Hi everyone, my SC’s idle stays at 1100 rpms once warm, and as I drive it around, the idle gets lower and lower when I stop or hold the clutch until it is eventually at around 200-400 rpms and the car is shaking. If I turn it off and then back on again, the idle goes back to over 1000 rpms and repeats the same way. The car has no other issues with running other than this.

 

Hello,

Well it sounds like it could be an IAC Valve, have you tried looking into it?

Hope this helps and best of luck!

 

Hey, I did try using a new iacv and it seemed to maybe help but didn’t fix it, I may buy another one (I returned the other one) with a new connector because my connector looks horrible aswell and I’ll update whether that works!

 

Well, that's nice to know..

What Brand did you get?
Did anything change after you replaced it, did the Engine feel differently at all?

Does it have any Corrosion in it?

Here is a thread on Connector Replacement and Wiring Repair, including the Part Numbers for the majority of Toyota connectors, and all the tools required.

Hope this helps and best of luck!

 

i’m having the same issue but auto trans. My car shakes at idle and sits at low rpms but when i cut it off and start again the issue temporarily fixes. I’m not sure about yours but mine is also backfiring at idle and at acceleration. I haven’t fixed it yet but i can recommend you what i have tried to fix this, since replacing these my car is running significantly better than before although still not great. First cheap option is buy a new maf. After that i did new spark plugs, make sure you buy ngk or denso and space them. I did not replace the wires but for ~$120 it’s worth it to eliminate that as an issue, i currently have some wires otw and i’ll let you know if this fixes it. I bought a smoke machine on amazon for $60 to fix all my vacuum leaks, clean your tb. with all the problems that can occur with your tps not being lined up or a faulty iacv i chose to buy a tb brand new from aisin japan, that cost me $500. If you can adjust your tps don’t bother spending that, though i had gone through a lot of trouble adjusting mine and wanted to be sure it was lined up so i bit the bullet and bought the assembly. After this my idle did sit a lot more normal compared to how sporadic it was before. Your cats can be clogged, you can gut them or take them off to figure that out. You may need new engine or transmission mounts. I replaced all mine and it turned out every single mount was torn, this did help fix the shaking significantly.

so far this is what i’ve done, i also bought a new transmission and replaced it but it did not fix the issue. One more culprit could be your fuel system. Clean all your injectors and filters and replace o rings. Check your fuel rail and make sure it holds pressure and replace your fuel pump and filter if needed.

 

I think the IACV made it a little different, possibly better but it was very hard to tell. It doesn't look like it has corrosion, however the connector for it doesn't clip in anymore just plugs in, and also the 6 wires are only connected to the plug itself very lightly and are super easy to pull off. I think I will order an IACV and new plug for it and see if that is the issue as I am thinking it is the most likely culprit. Thank you for the response

 

I would definitely replace that clip if it’s broken. The issue i said before with my car backfiring was caused by one of my clips on my coil pack being broken and the wires were arcing. I just replaced all my coil pack connectors and it fixed that issue. I want to mention after doing some research that some people get these issues because of bad ecu capacitors. Look up a thread on it and see if any of the symptoms listed for a bad capacitor are happening to you. One of them is your rms at idle going up and down and another symptom is rpms dropping and going back up after letting off the gas. There is a list of issues that can happen that are all very strange. Worth a shot doing yourself if you buy the oem capacitors and know basic soldering.

 

i've replaced a ton of stuff on the car, i think everything you listed lol, already over that years that would normally be causing problems, but anyways i replaced the clip with a new one and it still doesn't work correctly so I have a new IACV coming ill try that and also check the ECU and make sure!

 

Well I installed a new IACV, IACV clip (mine was broken), and no luck the idle still will not remain consistent after driving around for a while. If anyone has any ideas on common vacuum leaks, or any other sensor that could cause this please let me know 🙏

 

Try starting the car and when it still holds 1000 RPM, Disconnect the Pigtail for an IAC Valve and see if the Idle will keep dropping anyway, or what changes would there be. ECU would be a prime suspect at this point, there isn't much that can affect the Idle without causing any other side effects on the vehicle, IAC and ECU are the only two I can think of so far. It's pretty easy to take the Covers off of the ECU and inspect the Condition of the Board, so it is something you can do as well.

Hope this helps and best of luck!

 

Hey, I swapped around some stuff and disconnected reconnected ETC sensor and now it mostly idles at 700, but still goes down to 200 eventually or if go to neutral coming to a stop it’ll go to 200 consistent, I just unplugged the new iacv while it was running and the idle went up a little to I believe 700 and nothing else has happened, I cracked open the ECU and it looks very mint.

 

Update: I THINK I have figured it out, I noticed it mostly happened when braking to a stop or going clutch in, so I pressed the brake pedal rapidly and noticed the idle getting worse and revs going down. Because of this, I checked the vacuum line and the hose clamp was on the hose, but not properly on the bung so I put it back, and it seems to have *mostly* fixed itself though idling between 650-750, but I may need new hoses as they are very hard.

 

welp after driving around for a little, the idle just isn’t working how it is supposed to, it sits at 1000 every time I start the car (except cold) for about 5 seconds then goes to 700. If I rev the car, once the revs come down they go past idle to 200 the car shudder for a little and then they go back up. The brake pedal also effects the idle as when I pump it or press it fully in the idle slightly goes down, then when I let off, it goes up a little. I really am unsure of what could be wrong at this point. If anyone has had similar problems please let me know 🙏

 

Sorry for the delay.

Are you sure that, aside from this issue, the engine runs normally? Can you record a Video of it Running?
When you disconnected the IAC Valve, did the sudden Drops in Idle RPM to 200 RPM persist, or did it remain more or less Constant?

One of the strategies for cases like that is to disconnect All non-essential Sensors to rule out a Mechanical Fault, with the ECU in the Limp Mode, it will definitely try to avoid Idle Fluctuations at all costs, so if they still persist, you will have to dig deeper into the engine. If the issue goes away, you can start Reconnecting all the sensors, one-by-one, until it comes back. It is not a definitive test for a failed sensor, but at least it will give more information on where to start digging deeper.

Also, just in case, you run a small test to see if you have any Vacuum Leaks, all you need is to take the Air Intake Hoses off, Disconnect the MAF Sensor, and start the Engine, then Plug the Throttle Body with either a hand or the rug and see if the Engine would Stall, if not, you have an Unaccounted source of Air for the Engine, aka a Vacuum Leak, which can cause issues like that.

Hope this helps and best of luck!

 

Hey thank you for the response! I will try these as soon as possible