| Author | Message | ||
     Dale Mattson Experienced User Username: wookieecantina Post Number: 15 Registered: 5-2009 |
Hi All, I recently adjusted our carbs, synchronized them, but I'm having issues with the correct idle speed. The Shadow Owners' Companion recommended 600 RRM, but tonight when driving the car for the first time, when the Air Con. was turned on, the vehicle began to stall frequently at lights and stop and go traffic. Any suggestions from the pros? Thank you all very, very much. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 341 Registered: 6-2006 |
I haven't read the Companion, but it does sound low, is that 600 RPM when in gear with the A/C on. I'd increase it as necessary, and see what it is then idling at in Neutral. Ensure the brakes are held on ( all H&S warnings apply etc.) What year is your car again? | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1122 Registered: 4-2003 |
Paul is quite right Dale but the book as I do recall says 600 rpm but if you think of it given the tune and condition of the engine if it can't idle at that speed with the car in drive and the aircon going (and that means the compresser actually running) there's is not much point in setting to that figure. If having set these conditions up and set the idle to 600 and then when you turn the aircon off and the speed really leaps up it is time to get a professional look at the aircon and compressor! | ||
| Dale Mattson Experienced User Username: wookieecantina Post Number: 16 Registered: 5-2009 |
Thank you both so much! This Shadow is a 1976 but it's a California car which means it's loaded with smog equipment. It has only 48700 original miles, so it's not been driven much these past 7 years after the owner passed away. His wife did drive it monthly and maintain the car as required. I set the 600 RPM with the car in park, AC off. The AC seems to drop the RPM approx. 500 to 700 when engaged and of course, when the car is gear, the RPM drops to approx. 450 so that when you start to move forward and then let off the throttle, the car starts to stall. I was worried that perhaps I had the air volume a bit too low, but I set them at 1 1/2 turns and then adjusted accordingly. I'll take a listen to the AC compressor today. I think all in all, I was just worried about the idle being set a little too high and then dropping into gear. Is this hard on the drive train? Thank you again for your wonderful advise. This is a terrific forum! Dale | ||
| Brian Crump Experienced User Username: brian_crump Post Number: 41 Registered: 2-2007 |
If you have followed the instructions in The Shadow Owners' Companion, and all other parts of the ignition and fuel system are in order, then perhaps you are simply setting the idle speed a little too low? To my way of thinking, it should read 600rpm when the car is in D and the aircon is on. Of course you do not want it so high that it clunks into D. However, are you sure of the carburettor settings - are they correct? Good luck. Regards, Brian Crump | ||
| Dale Mattson Experienced User Username: wookieecantina Post Number: 17 Registered: 5-2009 |
Hi Brian, Thank you very much for your input. Yes, you are probably correct, perhaps I was worrying too much about the clunk going from park to drive. Based on everyone's input, I'll reset the idle a little higher and perhaps ask the wife to sit in the car while in drive with AC on. That should take care of the problem. I guess the car is actually in drive more than in neutral. If the AC draws too much RPM, then we'll check that next. I've noticed smog/air pump is a little noisy, but that should not affect the idle. Its really odd, but I've looked in the manuals and cannot seem to locate the exact linkage set up this vehicle has, my guess is RR tried it and was not pleased with the result  Thank you all for your help! Dale | ||
| David Gore Moderator Username: david_gore Post Number: 889 Registered: 4-2003 |
Unfortunately, my archives stop at the 1975 California specs but the 600rpm idle with the A/C OFF seems universal. My opinion is that this could be too low for "smogged" engines of this era [and more so for the more stringent Californian requirements at that time] especially if it is purely to minimise transmission "clunk" when hot. However, I would suggest transmission "clunk" is more of a problem when the engine is cold and running on "fast idle" settings than when hot and running at lower revs. For this reason, I would set the idle speed around 750rpm to compensate for the inherent loss of idle revs when the A/C compressor cuts-in or alternatively set the idle speed to 600rpm with the A/C ON and compressor engaged if you always leave the A/C on during normal daily use. A possible cause for the stalling/rough idle could also be a faulty hot idle mixture compensator valve. | ||
| Dale Mattson Experienced User Username: wookieecantina Post Number: 18 Registered: 5-2009 |
Hi David, Thank you so much, the faulty idle mixture compensator valve sounds interesting. I'll check my manuals tomorrow to learn more about that. This afternoon I re-set the idle RPM to 600 with AC compressor engaged, and when the AC was turned off, the RPM jumped to approx. 700. So, when sitting idle it didn't jump too terribly badly when placed in gear with the AC off and with the AC turned on, there was a big improvement. However we pulled into Disneyland and sure enough, she stalled. I turned off the AC and it ran fine but the RPM were up at approx. 700. David, you may right, I'll try to the 750 setting and see how she performs. I was able to correct the linkage issues by drilling the outer nut and using a cotter key, the connector linkage can move freely and not bind up. I wonder if perhaps my Opus ignition or coil is perhaps getting weak? Once again, THANK YOU ALL SO MUCH for your patience and wonderfully helpful advice! | ||
| David Gore Moderator Username: david_gore Post Number: 890 Registered: 4-2003 |
Hi Dale, If the 750rpm setting does not work then head straight to the idle mixture compensating valve - this is supposed to activate after "long" periods of idling to prevent stalling. Only problem is what is the factory definition of "long"!!!! Given the history of the car - I suggest the first thing to do before any further experimentation is to take the car for a good, long drive at freeway speeds for 200/300 miles to get everything back into working order - the Shadow loves to be driven and the worst thing for it are long periods of intermittent short-distance use; this is almost as bad as not driving the car at all. A good long "weekend-away" trip every 2 or 3 months is the best thing you can do for a Shadow in my experience. | ||
| Dale Mattson Experienced User Username: wookieecantina Post Number: 19 Registered: 5-2009 |
Hi David, Thank you truly, I will check the idle mixture compensating valve, that also makes very good sense. Yes, the poor car has sat a great deal for the past 6 years, but the engine seems very strong, no smoke, no odd noises, plenty of power. Its just these small issues which are somewhat troublesome. With the engine appearing so strong, one would not think the AC should affect the idle to such a great degree. Last night when I started the car, now the air diverter valve is howling quite badly. Even idling the valve is allow pressure to escape. I'll have to do a vacuum test tonight on it. I'm thoroughly the car is possessed! Perhaps a little holy water will help!  I called our local RR dealer and they wanted $285.00 US for the part. | ||
| Dale Mattson Experienced User Username: wookieecantina Post Number: 20 Registered: 5-2009 |
Hi Richard, Thank you for the suggestion! I have adjusted the idle screw with the A/C both on and off, but if adjusted with the A/C on, the idle is very high, approx. 750 RPM (compressor off) and it does make changing gears rather awkward. Please pardon my ignorance and I'm embarrassed to say this, but I'm not familiar with the A/C idle adjustment on this vehicle. I've looked closely at the linkage and cannot seem to find anything which would allow for an idle increase to compensate for the compressor while engaged and thusly return to normal idle when not engaged. I must be looking right at it and not seeing it. Thank you Richard for the assist! Dale |
