Guys,

96 SC300 with 86k Whenever I first start it, it idles very high - around 1500rpms. As soon as it warms up, or I put it into gear it drops down to around 650-700 rpms (normal idle)... Any ideas what would cause it to do that? New plugs, wires, rotor, cap etc. Can barely tell it is running it idles so well when it is warmed up...

Jonny

 

sounds normal. You can try disconnecting the battery for a little and reconnect it. This will reset the ecu. Try starting it up after that.

 

That's totally normal. I'd be much more worried if it didn't do that.

 

1500 rpms is normal None of my SC's (and I have owned at least 10) have ever idled that high at start... maybe 1000-1100... But not 1500.

Jonny

 

hmm..mine idles at 1200-1500 when its cold...seems normal..:P
I think my friends integra gsr idles @ 2k+ when cold...lol;;

 

The high idle is completely normal, it's caused by your ECU being in open loop when you first cold start the car because it is not up to operating temp and cannot properly adjust fuel mapping, so on cold starts it just dumps a predetermined amount of fuel. Due to it dumping a larger amount of fuel than normal its as if you're engine is accelerating because when it burns this extra fuel it creates extra power on the down stroke causing the idle to bump up.

So your condition is perfectly normal, just be happy you don't have my symptoms that when I cold start the vehicle in the morning and try to shift into gear at the 1500rpm idle it slams into gear like I'm trying to do a 1/4 mile dig for a personal best time lol.

 

It might be a tad over what a new and perfectly tuned model might do, but I'd say it's definitely within tolerance for a 15 year old car with 86K on the clock. If you're really worried then try cleaning the TB and perform the TPS and IAC adjustments to factory specs. I doubt you'll see much difference though.

 

Remove and clean the Idle Air Control Valve to make sure its not gummed up and getting in a bind...Have a shop check IACV response vs command. Insure TPS voltage is within factory spec, ensure no post maf air leaks, and ensure coolant temp sensor and intake air temp sensor (might be incorporated into the MAF) are reading correctly.

 

Ha, you're saying 1500 is high
I live in San Diego, CA and on cool mornings my SC300 idles at 1800 rpm. It slowly eases down to 700 as the engine gets warmer. Most if not all Toyota/Lexus vehicles are/were designed this way. It's built-in, not a fault.
Oh, and yes, this is a perfectly healthy 96 SC300 with 125k miles on it.

 

All depends on the Intake Air Temp.

 

depending on how cold the area when starting up, it could start real high. also low miles good compression could start high to as well. sounds normal to me idles 1k-1.5k at cold start and warm up 400-700 is about right. Mine idles at 100 rpm =X lol i adjusted the tps.