jjay911

Ok I have the M104 engine. It has had 3 owners and 85,000 miles on it now. THe car is also a Manual transmission. Here are my symptoms. When the engine warms up it vibrates and seems to miss between 600 and 1800 rpms. It idles fine but is hard to go in first gear. Once your going it does OK. When its cold it runs great. I have cleaned the Plenum new spark plugs, New wires, New cap and Rotor New EGR valve and Cleaned fuel Injectors. All completed by Mercedes. They tell me my Valves are Clogged with Carbon. What do you guys think.

Im Guessing Fuel Pressure Reg Thats the only thing I havnt changed yet. JJ

oneill_1

they probably are right ....did they give you a quote on how much that would be to fix?

-OG

jjay911

Im sure its not cheap. I will do a compression text next. Then I will see about replacing the Fuel Presure Regulator. That part is 425 bucks. JJ

mgw_300e

how's your wiring harness?

C43AMG

http://www.seafoamsales.com/motorTuneUpTechGas.htm

jjay911

THis car is in almost mint condition it was garaged and driven 6000 miles a year. The wireing harnes is perfect everything is perfect. All electronics work great. I have run every fuel additive on the market. The problem has gotten worse and I have yet to find any mechanic that can diagnose the problem. Even Mercedes cant nail this down. I guess Im stubborn but I refuse to believe that the engine needs a valve job after only 85000 miles.. JJ

rooney2006

that might not be a bad thing, you could get somebody to port and polish and get lighter pistons and everything at the same time... would raise your horse power by a **** ton.

shadowgriffen

I somehow got caught up in the "tune-up-in-a-bottle" thing, so not too long ago I bought myself some expensive fule additive from my local Autozone.

My car never stalled or vibrated until after I put that stuff in the system, have no idea but it had a reverse effect on my ride. It even died on me while food shopping, two days after the fuel mixture was put in, coinsidence? I think not...

oneill_1

where in socal are you located...i remember seeing your r129 at the irvine meet...i know of a mechanic in orange that deals with only mercedes.

-OG

jjay911

I know lots of mechanics as well. None of them have been able to pinpoint this correctly. I live in Costa Mesa. JJ

w124uk

Hi,
Looks like I have a similar problem. It shakes after the engine warms up, from around 1000rpm nice idle. It only reaches 80 C if it's important at all. The car is 1991 with under 80K on the clock, just 1 previous owner. 300e 2.6 103 engine. Nice and clean car with full service history (mainly Mercedes main dealer).

I've done the following:
-new spark plugs
-new HT leads
-new air filter
-cleaned distributor cap
-cleaned rotor arm
-cleaned ICV
-new OVP relay
-checked injector o-rings (used brake cleaner and it didn't increase the revvs)
-checked compression - 10.5 on all 6 cylinders
-3 bottles of injector cleaner

not to mention basic stuff like new oil and oil filter.
I'm running out of ideas, hope someone can help.
Local Mercedes garage has no clue what may be causing the problems - they thought it may be carbon residues in the injection pump...but then I did remind them it's not a diesel so it doesn't have an injection pump as such ;-)

And one more question - does the old engine mngmt system have diagnosttic socet where I could try to ger the fault codes? I work at a dealership but all we have is tech1 and tech2 for obd1 and obd2 cars as far as I know - the merc is 'to old' for our mechanics - they don't have a clue

And one more thing - looks like the colds start valve is playing up - when cold it does take 3-5sec to start (it used to take even more till I disconnected the wiring from the cold start valve). I guess the cold start valve may have been leaking and flooding the engine.

HELP please!!!
Thanks in advance!

TREZ63

Have you checked your oil pump? It might also be a sensor.

w124uk

How do I check the oil pump? Is there a common problem with oil pumps? The oil pressure seems fine on the dashboard (but I know it's not that accurate).
Is there a way of diagnosing which sensor might be shot?
thanks in advance!

jjay911

Your not going to believe this buy My mechanic has had the car for 2 weeks and thinks he has the problem narrowed down. I did replace the Spark plug wires and the cap and rotor Now It seams I just need a few new fuel Injectors. I will keep you guys informed. JJ

shdoug

I don't believe the plugged valve theory for a second. Injectors sounds more likely.

tokleman yanass

yeah the clogged valve theory sounds pretty far fetched to me too - 85000 miles is nothing on one of these engines, barely run in. If you've recently acquired the car a set of injectors is a good idea - I think I replaced all of mine at about 80000...
sorry to bang on about the same thing but you might want to check your coolant temp sensor - it sends a resistance signal to the ecu and if its not working properly it causes quite a bit of bad behaviour - the damned thing only cost $40 so try a new one if its even slightly suspect

jjay911

Runs great. Like a new car I never new it had this much power. JJ

shadowgriffen

was it the injectors?