lex1220

I have a 92 sc300 auto and im having an idling problem. I took the IACV off to clean it and the TPS off as well. After putting them back on and setting the TPS my car will not stay running at cold start, I have to give it some gas to get to an idle speed until it warms up and then it will idle. After it runs for a bit and I put the car in park the RPM's slowly climb to 1500 then soar to 2200-3000 then it will drop to about 200 stumble and climb back up. It keeps doing it. I checked the IAC and it seems to be working. Does anyone have any ideas? I have been dealing with this problem for a month now and it's driving me nuts. I have done lots of forum searches and can't find a thing.

cartmill

iTrader: (3)

this kinda sounds like a fuel pump problem to me.

lack of fuel volume

Sullen0313

search for vacuum leaks, try alternate fuel on a cold start, look at the I/M vacuum, have you pulled codes yet?

88supramki

check your hoses, probably a vacuum leak somewhere

lex1220

Well it ONLY started AFTER I took the IAC off to clean it, didn't touch a hose. Ive found no leaks though. I rather doubt its the fuel pump because it happened immediately after putting the IAC and TPS back on. No trouble codes are being thrown at all. My TPS is giving mildly odd voltage and it doesn't seem to swipe to healthy either on the voltage meter, I hope its the TPS.

kt636

From what it sounds like, there's something going on with with IAC valve. How did you check the IAC valve and did you check to make sure the adjustment of the TPS is correct?

lex1220

I found a Lexus PDF file on how to check the IACV and I did the stepper motor test that they show. I'm not entirely sure the TPS is set properly, I think it is though. I do not know what its required to be set at.

ThomasGS4

iTrader: (19)

Sounds like the TPS needs adjustment. These things are VERY sensitive.

lex1220

I hope thats all it is. My dad has been a mechanic for over 20 years and tried setting it and it still is being crappy. Does anyone know how to properly set it?

cmh

ok u might think this is stupid but just try it... if u adjust the idle do it with the TPS unplugged and then plug it back in. see if that works. if u adjust idle with TPS connected (ON SOME CARS) it will just adjust itself back to where it was before. i dont know if im explaining myself so u understand me but just try it. its worth a shot.

p.s. correct me if im wrong i know some of u will this time u have my consent

note:do this while car if off duhh i should have said that

lex1220

You mean adjusting it with a volt meter whilst the car is off and TPS unplugged, correct?

cmh

yes sorry i suk at explaining myself

lex1220

there are four terminals on the TPS for the SC300, which two do I use for setting the TPS

lex1220

Also does anyone have any information on the "TRAC" light at the top of the cluster, it's orange and just says "TRAC" Ive read somewhere it can be MAF related but it was a pretty limited thread. Thanks.

soarer93

The traction control works in conjunction with the controlling of the throttlebody and ABS
meaning it not only applies brakes to the wheels that need it but it also controls the opening and closing of the throttle body to reduce power made by the car..
Post 9 in the following link may be what your referring to?

ABS and TRAC off lights are NOT on but the TRAC light is..
https://www.clublexus.com/forums/per...ck-engine.html

assuming its showing up when your doing a diagnostic when u were checking for codes - if its just on all byitself.. im not the one to know