91 Mercedes 560 SEL Low Compression & Shaking... - PeachParts Mercedes-Benz Forum

nissandotson · #1 12-09-2008, 02:23 PM

Can someone please "Help" me with figuring out what is wrong with my car?

I have a 91 560 SEL w/153K miles on it ,that is in otherwise good condition. Except that since February, the car has a constant skip/shake especially when stopped. I had a tune up done in March and all spark plugs and the distributer cap was changed (the spark plug wires were not changed). However, the problem still continued. I kept taken it back to the shop, but to no avail. They thought it might be calibration, but did not know. I even paid for diagnostics from 2 different shops, still noting.

Finally, I was told the problem was the intake gasket manifold by the 3rd shop. I took the car in on 11/18 to have repaired and the shop broke everything down, but never completed the repair. It turned out to be a nightmare! I ended up having my vehicle towed to another Mercedes shop last Tuesday and that is where it is currently. They have put everything back together. However, they now say that there is low compression and the car still skipping. Might be the fuel injectors. They are still working hard to repair. In addition , the fuel gauge does not work. The car appears to have a full tank of gas and than runs out all in the same day. What do I do to have these problems rectified, without it continuing to cost me a small fortune? So far it is costing me $1600-$2000 for the current shop alone.
I would appreciate any help and/or suggestions.

ARNOLDLewis · #2 12-09-2008, 06:38 PM

leakdown test. pressurize the cylinder and listen for hissing noises coming from either the exhaust, the intake, or the oil cap. exhaust= toasted exhaust valve. intake= toasted intake valve. oil cap= toasted compression rings.

johnathan1 · #3 12-09-2008, 06:48 PM

Is the low compression just in one cylinder? Low compression means the engine needs to be rebuilt...but of course the mechanics could just be telling you this to get money out of you, when the problem could be something much simpler.

ILUVMILS · #4 12-09-2008, 08:03 PM

Did any of the shops inspect the camshafts/rocker arms, or check the camshaft timing??? If not, this should be checked before any more time or money is wasted!!!

560 SEL · #5 12-10-2008, 12:19 AM

I think you are getting a run around.. I would replace the spark plug wires and new fuel injectors with seals.. I had the same problem with my 560 when I got the car.. the problem was plug wires the injectors had problems also.. when I installed the parts it solved the miss problem..
Bob

nissandotson · #6 12-10-2008, 10:23 AM

Thanks to everyone for your suggestions. I am truly appreciative and will be discussing it with the shop today. Yesterday they stated that the low compression was in eiether cyl 4 or 6 (140). But they were still checking. In the meantime, they ordered new spark plug wires and injectors and will be checking to see if clogged. I will keep you updated.

Thanks again!!! I love this forum!

nissandotson · #7 12-10-2008, 10:39 AM

Hi Bob,

You were right on the money! It was the spark plug wires and fuel injectors. The shop says the car is running smoothly now. Thank you again!

nissandotson · #8 12-10-2008, 10:44 AM

Finally the car is running smoothly. However, the shop is stating that it is costing me $500 extra for them to add the new spark plug wire set,spark plugs and injectors. Ooocch!!! This brings my total to around $2000+ Is this a fair amount? My original spark plugs were fine (new 3/08), but they changed anyway.

560 SEL · #9 12-10-2008, 05:31 PM

can you work on this car have you worked on cars before if not you are gng to pay through the nose to keep this car on the road..YOu are at there mercy if you can't do the work yourself.. I can tell you with the milage you have on this car its in need of other work the list goes on I am not trying to scare you just giving you a heads up. these cars are great but they do require constant care.. I think you are getting ripped off to go to the compression check and ignore ingnition wires on a miss, these engines are tough and were built to last but there are things need to be done to the upper end the lower end of engine bullet proof
Bob

560 SEL · #10 12-10-2008, 05:41 PM

one thing you need to do also while they are putting new wires on is change the ignition coil. here is the reason ,since the coil handles high voltage over period of time the coil breaks down internally and what happens is the internal resistance changes causes heating.. there is a module called an EZL, find it on the left fender well under the hood.. that module is very expensive, an bad coil will take it out cause it to fail.. your cars engine will just die and you won't be able to start it.. you will have to replace the EZL you can find them used on ebay but change the coil before this happens to you, now is good time.
Bob

560 SEL · #11 12-10-2008, 05:50 PM

while your mech has the car ask them to check the timing chain for stretch if more then 10 deg it should be replaced along with guides.. this is very very very important for reason explain later
Bob

nissandotson · #12 12-11-2008, 12:39 AM

Wow...what "Great" information! I appreciate it Bob. You are right, I am at their mercy since I don't know how to repair myself. But receiving this information to better prepare me is so helpful. I will be going to the shop to pickup the car in the morning. However, before doing so, I will have them check the information you mentioned first. Because of the cost factor, they opted to clean the fuel injectors and changed the wires (result of me trying to negotiate). I will find out how it really runs tomorrow. The work that was done included: Intake Gasket Manifold repair and sealing*brake job rear/front pad & front rotors replacement *fuel injectors cleaning*New spark plugs*new spark plug wire set). Thanks again for your help!!