During the past 5-6 weeks ive noticed a loud whine that begins about 2-3 seconds after starting the engine just as the oil pressure guage comes up to 45psi/max on my guage. The humming is obviously under the engine in the area of the oil pan. The vibration is very easily felt by putting your hand on the oil filter housing. The vibration goes away as the temp reaches normal, on my car this is 175 F Additionally, while cold the pressure stays at max then drops to around 30 while cruising and around 15 at idle. The oil had been changed w. filter as soon as this problem started and it continues. Other current problems include a rough running engine at idle, replaced plugs, vaccuum lines ok, new air filter, fuel filter, pressure of fuel ok, compression good, 125K on car, and new rotor and cap, ohmed all wires and resistance is well within acceptable range, including coil wire. Adjusted timing to TDC, and tried to adjust CO to smooth out mixture with limited positive results. Still hesitates when warm on takeoff or speedup. Additionally, i believe warm up regulator is bad as it does not come off high idle 1600 or so for a long time when cold. Also requires 10sec worth of cranking at times when warm restart attempted. Any help is welcome. Oh also cant get trans to downshift at speed into 2nd, ie passing situations, Thanx


[This message has been edited by Hunter (edited 04-15-99).]

The idle is controlled by a temp sensitive idle valve and they do fail. The whine I have no idea except to check the timming chain and tensioner(the only things I have ever seen faulty on this model engine). On the warm re-start check the fuel accumulator.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Thanks for the reply. Where is the idle valve you spoke of in your reply. Is their a test to determine if this is the culpri? Thanx.

The idle valve is located in front of the air cleaner and is standing upright...It has what appears to be a slot in the top of it for adjustment, but it is sealed and can't be adjusted. If the coolant temp is OK and the throttlr plate is adjusted properly and the idle is too high, the idle control valve is most likely faulty.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM