Yes I recently purchased my 97 E420 only 4 months ago and this car only had 1ne owner. I think my friend put 87 gas and some octane booster in my car and now they check engine light is on. I never had a problem with this car until the car got some 87 gas in it. I took the car to Merchants and spent 436.00 for them to put new spark plugs in the car, the old ones looked so bad like they were the originals. This car only has 130,000 miles on it, so I put some sea-foam in the gas tank and the engine stills runs rough but it seems like it helped a lil', but my check engine light came back on after I disconnected the battery several times. Someone at autozone told me that it might be some wiring to the spark plugs that are bad? After new spark plugs the check engine stills reads misfire on cylinder 3, the guy at merchants said he took the spark plug from cylinder 5 and put it in cylinder 3 and the computer still said misfire after new spark plugs. I think there is still bad gas in the tank and I even added another octane booster, check engine light won't go off. Does anybody know what I need to do in order for my baby to start running smooth again? Please help me, thanks!

 

i would check the wires now..they do go bad over time. maybe a coil at #3. make sure the wires are good first. you shouldnt put 87 in the car either. that can contribute to poor performance.