SL/R107: Rough bouncy idle, clicking under dash, tachometer behaving erratically
02-07-2024, 11:55 PM
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1985 380sl 220k miles
Rough bouncy idle, clicking under dash, tachometer behaving erratically
Hello all,
Apologies for the big story post but I just wanted to give you guys all the details.
Preface: My 1985 380sl has had the occasional high idle for about 2 months before I took her in for the story below. It has also had a good used idle control valve put in about 7 months ago. The car also ran fine when I dropped it off at the mechanic with none of the symptoms below.
I just had a new(good used part) monovalve put in my car, and my mechanic said my key ignition switch should be replaced as well for grounding reasons, but I declined it for right now(in hopes to get my next paycheck first) and had him just put in a monovalve. I also had him make the car idle a tiiiiny bit richer as I felt it wanted more gas at idle.
Upon receiving my car, everything ran fine for the first couple miles on my way home, but then I heard a very rapid, loud clicking coming from around the OVP relay's area followed by my tach going crazy (separate from the actual revs of the vehicle, i.e bouncing between 1k and 3k rpms when the car was actually idling around 600).
I drove another couple miles and then at the next traffic light the car started idling extremely rough and the rapid clicking started again. Very bouncy, barely wanting to stay on, felt like a couple cylinders weren't firing, even stalled a few times.
I drove the limping vehicle back to the mechanic and he said he'd look at it again.
The next day, I get called back to pick it up with him saying that they just tuned the car up and its fine now. When I started her, the idle was still bouncy but it was now staying on. I then had him adjust the idle mixture and the timing on the spot and it got a bit better. I then drove the car for another few miles before I heard the rapid clicking followed by more bouncy, rough idle.
I checked the OVP relay when I got home and the fuse on it was fine, but I'm not sure about the state of the relay itself.
I'm taking her back to get the key ignition switch replaced in hopes that there's some grounding issue that could be shorting out stuff and causing this.
I have attached a link to a video of the click, although when the car was freaking out the click was 10x more rapid, but it came from the same spot. The change in pitch in the engine is from me putting the car in reverse (went down from 1k rpm to about 700)
Any thoughts or ideas from the best merc mechanics on the internet?
Apologies for the big story post but I just wanted to give you guys all the details.
Preface: My 1985 380sl has had the occasional high idle for about 2 months before I took her in for the story below. It has also had a good used idle control valve put in about 7 months ago. The car also ran fine when I dropped it off at the mechanic with none of the symptoms below.
I just had a new(good used part) monovalve put in my car, and my mechanic said my key ignition switch should be replaced as well for grounding reasons, but I declined it for right now(in hopes to get my next paycheck first) and had him just put in a monovalve. I also had him make the car idle a tiiiiny bit richer as I felt it wanted more gas at idle.
Upon receiving my car, everything ran fine for the first couple miles on my way home, but then I heard a very rapid, loud clicking coming from around the OVP relay's area followed by my tach going crazy (separate from the actual revs of the vehicle, i.e bouncing between 1k and 3k rpms when the car was actually idling around 600).
I drove another couple miles and then at the next traffic light the car started idling extremely rough and the rapid clicking started again. Very bouncy, barely wanting to stay on, felt like a couple cylinders weren't firing, even stalled a few times.
I drove the limping vehicle back to the mechanic and he said he'd look at it again.
The next day, I get called back to pick it up with him saying that they just tuned the car up and its fine now. When I started her, the idle was still bouncy but it was now staying on. I then had him adjust the idle mixture and the timing on the spot and it got a bit better. I then drove the car for another few miles before I heard the rapid clicking followed by more bouncy, rough idle.
I checked the OVP relay when I got home and the fuse on it was fine, but I'm not sure about the state of the relay itself.
I'm taking her back to get the key ignition switch replaced in hopes that there's some grounding issue that could be shorting out stuff and causing this.
I have attached a link to a video of the click, although when the car was freaking out the click was 10x more rapid, but it came from the same spot. The change in pitch in the engine is from me putting the car in reverse (went down from 1k rpm to about 700)
Any thoughts or ideas from the best merc mechanics on the internet?
