Idle issue making me go wacko.
11-12-2020, 05:27 AM
#11
If I rev the engine while stationary, the car revs then drops down to 400-500 RPM before recovering. When taking off, I have to rev to 2-3 to avoid stalling on takeoff. Can't move at all with the "friction zone" at idle, car just stalls out. While idle and stationary, RPMs go from 800-850 down to 700 and the car shudders, before the car recovers back to 800-850, before doing the same thing again.
Happens mainly when the engine is warmed up. Less often when cold.
Happens mainly when the engine is warmed up. Less often when cold.
11-12-2020, 05:57 AM
#12
If I rev the engine while stationary, the car revs then drops down to 400-500 RPM before recovering. When taking off, I have to rev to 2-3 to avoid stalling on takeoff. Can't move at all with the "friction zone" at idle, and even with a small bit of gas, car just stalls out. While idle and stationary, RPMs go from 800-850 down to 700 and the car shudders, before the car recovers back to 800-850, before doing the same thing again.
Happens mainly when the engine is warmed up. Less often when cold.
The only reason it's jarring for me is my motorcycle doesn't behave like this, and neither did the Boxster I owned before. Smooth manuals on those, let the clutch out slowly, give it a little gas, smooth takeoffs. The S2000 it's either I'm dumping the clutch practically to avoid stalling out, or I stall and have to restart the car. No in-between, no smooth takeoffs because if my RPMs are too low, the car just stalls. Very frustrating, and especially embarrassing around town. I've never had to do this much work to drive a manual before.
A total list of what I've done now:
- Cleaned the IACV 3 times.
- New Skunk2 70MM Throttle Body
- New MAP sensor
- New TPS sensor
- New OEM Clutch Master Cylinder
- 10+ Idle Relearns
- Oil change
- Coolant Flush and Change
- Transmission Fluid Service
- Differential Fluid Service
- New OEM Spark Plugs
- Vacuum leak test
- Fuel Pressure test
Previous Owner Mods:
- AEM Cold Air Intake
- Skunk2 Headers
- Skunk2 Exhaust
- Test pipe
- Aftermarket Clutch (no clue what brand or model)
No clue why the RPMs drop below Idle.
Happens mainly when the engine is warmed up. Less often when cold.
The only reason it's jarring for me is my motorcycle doesn't behave like this, and neither did the Boxster I owned before. Smooth manuals on those, let the clutch out slowly, give it a little gas, smooth takeoffs. The S2000 it's either I'm dumping the clutch practically to avoid stalling out, or I stall and have to restart the car. No in-between, no smooth takeoffs because if my RPMs are too low, the car just stalls. Very frustrating, and especially embarrassing around town. I've never had to do this much work to drive a manual before.
A total list of what I've done now:
- Cleaned the IACV 3 times.
- New Skunk2 70MM Throttle Body
- New MAP sensor
- New TPS sensor
- New OEM Clutch Master Cylinder
- 10+ Idle Relearns
- Oil change
- Coolant Flush and Change
- Transmission Fluid Service
- Differential Fluid Service
- New OEM Spark Plugs
- Vacuum leak test
- Fuel Pressure test
Previous Owner Mods:
- AEM Cold Air Intake
- Skunk2 Headers
- Skunk2 Exhaust
- Test pipe
- Aftermarket Clutch (no clue what brand or model)
No clue why the RPMs drop below Idle.
You do, however, have some sort of issue of course. But do not expect the launch rpm to change much when it is fixed.
You can try a valve adjustment if it has not been done. I seriously doubt it is going to fix your idle. If the valves are out of adjustment enough to cause poor idle and have been that way I would worry about burned valves. But try it if it has not been done anyways. Could be that someone else did one and set them way off.
IACV is a typical cause of a car stalling or stumbling when returning to idle. But there could be a few causes though.
11-12-2020, 06:26 AM
#14
Moderator
Your symptoms are classic IAC inability to react to ECU command.
I still think your problem lies in the IAC. Can you spin the shaft with your finger like a top, and have it spin for an additional second?
It is also imperative that the motor is centered. The mounting holes are slotted and allow timing/rotation of the motor.
I still think your problem lies in the IAC. Can you spin the shaft with your finger like a top, and have it spin for an additional second?
It is also imperative that the motor is centered. The mounting holes are slotted and allow timing/rotation of the motor.
11-12-2020, 06:35 AM
#15
I am thinking I just need to replace the IAC.
The shaft spins freely with minimal friction, and I'm pretty sure I centered the shaft when I re-assembled it the one time I took it apart, but I have no clue if the motor is working. No check engine or error codes.
Also, slight off topic, is the overflow container for coolant supposed to just be loose in the engine bay? I don't see a mount for it, and it's just laying there.
The shaft spins freely with minimal friction, and I'm pretty sure I centered the shaft when I re-assembled it the one time I took it apart, but I have no clue if the motor is working. No check engine or error codes.
Also, slight off topic, is the overflow container for coolant supposed to just be loose in the engine bay? I don't see a mount for it, and it's just laying there.
Last edited by Rewire; 11-12-2020 at 06:39 AM.
11-12-2020, 06:53 AM
#17
Thanks for that.
I'll try disassembling the IAC once more, ensuring it's operating properly, reassemble it (center the shaft so air flows when it's reassembled, correct?) and then if all else fails, I'll replace it.
Thanks.
I'll try disassembling the IAC once more, ensuring it's operating properly, reassemble it (center the shaft so air flows when it's reassembled, correct?) and then if all else fails, I'll replace it.
Thanks.
11-14-2020, 09:41 AM
#19
Hi Billman, are there any steps you can advise on how to recenter it? Or know it's recentered? You've mentioned this before in other posts but I've come up empty on a procedure.
This might be a good sticky as well IMO.
Thanks!
This might be a good sticky as well IMO.
Thanks!