steve665 Posted August 27, 2009 Report Share Posted August 27, 2009 I recently bought a '79 Eldorado Biarritz with the EFI gas engine. When started cold, it idles faster than I would like. Can someone tell me how to adjust it lower? Link to comment Share on other sites More sharing options...
KHE Posted August 27, 2009 Report Share Posted August 27, 2009 I seem to recall a bad coolant temperature sensors on the Olds 350 would affect the idle speed. There should be a chart in the shop manual comparing resistance to ambient temperature. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
steve665 Posted August 27, 2009 Author Report Share Posted August 27, 2009 I seem to recall a bad coolant temperature sensors on the Olds 350 would affect the idle speed. There should be a chart in the shop manual comparing resistance to ambient temperature. When the engine warms up, the idle speed goes down like it should. I'm just wondering if there is a way to adjust it so that it doesn't idle so fast when the engine is cold. I gave away my shop manual with a '79 deVille I sold three years ago. I see there is a black, square Bosch device attached to the right side of the throttle body that is set to the middle of a range fastened by a set screw with a dab of blue paint intact. Would adjustmet of that in one direction or the other change the fast idle speed? Link to comment Share on other sites More sharing options...
KHE Posted August 28, 2009 Report Share Posted August 28, 2009 I seem to recall a bad coolant temperature sensors on the Olds 350 would affect the idle speed. There should be a chart in the shop manual comparing resistance to ambient temperature. When the engine warms up, the idle speed goes down like it should. I'm just wondering if there is a way to adjust it so that it doesn't idle so fast when the engine is cold. I gave away my shop manual with a '79 deVille I sold three years ago. I see there is a black, square Bosch device attached to the right side of the throttle body that is set to the middle of a range fastened by a set screw with a dab of blue paint intact. Would adjustmet of that in one direction or the other change the fast idle speed? I wouldn't start messing with things without the shop manual - if your luck is like mine, you might buy yourself all kinds of additional trouble... I seem to recall that my carbed cars would idle what seemed too fast compared to today's fuel injected cars but that's the way they were. It could be the early EFI systems like what is on your Eldorado are the same way. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
steve665 Posted August 28, 2009 Author Report Share Posted August 28, 2009 I wouldn't start messing with things without the shop manual - if your luck is like mine, you might buy yourself all kinds of additional trouble... I seem to recall that my carbed cars would idle what seemed too fast compared to today's fuel injected cars but that's the way they were. It could be the early EFI systems like what is on your Eldorado are the same way. I gave away my shop manual so it pains me to buy another one for the $60 that they cost! At some point, may have to. Meanwhile, I found this description of my 79 Eldorado's fast idle valve on the internet: "FAST IDLE VALVE The EFI system fast idle valve, installed on the top of the throttle body, consists of a plastic body that houses an electric heater, a spring and plunger, and a temperature sensitive unit. The fast idle valve is connected electrically to the fuel pump circuit through the ECU. When the engine is started cold, the open valve allows extra air to bypass the throttle valves. The heater warms the thermal element which expands and forces the spring and plunger toward the air orifice, restricting the flow of extra air and gradually reducing the engine speed to the normal idle rpm. The fast idle valve has no effect after the thermal element reaches about 140°F. The rate at which the valve closes is a function of time and temperature. The warmer the air, the faster the valve closes. At 68°F (20°C) the valve will close in about 90 seconds and at -20°F (-29°C) the valve will require about 5 minutes to close." To get this valve to close faster, I wonder if partially blocking the air flow to the valve would be effective? What do you think? Link to comment Share on other sites More sharing options...
Ed Hall Posted August 28, 2009 Report Share Posted August 28, 2009 You might also be able to play with the spring. Seems like weakening the spring might cause the fast idle to come off faster. Link to comment Share on other sites More sharing options...
steve665 Posted August 29, 2009 Author Report Share Posted August 29, 2009 You might also be able to play with the spring. Seems like weakening the spring might cause the fast idle to come off faster. Thanks for the tip, Ed. I took the spring out. That disabled the fast idle valve. The car has been sitting for six days and it started and ran fine at normal idle speed (temperature here is 70 degrees). This is a fair weather car only, at this point in its life. Car shows, cruises close to home, etc. If I need fast idle to keep it from stalling I can fast idle it with the accelerator for a few seconds. I hate the unnecessary fast idle that the earlier fuel injected cars used to prevent any chance of cold stalling. Link to comment Share on other sites More sharing options...
lothos Posted August 30, 2009 Report Share Posted August 30, 2009 Nice car! WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn. Cheers! 5% discount code at RockAuto.com - click here for your discount! Link to comment Share on other sites More sharing options...
steve665 Posted August 31, 2009 Author Report Share Posted August 31, 2009 Nice car! Thanks for the compliment lothos! Appreciate it! Link to comment Share on other sites More sharing options...
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