scRuss

1992 sc400 135xxx miles
Just cleaned the throttle body and IACV.
Changed the plugs and wires, and double checked them
Runs strong
No hesitation/hiccups
Almost like its skips
No visual RPM Surging/Purging But can Definitely feel it
Basically asking what is happening/problem?
Purging and why the idle is so low?
Thanks in Advance
No Mods All Stock

eknine9

iTrader: (8)

Did you reset the ECU after you did that work?
I was told to always reset the ECU after doing any cleaning of sensors or change to the ignition system or intake.

Leave the battery unplugged for at least ten minutes then hook it back up. Start the car and drive it around for a bit and the ECU will re-learn the car basically.

Also when you say purging do you mean you're purging radiator fluid or what?

scRuss

Turns out when I put the plastic cover back on over the plugs/wires I nicked 1 wire while screwing it down 😷 (fixed)
But still doesnt resolve the low rpms....
I have already restarted the ecu.
And my hiccups have returned

What I mean by purging/surging is the engine revving all by itself. Rpms go up and down consistently

soarer93

The problem started after you cleaned the IACV/throttle assy. ?

have you checked diagnostics on your computer yet? jumping the appropriate terminals, and checking your cel flashes..?

scRuss

Yes I have diagnose the codes and No errors.
No its always been a problem ever since I bought her.
I tickled the TPS and got it to idle between 500-1000 rpms but as soon as I put into Drive it jumped waay to hard. I put the rpms back down , and that makes me belive my rpm gauge is off or something of the sort.

SC400slide

iTrader: (11)

Your TPS needs to be calibrated. I had an idle of 1500 in park, while the vehicle is on idle, just twist the TPS very slowly and see how the idle changes.

scRuss

I adjusted the TPS and got the rpms where it needed to be, but because of that as I put it in drive or reverse it jumps waay to hard/much.
The wierd thing is when the engine is warmed up it sounds almost perfect idle Yet the rpm gauge us telling me 0-150 rpms

fried_rice

iTrader: (20)

You calibrate the TPS by reading the ohms it produces, it's not for adjusting idle. You can adjust idle with the allen screw on the throttle cable bracket, but it's most likely something else that has changed on the car to make it idle or read lower. If you really want to be sure get a multimeter that has a tachometer feature, or take it to someone that has one and can read it easily for you. Put the TPS back in the same position it was, and raise the allen screw, for a quick fix.
https://www.clublexus.com/forums/mai...ti-tester.html

Or make the diagnostic cable that reads engine functions, but that is a lot more in depth and requires a computer with a serial input.
https://www.clublexus.com/forums/per...ger-found.html

mecheng10

it is very possible that your gauge is off.
just throwing it out there. even though your car is stock the motor that drives the need might be dieing and cant move the needle.
what about when you are cruising on the highway. does your RPM seem right?

fried_rice

iTrader: (20)

^ Thanks, that is what I was trying to get out by suggesting using an alternative tachometer to verify the RPM. If it sounds like it's idling correctly and not dieing, it's most likely not idling at 100rpm.

scRuss

Wow okay thanks guys much appreciated. I will find a multimeter and get to it
Idk this is my first lexus and iv only had it about 5-8 months. With o/d On its about 2500 rpms and thats around 65mph.
When cold It warms up around 1100-1300rpms