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#1
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Whistling from behind air cleaner
Hi guys, 85 380sl 69k miles. Bought back in December, it ran great but developed a miss in #4 the day after I got it home. turned out to be the fuel dist. It cured the miss but created a surging idle at operating temp.
Replaced fuel dist, cap, rotor. Still have surging idle. When it warms up and is in gear the car feels like it's humping the road (best way to describe it). While trying to set the mixture I noticed a whistling coming from the back of the air cleaner. The air cleaner is in place and it sounds like it is coming from just underneath the rear of the air cleaner. Any ideas? Is this just the air intake? Is there a vacuum hose back there prone to leak? I do have a K&N filter installed. Thanks in advance. |
#2
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Sounds like a vacuum leak. Have you examined all the vacuum hoses? Look for cracks, splits, etc at the little rubber elbows that join the hard vacuum lines to various fittings. Do you have a vacuum guage? If so, what vacuum reading are you getting at idle?
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I choose to be happy, even when the Mercedes is being awkward, lol |
#3
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Rechecked all the vac lines again, found no issues with any. The whistling stops when air cleaner is removed so I made sure it wasn't interfering with any lines. Sprayed starting fluid around, no change.
I know the mixture still needs adjusted since I replaced the fuel dist and it's rich. I pulled the plugs and they were heavily carboned black. Cleaned them all, leaned it out a bit and most of the surging went away. Just down to a lumpy idle. Tried using a friend's old Sears diagnostic station but the dwell needle didn't change when tuning the mixture. |
#4
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Quote:
Sounds like you are doing the right stuff; except for the dwell meter. The dwell meter is used to set up points in a non-electronic ignition vehicle. Adjusting the mixture won't show on a dwell meter at all. Does the diagnostic rig have a fuel mixture guage? The ideal mixture should be 14:1 Or if the machine has a c0 meter, somewhere around 1.5 to 2 5% would do it.
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I choose to be happy, even when the Mercedes is being awkward, lol |
#5
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on mine ( djet) it was getting the co reading with a fuel gas analyzer meter that finally got her sorted out. It took a long time for me to find a unit , but I am glad I did!
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Ron 2015 Porsche Cayman - Elizabeth 2011 Porsche Cayman - Bond,James Bond Sadly MERCEDESLESS - ALways LOOKING ! 99 E320 THE Queen Mary - SOLD 62 220b - Dolly - Finally my Finny! Sadly SOLD 72 450SL, Pearl-SOLD 16 F350 6.7 Diesel -THOR 19 BMW X5 - Heaven on Wheels 14 38HP John Deere 3038E Tractor -Mean Green 84 300SD, Benjamin -SOLD 71 220 - W115-Libby ( my first love) -SOLD 73 280 - W114 "Organspende" Rest in Peace 81 380 SL - Rest in Peace |
#6
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Not to be a smartass, but could something as simple as the rubber gasket on the bottom of the air cleaner housing be the problem? There is a rubber gasket on mine to seal to the throttle body, if yours cracked, folded, broke from age/heat, etc...
Go for the "inexpensive" stuff first, you might just learn enough to know which expensive thing to buy. Scott
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Remember, it's not just a car. It's an Adventure. |
#7
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Thanks guys, no smart ass at all, every suggestion is always appreciated.
The rubber gasket is soft and in great condition like all the vac hoses. I read in some searched out posts that you use a Sears analog dwell meter attached to diagnostic pin #3 and adjust mixture till it reads 22 deg.? or 50% duty cycle? This one had no duty cycle reading, it looks like it may be from the 70's. A littel background on me: I've built American muscle cars and engines for years so I'm very mechanically inclined, but I still have a lot to learn about these Benz engines. When the air cleaner is off you hear the sucking noise from the intake, when I put it on I believe the noise is coming thru the air intake nose on the filter housing due to the increased flow thru the K&N filter. Could the engine be getting TOO much air thru the K&N and acting like a vac leak? |
#8
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could be , I have been dealing with MB's a long time- for the most part , as designed is the way they should stay - messing with the design tends to cause a chain reaction of issues...
__________________
Ron 2015 Porsche Cayman - Elizabeth 2011 Porsche Cayman - Bond,James Bond Sadly MERCEDESLESS - ALways LOOKING ! 99 E320 THE Queen Mary - SOLD 62 220b - Dolly - Finally my Finny! Sadly SOLD 72 450SL, Pearl-SOLD 16 F350 6.7 Diesel -THOR 19 BMW X5 - Heaven on Wheels 14 38HP John Deere 3038E Tractor -Mean Green 84 300SD, Benjamin -SOLD 71 220 - W115-Libby ( my first love) -SOLD 73 280 - W114 "Organspende" Rest in Peace 81 380 SL - Rest in Peace |
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