Idle Rpm dropping ?

[YEN96]

Recently, idle rpm dropping...

wat is the reason ? dirty Throttle body or idle valve ??

 

[nyantong]

Is the idling still stable or does it feel rough? It could be a number of things: dirty throttle body, dirty or spoiled idle air valve, sometimes dirty fuel filter, ignition timing off...

 

[ddv_nk12]

Could be because of tuning as well. Mine was unstable when idling until I tuned my car. Now, it's fine. Start with the cheapest thing first, then slowly troubleshoot from there. Mind to share what are the mods? Does the engine die when the RPM drops?

 

[infinity.melvin]

im facing this issue too! rpm drop till 500rpm or less & whole car shake during idling, when ac compressor off..

when ac compressor kicks in, idling back to normal 1000rpm and stable..
time to time when compressor off, idling very rough. especially after long hrs of driving or after spirited drive when engine fully warmed up.

done some mods such as full exhaust system & ligthened crank pulley..

any idea how to solve this issue?? been haunted with this for few months already

 

[stingg]

This issue seems to be plaguing B series alot. I got hit by it from times to times on my car and everytime its different problem. Like most seniors write up there I would try to restore everything to stock first before going any further. Tips

1) warm up engine, until the radiator fan runs and stops. Make sure aircond, light and all electrical item is switched off.
2) unplug the IACV electrical connector. Yr rpm should be idling at 450rpm. IF yr engine died, start the car with some throttle and slowly let the throttle off.
3) Adjust the idle screw until you get 450rpm. That is the right position it should be and dont touch it anymore.
4) start by looking at the easy stuff, timing is good
5) throttle voltage at idle should be about 0.47V
6) throttle body is fully closed - some mechanic adjust the screw to open the throttle body a little to compensate the low idle which is not the right thing to do because it caused the throttle voltage to go up. ECU will think you are constantly pressing the throttle and somehow it screw the idle up.
7) clean throttle body and iacv valve.
8) check the TB gasket and iacv o ring to make sure no leak

 

[6UE5t]

Another item that can cause idle rpm dropping or unstable is the stepper motor or idle up motor already getting weak/malfunctioning.

 

[mysayasan]

Another item that can cause idle rpm dropping or unstable is the stepper motor or idle up motor already getting weak/malfunctioning.

What stepper motor are u talking about?.. got stepper motor? idle motor also have? thought b-series only have engine and starter ony..are you talking about hybrid?


TS
1st step, try to clean throttle body with carb cleaner or wd40, remove air intake arm, warm up engine for few minutes, pull the throttle cable, butterfly will open, shots some carb cleaner or wd40.

2nd try clean your IACV by disassemble and spray with wd40 or carb cleaner at the hole, clean mating surface, buy new gasket.

3rd if you are using injection, clean your injector, there are some shops that can clean fuel injector. Or you can clean it yourself by finding at youtube, DIY fuel injector cleaning.. or something like that.

*Make sure all your hose,gasket, mating surface are leak free, this is to ensure stable idling.

 

[6UE5t]

What stepper motor are u talking about?.. got stepper motor? idle motor also have? thought b-series only have engine and starter ony..are you talking about hybrid?
...

No no, not motor in that literal sense. :) It's just a name. It's actually small electric motor which moves a valve that provide bypass air through the throttle body. This motor gets signal from the ECU to dictate how much opening to give to maintain the normal level of idle rpm. It's called idle up because it automatically bring up idle if there's extra load which can reduce the idle (for instance when you turn on the AC, or turn the steering). It's also sometimes called stepper motor cause it works in steps of opening.
Btw CMIIW since I'm just a newbie and not a mechanic. :)

 

[Autopiazza]

Experienced the same problem before, it was bcos of dirty throttle body, cleaned it up it will be okay.

Also maybe occurs after u change your intake from box type (standard from factory) to air pod filter (Apexi, K & N etc.), bcos once happened to me that the rpm goes up n down like crazy chick during idling!!! But no more after i change back to box, it was because it sucks heat directly from the manifold.

 

[YEN96]

this will clean throttle body ?? how to diy clean ??

1st step, try to clean throttle body with carb cleaner or wd40, remove air intake arm, warm up engine for few minutes, pull the throttle cable, butterfly will open, shots some carb cleaner or wd40.

 

[camshaft]

i've got the same problem before....i changed the IACV for RM80 and idle problem solved! and make sure u use the correct IACV that matched with your car model...

 

[sweelt]

Another item that can cause idle rpm dropping or unstable is the stepper motor or idle up motor already getting weak/malfunctioning.

i Ask again.
my 93t. Previously idle problem when aircon kick in.
Replace ISC myslef, all well. BISS adjust accordingly. No more low idle surge.
Problem with "warm start", idle lower than 500rpm or feel engine struggle. Not die. It happened intermittent.
Not on every warm start pulak.
Drive for few minutes, all back to normal.

Any idea dear Sifu ?

 

[6UE5t]

i Ask again.
my 93t. Previously idle problem when aircon kick in.
Replace ISC myslef, all well. BISS adjust accordingly. No more low idle surge.
Problem with "warm start", idle lower than 500rpm or feel engine struggle. Not die. It happened intermittent.
Not on every warm start pulak.
Drive for few minutes, all back to normal.

Any idea dear Sifu ?

Hmm not sure, coz never experience before, maybe ignition problem? Have you checked your spark plugs or plug cables? I assume your ignition timing is still within std ya, not over retarded due to knocking?

 

[vr2turbo]

i Ask again.
my 93t. Previously idle problem when aircon kick in.
Replace ISC myslef, all well. BISS adjust accordingly. No more low idle surge.
Problem with "warm start", idle lower than 500rpm or feel engine struggle. Not die. It happened intermittent.
Not on every warm start pulak.
Drive for few minutes, all back to normal.

Any idea dear Sifu ?

Could be symptoms of old Mitsu engine. I get that all the time :rolleyes:.....lol

 

[sweelt]

Hahaha....ok. At least got partner.
Is not permanent happen on warm start.
Hard to trace.
1994 engine. Old brain kut.

 

[vr2turbo]

Hahaha....ok. At least got partner.
Is not permanent happen on warm start.
Hard to trace.
1994 engine. Old brain kut.

Mine after warm up hard to start and idle, but once started and step on accelerator to bring up the revs, then will idle properly......lol