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.

Ryu · 02-24-2009, 12:44 AM

My suggestion is to bring it in to Toyota and see what they have to say.

YarisSedan · 02-24-2009, 01:09 AM

From my experience the dealership has little diagnostic experience. Thier approach to repair is to replace all sensors or components that could be possible causes of the problem. I dont need to go to the dealer for that. Otherwise i woudl jsut change the TPS IAC and VAF sensors and be done with it.

FunctionSpec · 02-24-2009, 01:18 AM

Idle Air control valve. Take it off and clean it thoroughly. Thick carbon probably came off and got caught into the screen of the idle air control valve

Shroomster · 02-24-2009, 01:43 AM

did you probe the 'new' sensor to see if its actually sending a signal?

able to obtain a copy of a service manual?

wait..wait....wait......

i-man cleaning with seafoam...first try checking the air filter....then try checking the pressure for the rail and then the injectors.....

YarisSedan · 02-24-2009, 01:54 AM

I think i have to agree with function. I jsut realized it the car has a very low idle which is why the car wants to die. Which will also set a code 31 the maf is functioning properly its detecting the low amount of air volume. Tomorrow i am going to remove the iac valve i bet its really gummed up. Only thing is i think i have to remove the throttle body to do that because of where the bottom screw of the valve is.

Only other thing i can think of is if the car hydrolocked and skipped timing.

Bob_VT · 02-24-2009, 08:18 AM

Ye Olde School..... ignoring codes and electronics for a moment (you said old ;) )

The shaky idle is normally caused by a vacuum leak. If it suddenly gets worse after something was done..... I would recheck the fuel system and hunt for the leak.

Now moving to modern times...... once a code is tossed with the CEL then the ecu will revert to a base program. There are I believe 4-5 systems that "check in" with the ecu on the toyota lexus (circa 1993).

If you did a top end cleaning I agree that something may have broken loose and is blocking a line.

I highly doubt it was " hydrolocked and skipped timing"

Tamago · 02-24-2009, 08:42 AM

not sure if it's been said yet, but try replacing the PCV valve.. it's a 2jz.. so there's plenty of opportunity for vacuum leaks

spray starting fluid around the engine bay on vacuum hoses and if you get a sputter, you've found a leaking point.

IllusionX · 02-24-2009, 08:57 AM

just a question though... Was it working fine before you tried to "fix" it ?
If so, why did you try to fix it when there wasn't any problems? :)

ok i'm not helping in any way..

Tamago · 02-24-2009, 09:22 AM

Quote:

Originally Posted by IllusionX

just a question though... Was it working fine before you tried to "fix" it ?
If so, why did you try to fix it when there wasn't any problems? :)

ok i'm not helping in any way..

do you not know what seafoam is?

IllusionX · 02-24-2009, 09:31 AM

it will dissolve carbon build ups on the pistons. but why? If there's no problems with the engine in the first place, i don't see why one would do that. Now his engine is not running fine and throws a check engine...

Anyways, i made my point. thank you. :)

Tamago · 02-24-2009, 09:33 AM

Quote:

Originally Posted by IllusionX

it will dissolve carbon build ups on the pistons. but why? If there's no problems with the engine in the first place, i don't see why one would do that. Now his engine is not running fine and throws a check engine...

Anyways, i made my point. thank you. :)

so, if it dissolves carbon buildup, wouldn't that help dissolve carbon buildup in the engine, thereby making the vehicle run better?

your attempt at sarcasm is so far a serious fail

IllusionX · 02-24-2009, 09:43 AM

hey.. my point is:

It's old, it's working. don't touch it. It's as simple as that.

No offense to YarisSedan, but good luck with the car.

TLyttle · 02-24-2009, 12:02 PM

It may be that I am just lazy (well, I am, really), but I agree with illusion: if it ain't broke, why fix it? SeaFoam has its place, but personally, I don't think that place is in a vehicle that is running fine.

Tamago · 02-24-2009, 12:31 PM

Quote:

Originally Posted by TLyttle

It may be that I am just lazy (well, I am, really), but I agree with illusion: if it ain't broke, why fix it? SeaFoam has its place, but personally, I don't think that place is in a vehicle that is running fine.

"fine" is relative..

YarisSedan · 02-24-2009, 01:34 PM

Quote:

Originally Posted by Tamago

not sure if it's been said yet, but try replacing the PCV valve.. it's a 2jz.. so there's plenty of opportunity for vacuum leaks

spray starting fluid around the engine bay on vacuum hoses and if you get a sputter, you've found a leaking point.

Belive me i checked all that. I sprayed carb cleaner at base of intake manifold checked all vacuum lines removed the pcv valve and checked operation and then cleaned it with carb cleaner.

I think what im going to do tonight is remove the throttle body and clean it out and remove the idle air control valve. I am assuming its completely gummed up.

I did the seafoam to try to help him out. He was getting poor gas milage. I have done atleast 50 seafoam treatments with no problems. But i guess this particular car decided to act up. From now i i dont think i will do seafoam on any car that has more than 100k miles unless its been regularly serviced and maintained for fear of causing a problem. I guess live and learn.

mikenacarato · 02-24-2009, 01:44 PM

on my 93 lincoln i seafoamed and literally drove the crap out of it. all better. :)

Tamago · 02-24-2009, 02:13 PM

clogged IAC valve?

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. __________________ http://www.cardomain.com/ride/3210549

02-24-2009, 12:44 AM	#2
Ryu View User's Garage Drives: Copper Orange Mica Yaris Join Date: Feb 2006 Location: Surrey, BC Posts: 503	My suggestion is to bring it in to Toyota and see what they have to say. __________________ My Copper Orange Mica Yaris with 9.3lb Kosei K1 TS http://www.yarisworld.com/forums/showthread.php?t=10951 http://www.yarisworld.com/forums/showthread.php?t=13882 http://www.yarisworld.com/forums/sho...180#post472180

02-24-2009, 01:09 AM	#3
YarisSedan Drives: 08 Yaris Sedan Join Date: Oct 2008 Location: California - Bay Area Posts: 2,773	From my experience the dealership has little diagnostic experience. Thier approach to repair is to replace all sensors or components that could be possible causes of the problem. I dont need to go to the dealer for that. Otherwise i woudl jsut change the TPS IAC and VAF sensors and be done with it. __________________ http://www.cardomain.com/ride/3210549

02-24-2009, 01:54 AM	#6
YarisSedan Drives: 08 Yaris Sedan Join Date: Oct 2008 Location: California - Bay Area Posts: 2,773	I think i have to agree with function. I jsut realized it the car has a very low idle which is why the car wants to die. Which will also set a code 31 the maf is functioning properly its detecting the low amount of air volume. Tomorrow i am going to remove the iac valve i bet its really gummed up. Only thing is i think i have to remove the throttle body to do that because of where the bottom screw of the valve is. Only other thing i can think of is if the car hydrolocked and skipped timing. __________________ http://www.cardomain.com/ride/3210549

02-24-2009, 08:18 AM	#7
Bob_VT View User's Garage Drives: 08 Yaris LB Join Date: Oct 2008 Location: Vermont Posts: 1,704	Ye Olde School..... ignoring codes and electronics for a moment (you said old ;) ) The shaky idle is normally caused by a vacuum leak. If it suddenly gets worse after something was done..... I would recheck the fuel system and hunt for the leak. Now moving to modern times...... once a code is tossed with the CEL then the ecu will revert to a base program. There are I believe 4-5 systems that "check in" with the ecu on the toyota lexus (circa 1993). If you did a top end cleaning I agree that something may have broken loose and is blocking a line. I highly doubt it was " hydrolocked and skipped timing" __________________ some people are little slinkies. . . . .they are really good for nothing. . . .but they still bring a smile to your face when you push them down a flight of stairs. Come to the DARKSIDE..... We have candy

02-24-2009, 01:18 AM	#4
FunctionSpec Super Newbie View User's Garage Drives: 2007 Yaris Liftback White Join Date: Jul 2007 Location: 626, Southern California Posts: 180	Idle Air control valve. Take it off and clean it thoroughly. Thick carbon probably came off and got caught into the screen of the idle air control valve

02-24-2009, 01:43 AM	#5
Shroomster '07 to '12:2 wipers to 1? View User's Garage Drives: '12 5-door LE & '14 5-door LE Join Date: Apr 2007 Location: Orlando Posts: 1,999	did you probe the 'new' sensor to see if its actually sending a signal? able to obtain a copy of a service manual? wait..wait....wait...... i-man cleaning with seafoam...first try checking the air filter....then try checking the pressure for the rail and then the injectors.....

02-24-2009, 08:57 AM	#9
IllusionX It's the illusion you see View User's Garage Drives: 07 Yaris Sedan Aero Join Date: Oct 2006 Location: Brossard, QC Posts: 3,888	just a question though... Was it working fine before you tried to "fix" it ? If so, why did you try to fix it when there wasn't any problems? :) ok i'm not helping in any way..

02-24-2009, 09:31 AM	#11
IllusionX It's the illusion you see View User's Garage Drives: 07 Yaris Sedan Aero Join Date: Oct 2006 Location: Brossard, QC Posts: 3,888	it will dissolve carbon build ups on the pistons. but why? If there's no problems with the engine in the first place, i don't see why one would do that. Now his engine is not running fine and throws a check engine... Anyways, i made my point. thank you. :)

02-24-2009, 09:43 AM	#13
IllusionX It's the illusion you see View User's Garage Drives: 07 Yaris Sedan Aero Join Date: Oct 2006 Location: Brossard, QC Posts: 3,888	hey.. my point is: It's old, it's working. don't touch it. It's as simple as that. No offense to YarisSedan, but good luck with the car.

02-24-2009, 12:02 PM	#14
TLyttle Drives: 07 Yaris sedan Join Date: Jun 2007 Location: Keremeos BC Posts: 986	It may be that I am just lazy (well, I am, really), but I agree with illusion: if it ain't broke, why fix it? SeaFoam has its place, but personally, I don't think that place is in a vehicle that is running fine.

02-24-2009, 01:44 PM	#17
mikenacarato SIPNDEW View User's Garage Drives: 15 STI Join Date: Oct 2008 Location: Brentwood, TN Posts: 2,281	on my 93 lincoln i seafoamed and literally drove the crap out of it. all better. :)