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Location:
Sydney
Registered:
September 2004
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3SGTE idling problem Need info on EGR
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Thu, 12 May 2005 04:06
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Hi Guys,
Having searched similar problems they all appear to be different from mine. So i need some help
I have fast idle when cold, and it settles down when warm as per usual. However when im driving once its well and truly warmed up ill come to a stop and the engine will have trouble idling.
To be more specific when the car is behaving itself my vacuum guage normally sits at 20 mmhg, idle speed is at around 850rpm but when its having trouble the guage sits around 10-12 mmhg and the idle fluctuates around 600rpm and it sounds like its missing.
If i hold the throttle slightly open to bring it up around 800 - 1000 rpm the missing becomes more pronounced, and is fairly regular.
When I take off the car behaves completely normal, and next time I come to a stop, it may play up again, or it may idle normally....I havent been able to determine a pattern yet.
Its behaving like there is a loose connection to a component or something, although I checked every sensor and it appears to be fine.
Please help!!! 
[Updated on: Tue, 24 May 2005 09:38]
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Location:
Syd
Registered:
October 2004
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Re: 3SGTE idling problem
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Thu, 12 May 2005 04:31
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ummm...
i had the same problem and my head gasket was blown....
u checked ur tempreature gauge at the stops... took me awhile to realise wtf was goin on.
well for ur sake i hope im wrong and some one comes up wit a more easy and logical answer
goodluck
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem
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Thu, 12 May 2005 04:43
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hey opasan,
thanks for gettin back dude. I had the HG done about 12 months ago and have been runnin standard boost since.
temp gauge is rock steady, so i doubt it would be a BHG. the thing that turns me away from thinkin its a mechanical problem is the intermittent nature of the problem.
Just to add to this I have pulled error codes, but there are none stored. I will do a compression test and check ignition timing tonight, but apart from a Turbosmart boost controller, S-AFC2 and 540CC injectors the car is stock as far as tuning goes.
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: 3SGTE idling problem
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Thu, 12 May 2005 05:17
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It'll probably just be a leak in your intake pipework somewhere.
Mine acts exactly like this when I don't reassemble the intake properly.
Assuming your boost gauge is hooked up to the wastegate vac line then the leak will be between the turbo and intake.
Mine always leaks between the AFM and turbo though... and now from the stupid PCV hose.
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem
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Thu, 12 May 2005 06:06
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a leak is a valid theory, although I was very careful reassembling my intake.
My boost gauge is connected after the throttle body. The vacuum line that goes from the plenum chamber to the fuel rail for the FPR has a t piece put in it.
so if my guage is sensing a lower vacuum after the throttle body tht that shed some light on the problem??
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: 3SGTE idling problem
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Thu, 12 May 2005 06:18
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Doesn't really leave much does it... intake manifold gasket, head gasket, valves or piston rings
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem
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Thu, 12 May 2005 06:29
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so if the guage gets the lower vacuum reading from within the intake, does that mean the leak can no longer be earlier in the intake i.e. plumbing after the AFM?? can this be confirmed as i cant picture it in my head.
To add to this the S-AFC tells me how much my AFM is opening. When its idling fine, its open 0.8% when its playing up and idling around 600 the AFM is open 1.2%
Ive got a reconditioned head on there as well so a compression test tonight will confirm if thats still up to spec, so if you are correct the only weak point would be intake manifold gasket.
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: 3SGTE idling problem
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Thu, 12 May 2005 07:07
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I suppose it could be your idle bypass valve thingy.
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem
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Thu, 12 May 2005 07:14
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If it was an electrical problem, say my distributor or igniter is sending erratic signals to the ECU causing the motor to miss and idle low and rough...the lower vacuum could be the ECU trying to compensate for the low idle by opening the Bypass valve to pick up RPM's but because its not firing properly it still struggles...
one way to test i suppose would be to unplug the air bypass valve while the engine is running rough to see if it picks up...
im not sure where to go from there though....
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem ** Solved**
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Mon, 16 May 2005 07:10
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Hi Guys,
Just letting you know that over the weekend I confirmed that it was my EGR valve not closing properly that caused issues at idle.
As im sure you all know EGR lowers the oxygen content of the intake, not a helpful thing when your sitting at idle. it made my engine struggle and miss.
Though im sure what i did to fix it, removing the vacuum lead to it cause the diapraghm to spring shut, since replacing the hose it has funtioned normally. Perhaps it was jamming somehow. If anyone has a similar problem I would check the whole EGR system. Maybe the VSV isnt doing it job, or the actuator is jammed as was in my case.
Either way thank you all for your input, I hope this helps others with a similar problem.
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem Need info on EGR
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Tue, 24 May 2005 09:42
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Hi Guys,
I was wondering if anyone can explain the function of the EGR Vacuum Modulator? Sounds like one of marvin the martians toys except it doesnt have 'space' in the title  
Anyhow, here is a vacuum diagram of the EGR system:
I would have thought that the EGR VSV would just act directly on the Valve controlling when it opens and closes. The only thing I can think of is that air needs to come from somewhere to allow the EGR valve to close again after the throttle closes. A further assumption is that it uses either atmospheric or exhaust gas to achieve this, but I would like an expert opinion as it appears the modulator doesnt really change between the 2 diagrams except it has vacuum flowing through it to the EGR valve when the VSV lets it through.
The reason for my question is that when my engine warms up sometimes when i fall back to idle (i.e. when coming up to lights) the engine has trouble staying alive, I found out this is because my EGR valve remains open allowing exhaust to 'choke' the engine. I thought the problem had solved itself, but it has returned. 
I want to determine what component could cause this as it appears that the valve itself moves freely.
Thanks for your help
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Location:
South Australia
Registered:
July 2002
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Re: 3SGTE idling problem Need info on EGR
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Tue, 24 May 2005 15:56
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Good question - I can hardly make out what it's doing in the diagram!
If exhaust gas is getting into your intake at idle, then either the VSV is not closing like it should or your EGR valve is leaky or worn down or jammed (carbon in exhaust could work it's way around the place I suppose) and allowing air under lowish pressure to escape back into the intake.
That's what I'd check first, otherwise look at the vacuum modulator closely - take it apart even  I just can't quite see what it's supposed to do in that diagram. Probably serves some function when the engine is in over-run (ie high rpm with little or no throttle). Let us know how you go 
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 02:21
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Your theory could very well be correct as i see no other function for it either at this point...
i figure the whole thing..modulator and valve could probably do with a good clean out, hopefully in the process i figure out what its for and ill let u guys know!
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Location:
Brisbane, Queensland
Registered:
January 2004
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 03:30
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Hi Lance,
Yeah its definitely the EGR, because when i disconnect the vacuum line from the valve and plug it the problem goes away.
The question with removing EGR altogether is doesnt it raise combustion temps?? isnt the ecu tuned to allow for the exhaust gas lowering oxygen content?
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Location:
Brisbane, Queensland
Registered:
January 2004
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 03:34
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| SilverGhost wrote on Wed, 25 May 2005 13:30 |
Hi Lance,
Yeah its definitely the EGR, because when i disconnect the vacuum line from the valve and plug it the problem goes away.
The question with removing EGR altogether is doesnt it raise combustion temps?? isnt the ecu tuned to allow for the exhaust gas lowering oxygen content?
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The whole point of EGR is to recirculate exhaust gas twice to lower emissions. It also saps power since your recirculating spent gases already.
Im not condoning the removal of EGR though. Im mearly suggesting it.
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 03:46
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Yeah, EGR definitely saps a bit of power ...but with legalities aside, from a tuning point of view EGR lowers combustions temps as there is less oxygen in the A/F mix to burn...if you have removed EGR on a 3SGTE in the past have you found any heat related problems pop up?? pinging?
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Location:
South Australia
Registered:
July 2002
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 13:48
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EGR lowers combustion temperature by introducing inert matter into the combustion mixture - this slows down the rate of heat propagation and reduces the peak temperature at the flame front. The air introduced by the EGR is not 'metered' for calculations regarding fuel injector duration - so you can see that it's purpose is not entirely to 'sap power'. Although the 'peak' combustion temperature will change significantly without the EGR, the overall production of heat will not change by much (ie it's not like you are going to gain a massive number of kW by removing it, so it's not like you are producing a massive amount of heat compared to an EGR engine). So you don't need to worry about detonation etc - if anything I suspect the temperature around the spark plug will decrease slightly.
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 14:26
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hmmm....interesting point, why would you say that the temp around the plug would decrease slightly?
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Location:
South Australia
Registered:
July 2002
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 15:30
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When I think about it - it *is* possible that you will get pre-detonation without EGR, but it'd have to be a pretty knife-edge tuned engine (A/F ratio wise) to begin with.
Main issue would be the temperature at the piston crown and the piston retaining too much heat.
Anyway as you are no longer re-introducing heated matter into the intake charge the engine will deal with waste heat much better. All the heat in the exhaust gases will go out the exhaust. By not re-introducing heat into the charge the engine will *probably* deal with it's heat alot better....like I said though the flame front temperature might be hotter without the inert matter (EGR) in the intake charge, and the flame front doesn't stay near the spark plug for particularly long - in fact it tends to go away from the spark plug towards el piston The piston crown temperature might get slightly higher during combustion, but hopefully in an overall sense it won't change by a great deal as the period of cooling is longer, the period where it gets heated up is shorter (faster combustion) and the intake charge will also be slightly cooler than usual.
In terms of tuning without the EGR, I guess you probably would richen the mixture slightly to slow the flame front propagation (for power purposes) and to reduce the temperature at the piston crown to a more 'stock' level.
EGR has long been used to reduce the toxicity of emissions (via absorbing heat and slowing flame front propogation), improvements in fuel economy (at times it was used to fine tune the A/F ratio in older cars) and to accomodate the idea of a lean-burn engine - in fact Toyota did alot of research into this using multi-port, direct injection and other doo-flickeys like intake swirl bollocks. EGR is a very good solution to the problem of emissions and fuel economy....the other good option is water injection - but you end up consuming water rather than just recirculating spent gas (recycling is good - eh?).
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Location:
South Australia
Registered:
July 2002
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Re: 3SGTE idling problem Need info on EGR
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Wed, 25 May 2005 15:34
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Anyway we got plenty of metallurgists, chemical engineers, and automotive engineers on this board who can answer these questions better than I can! I'm just a drop out applied maths student - I wouldn't know combustion from a glass of water! So feel free to ignore shit that I post cause it's not backed up with any qualifications or annoted bibliographies/references 
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Location:
Sydney
Registered:
September 2004
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Re: 3SGTE idling problem Need info on EGR
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Thu, 26 May 2005 02:14
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Thanks RWDboy, that made sense to me aswell. My only concern is because my car has a bit of a pinging problem to begin with I didnt want to compound the matter.
Last night I pulled the EGR VSV and modulator off and tested them both...they appear to work fine, i cleaned the filter elements a bit and put it back in so if the problem remained it would have to be my EGR valve...
sure enough when she warmed up the problem returned so I pulled the vacuum lead off the EGR valve exposing it to atmo pressure and it didnt budge...i actually had to blow into the hose for the EGR valve to get it to snap shut so its definitely jamming when hot...( i tested the EGR valve when cold and it appeared to move freely so im thinkin carbon buildup and smaller tolerances when hot cause it to jam....
thanks for everyones input, i think i might disable the EGR for a bit and see how she drives without it...
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Location:
South Australia
Registered:
July 2002
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Re: 3SGTE idling problem Need info on EGR
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Fri, 27 May 2005 04:40
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You are running gen 2 3S-GTE right? Don't worry too much about heat in the pistons, they are quite strong - pinging may not be healthy for them, but I wouldn't panic as they don't have an inherently weak casting.
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