I have a W140 500SEL. I recently added a bottle of Mobil Injector cleaner to a 3/4 full tank of petrol. I notice that the car run rough at idle after half a tank of petrol.

I suppose it is not all that bad but it used to be smooth that one cannot detect any vibration from the engine.

Could it be possible that the injector cleaner clean the injector and make it runs rough?

Thanks

Michael Tse

If thats what you say, I'd say too that your injectors and inlet valves are much cleaner. However, the vibration shouldn't be that bad is it? It should be ok after awhile - if not, its time for tuning and all will be well.

Hopefully. :)

also ran additive.. running rough
 

Hi... I've been hanging around for about a month already.... new user... I'm from Guam and was referred to this site from a couple of friends. I have a 1994 MB C280 (W202) that I put some fuel injector cleaner in... it's been running pretty rough since after I put it in. I've already replaced wires and sparkplugs. What sort of tuning must be done in order to get the engine purring like new again?

Logically, when using such cleaning additives, it washes away all the layers of whatever you already have on the injector points and more significantly on your valves.

When that happens, its no longer the same as you had them before, and thus the engine reacts with confusion as its not able to configure and compute the control of fuel mixture.

After a while it should be back to normal albeit a little rough conditions. Tuning may help, and that would be the cheapest start. If indeed the cleaning has got right to the injectors to the point that its leaking (after the cleaning - such an irony), then it may have to be replaced.

Is the vibration still as aggresive and not toning down?

The above is my common approach, and perhaps the expert techs living in this site may be able to correct my understanding if I have strayed.

Thanks a lot. Actually, the vibration is only very very minor. The car is due for service in 2 months anyway. I can wait till then.

I think I should use those cleaner every now and then to keep my system clean then.

Thanks...

Michael Tse

Whoa .. using cleaners may not be recommended. My MB service centre thinks it does more harm than good.

I see a premium fuel which I believe (in the long run) will produce a cleaner fuel system, and engine - rather than using regular fuel and having to clean them every so often.

Have you tried an Italian tuning lately?

:)

Have Been Scolded By Mechanic in the Past
 

Greetings All,

Although, I own a diesel MB I do have an American vehicle with fuel injection that I had added injection cleaner to the fuel tank, and ended up with the same results as you describe. Luckily is was still under warranty and I pushed my own made problem off on the dealer who kindly informed me that I had used a cleaner and although I though I purchased a quality cleaner it actually just dislodged the garbage that either clogged the injector, causing the rough idle or did little good at all. They of course used a high dollar cleaner to dissolve the crap I dislodged in the system and all was fine after they ran it through the engine. I guess the moral of the story was one of the following. Don't fix what isn't broke, and if you decide to anyway, spend the money on the right product, otherwise you just create yourself more headaches.

Charles

After hearing all these, maybe I should either use a good fuel additive (any recommendations?), or do a injector clean with the dealer. Is this cleaning included in the regular MB service?

Michael Tse

Use BG-44k :cool:

Michael,

I noticed you said that you used a bottle of injector cleaner on only 3/4 tank of gas. On some brands of cleaner you are only supposed to use about four ounces per full tank of gas. Did you read the instructions before adding the cleaner? Too much will cause problems.

I have heard by everyone here and on the MBCA tech discussion to use TECHRON, and it works like a charm. It did for me too. I'd recommend it. GIve it a try, for a couple of bucks, give it a shot...?

The additive I used can treat up to 60L of fuel. I have a 95L tank, so I purposely added the content to 3/4 of a tankful.

A lot of the brand you quoted I have not seen in Australia. I will try mail order for those. Over here, we have Wynn, Mobil, Shell, and a couple of others.

Thanks a lot of your help.

Michael Tse

Australian stations do sell a higher grade premium fuel. That would be excellent for a few cents more.

While on the topic of premium fuel, I just want to post my own findings.

In Australia, we have unleaded (91RON) and premium unleaded (98 RON). I tried both fuel. The fuel consumption of normal unleaded is about 15-20% more fuel and lack of power. After taking this into account, I think the premium unleaded fuel is the way to go. Well, at least for the W140.

My 2 cents worth.

Michael Tse

I'm glad you find the same advantages for the premium fuel. :)