Lvangundy

I'm seen hints of these symtpoms in other threads so I'm basically reporting mine as well.

1995 SC300 - 76K miles.

On a cold start (or what the car thinks is a cold start) the idle is up near the 1850RPM mark, close to 2000. After 3-5 minutes, the idle drops to 1250 and eventually down to 600-800RPM.

During idle in any of the above conditions there is a strong gas fume. Noticable enough to smell through the cabin when you reverse out of a driveway for example.

No check engine lights.

I do not know if the spark plugs, wires, etc.. have been changed. I should check the dates on the plug wires however..

Gas mileage is 19.5-20MPG city & highway. Long distance / highway I achieve ~24MPG.

simonsays

i have the same exact problem.
during the morning, it idles REALLY high. then goes back down after 3 to 5 minutes.
i have problems with the O2 sensor. i'll probably change the spark plugs soon and fix the O2 sensors.

SUPRMSC

iTrader: (7)

Its normal. The car is warming up to transition to open loop. Just sit there for a second for the car to warm up.

But just incase you guys should check all your sensors to make sure they are working properly.

Mikethe1st

Are you sure it's normal. With most other cars I've had the cold idle would be around 1200 then drop once it was warm. Mine too jumps to 1800rpms when cold. Sometimes I detect some light knock for a few seconds when it first starts which I do not like at all.

SUPRMSC

iTrader: (7)

If it really worries you, then having a good tuneup and inspection wouldnt hurt. It is most likely the sensors that have gone wrong which is sending the wrong input to the ECU.

qmanlexus2

I have the same problem with the RRM's and the light knock how did yoiu solve the issue.

Luke_in_SD

what do you guys mean by light knock?

I'm kinda in the same boat here

qmanlexus2

what I meant was like oil was not coming up to the heads fast enough to the heads. It last about 2 to 3 seconds. It sounds like a lifter leaked oil out overnight. I know our SC's dont have Hydrolic Lifters.

qmanlexus2

Hey luke I started another thread since this one looks like its old and dead. here is the name of the new one I just created yesterday.

High RPM's @ cold Idle

Ali SC3

iTrader: (10)

theres a screw that controls the butterfly's starting position by the throttle cable holder right on top of the manifold. I was playing with this on my SC and you can adjust it to allow the plate to stay slightly open as a default position if you like. People do this as a shortcut to completely cleaning a throttle body that is gunked to ensure optimum flow.

the ecu adjusts for your regular idle all well in time but one thing that will still be affected is your cold start rpm's will be on average higher before the cpu starts adjusting to base map. if you play with the screw you can get it to work as intended but you might run into the reason someone adjusted it in the first place.

might not be your problem but i figured this out one day.
chances are your car was at some point fixed by a shortcut mechanic.
maybe ill take a pic of what im talking about.

qmanlexus2

Thanks for the quick responce. hey If you can take a pick it will be appreciated. This is driving me crazy. I had the TB off when I did valve cover gaskets after lexus did a tune up. When I looked at the TB it was clean so I just cleaned it a Bit more with Carb cleaner on a rag. I didnt spray any inside. It was fine for a while and then this started to happen.

Ali SC3

iTrader: (10)

The throttle body will look clean, its the part directly behind the throttle plate thats kinda hard to reach. I bet you unclogged something and now your getting correct flow. ill update with a pic later tonight when i get off work. It was driving me crazy too

here is some more info: http://minimopar.knizefamily.net/idleproblems.html
what happened at one point is described under dirty throttle body
and what someone did is described under minimum air adjustment

the resulting symptoms makes it clear as to why this was put there to set your engine base idle properly and not use it to compensate for a dirty plate.
notice they say do this after you clean it thoroughly.

qmanlexus2

Thanks I will wait for the Pick when you have a chance

Ali SC3

iTrader: (10)

umm, this is is informative only, I take no responsibility for anyone doing anything anybody suggests properly or improperly or anyhow anywhere.

that being said locate this part of your engine (sc300)

shonuff53

iTrader: (3)

the way most cars normally operate is higher rpms and they should run richer at warm up especially in cold climates. with cooler air and a cold engine it takes more parts of fuel to air to ignite hints the rich smell you guys are getting when you just start up on most efi cars they are set to run richer untill your coolant temp reaches whatever temp for its normal operating temp then your ecu should switch to a normal operating fuel maps and corrections from its senor inputs. first closed loop (warm-up) then open loop. Try driving your cars around till they warm up good then shut them off and turn it on a min later and it shouldn't idle higher since your coolant temp will still be high.. now if your problem is still occuring then look into your sensors, I would check your coolant temp one first.