M.B. 300TE

[EARLYBIRD]

Hi everyone.
Two problems that i need advice on.
I own a nice 1990 300TE but I have a very annoying couple of niggles.Firstproblem-it starts to run very rich-pumps grey fumes that smell very strongly of petrol and runs erratically-this can happen anytime-but usually when the engine is hot.It can also happen if I stop for a few minutes then restart the engine.This problem is only intermittent but happens at the most awkward times,usually in traffic, and progress is not as elegant as befits such a lady.Second problem is the heater-it only runs slightly warm -all the time-no matter what the setting and I,d love to be warm this winter.Engine temp is always steady and warm-up time is minimal.
If anyone has any ideas I,d be eternally grateful

 

[Andy]

Hi

You don't say what temp the engine reaches!!! If its not 80 or above then you have to start with basics,thermostat.


Andy @ www.mercedesservicing.com

 

[EARLYBIRD]

Hi Andy
Thanks for your interest.
Temp gauge shows just above 80 when warmed up...when miss-fire starts ...no noticable drop/rise in temp.Heater is only blowing warm on passenger side...cold/cool drivers side...could it be air lock in heater system.
Tony

 

[abeesley]

Hi earlybird. I have a similar problem with my 300CE 24. The car develops a misfire when hot and is particularly noticelable when crawling through traffic or pulling away from a standstill. Out of all the components I have replaced (plugs, dizzy cap, rotor arm, leads, coil, injectors, fuel pumps, thermostat, coolant, OVP relay, battery) I have found that changing the spark plugs cures the misfire. Unfortunately this fix seems only to be temporary as the misfire returns after a couple of months. I have had the car for nearly a year and I am on my 4th set of plugs. I have tried Bosch super 4s, Champion, NGK and genuine MB plugs. But I have found that the results all seem to be the same. To say that this is frustrating would be an understatement! Hopefully someone out there knows what might be causing this fault and shed some light on this elusive misfire. What else could it be? :roll:

 

[Peter 300TE]

plugs as well

I appear to have a similar problem though not as bad. When starting with 'old' plugs the car needs to turn over five or six times before catching. With 'new' plugs it will catch on the first turn. It does not matter if the engine is hot or cold. I have tried cleaning the plugs etc and there is no untoward residue on them at all.

In the end I change than about every 6k as this appears to be the point at which they deteriorate rapidly. Have tried different plugs and am now on NGK with 2k on them and starting on the 2nd turn.

 

[EARLYBIRD]

Thanks Guys
Ive been down the same road as you..change all components in ignition system...never thought about plugs having limited life..I,ll change then today and maybe experiment with different makers/types..seems like it could be a long project....spoiling a lovely car.
I may get a solution from a member yet....cant be limited to our model only.

 

[Spike]

Have you both done pressure leakage tests?

 

[abeesley]

No I haven't tried a pressure leakage test. Please could you elaborate? Do you mean the fuel system? I have replaced the fuel pumps and filter, but it didn't make any diference.

 

[Spike]

Sorry, what I meant to say was a cylinder leakage test - note that I didnt say compression test.

The leakage test will pinpoint the problem accurately should the problem be linked to compression - which seems likely since you have both tried other avenues.

The only othe thing that immediately springs to mind is that you have a vacuum leak somewhere or perhaps a leak on the inlet manifold side somewhere.

 

[EARLYBIRD]

Hi There.
My problem with mis-fire is "intermittent"... I can drive for 200/300 miles.(I drive to and from Scotland every week)and have no problems.I have noticed that if I stop ..to fill up...with the engine fully at working temprature..restart..and after approx 30miles..the mis-fire will start..continue for about 10/15 mins then run as smooth as silk...this problem is really frustrating.
I,ll try the leakage tests at first opportunity...and keep everyone informed.

 

[Peter 300TE]

I had not considered this as a new cylnder head gasket was fitted less that 30k ago however its worth a try

Thanks

 

[JonathanC]

Earlybird

Possibly a really stupid suggestion but is it possible that the fuel tank is not venting properly leading to a vacuum in the tank and reduced fule pressure? Seem to remember there is a filter in the tank venting system that could be partially blocked, not allowing the tank to vent properly. It's a quick and easy (and cheap!) check that might be worth considering.

Cheers

 

[simon j paynter]

this is an interesting one, i've got a hot start problem on my 300te 4matic it fires readily catches then conks out, a careful amount of throttle can prevent this, i have changed the fuel quality adjustment setting to see if it makes any difference and it does seem to start a bit better now -perhaps that is worth a try for some of the symptoms you guys have been experiencing?
Simon

 

[Spike]

I have just spotted this article that may or may not be relevant - but definately worth a read.

http://www.mbca.org/pages/tech/MBCA_Rough_starting.htm

 

[simon j paynter]

Thanks for that spike I am going to act on it, I have to take the car off the road for a while in February to replace front drive shaft gaiters and exhaust system, so I'll do it then
simon