one pnt 8 hatch

ok its a 93 sc300 with a 2jz something in it. bone stock. its a friends car.and it has 2xx,xxx miles on it. car runs fine after disconnecting the battery for 30 mins and reconnecting it, but as soon as it warms up it acts like a miss fire and starts smoking its ass off and smells of nothing but straight fuel. changed the plugs and there wasnt any massive carbon build up and looked like they were burning clean. new plugs made it run stronger but the problem still persists. i did the timing belt on it maybe 6 months to a year ago and car ran great... problem jus started two weeks ago. anyone got any ideas.

hottscennessey

Bad ECU. Take off the cover and inspect for leaking capacitors.

Fabrik8

Could be a coolant temp sensor problem or something along those lines also. If that's the case, it's something that's messing up a learned parameter (short term fuel trim of some type probably) that is getting reset when you disconnect the battery.

Is the capacitor problem a known issue or is that just a stab in the dark based on DSM problems? I'm not really familiar with the quirks of SC300s...

one pnt 8 hatch

well the ecu prob is what ive been hearing on most lexus forums. my question is it the main ecu or the fuel ecu? and a bad coolant temp sen? could an electric fan f that up?

hottscennessey

It's a known problem. It's most common on JZA70 Supras.

Google "SC300 bad ECU" and you'll see some examples.

AFAIK the SC300 only has one ECU, are you asking about the fuel pump computer? It's the one in the dash board on the passenger side, connected to the main engine harness.

A bad coolant temp sensor would throw a code, and the ECU would set a default value to keep it from overfueling (as per TSRM).

one pnt 8 hatch

k thanks and ive read online that theres a ecu under neath the rear driver side window for the fuel pump...i thought it odd too.

Fabrik8

A failed coolant temp sensor would throw a code if the signal was out of range.. Other problems generally don't. It can be completely inaccurate and the ECU won't care, it will just keep going along thinking the coolant temp is a completely wrong value.

one pnt 8 hatch

the check engine light isnt on. im super baffled. i checked the ecu and it looks new. cant really see anything leaking out of the capacitors i can see. whats it gonna look like? glossy or will u clearly be able to see it leaking? doesnt smell like anything is been melting and theres no burning on the circuit board. looks brand new still. ive been told head gasket, rings, ecu, traction control control module, abs control module, fuel pump control module. im leaning away from ecu more towards mechanical failure..cant find anything wrong though.

hottscennessey

Yep, I'm with you.

OP, you could always measure the Ohms of the sensor while the car is warm using a multimeter. That way you can see if the readings are so off the wall that it would make your motor drown in fuel.

hottscennessey

Capacitors don't always show signs of leaking; however, usually when capacitors fail, they leak and corrode the circuit board.