This is a long post, but I wanted to be very precise on the details:

Last December I finally bought a car I always had an interest in - a 300E W124 with the 3.0L straight-six automatic. Fantastic car and certainly shows the excellence that is German engineering. It only cost 300 quid, has 160,000+ miles on it, so it's not a show-room example by any means! As such, besides the rust, it wasn't without problems.

First up it was really rough running, that turned out to be a worn-out rotor-arm and distributor cap.

Then the fuel economy was seriously lacking, peaking at 16mpg. From the forums the recommendation was a new fuel filter. This was changed and I am now getting 21mpg, which also from the forums suggests that this is normal.

What I am finding now is the performance is seriously lacking to the point of being disappointed by it. Considering it is meant to have around 180hp and do a 0-60mph in 7.9s it wheezes its way to 50 in around 13s (the speed limit on this island is 35mph! So I'll have to find a quiet stretch of road long enough to get to 60mph). When traveling at a steady speed and I begin accelerating it edges up 100rpm at a time very slowly. My last car was the Accord Aerodeck 2.2i and that was rapid by comparison and that had just 130hp.

What I have done so far:
* New fuel filter;
* New air filter;
* New rotor arm;
* New dizzy cap;
* New spark plugs (Mercedes dealership OEM Bosch parts);
* Used lots of Redex and other injector cleaners;
* Inflated tires to Mercedes maximum guide specification;
* Tried 97 RON fuel, usually 95 RON - both unleaded;
* Compression tested (gives 13 Bar give-or-take per cylinder, hot);
* Checked o2 / lambda sensor - doesn't exist, wiring tucked away under carpet (some posts suggest euro-market cars don't have this fitted?);
* Checked EGR valve - (from reading posts) does not appear to exist;
* Became confused how an EFi car can run without either o2 or EGR... ;
* Got a per-unit price of new injectors - I multiplied by six, and got rushed to resus!;

I replaced the spark plugs as the NGK ones we dark black (dry, not particularly oily). They appear to be NGK's equivalents so I do not think being non-Bosch was the problem. The diagnosis of such spark plug conditions is non-clean burning of fuel or over rich mixture.

One thing I considered was HT leads however the pattern parts shop didn't have suitable replacements so guess that's a trip to the dealership.

So, here I am running out of ideas - perhaps the issue with the spark plugs might indicate something? As mentioned there is no o2 sensor and from reading posts the default action of a failed sensor (or indeed having no sensor connected) is to 'sense' lean and go rich, so how does the ECU know to lean the mixture on such a car?

The engine itself starts alright and runs smoothly at all speeds, most of the forums mention hesitation or rough idling - I am not experiencing that at all.

Would you forum members offer a fellow Mercedes fan your wisdom?

Many thanks,

Glyn B,

What year was it made. The 300E was shipped to the US from 1986 to 1993 or so. Many things changed in the emissions systems and the Euro cars were different from the US cars. For the most help, always give all the details about the car. Year, make, model, US/Euro, engine (there were 3.0, 2.6, and 3.2 I believe), trans, etc.
With more information, you may get more responses.
Thanks

__________________
84 500 SEL (307,xxx miles)

Glyn, check the condition of the ignition wires. If original, install new Beru wires. Also, the coil may be suspect.

__________________
Fred Hoelzle

Thanks Fred, the leads are probably the last thing I can replace without costing the earth - I had a quick look for a Beru supplier in the UK but nothing yet, I shall take a better look later or failing that go to the dealership for OEM ones. It would be almost certain they are factory originals still in there.

pmckechnie - if it helps I can state the following from what I know:

The car is the 300E with the 3.0 straight (inline) six with what would appear to be the Bosch K-Jetronic system. The car was imported into Guernsey (Channel Islands, essentially part of Britain) in 1993. The motor office never signify the original manufacturer date of the vehicle when imported, so 1993 or earlier is the best I know of. It looks like this one whether that helps (albeit silver and with tin-worm):

http://www.peachparts.com/300e.htm

(is that what is referred to as the later 'face lift' version?)

When I replaced the fuel filter the parts supplier matched it to the early 90's model, which may help?

The chassis number is WDB 124 030 2B 246 816. I shall locate the log book to determine the engine number. It has the standard function automatic gearbox. Is right-hand drive so that limits its origins to key markets, but strongly suspect it to be a UK model.


I forgot to mention in my original post that I have adjusted the ignition timing dial through the seven positions with no noticeable difference.

Thanks once again,

Glyn B.

I have just been to my car and found the service manual. The car was originally owned by a leasing agent and first registered 1st August 1990. I still haven't found my log book (strange how all the log books of the cars I had in my past have turned up though!).

I also found the sales note from when I purchased the OEM Bosch spark plugs from the dealership - the parts guy noted down "Engine type M103" so I guess they have had this car in previously, prior to my owndership of it, and have that on record.

Hope that helps you with the details you need?

Thanks once again,

Glyn B.

Thanks to the people at:
http://www.ignitionleads.co.uk/
I have replaced all the HT leads with nice shiny new ones but the performance is still lacking. The engine starts and runs fine, however trying to accelerate while driving has no get-up-and-go.

From what I can determine my W124 has the basic CIS running in open-loop (no lambda), so is adjusting the idle mixture the only thing I can reasonably do?

As an aside, can someone clarify for me the 'continuous' part of CIS - does that literally mean that each of the six injectors are running like a tap left on? That is to say, it fills the intake port until the valve opens?

I don't know about Euro cars, but I don't understand how the fuel injection system can function properly without an O2 sensor.
The system needs to have some means of measuring fuel/air mixture. If there's no O2 sensor, how does it do it?

Does you car have a catalytic converter?

__________________
Jeff Pierce

Current Vehicles:
'92 Mercedes 190E/2.3 (247K miles/my daily driver)
'93 Volvo 940 Turbo Wagon (263K miles/a family truckster with spunk)
'99 Kawasaki Concours
Gravely 8120
Previous Vehicles:
'85 Jeep CJ-7 w/ Fisher plow (226K miles)'93 Volvo 940 Turbo Wagon
'53 Willys-Overland Pickup
'85 Honda 750F Interceptor
'93 Nissan Quest
'89 Toyota Camry Wagon
'89 Dodge Raider
'81 Honda CB 750F Super Sport
'88 Toyota Celica
'95 Toyota Tacoma
'74 Honda CB 550F

It could be possible that you have a huge vacuum leak...what does your "economy" gauge read at idle? From what I understand, it should be all the way to the left.

__________________
Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Thank you for your responses TVPierce and Johnatahn1.

There does appear to be a cat but certainly no position to fix a lambda sensor in. I have checked under the carpet and found wiring for one, attached to one side in a special holder.

I can only guess that the fuel injection on this car is no more sophisticated then the SU carb on my old Rover Metro!

As for the vacuum gauge it shows roughly 1/5th to 1/4 from the left when started from cold ('choke' on) and near-fully to the left once warm running idle.

Just to reiterate the fuel consumption remains around 20-21, consistent with urban traveling and the engine has none of the signs of hesitation or rough idling. It's just the get-up-and-go-go-go! There are kids around here with Nova's and Clio's that need knocking down a peg or two! (because I'm fed up of them being able to overtake me )

Thanks once again,

Glyn B.

I have a Euro market 190e 2.6 M103 engine. This car was exported from the channel islands to the U.K. and then to Australia, The car has no Cat or O2 sensor.(wiring for O2 sensor in place). It features the rotary EZL switch as mentioned above in your posts. My car suffered from lack of pickup power also. Had the fuel mixture adjusted a little bit richer and this improved things at the expense of consumption.

According to a Bosch Injection specialist I took my car to, by installing the O2 sensor, this will improve consumption and engine performance - depends on the cost to do this. As my car doesn't have a cat and also features dual engine pipes to the first exhaust muffler, installation would require some extensive work, so maybe not justified.

Settings for the EZL switch. S is for premium fuel - 95 Ron and above. N is for lower quality fuel 91 Ron. The EZL switch was designed for use in countries with some really crappy fuel and adjustments accordingly. The higher the number the lower quality fuel to be used - right down to 89Ron.
According to the user manual. Using the S setting with low octane fuel can damage the engine. - so make sure you set the wheel correctly for the type of fuel.

Cars not fitted with the cat can use unleaded or leaded fuels. Cars with a cat must use unleaded.

Getting the fuel distributor tuned correctly makes a big difference to performance. The coil can affect performance also. Only use Beru or original MB leads cap and rotor. NGK make the equivalent non resistive plug for the M103 - MP6ES.

Have you checked that the spark plugs are gapped correctly?
Should be 0.8-0.9mm gap.

__________________
2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Thank you for taking the time to respond Ivanerrol, and ps2cho.

Does that mean you were a former Channel Islander, Ivanerrol? (tell me you weren't a crapaud !!) - sounds like I have the same model car as you feature-wise (or lack of features).

I read elsewhere that your present home country and other parts of the world have low octane petrol such as those you mention. In the UK and CI you cannot get lower then 95 at the pump and 97 is available as 'Super Unleaded'. The EZL is set as appropriate for 95 RON.

I twiddled the idle adjustment and now it sounds like its almost going to stall when stopped in gear - not a simple thing to play with, clearly... will have to tweak that back to normal now.

The air temperature recently has been around 5.0-6.5C according to the dash readout and I have noticed the engine temperature has not gone much above 40C and from reading other posts on this site the engine should be at 87C under normal conditions. I suspect the usual cheap-o-mechanic job of not fitting one when the water pump was replaced, if not simply rusted 'open'. Some replies to those posts suggest that fuel economy will suffer as a result of the temperature sensor not detecting a warm enough engine to switch off the cold-start injectors, etc. As this should be cheap to replace I will venture down this route next. Might driving with 'choke' effectively on impact on performance?

Regarding the spark plug gaps, ps2cho, I asked the parts guy whether I'd need to adjust them and he was fairly sure they were correct being OEM items - but I intend on checking the condition of the new plugs and cleaning them as necessary so I shall find the long-lost feeler gauge and verify.

As a general question on coils do they really become 'weaker'? I would have thought they either work or fail. I am happy to replace the coil if someone can confirm that changing a coil gives a definite improvement?

Many thanks,

Glyn B.

Not from the channel Islands - Cheltenham and Edgware- many many moons ago (with wet nappis on).

The car I bought was imported to Australia as an export model from the U.K. via Singapore. Technically this car should not be allowed on our roads as there is no cat fitted. In Australia we have 91,95 and 98 Octane. Leaded is now outlawed. The EZL switch can be adjusted to let the car run on the lower 91 Octane , However the 98 Octane has additives that "clean" injectors and fuel injection components. It's always better to run the car on the better petrol for this reason. Anecdotal evidence from Benz mechanics here have confirmed that cars run on 98 Octane have "cleaner components" than those which are run on lower octanes.

Coils can slowly deteriorate and the heat affects them. They are positioned in an area that can catch the heat from the radiator. Replacement is a good option. If the electrical system - plugs, leads, dissy and coil are not in good shape then the car can never be tuned properly.

The thermostats are cheap and easy to replace.The car should have the 87 degree one as OEM'd by Benz.

You car will not go over 40 degreesC. Last week we had 40 degreesC as an ambient temperature.(in the shade).

And I'm from Stroud originally.

You can pin down all the original details of the car by going to:

http://old.mbclub.ru/mb/vin/?lng=eng

Note: the VIN has 17 characters, including "WDB"; the one you have given doesn't.

Thanks for taking the time to reply again Ivanerrol. I tried a tank of 97 the other day - I was sure I could see the fuel gauge move with a distinctive cartoon-style sucking sound as I was driving! After checking the mileage it was only down to 19 from the usual 21MPG, give-or-take errors in my measuring.

My son's child minder is next door to an copy-parts supplier and considering the long weekend (Happy Easter folks!) I quickly went in and ordered one. If it doesn't work then it wasn't a great loss cost-wise and I'll go to the OEM dealership.

I re-adjusted my idle to get it back to normal, or as it was before, and then took off my air filter and poked around the various CIS sensors (the ones I could locate and get access to) using my trusty multimeter.

The engine temperature sensor is one of those with four-connectors and from reading the forums the the pins are diagonal and the resistance equated to the dashboard temperature reading (within reason) or both pole-pairs. There was also a single-wire temperature sensor ahead of that and seemed to show resistance too.

The air temperature sensor I didn't have a guide for however on testing it outside the car and moving it into the hot-air flow from the radiator fan it showed functionality.

The throttle position sensor (perhaps called something else on the Benz?) showed variation when moved.

At the same time I tested the X11 socket for the ECU's fault code. Since this is a non Lambda car / open-loop car the ECU presents a value representing an error code. This is steady at 50% normally but did show 70% with the engine temperature sensor off, 20% with the air temperature sensor off and either 60% or 90% value (can't recall which just now) with the throttle position sensor off.

Now I was puzzled by these values, since another article stated that failures in these sensors should generate 30%, 80% and either 10% or 40% respectively. Then I realised that these figures, when inverted, worked out right: 100% - 20% = 80%. This may be down to how my multimeter works, but it left me scratching my head for a bit!

Clearly this shows that the ECU sensors are not 'failed' and the ones I tested with references seem to be within tolerances.

Still with the air filter off I checked other components and found a switch on the throttle linkage. It never seemed to engage under normal usage but if I pushed it in by hand the revs would drop down a little bit. Should I somehow 'modify' (read: bend) the switch actuator with the roller to make better contact so it's activated normally? Or is it movable to reposition it?

Furthermore I disconnected a device on the front-side of the fuel distributor and the revs dropped right down from around 8000rpm to 6000rpm. I'm guessing this is the extra air enrichment device, the technical name of which I cannot recall. The engine seemed slightly more responsive when driving with this left off and, although I cannot determine until my next fill-up, the fuel gauge seemed to go down slower then usual.

Would I be right in thinking that this along with the cold-start injector are temperature dependent and therefore the current guess at the thermostat issue would be resolved next week upon fitting the new one? I know I'll find out when I fit it, but as is typical when you're keen to fix something a raft of bank holidays get in the way! (the workaholic in me can't cope with such long breaks off )

I shall keep you updated with progress.

Kind regards,

Glyn B.