300d Rough idle with A/C on, only in drive. Valves?

[bpdresser]

Hi Diesel friends,

With some help, I've solved most all my climate control issues in my 83 300d this year. List includes: replaced the thermostat, replaced the OEM mono valve with a Klima, replaced the CCU and replaced the aux water pump (with fuse to protect the CCU).

So, I now have both heat and A/C that are working properly! That's the good news.

However, when running the A/C (modified to 134 years ago), the idle is sluggish...but only at a stop and in Drive. On the road, it's fine. And at a stop, if I shift into neutral, idle is perfect.

(Note that this oddity of sluggish idle with A/C on was the same before replacing all the items listed above).

Wondering if anyone has solved this mystery and can share. I'm thinking that perhaps adjusting the valves would help (it's been 24,000 miles since last valve adjustment) or if there might be something else.

FWIW, car has 361K miles!

Thanks in advance, BD

[Sugar Bear]

Yes do the valves, IMO they should be done at 12k and if they are notably out-of-adjustment done again at about 1-2k until they hold the adjustment

If the roughness continues try upping the idle speed about 100 rpm.

Congrats on the high miles! A compression test may be in order but do you really want to know? I wouldn't.

[ykobayashi]

Hi Bruce

There can be a number of things going on.

I’ve done well adjusting my idle up a bit. Some makes of cars have controls that speed up the engine a bit when you turn on the compressor to compensate for loading by the compressor. Ours do not.

If your engine is working properly (compression, valves, injectors, filters, timing and throttle linkage) are all working as they should you may want to consider a Sanden AC compressor conversion. I’ve found the OE systems quite marginal when converted to r134. They run higher pressures and the condenser is under capacity. The Sanden seems to put a lot less load on the engine in the installs I’ve seen. MPG and power goes up noticeably. My understanding is the efficiency is better than the old R4 units. Around here the hot setup is Sanden + parallel flow condenser.

The easy path is check the idle. Then check for basic tuning stuff I mentioned above.

[Volvo Diesel]

I had what sounds to be a very similar issue with my 1985 300D. Here's the thread: http://www.peachparts.com/shopforum/diesel-discussion/401226-85-300d-ca-version-low-idle-c.html

COVID happened between the initial post and the eventual solution (see quote below) but several members offered helpful advice.

Originally Posted by Volvo Diesel

I think a lot of the issue was just deferred maintenance. I did the following work and the car is running much better: changed engine and transmission mounts, adjusted valves, changed fuel pre-filter and main fuel filter, and adjusted hot idle speed to ~775 rpm.

[bpdresser]

Hello folks and thanks for the quick replies today.

Carl, nice to hear from you! The tach amp sensor still behaving beautifully. Grounded the cluster from the fuel and temp pins earlier this year which reduced a lot of driver anxiety!!

I don't think throwing a new compressor it in the plan.

Sugar bear, thanks for the suggestion on valve adjustment.

Related question for any/all of you...I've just changed the oil less than 500 miles back. I've not done a valve adjustment myself, and aren't going to do this one. While I obviously need a new valve cover gasket, does the valve adjustment require all new oil or can that be performed with the (new) oil still in the engine??

Volvo Diesel/Christopher, Hope you're fully recovered. Completely agree on maintaining these cars (as well as driving them). And put in new pre-filter and filter earlier in the year. While I "could" adjust the idle a little, that seems like a symptom rather than a cure...plus the idle is perfect w/o AC running.

I'm leaning towards valve adjustment, timing based on what you folks advise on whether I need to get rid of the new oil.

Thanks all, BD

[Sugar Bear]

Valve adjustment procedure has no effect on oil and/or filter.

[vstech]

Are you taking the car to a garage to have the valves adjusted?
It really isn't a difficult job, but I understand wanting to farm out engine service.
I do still have adjustment kits available... just a bag of feeler gauges, a pair of bent wrenches, and a link to the adjustment order to print out for keeping track of what you have adjusted.

[bpdresser]

Sept 25 update:

Thanks again to each of you for your thoughts and suggestions. Here's an update, along with the start of a potentially new thread.

The update:

We tweaked the idle up over the weekend to approximately 775 or so. That softened out the A/C idle issue for now! In terms of valve adjustment, I'm going to wait till it gets colder here in Northern CA and see how starting in the morning goes in November/December. Unlikely to need A/C till next summer.

Winter/Cold idle related...last year, driving but ONLY after the first start in the morning would have a weak enough idle the first mile that I'd break with my left foot and keep my right on the gas pedal. Am anticipating that the combo of upping the idle along with my new glow plug relay and plugs will make that better. Time will tell and I'll let you know.

Separate issue: Weeping between turbo and air filter housing even with new gaskets.

Figured I'd ask you folks before creating a new thread on this one. The only engine leak I had/have was from the plastic housing that connects the turbo and the air filter housing. Took that out, and saw that one of the 2 rubber gasket/o rings was dried out and had a small break. So we removed and replaced both the gaskets/o rings: one connecting to the air filter and the other to the turbo.

Now, not leaking nearly as much but still a small amount of leak that i've got about 10 drips on the cardboard underneath the car (in the last 60 days).

I believe both ends are tight enough.

Have any of you folks dealt with this same leak in this area, and what if anything made it either improve or go away? My mechanic buddy is contemplating that it could be the actual plastic connector between the air filter and turbo, but I'd hate to waste the time/effort and dollars thrown at something that won't make a difference. I can't imagine the plastic wearing out from the years of temp change between hot and cold, and there are no drips from the connector itself, just the connections.

Thanks in advance...much appreciated. Best, BD

[vstech]

I have pulled apart the oil separator, thoroughly cleaned it out and sealed all seams with ultra gray RTV, and had good results stopping the leaking.

[bpdresser]

February 12, 2023 update:

Hello Diesel friends. I have an update (again) to the recent September update above.

Finally got the valves adjusted last week (I had waited till the winter on purpose), along with replacing the valve cover seal (that was the source of 99%+ of oil leaks). For the remaining 1%, I have already a new boot from turbo to air filter housing (from Pelican Parts), but the gasket/seal to the turbo portion of the boot is too small in the new boot. So, another gasket on the way. Hopefully this one will fit.

Results: After the valve adjustment, shifting seems smoother all around, and engine temp is a bit cooler than pre adjustment, now right at approx 85 degrees. That's all good news.

As I told my tech assistant and friend, i always test everything after getting work done on this old 300d. Which yielded 2 new issues to fix:

1) Idle seemed still a big sluggish again.
2) A/C compressor didn't turn on (either for actual A/C or defrost).

Turns out there's a small leak from the gaskets on the rear side of the compressor (fortunate news!). We put in a little freon - just enough to engage the clutch on the compressor - and then heard the whizzing sound of a leak. Put the car up in the air and saw the visible leak. This should be an easy fix...

Which brings me full circle back to idle speed...which I'll want to tweak just a bit more once the A/C is working to properly set the idle.

But (and this is a big butt)..my idle pin that you loosen with a 14mm socket no longer wants to operate properly. After one turn on the pin in either direction, the pin slips off and the engine dies. We were able to tweak with a 14mm clawfoot wrench that allows turning the nut while adjusting the pin with a screwdriver simultaneously, but that seems like a hassle. Right now, idle is at around 800 and the car started fine this morning (37 degrees F) and drove immediately with NO stalling in that first half mile like in the past.

That's momentarily great, but I'll likely need to adjust the idle again once the compressor gasket leak is fixed and the AC system is fully charged and I can work the idle under AC load.

I'm now wondering: a) has anyone had this similar problem with the idle pin and b) might any of you have an extra idle pin lying around that you'd be willing to part with in case mine is simply worn out?

Thanks as always for your helpful suggestions and input...

Best, BD