lexdud

I just had a local (1.5 mi) repair shop (they work on Porsche, Mercedes, etc.) do a full diagnostic on my car and they have absolutely no idea what's wrong with it. I guess the next stop is the Lexus stealership.

Woe is me ...



I decided to take my SC4 to work this morning ... but to no avail. The car starts up right away but as soon as you let off the gas it stalls, dead. I have had intermittant stalling issues with the car for the last 6 months or so that I suspect are related to the IACV. In the past it would always start and stay running ... even if the IACV was acting up. All you had to do was run it for a few seconds at 2,500 RPMs and it would clear up. Now it just dies ...

The engine has 52,000 miles on it.

Anyone have this happen to you before? What was the fix? I am prepared to remove and clean out the IACV if that is the problem.

Thanks ...

vangb2

iTrader: (2)

If it's your IAVC, you should be able to start the car with throttle semi-open. If you let go the throttle and it kills, it may be your IAVC.

lexdud

I just got home from work and started the car again. It starts fine and runs fine (even though the smell of the exhaust is a bit strong). When I let off the gas pedal it just dies.

grindin8o8

i have the same problem. car idles rough with rpm bouncing up and down from 0-1500. bounces up and down until car shuts off. if i step on the gas pedal it's fine. did a diagnostic test and got code 24 which is my maf. my maf i replaced a month ago which i bought off aliga. i guess the part i bought was faulty as well. i would also check the iacv. might be my problem as well. when i unplug my maf sensor car runs and idles fine.

lexdud

I got the IACV valve off ... and the thing is clean and looks almost as good as new. It looks great for being 16 years old. The motor and bearings look mint. I am cleaning off any dust/residue and then reassembling it for re-installation.

I guess I should refocus my attention on another possible culprit ... possibly the MAF?

Any suggestions would be appreciated.

grindin8o8

try unplugging the maf and tell me if it runs better. btw you have any cel on?
btw by watching a maf sensor video I figured I'd tap the maf sensor while on the car at idle with a screw driver using it's handle. To my suprise when ever I tapped the sensor the car would idle rough, sounds like it actually shuts down, but idles back normally when i stop tapping in. im guessing that I do have a bad maf for sure? or is it normal for a maf sensor to react that way if it is tapped by an object? if i tap the air box hard enough the car would idle rough as well. is it normal?

LEX_MAN

iTrader: (2)

Sounds like MAF.

lexdud

I checked at my local Advanced auto parts store and they sell MAFs for the SC400 ... but they have not one in their system.

Well, I took the MAF out and it (like about every other part that I have removed looks almost brand new. I blew (gently) into the MAF holes and then reassemble it into the car. I started the car and it runs much better but I am almost sure that teh MAF is the culprit.

I bought a Purolator air filter because I am concerned about the K&N filter I already have installed causing the MAF to fail.

If you had a choice between a K&N of parts-store brand filter ... which would you choose?

Thanks ...

lexdud

That's what I thought. I just pulled the MAF and measured the resistance between the 2 terminals listed in the manual ... and it checks OK.

I took the car to the store this morning with absolutely NO problems. A few hours later I tried to take the car to the gym ... and you guessed it, the car starts wonderfully but stalls immediately after taking your foot off the gas.

I've checked both the IACV and MAF and both check out OK.

Now what to do?

lexdud

Updated ...

The shop owner and his master mechanics came up empty ... but as I was leaving told me that he would focus on the IACV.

Where to buy a new IACV????

lexdud

Final update ...

The car is fixed. Replaced (with used) IACV and ECU. The car runs wonderfully now. The problem was most probably the ECU.

carbophat

Does anyone have pics/DIY of the MAF and IACV... Also, Lexdud, I would assume the ECU you are referring to is the Fuel ECU? :cheers

grindin8o8

weird? mine is opposite im guessing? i measured resistance for both my maf and iacv and the maf failed and the my iacv passed. so im guessing i need a new maf. if that maf doesn't work im almost certain it's the ecu.

lexhere27

I am having a similar problem. My car will start fine when it's cold, but if running an errand it will stall when I try and leave the store. The MAF came from a working car, IACV looked clean when I took it apart...Anyone please help, just trying to get the car sold so I can focus on my 97

HDSC300

I had the same problem with my SC300 and the Fuel Ecu was the problem. Unfortunately I do not remember the exact location but someone has written up a great review on how to test the fuel pump from the diagnostic box under the hood. On my SC300 its right of the engine when standing in front of the car facing in.
The part is located behind the side panel of the left rear passenger seat. You must remove the seat and the back piece before you can access the bolt and clip to remove the side panel.

http://imageshack.us/photo/my-images...mag0182bg.jpg/