v6 Idling rough at 500 rpm

weakyota91 · 12-25-2005, 03:52 PM

my 91 toyota v6 is idling at about 500 and pretty rough for the past month. I had a blown head gasket couple months ago and had whole top end rebuilt new valve guides, seats etc. replaced knock sensor, plugs, wires, cap and rotor, water pump and timing belt. I know there is no idle adjustment on the v6. Its all in the computer i have checked all plug wires. the rough idle goes away if I bring rpm up to 800 where its supposed to be. do I have a sensor possibly shot? any suggestions thanks.

P.S. had toyota check new h/g by sniffing radiator the said its fine.

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SolidDigital · 12-25-2005, 04:09 PM

The idle adjusting screw is on the TB you can turn it with a regular screw driver.. mine was filled with gunk and couldn't even tell it was there at first =p

Edit: here's a link to a pic Corey posted in response to a thread I made asking about the idle screw http://pnw4runners.com/tech/V6_3.0_e...e_screw_V6.jpg

suprathepeg · 12-25-2005, 04:46 PM

Check your TPS if its bad of out of adjustment it will cause that. Timing can also cause it. I am currently chasing down a simular problem.

91Toyota4x4 · 12-25-2005, 04:51 PM

Well the V6 is supposed to idle more like 750-800 IIRC so if it is idling at 500 im sure it would be a little rough.

ogclew · 09-20-2007, 04:59 PM

how do you adjust the idle??????? turn all the way to right?

MudHippy · 09-20-2007, 05:12 PM

Clockwise=Idle DOWN, Counter-clockwise=Idle UP

If the idle doesn't change much with that screw, there's another issue to address. More on that if need be...

ogclew · 09-20-2007, 05:17 PM

probaly, i bought this truck with most of all the tune up parts in a box!.....it starts then dies down immediately? injectors maybe?

MudHippy · 09-20-2007, 05:54 PM

If your having no luck with the idle adjustment screw, you may need to set the throttle stop screw. First, make sure you don't have the idle screw turned all the way down(clockwise)by backing it off(counter-clockwise) 'till it's about flush with the housing(throttle body) if it isn't there already. Then, here's a pic of what's next.

The trick is to have it set just far enough so the idle smooths out. Start by loosening the nut,then turning the allen head screw all the way out(throttle closed as far as possible). Engine SHOULD be running rough at that setting. Then slowly screw it in till the idle smooths out. You'll notice a point when it "jumps" from around 500-600 rpm and rough, to around 800(or higher)and smoother. Stop turning it in when you find the "sweet spot" there, don't go too far in. And don't forget to tighten the lock nut when your done.

What your adjusting is how far open the throttle plate(butterfly valve)will close when the accelerator is fully released. It needs to be open a little bit, but not too little or too much for the engine to run smoothly.

ogclew · 09-20-2007, 07:10 PM

ohhh, thanks i do this sat...would a cloogged injector/s cause it to die down immediately? Like as soon as starts it boggs down to the end?

MudHippy · 09-20-2007, 07:55 PM

Quote:

Originally Posted by ogclew

would a cloogged injector/s cause it to die down immediately? Like as soon as starts it boggs down to the end?

Yes, it/they could. Next on the checklist though would be the Engine Coolant Temp Sensor Circuit(1 on the list, really, 2 being the idle adjustment) then the Volume Air Flow Meter Circuit, then the injectors. If we go by the FSM troubleshoot list.

HERE: http://personal.utulsa.edu/~nathan-b...63troubles.pdf

The rest of the manual HERE: http://personal.utulsa.edu/~nathan-buchanan/93fsm/

ogclew · 09-21-2007, 09:59 AM

Okay,thanks I appreciate the info! I guess ill go down the list....and one thing at a time.

stormin94 · 09-22-2007, 01:18 AM

Mine idles at like 300 RPM sometimes. It Idles high at start up until it is warm, then it dies down to below 500. I'm not quite sure what is wrong. Couldn't a vacuum leak cause this?

yotasavg · 09-22-2007, 01:46 AM

i'd check the tps. that's exactly what mine did...listen to mudhippy.

ogclew · 09-26-2007, 07:59 PM

What the TPS? I VE heard about that!.....whats it do?

MudHippy · 09-27-2007, 01:19 PM

Quote:

Originally Posted by stormin94

Mine idles at like 300 RPM sometimes. It Idles high at start up until it is warm, then it dies down to below 500. I'm not quite sure what is wrong. Couldn't a vacuum leak cause this?

Maybe, but it would make the engine run rough too.

Quote:

Originally Posted by ogclew

What the TPS? I VE heard about that!.....whats it do?

The Throttle Position Sensor.

It tells the ECM how far the throttle is open, it then uses that input to help calculate the proper injector timing.

The FSM only says to check the TPS circuit if your experiencing a "High Engine Idle Speed" condition on the Poor Idling troubleshoot list. It shouldn't cause any other idle issues than that.

MIKEMOKAS · 09-27-2007, 01:38 PM

Quote:

Originally Posted by stormin94

Mine idles at like 300 RPM sometimes. It Idles high at start up until it is warm, then it dies down to below 500. I'm not quite sure what is wrong. Couldn't a vacuum leak cause this?

mine does the same.. idles up in the 1000- 1500 range untill it warms up, then it stays steady at 600rpm without any stumble...

id try adjusting the tps as stated before...

MudHippy · 09-27-2007, 03:59 PM

Quote:

Originally Posted by MIKEMOKAS

mine does the same.. idles up in the 1000- 1500 range untill it warms up, then it stays steady at 600rpm without any stumble...

id try adjusting the tps as stated before...

600 rpm is too low for idle when warmed up. The specs for the 3VZE is 800 rpm +/- 50 rpm.

And I wouldn't go fiddlin' with the TPS untill you make sure all other things are eliminated. I haven't heard of them coming out of adjustment too often. It could be malfunctioning electronically though. Then you'll need a new one, if the circuits don't test good.

As I stated previously however, unless you can't get your idle low enough by all other means, don't worry about the TPS.

the_4runnin'_beast · 09-27-2007, 04:18 PM

MAP sensor? Any vacuum leaks?

stormin94 · 10-02-2007, 12:20 AM

Quote:

Originally Posted by MudHippy

Maybe, but it would make the engine run rough too.

It does...it feels like it's missing a little bit.

n4ynu1010 · 10-04-2007, 10:58 AM

Maybe after re-building the motor the mechanics did not re-adj your idle , was it like that before ? If not then maybe all you need to do is re-adj back to the 800-850 rpm and you will be fine .

The TPS can create a idle problem as well as performance problems (ie power and throttle response), it can be diagnosed without removing , it basically tells the ECM when your motor is in or out of idle circuit operation as well as controlling VAFM operation in respect to throttle plate opening .
This link will give you the testing proceedure for your TPS :
http://www.4crawler.com/4x4/CheapTri...PositionSensor
* do not loosen screws unless you are going to replace , if it tests good then leave it alone

.
When my TPS went bad it caused power/acceleration issues and generally unstable/high idle as opposed to low idle.
The Throttle Stop Adj should not be a adj you would have to make unless the throttle plate is sticking in idle postition from wear and if you have that problem then it is best to remove and clean Throttle Body thoroughly before adj.ing the throttle stop , that is why the idle adj is there

.
Also I had problems with a vacumn leak at the Idle adj screw - it had a o-ring on it to prevent vacumn loss from around it and by the threads of the srew , dealer could not order but I replaced with one out of generic plumbing repair o-ring kit , lubed with dielectric silicone and re-installed and it sealed well and had resistance when turned again from good airtight seal from new o-ring , but this vacumn leak resulted in idle creeping up after stopping , not a low idle condition .

n4ynu1010 · 10-04-2007, 11:13 AM

I also had a rough Idle problem with my truck after doing a tune-up and it turned out the factory gap in the after-market plugs was .044" , I found out later thru some surfing and correction reference the FSM that the 3.0 is supposed to be a .031" gap , re-gapped the plugs and idle smoothed out drastically and acceleration and throttle response improved also , not saying that is your problem here but may help you if you installed aftermarket plugs without checking gap like I did .

Gator · 10-04-2007, 11:42 AM

Quote:

Originally Posted by stormin94

It does...it feels like it's missing a little bit.

Have you checked to ensure proper spark plug gap?

I have read a couple of posts where people have had similar issues (myself included) where re-gapping the plugs fixed the issue. I will be checking mine this weekend trying to fix a rough idle / miss at low RPM problem. It feels like it is missing when stopped at a red light, and for the first couple of feet after take off, then it clears up and runs like its supposed to. It doesn't act like it's missing at speed under hard acceleration, so I know all cylinders are firing, just not firing good at low RPM. It could also be a vacuum leak or something else since I too recently had HG work done. This is where I plan to start though.

n4ynu1010 · 10-04-2007, 12:07 PM

Quote:

Originally Posted by Gator

Have you checked to ensure proper spark plug gap?

I have read a couple of posts where people have had similar issues (myself included) where re-gapping the plugs fixed the issue. I will be checking mine this weekend trying to fix a rough idle / miss at low RPM problem. It feels like it is missing when stopped at a red light, and for the first couple of feet after take off, then it clears up and runs like its supposed to. It doesn't act like it's missing at speed under hard acceleration, so I know all cylinders are firing, just not firing good at low RPM. It could also be a vacuum leak or something else since I too recently had HG work done. This is where I plan to start though.

That is what mine did and it was a combination of the plug gap , vacumn leak(idle adj screw o-ring bad) and the TPS .
The TPS was responsible for a bit of a stumble/miss off idle and even a occasional spit through the intake , I tested the TPS and it was open all the time on the terminals that controlled the VAFM so the ECM would have no idea of how far open the throttle plate was , also it was open when at idle on the other test point so the ECM never knew it was supposed to be on the idle circuit .

stormin94 · 10-04-2007, 03:13 PM

Quote:

Originally Posted by Gator

Have you checked to ensure proper spark plug gap?

I have read a couple of posts where people have had similar issues (myself included) where re-gapping the plugs fixed the issue. I will be checking mine this weekend trying to fix a rough idle / miss at low RPM problem. It feels like it is missing when stopped at a red light, and for the first couple of feet after take off, then it clears up and runs like its supposed to. It doesn't act like it's missing at speed under hard acceleration, so I know all cylinders are firing, just not firing good at low RPM. It could also be a vacuum leak or something else since I too recently had HG work done. This is where I plan to start though.

Seems to have the same amount of power as it always has, just a little problem with Idleing

MudHippy · 10-04-2007, 03:27 PM

Quote:

Originally Posted by stormin94

Seems to have the same amount of power as it always has, just a little problem with Idleing

Have you tried SeaFoam through the intake? Maybe somethings plugged instead of leaking. It smoothed my idle out a bit the first time I did it.

Malfunctioning EGR valve will make your engine act like it's got a vac leak too.

12-25-2005, 04:09 PM	#2 (permalink)
SolidDigital Registered User Join Date: Oct 2003 Location: va Posts: 540	The idle adjusting screw is on the TB you can turn it with a regular screw driver.. mine was filled with gunk and couldn't even tell it was there at first =p Edit: here's a link to a pic Corey posted in response to a thread I made asking about the idle screw http://pnw4runners.com/tech/V6_3.0_e...e_screw_V6.jpg __________________ 89 Deluxe Short Bed, 3.0 V6 5spd, 4x4, 31x10.5 BFG Radial Long Trails on 15x8 Pacer rims, K&N air filter, high flow cat, Dynomax 2.5" Super Turbo muffler, Sunpro tach... Fiamm 125db. low note horn Pioneer 50w x 4 cd player, Polk speakers Last edited by SolidDigital; 12-25-2005 at 04:13 PM.

12-25-2005, 04:51 PM	#4 (permalink)
91Toyota4x4 Registered User Join Date: Feb 2005 Location: Gainesville, FL Posts: 215	Well the V6 is supposed to idle more like 750-800 IIRC so if it is idling at 500 im sure it would be a little rough. __________________ SASed 91 V6 Extracab

09-20-2007, 05:12 PM	#6 (permalink)
MudHippy Registered User Join Date: Jan 2007 Location: The Realm Of Fecal Cohesion Posts: 2,014	Clockwise=Idle DOWN, Counter-clockwise=Idle UP If the idle doesn't change much with that screw, there's another issue to address. More on that if need be... __________________ Sonoran Steel Early IFS Truss Your IFS is SPINELESS without it SonoranSteel.com I'm Cuckoo For YOTA Trucks! Last edited by MudHippy; 09-20-2007 at 05:15 PM.

09-20-2007, 05:54 PM	#8 (permalink)
MudHippy Registered User Join Date: Jan 2007 Location: The Realm Of Fecal Cohesion Posts: 2,014	If your having no luck with the idle adjustment screw, you may need to set the throttle stop screw. First, make sure you don't have the idle screw turned all the way down(clockwise)by backing it off(counter-clockwise) 'till it's about flush with the housing(throttle body) if it isn't there already. Then, here's a pic of what's next. The trick is to have it set just far enough so the idle smooths out. Start by loosening the nut,then turning the allen head screw all the way out(throttle closed as far as possible). Engine SHOULD be running rough at that setting. Then slowly screw it in till the idle smooths out. You'll notice a point when it "jumps" from around 500-600 rpm and rough, to around 800(or higher)and smoother. Stop turning it in when you find the "sweet spot" there, don't go too far in. And don't forget to tighten the lock nut when your done. What your adjusting is how far open the throttle plate(butterfly valve)will close when the accelerator is fully released. It needs to be open a little bit, but not too little or too much for the engine to run smoothly. __________________ Sonoran Steel Early IFS Truss Your IFS is SPINELESS without it SonoranSteel.com I'm Cuckoo For YOTA Trucks! Last edited by MudHippy; 09-27-2007 at 12:43 PM.

09-22-2007, 01:18 AM	#12 (permalink)
stormin94 Contributing Member Join Date: Jun 2007 Location: Lake County, CA/Sacramento Posts: 3,535	Mine idles at like 300 RPM sometimes. It Idles high at start up until it is warm, then it dies down to below 500. I'm not quite sure what is wrong. Couldn't a vacuum leak cause this? __________________ 1994 Toyota 4Runner SR5 4X4 213,000 miles and counting 3.0 V6, 5 speed 10/15 MPG city/hwy(with 33's) Current Mods Headers, 2.5" Flowmaster custom exhaust, K&N FIPK KC Daylighter 100 Watt lights Ranchos x4, 2" Lift Downey coils 33-12.50 M/T's, 1" t-bar lift, 1" body lift Tow pkg w/ lighthookups Silverstar Headlights, Pioneer Deck w/XM Brushguard 250Watt JLAudio 8" W3 Sub Future Mods 12V Aux outlet-400/800peak inverter roof basket/lights Air locker 4.88 gears H.O. Alternator

12-25-2005, 04:46 PM	#3 (permalink)
suprathepeg Registered User Join Date: Dec 2005 Location: Winnipeg Canada Posts: 789	Check your TPS if its bad of out of adjustment it will cause that. Timing can also cause it. I am currently chasing down a simular problem.

09-20-2007, 04:59 PM	#5 (permalink)
ogclew Registered User Join Date: Sep 2007 Location: El Paso Posts: 103	how do you adjust the idle??????? turn all the way to right?

09-20-2007, 05:17 PM	#7 (permalink)
ogclew Registered User Join Date: Sep 2007 Location: El Paso Posts: 103	probaly, i bought this truck with most of all the tune up parts in a box!.....it starts then dies down immediately? injectors maybe?

09-20-2007, 07:10 PM	#9 (permalink)
ogclew Registered User Join Date: Sep 2007 Location: El Paso Posts: 103	ohhh, thanks i do this sat...would a cloogged injector/s cause it to die down immediately? Like as soon as starts it boggs down to the end?

09-21-2007, 09:59 AM	#11 (permalink)
ogclew Registered User Join Date: Sep 2007 Location: El Paso Posts: 103	Okay,thanks I appreciate the info! I guess ill go down the list....and one thing at a time.

09-22-2007, 01:46 AM	#13 (permalink)
yotasavg Registered User Join Date: Jan 2007 Location: Chico Republic, NOR*CAL Posts: 1,625	i'd check the tps. that's exactly what mine did...listen to mudhippy. __________________ -Andrew 94 4Runner 3.0 Auto. I got mods Now Back in Action!

09-26-2007, 07:59 PM	#14 (permalink)
ogclew Registered User Join Date: Sep 2007 Location: El Paso Posts: 103	What the TPS? I VE heard about that!.....whats it do?

09-27-2007, 04:18 PM	#18 (permalink)
the_4runnin'_beast Registered User Join Date: Aug 2005 Location: Suisun City, California Posts: 970	MAP sensor? Any vacuum leaks? __________________ The name is Steve...Housewares. "Good... Bad... I'm the guy with the gun." My Rides -1989 Toyota 4Runner SR5 V6 AT 4WD -1993 Toyota 4Runner SR5 V6 MT 4WD K&N filter Crappy DynoMax Super Turbo exhaust *Marlin Crawlers Offroad clutch

10-04-2007, 10:58 AM	#20 (permalink)
n4ynu1010 Registered User Join Date: Sep 2007 Location: Richmond , Va / Henrico Co. Posts: 1,062	Maybe after re-building the motor the mechanics did not re-adj your idle , was it like that before ? If not then maybe all you need to do is re-adj back to the 800-850 rpm and you will be fine . The TPS can create a idle problem as well as performance problems (ie power and throttle response), it can be diagnosed without removing , it basically tells the ECM when your motor is in or out of idle circuit operation as well as controlling VAFM operation in respect to throttle plate opening . This link will give you the testing proceedure for your TPS : http://www.4crawler.com/4x4/CheapTri...PositionSensor * do not loosen screws unless you are going to replace , if it tests good then leave it alone . When my TPS went bad it caused power/acceleration issues and generally unstable/high idle as opposed to low idle. The Throttle Stop Adj should not be a adj you would have to make unless the throttle plate is sticking in idle postition from wear and if you have that problem then it is best to remove and clean Throttle Body thoroughly before adj.ing the throttle stop , that is why the idle adj is there . Also I had problems with a vacumn leak at the Idle adj screw - it had a o-ring on it to prevent vacumn loss from around it and by the threads of the srew , dealer could not order but I replaced with one out of generic plumbing repair o-ring kit , lubed with dielectric silicone and re-installed and it sealed well and had resistance when turned again from good airtight seal from new o-ring , but this vacumn leak resulted in idle creeping up after stopping , not a low idle condition . __________________ Guy '91 ExCab Dlx Longbed/3VZE-Fast/Stock 2WD/5spd Manual '95 GMC Jimmy SLS 4WD/4.3L Vortech/Euro Susp and Motor Package/Tow Package F.A.I.T.H. Forsaking All I Trust HIM Matthew 19,20 : 19 I say again unto you,that if two of you shall agree on earth as touching anything they shall ask,it shall be done for them of my Father which is in Heaven 20 For where two or three are gathered in my Name,there Am I in the Midst of them Last edited by n4ynu1010; 10-04-2007 at 11:22 AM.

10-04-2007, 11:13 AM	#21 (permalink)
n4ynu1010 Registered User Join Date: Sep 2007 Location: Richmond , Va / Henrico Co. Posts: 1,062	I also had a rough Idle problem with my truck after doing a tune-up and it turned out the factory gap in the after-market plugs was .044" , I found out later thru some surfing and correction reference the FSM that the 3.0 is supposed to be a .031" gap , re-gapped the plugs and idle smoothed out drastically and acceleration and throttle response improved also , not saying that is your problem here but may help you if you installed aftermarket plugs without checking gap like I did . __________________ Guy '91 ExCab Dlx Longbed/3VZE-Fast/Stock 2WD/5spd Manual '95 GMC Jimmy SLS 4WD/4.3L Vortech/Euro Susp and Motor Package/Tow Package F.A.I.T.H. Forsaking All I Trust HIM Matthew 19,20 : 19 I say again unto you,that if two of you shall agree on earth as touching anything they shall ask,it shall be done for them of my Father which is in Heaven 20 For where two or three are gathered in my Name,there Am I in the Midst of them

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