New head gasket, new problems... - PeachParts Mercedes-Benz Forum

JEdwards · #1 02-19-2008, 11:08 PM

Well, similar problems, only worst.

car= 1987 300E

Head gasket and valve stem seals were just done (no more leaking coolant).

As a result, the "rough idle" has gotten much worst. Prior to head gasket, it was controllable, now however, when it is wet I can feel the car acting like its rough when I'm driving down the highway. The rough idle seems to be the typical rough idle that many people describe on the forum, with the vibrations in the chasis when stopped at a light in drive.

Where should I look now?
-head gasket is brand new
-new valve stems
-replaced ovp, fuel relay, cap, rotor, plugs, ezl ignition, cps
-tested the icv (tapped the icv repeatedly and the idle did not change)
-new breather hoses are in the mail, although they looked fine to me

could an overly rich mixture cause similar problems?

thanks

John

Ferdman · #2 02-20-2008, 05:47 AM

John, you failed to mention the spark plug wires (ignition wire set). Old, deteriorated wires can cause an engine to run rough.

JEdwards · #3 02-20-2008, 12:25 PM

I haven't replaced the wires yet. My mechanic said they were fine and I double checked with the water spritz test in the pitch black and there was no visible spark arching out of the wires. Should I replace them anyways?

david s poole · #4 02-20-2008, 01:59 PM

this won't fix idle but how are your motor mounts?if you can feel engine thru seat of pants at idle they are bad.when the head was done were the bolt holes that hold down the rocker assemblies helicoiled?it is common for those threads to strip out and leave you with loose rockers on a couple of valves.

JEdwards · #5 02-20-2008, 04:40 PM

I don't know about the helicoiled rocker assemblies (I'll ask my mechanic the next time I see him, which coincidentally is really soon to have the bolts re-torqued). Would the bad rockers cause this problem?

Motor mounts are brand new though (and the bracket which holds the drivers side one to the engine). The idle that I feel in the chasis seems like its vibrating only in the A pillar on the driver's side.

There are a lot of questions floating around in my mind about this, like if its possible the O2 sensor is at fault or the coil is at fault (although every mechanic I've talked to says its not possible), or if its maybe the ECU acting up.

Sorry for leaving some of the other maintenance out of the original post.

Side note, I just calculate my mpg and it seems I'm getting around 21 for highway driving (75mph around 3krpm). Is it possible I'm running overly rich?