Hey guys

I am trying to fix my low idle and surge on my 87 300D.

Symptoms:
1. Idles around 550 or so
2. At low speed, abrupt release of the throttle causes rpms to drop to 500, even 490ish, for a second. Sounds and feels pretty rough, but that part could be motor mounts.
3. Sometimes at idle, in park, the engine makes a faint cycling sounds, as if the rpm are varying +/- 20 or so...but this does not register on the tach, and might be a whole different problem. I'm more concerned about 1 and 2.

Anyway, after reading as much as I could about the ELR, I went and tested that out and it seems that the knob itself doesn't change much (it was at 4, I put it up to 6...it worked for a bit, but once I started driving it went back to being 550)
I disconnected the line on the ELR actuator and that is working - the idle dropped and was pretty rough...
It seems like when the engine surges, the ELR is off for that split second and then comes back, just not where it should be. What can I do to try to fix this? From what I hear, they don't go bad, so would a good cleaning help maybe?
I also read that a dirty tank strainer could cause low idle and surging.

I've seen a couple of posts with the same problem, but there hadn't been any responses to them.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

Have you checked the OVP relay (ABS warning light on also?)?

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Gone to the dark side

- Jeff

Well, the OVP is new, so that shouldn't be the problem, unless the port that it connects to is bad...but other OVP-symptoms are not present. The ABS light does come on, but I still need to get my ABS checked. Seems like the "self test" happens more than once, along with abs-like pumping after 1st use of brakes (I think bad sensors, pump, or brain)
I just sprayed to ELR knob with some contact cleaner, so we'll see if that changes anything. I doubt it though
It's just weird, because with the actuator unplugged, the idle is really rough, so I know that it is at least somewhat working, just not at the rpm that it should be.

__________________
Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

bump

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

I am curious; is 550 rpm within spec for a normal idling speed for your model and year of car?

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84 300D, 82 Volvo 244Gl Diesel

It might be; I'm not entirely sure, though. From what I've read on here, 630 rpm seems to be the factory setting (or around there)
I think 550 is acceptable if it was set to be there, but I have the ELR knob set at position 4, which is factory setting, so I think it should be higher.

I'd also like to mention that the surging / shudder part seems to go away after the engine has been at operating temp for a while; or at least, is not as apparent (For example, after a 15-20 minutes drive at 80+C)
Idle remains low though.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

I had a similar issue that was caused by the manifold (boost) pressure sending unit vibrating loose. I got curious and briefly took it out. Upon further investigation, I found the aluminum threads were all but gone from the steel in the sending unit. Eventually I helicoiled it. Both out and loose caused the slightly low, slow 'fluctuating idle' that you describe. From that I surmise other manifold leaks might cause the same thing.

ALSO, there is a factory ALR test procedure I'm looking for in the FSM. I'm pretty sure it's too big to post so when I find it I'll send it to you.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

You know what, my sending unit (you mean Y30?) is not bolted to anything, it is just kinda hanging there! I'll try to attach it to something so it is sitting right side up and see if that helps at all.
Or are you talking about the two pronged connection next in the middle of the manifold? I haven't done anything with that, so I can check on it as well.
I'd still like to see that ALR test though, if you could send it once you find it.
Thanks

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

Listed in Fast Lane as "Boost Pressure Sensor"

It's rather heavy for its size and can get clogged with soot. DO NOT over tighten it. IF the hole is stripped, it can be helicoiled but the kit is kind of 'spendy.' (mmm hmm first hand experience ) It's 12 x 1.5 mm and isn't a commonly used thread.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

Ah, that one. I have not taken a look because I thoght it was soley an electrical connection...but since the outlet that goes to the overboost valve was clogged, this one probably is too. I'll have a look after work!

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k