rafiqi Posted June 3, 2008 Share Posted June 3, 2008 Hi peeps, my 93 SC400 every now and then and at least once a day will idle upto 1700 rpm and then down then up... several times before finally settling down. I have done a vacuum hose check and changed the idle valve. Any help would be appreciated . Thanks, Rafiqi. Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted June 3, 2008 Share Posted June 3, 2008 When does this happen? With a cold start or with a warm engine restart or anything in between? Quote Link to comment Share on other sites More sharing options...
lemaylexus Posted June 3, 2008 Share Posted June 3, 2008 Don't know if this helps at all but on my 97 SC300, in the mornings when I go to work and the car has sat all night, the RPM's run high, between 1 and 2k until the car starts getting warm. If you take off immediately its a high enough idle to roll the car. I think it just does that to warm the engine quicker. Simple solution: Let the car warm up for a few minutes before driving. That's what I do anyway.. Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted June 3, 2008 Share Posted June 3, 2008 Don't know if this helps at all but on my 97 SC300, in the mornings when I go to work and the car has sat all night, the RPM's run high, between 1 and 2k until the car starts getting warm. If you take off immediately its a high enough idle to roll the car. I think it just does that to warm the engine quicker. Simple solution: Let the car warm up for a few minutes before driving. That's what I do anyway.. You're right. This is normal. It's similar to the old manual choke. You can drive off after less than a minute except in the winter. I let it warm up until the revs come down to 800 or so before driving off. Less stress on the tranny and gives all the fluids a chance to pressurize throughout. Quote Link to comment Share on other sites More sharing options...
rafiqi Posted June 4, 2008 Author Share Posted June 4, 2008 Mine idles up and then down and then and so forth for about 20 cycles. I don't think this by design. Don't know if this helps at all but on my 97 SC300, in the mornings when I go to work and the car has sat all night, the RPM's run high, between 1 and 2k until the car starts getting warm. If you take off immediately its a high enough idle to roll the car. I think it just does that to warm the engine quicker. Simple solution: Let the car warm up for a few minutes before driving. That's what I do anyway.. You're right. This is normal. It's similar to the old manual choke. You can drive off after less than a minute except in the winter. I let it warm up until the revs come down to 800 or so before driving off. Less stress on the tranny and gives all the fluids a chance to pressurize throughout. Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted June 4, 2008 Share Posted June 4, 2008 Mine idles up and then down and then and so forth for about 20 cycles.I don't think this by design. Sounds like a typical vacuum leak somewhere between your TB and intake manifold. Some other parts that could be starting to fail: cold start injector, coolant temp sensor, IC motor. Quote Link to comment Share on other sites More sharing options...
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