engine shake help
started having rough idle issues a month ago and with 100k miles on my clk55, figured it was time for a major tune up. I had most done at a merc indy:
16 oem bosch spark splugs
16 oem bosch spark plug wires
two oem engine mounts
maf sensor from autohausaz
all fluids flushed/drained/filled
oem air filter
oem fuel filter
replaced valve cover gaskets
replaced engine belt
he reset the adaptation figures and i drove it 200 miles and still same issue...these are things we have done:
replaced 16 spark plugs again
replaced 16 spark plugs wires again
recheck engine mounts
started digging some more and monitored the cylinders and found that cyl 4 was behaving a bit weird...not sure the terminology but if at idle it's suppose to be 1.0, cyl 4 was fluctuating between -1 and 4.5...we swapped coil packs...still only cyl 4 had issues....could it be fuel injector? i only use premium 93, usually shell, but on occasion hess or mobile...i've used techron once and doing it again...
again started digging and started monitoring the o2 sensors...upstream o2 sensors were very erratic...spikes were all over the place....soon it will need to be replaced...could an o2 sensor wreck havoc on a cyclinder?
could it possibly be tranny mount? i can see the engine shake at idle...it looks like it's shivering...
i have no cel, no stored codes, and acceleration is still great for 100k mile engine, although at times when i punch it, there's a slight hesitation/choke...
it would make life so much easier if there was a check engine light or stored codes...i have nothing...ecu thinks its perfectly normal that i have a rumbling 5.5 liter old school muscle car
Last edited by slowsky; Apr 11, 2010 at 11:10 PM.
could the rear o2 sensors cause cold start/in park engine rough idle? could fuel injector cause an issue? still no malfunction codes...
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idle needle doesn't fluctuate, just can feel and see the engine shake...but if in drive, the idle is smooth and engine doesn't shake....only in park....could somehow the initial idle be too low? my idle is about 500-600...
another theory is the crank position sensor...could be on its way out since it measures the fuel/air ratios when cranking?
Last edited by slowsky; May 7, 2010 at 07:08 PM.
The CPS checks the crank position/engine speed. Also, air fuel ratios are not checked while cranking.
The 430 damper is $63 (list price is $84). The AMG part is a little bit more money - $278 ($370 is the list price). Some part searches show the 55 using the same part as the 430, but I think they're wrong. MB of Annapolis says they are definitely two different parts. You may want to buy a new bolt too. On many cars that's a stretch bolt.
Last edited by MarcusF; May 8, 2010 at 11:02 PM.
Last edited by slowsky; May 9, 2010 at 10:00 AM.
timothy: i didn't do the downstream o2 sensors because when we plugged the star diagnostic software in we didn't see any issues with any parameters...

after replacing just about everything, i've narrowed it down to trembling when idle at park only....idle in drive or neutral or reverse is smooth...under load its smooth as butter...
i'm thinking it's either fuel injector line is dirty or has water or the rear O2 sensors are creating a havoc on the trembling engine...
so odd that it only trembles when the engine is NOT under load...any ideas?
dealers may be more expensive, but usually they will try really hard to make you happy. they all live and die by customer satisfaction these days....and if you add up all the money you've already thrown at the problem, would probably be cheaper.
i too use a european indy for most things, but this kind of trouble shooting, electrical issues, conv top adjustments, i take to the dealer. worth the extra money in my mind. just my .02
i'm guessing since my car is old, they don't really want to deal with it...keeps telling me to trade up if i'm not happy with the idle....







