Chugging/hesitation
 

My mom has a 1994 S420..has 200k.... It has developed a chug and now has hesitation. When you first start it up there are no problems and is smooth, once under load the problems begin. If you change out the spark plugs the problem goes away for a short time. There is a severe lack of power off line but does alright once it gets up to interstate speed. The local dealeship told her to run 85 octane gas to fix the problem. Also the check engine light is on, according to the dealer that is not repairable and will always be on now...... We have had several problems with the dealer here, but the smaller shop said my moms car was out of their league..... I need help here.... It acts like a timing issue, or a low compression issue... Am I off here? My thoughts are head work/piston rings... maybe timing oe ECU... The car is currently at the shop and we will get it back tomorrow, I will do compressin checks, fuel pressure checks etc... any suggestions? or has anyone had this same problem? Thanks in advance, Aaron

also... I know in the past a little smoke came out at start up....... haven't seen lately!

The dealer is withholding the codes.... I REALLY HATE MB of COLORADO SPRINGS!!!!!!

If you want to avoid being at the mercy of dealers like that, it would be good to equip yourself to read codes. Try this article...

http://v12uberalles.com/pulling_codes.htm

Code 019... Injectors..... But what I have fouund is that it has no relation to the car???/ I need help here........ I have a friend in the business who helped out... This code has shown 57 times since 1996....... but this is only the 2nd time the light has ever come on! any advice would be great.... Thanks

Have you ever changed the distributor cap, rotor, spark plug and coil wires?

Wire Harness?

Oh yeah!!!! A few times...... The car has 200,000 miles!

Wiring harnesses are bad on 1993-1995 models.

It's worth it to have it inspected.

Chugging
 

You said if you change the plugs the problem goes away for a while, How do the plugs look that you remove? Oil fouled? wet with fuel? normal gap?
what color is the insulators?
The L.H. control monitors the operation of all the cylinders, if it detects a misfire it will turn off the injector to that cylinder(no fuel/no power)
The question about caps,rotors and wires is relevent but should also include testing the coils (2), I've also seen E.Z.L.s with weak output to one coil.
Mike

Thanks.. I will give it a look!!!! Where can I find specs on the coil?