Any oldschool obd1 mechanics here i need help with a diagnosis - Toyota Yaris Forums

YarisSedan · 02-23-2009, 11:28 PM

So story goes my friend has a 93 lexus gs300. I did a seafoam intake manifold cleaning for him. Next day he says his car is shaky at idle. I take it for a test drive and can feel what he is talking about. So i attempt another cleaning thinking that maybe a piece of carbon broke off and reattached itself to a valve. This time the car is worse now and occasionally stalling at idle. But luckly check engine light is on. It has a code 31 something to do with VAF sensor which i guess is a MAF sensor. I remove it and attempt to clean it with electrical contact cleaner but no change.

I assumed the massive amount of smoke went back up the intake and contaminated the sensor. I checked the price for a new one at lexus and wholesale cost is over 800 bucks. I ordred a used one on ebay and threw it in and car is doing exactly the same thing.

I am about to remove the throttle body and try to clean all the crap out and clean the idle air control valve. But i really dont want to go through all the work. Also i dont really think that may solve the problem. I guess its possible the used sensor is faulty. But the thing is there is absolutely no change in how the car ran before or after whichever sensor i use.

Any mechanics here work for toyota or lexus have experience with something like this. I am now responsible for the car since it had no problems running till i touched it and its sitting in my garage at home. So every day i get off work in working again in my garage till i fix this which is really stressful.

02-23-2009, 11:28 PM	#1
YarisSedan Drives: 08 Yaris Sedan Join Date: Oct 2008 Location: California - Bay Area Posts: 2,773	Any oldschool obd1 mechanics here i need help with a diagnosis So story goes my friend has a 93 lexus gs300. I did a seafoam intake manifold cleaning for him. Next day he says his car is shaky at idle. I take it for a test drive and can feel what he is talking about. So i attempt another cleaning thinking that maybe a piece of carbon broke off and reattached itself to a valve. This time the car is worse now and occasionally stalling at idle. But luckly check engine light is on. It has a code 31 something to do with VAF sensor which i guess is a MAF sensor. I remove it and attempt to clean it with electrical contact cleaner but no change. I assumed the massive amount of smoke went back up the intake and contaminated the sensor. I checked the price for a new one at lexus and wholesale cost is over 800 bucks. I ordred a used one on ebay and threw it in and car is doing exactly the same thing. I am about to remove the throttle body and try to clean all the crap out and clean the idle air control valve. But i really dont want to go through all the work. Also i dont really think that may solve the problem. I guess its possible the used sensor is faulty. But the thing is there is absolutely no change in how the car ran before or after whichever sensor i use. Any mechanics here work for toyota or lexus have experience with something like this. I am now responsible for the car since it had no problems running till i touched it and its sitting in my garage at home. So every day i get off work in working again in my garage till i fix this which is really stressful.