Everything about IDLING

2nd December 2012 (Sunday) Specifically for 20valves 4AGE only.

A consolidation of everything affecting idling and what to watch out in order to maintain and achieve brand new car perfect idling. By no order of requirements, items are listed as information are found. Credits to all the kind people who posted on web, you know who you are !!!!

Before digging into settings of whatever, TPS, AFM, first make sure: -

  1. No vacuum leaking through old, worn, cracked pipes, plastic, bad sealing air box cover, engine head cover, power steering vacuum, etc. check via spraying "Carburetor-cleaner" to the suspected spot. Listen to engine revs and sound changes, engine bogging down, etc.
  2. ECU capacitors DEAD, watch out of very minor black lines right under the capacitor, following the circuit route. The caps are normally intact, it's not blown apart, but a drop of two  black juice leaks.
  3. Sorry to repeat this, FUEL FILTER smooth & relatively still clean? clogged? need changing? This seems to be the last part anyone notice to check, apart from the repeated air filter, oil filter, new engine oil, etc.
  4. What else needed for a proper idling: -
    1. Air-cond compressor - who would have thought, 20v 4AGE ECU is designed to be in sync with it and not all 20v air compressor are same.
    2. AFM still working? by-pass valve set correctly?
    3. MAP still working?
    4. TPS still working? and not disturbed? i.e. still set correctly? check voltage though DMM.
    5. Exchaust O2 sensor the correct type? for the correct ECU? must be SVT ECU with SVT O2, and BT ECU with BT O2.
  5. Spark plugs are working properly? Plug cables? Short-circuit to chassis?
  6. ISCV (Idle Speed Control Valve) still working? not dirty? not jammed?

Oh, I hate where this is going, why a simple idling issue can be so much.

  1.  Idling vacuum, what is this? is it the VSV part number 90910-130005 192000-3111 Denso
  2.  Distributor & Crank angle timing?
  3.  Fuel pressure regulator working properly?
  4.  One of the vacuum pipe that pushes air, may be another pulls air, wrongly plugged in direction??? See lost post below.

not finished writing. When fonts turn to ARIAL means finished writing and this sentence crossed.


Old 11-15-2012, 07:06 PM   #2
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Default Re: AE101 20V compressor

AE101 compressor has 6 wire type (old gas) and 5 wire type (new gas).
AE111 compressor has only 5 wire type (new gas).
Please make sure yours is which type before you go look for it. Or, go see Ah Choy he can help you.

P/S: Old gas and new gas A/C system has diff in piping design which mean the compressor can't be interchangeable directly unless you use an old gas to new gas coupling that cost you about RM30/p.

Last edited by ; 11-15-2012 at 07:08 PM.


Unread 11-29-2012, 11:06 AM   #6
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Default Re: AE101 20V compressor

This is what I found, AE111 20V BT is TV12C Denso compressor HFC13A gas and 20V ST is TV12EC DENSO compressor with R134a gas. These are not the normal piston type compressor, its a light weight effecient screw/swash plate type compressor.


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Default Re: help!! my 20v idling problem!!

Early SVT wiring mated to BT ecu,need a/c idle up valve for a/c idle up
Late SVT wiring mated to BT ecu,not need a/c idle up valve

There is a difference in a/c on signal input to ecu between those two models,if your stock SVT ecu last 5 digit part number is 12770/12771 = u have early model svt,if 1A190 = you have late model,if your SVT is auto(ealy or late),then no problem with a/c idle up.

you know who you are,am i correct with this info,or you have new experiment,hehe


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Default Re: help!! my 20v idling problem!!

Hi all, just wanna share my experience.
I've converted my car to this spec:
SVT wiring mated BT ecu with BT aircon compressor.

And my stock SVT ecu is like this, donno early or later model. 9717500-552-1

What I notice is idle up valve is not active anymore after using BT ecu.
Thus, I've also experience engine stall intermittently. 
From my observation, my engine will stall immediately when I release throttle pedal.
After sometimes, I've DIY narrowband O2 sensor for monitoring.

What I get it, at the time I release throttle pedal i saw the narrowband sensor is too lean.
This is becoz fuel cut at that time and I also noticed that RPM gauge is at around 600rpm.
Sometimes it goes as low to 500 rpm and engine jerks a while before fuel is supply again.

What have I done is I increase fuel pressure using FPR (my AFR is still ok after tested with wideband). 
So as a result, my engine is less stall now but still I felt it jerk at fuel cut time.

Me too, added adjustable fuel pressure regulator, long time later, say one year, then piston ring burnt !!!!


 09-13-2011, 08:35 AM   #135
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Default Re: help!! my 20v idling problem!!

Originally Posted by View Post
Wow... this is brand new ECU that previous car owner bought from DENSO. Date code could be 1999 or 2000. Much more newer than stock (1992~1994)! From DENSO code, it looks like mated with 89661-12771. If you can show the internal picture, i will be able to identify.

, my car is running with '92 A/T wiring but it can run with all auto and manual ECU w/o any problem on the A/C system (run manual ECU with converter). So i still think that those ECU deliver tha same level of signal to the A/C controller... But thinking of which, there are R12 and R13 aircon gas being use in Silvertop so signal level might be difference in difference gas. But jus that i did not experince any significant difference on those ECU.

---------- Post added at 06:06 PM ---------- 6 hour anti-bump limit - Previous post was at 05:57 PM ----------

I have run a converter on my silvertop wiring to accept BT ECU. The result is good on the idling and eventhough with A/C turning ON/OFF.
If your idling is too low probably your conversion of the signal is not right or ISCV is clogg.

---------- Post added at 06:08 PM ---------- 6 hour anti-bump limit - Previous post was at 06:06 PM ----------

Alex, go find back your ori trumpet and rubber hose clamp (for AFM and Surge tank). Those are the area that you have vacuum leak.
Wong,yes you're correct...if your wiring is SVT auto,then it would not have a problem to accept BT auto/manual ecu,also the a/c will not affected because the SVT auto a/c signal to the ecu is same with blacktop auto/manual.

The problem only when converting SVT manual to BT ecu,but so far i've done almost 20 SVT to BT conversions,so far no customer complaint on low idle,for such conversion,it is necessary to use a/c idle up valve.

And also when convert to BT ecu,some may go the 'trumpet' route,hence the low end fueling is greatly affected,a fuel pressure regulator will usually fixed this.Also i will suggest to each customer to fit blacktop O2 sensor for proper running (although most of them didnt bother)...


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Default Re: help!! my 20v idling problem!!

can i park my problem and how i solved here in your thread... ?? to lazy to open new one...hehehe 

for the past few days my car been acting up...
the symptom were
1. rough/high rpm idling
2. massive knocking
3. no vvt feel / engine tone change...

i had some free time so i decided to DIY...i might as well clean my iscv while i'm at it...

this are the basic tools needed...
1. carb cleaner
2. Phillips screwdriver. (normal one also can)
3. pair of pliers 
4. replacement air hose (i'm using generic silicon hose 8mm...if you ask me...i'll advice using 6mm)

as a preparation...i highly suggest you remove your airfilter hose from the airbox to the plenum...

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locate the iscv outlet which directly connect to inlet manifold...i already remove the clip as seen here...

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remove the hose from the metal attachment...i prefer to do this from the top because its easier to do...a lot more working space compared to removing the hose from the iscv unit itself...

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now locate the air intake rubber hose which feed air to iscv from your plenum...

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here a view from another angle...

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detach the rubber hose from the plenum...here i turn the hose slightly upward so that carb cleaning chemical dont spill all over the place... 

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spray the carb cleaner...i normally let the chemical soak for a while before draining the fluid via detached the rubber hose from the plenum...(repeat until self satisfied)

once satisfied...reinstall everything in reverse order...

use the extra carb cleaner i had left to check for vacuum leak...just spray it at those vacuum hose joints and end...if there is a leak...you'll notice slight drop in engine tone...I've done this test after reassemble the the whole thing above...

please take note...there a big different between fuel line and vacuum...don't ever interchange between those two...

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what looks like your ordinary vacuum/air hose...

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but upon close inspection... yikes...its already cracked and torn... only the clip holding it in place...this end is connected to the power steering vacuum line...it is sandwiched between the firewall and the underside of air intake plenum...a little bit hard to reach but i still can manage pull out and reinstall new hose without removing the plenum...

this vacuum traces back to the throttle body assembly...you can see in the first pic...i replaced the hose (noticed the blue one)...no wonder my car been acting up...my best guess is that the vacuum leak messed up the whole map sensor reading...hence the problem i listed above...

since changing the hose is practically a straight forward procedure...i wont go into much detail...measure it...cut to fit...and replace the old hose...once done...double check using carb spray method again...and readjust if still got leak...

post mortem result

1. idling now spot on 950 rpm when engine is at operating temperature.
2. iscv function improve (tested as per service manual method)
3. improved and can feel the vvt kick in again... yeaayyy....
4. no more knocking

happy DIY'ing

this is by no right the right way to do things...and i will not be held responsible if somehow or somewhat you manage to f*&ked up your car/engine/ride by following this/my method... 

Last edited by  10-08-2012 at 01:50 PM. Reason: typo and info added...




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Default Re: help!! my 20v idling problem!!

Lucky both of you write together then reminded me there's a vacuum hose, when wrongly used, it will increase idling by 500rpm, or vise versa reduce by 500rpm. I also kena this before. 

Unfortunately I forgot what is the exact name. But the pipe quite big one, not small small one. i.e. around 25mm diameter. 

For my case, at first my mechanic didn't know where to plug it, then simply cucuk into the air-box plenum, causing idling increase from 950rpm to 1500rpm. But the funny thing is after driving one week, then idling slowly reduce to 950rpm. Beautiful, but everytime after remove ECU battery, reset, it will start at 1500rpm. So mafan. Another way to let it reduce to 950rpm (official target, see blacktop manual). Is to RACE the car, i.e. go Sepang 5 laps, or Batu_3 (rip) 5 laps, kautim. i.e. go find a place self racing then OK for me. But this is not the proper way lor. 

Later we found out, then my mechanic simply closed the pipe and lubang, but idling also OK but after some time idling drop to mati engine. i.e. after one week. This is exactly like above sentence, where ECU is self learning and compensating. 

So, could you guys be facing this issue?

Proper idling is start engine, rev will go up to 1200rpm for 2 seconds then drop to 950rpm. Always, cold morning, hot afternoon, cold night. Regardless next to sea side beach or up in Genting 6000 feet. Regardless of ECU has memory or not. 

Good luck.
Originally Posted by View Post

as i mention earlier after replacing the idling vacuum it was fine for 2-3days...
i've continue monitoring it.. but came back to its existing problemo.... 
its still revving up to 1200rpm or more... but the funny part is it goes up 
either when i hit the clutch to change the gear or else when i switch on the aircond...
sometimes it stays at 1000rpm... but most of the time its more.... relly funny... However, i got an advice from my fren...
he mentioned it could be due to VVT pulley as well. yea my engine has that
"diesel" noise yet does it effect the timing as well?? anyone could advice me on this please?
Originally Posted by  View Post
cronixz...my situaition is TERBALIK with u!!my rpm goes down to 500rpm
my car oso got noisy DIESEL sound...maybe it was TRADEMARK for 20v。。lol




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