank of Premium 93. Still has the same problem. It is so bad that it is undriveable. I did notice today when I drove it that the check engine light would come on and off when it was acting up. Anybody have any idea's? Could it be the CAT's?

Did you replace the wire from the coil to the distributor cap? What type spark plugs did you install? Refer to the Owner's Manual for the correct non-resistor spark plug for your engine. You may want to confirm that the ignition wires are routed to the proper cylinder from the distributor cap. Note that Bosch distributor caps have each terminal marked with the corresponding cylinder.

I presume you installed a new fuel filter.

Thanks for the help but I have already done all of that. I am thinking that the cat is clogged..Any Idea's?

Bump

Bump

Didn't you say that it still has periods where it runs fine? If the cats were plugged you wouldn't have that. Is the check engine light the only one that comes on? Does it start fairly easily or is it hard to start? Does it run hot and/or warm up quickly?
Regards, Eric

Have you checked operation of idle control valve? Could be possible the valve is stuck partially closed and won't open. Pull her off and shoot it with carb cleaner then give it some power and it should "click". If there is no click, then its dead.

The other culprit is the EHA.

Yes it is the only one that comes on. It only flashes on when the car starts to what feels like miss bably. Bad enough that the only thing that will take care of it is to floor it to get it to accelerate. Starts fine. Warms up normally. Runs at normal temp too

She idles with no issue's so I thought that wouldn't be a problem. Should it still be checked

I thought that somebody would have an Idea. Why is everybody clueless.

It never runs fine just better than not running at all. It idles Fine, starts fine. Doesn't like to go if just bearly touching the gas. You have to floor it then it accelerates poorly

When you pull the line that come from the bottom of the tank (with the gas cap off), does the gas gush out or dribble?

ERP - Ethanol Related Problem

We see this daily here in Florida.

Good Luck

I'm still not smelling bad cats here. The fact that the check engine light comes on when it's running it's worst tells me this is an electronic issue (CIS-E or EZL) not mechanical.
Regards, Eric

Gush

How can I check the codes it has stored?

I would have to rule those out as it idles with no problem. Also it usually runs pretty decently when I first start it and drive it. Gets worse once the engine warms up.

Also a cat is not mechanical.

The reason I sniff a cat is the reason that once it warms up it runs like total ****. I know that a cat takes a few minutes to warm to operational temperature. Thus causing the issue when the car has been driven for a mile or two.

Please let us know when you find out what it is.
Regards, Eric

If the symptoms appear only when the motor is warm, perhaps it's time to also check the main temp sensor, the one that supplies resistance signals to both the CIS and EZL.

Or the vacuum line to the EZL?

I just remembered that cars with plugged exhaust (this would include plugged cats) don't pull good vacuum. How good is the vacuum on this car?
Regards, Eric

I have an 88 300te. When I first got the car it would idle like it needed a tune up so I replaced the rotor, plugs and distributor cap, still ran the same. I found that there is a fuse behind the battery compartment that is a safety from mercedes that if anyone jumpstarted the car the wrong way this would go. After the fuse was replaced, my car idled without any problem. There was a plastic divider behind the battery I had to remove to access the fuse.

wheelsfan, that fuse was atop the OVP relay. If the solder joints inside the OVP relay crack the engine will run/idle rough too. On our 1995 E320 the OVP relay buzzed when there was a problem with it.

If the CEL comes on, YOU NEED TO PULL CODES
before trying anything else.

The OVP is a prime suspect for this type behavior

See, the low octane gas you put in caused a cold solder joint in the OVP to ,,,:rolleyes: (kidding) seems to me the gas had nothing to do with your problem, unless it was bad gas (unlikely)

I have seen problems like no start, or hard start, or starts and runs then all of a sudden dies all caused by the OVP relay. (One 190e I parted saw the better part of an ax because the PO couldn't start the car, I replaced the OVP relay and started first try)

It wouldn't hurt to ensure that the electrical contacts are clean too. And that there is no corrosion on the ground wires.

The symptoms of a broken temp sensor are slow starts and poor idling while the engine is cold, not warm. I can tell you this because I broke the sensor and the difference was immediate and noticeable. I got a new one and it went back to normal :cool:

Cheap spark plug wires can cause poor running. Did you use Beru wires or whatever was sitting on the shelf at the local auto parts house?

What did this turn out to be?
Regards, Eric

I just got back in town and thought that I would check a few things. When I started it, it was a little hard to start. I just primed the fuel system and it seemed to help. As soon as I put it in reverse it dies now. Also with it in park if I tap the brakes the ckeck engine light flashes. When I put it into reverse the check engine light comes on and it dies. I didnt try to go to drive. I am thinking that this may be the OVP relay now. I just went out and tried drive and it was fine. Also when I tap the brake pedal I have to let the car move a little before I tap the brake to make it stop abruptly then the check engine light comes on. Any Ideas?

Check the sockets of the OVP relay plug too. I just found out that my 88 300E has one of it's sockets recessed within that plug which may be what was wrong with it. When I get the time, I'm gonna fix it, start it and see if the car runs better. I'll need to post an update on that car's old thread too.
Regards, Eric

Guys still nothing. I replaced the OVP relay. Did nothing. I went through all of the chassis and motor grounds pulled them off and took a wire brush to them. It runs but now with a check engine light all the time. As soon as I put it into reverse to back out of the driveway it dies instantly.


I need some good advise on this please help.

check out your mass air meter
 

I had the exact same problem with my '90 420SEL. Turned out to be the mass air meter. Replaced EVERYTHING but that. Finally had to bite the bullet and get it replaced. The rubber diaphragm inside had deteriorated and torn.

Even if the mass air meter was bad it should be able to drive and idle while it is in closed loop. The computer is not using the mass air meter until it is warmed up. I really hope that this is not the problem as I will not spend that much more money on it. Time for a new car.

Alright,
I know there are some smart mercedes people around here. I have spent 1000 dollars on Ideas that have came to nothing but the same as my original post.

I seperated all of the new wires today with seperaters and got it to idle fine. I also put in a new coil.

During the drive (this dumb foundes me)It will not accelerate unless I Floor it. When I mean floor it I am talking as hard as I can push the pedal anything other and the car seems to have absolutly no power. It doesn't even feel like the engine is running. The exhaust is broken at the resonator (one pipe) so it is pretty loud when the engine is running. I can't even here that nothing but silence. It also seems to accelerate all right when floored. I may be wrong cause I never drive it my wife does.

What could cause this.

I have replaced so far
spark plugs
wires (8mm)
Distributor cap and rotor
Coil
Both fuel pumps
accumulator
filter.

It has not even gotten better.

What happens when the fuel distributor goes bad. What does it do.

Some body has got to have some damn good ideas.