I have a 1989 300E.

The vehicle failed emissions (HC & CO)and I had it looked at by a benz shop and they said the spark plugs need to be changed and the O2 sensor was only reading at 50%. After they changed those the vehicle still failed emssions but this time it faild for HC and NO. The car is also consuming alot more fuel then it used to.

We used to drive the car with a full tank for about week to week and a half and now with a full tank we only get a few days out of it. The enigne also revs up high to where there really isn't any need to push the pedal for starting from a stop.

Can anyone help?

 

Get to another shop,an independent mercedes shop with the proper smog and diagnostic gear to analyze what is going on.I would normally say check these things yourself but you cant get the test equip for those years without spending big bucks.They need to look at the o2 sensors run the tests that show the sin waves are being generated,check the injectors,operation and leakdown.then check for leaks in the emissions system.worn vac hoses,clean the egr valve,and check smog pump belt and operation.Don't go to the dealer they are not even trained in the old systems and will just run up a high bill.
good luck
ohlord
"GOT CODES?"

 

Nope no codes that I know of. I did take it to independent MB shop which did tests after the first time it failed. I'll be taking it back to them tomorrow to see what they can figure out this time. I do trust them a bit more because of the good things I've heard of them and they have people with 15+ years of MB experience with factory training.

 

Are you using synthetic oil? If not I suggest use synthetic oil (that is compatible with your engine), it usually will help in passing emission test. I suggest also to havethe enginetuned up if you have not. Hope it helps.

 

An 89 that has not run on syn oil since early life is not a great candidate for changing over to it now.It will not help a worn engine pass the smog test.
he put in new plugs,not the issue,have them check the above and run a compression test.
do they have a smog tester and a good scope?if not go to a shop that does.
ohlord

 

I agree with ohlord the 89 was not all that complex a system and the dealer usually has no idea aside from throwing parts at the car take it to a place that deals with older cars and what would synthetic oil have to do with anything.