Idle problem

[El_Boomo]

Pulled up at work a couple of weeks ago and suddenly had an idle of 3000rpm. With the Spoon N1 and 2.5 inch B pipe it sounded like the world was ending.

Anyway, I whipped the throttle body off, gave the IACV a good clean (wasn't moving at all but now spins freely), replaced the gaskets and put back together. During the process I lost a bit of coolant so topped up the radiator and bled the system.

She's running a lot better now but the idle is still high. It settles to about 1500rpm when static and warm. Also, if I press the clutch whilst rolling, the revs don't drop below 2500rpm until I come to a complete stop, then it returns to 1500rpm.

Anyone have any ideas what could be causing this, or if I can adjust or 'relearn' the idle in some way?

 

[Johngreen537]

Close the helper screw very slightly on throttle body?

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[RobS]

I believe theirs a method to have the ecu relearn the idle point, I think you disconnect the battery for 5 minutes, then when car is completely cold start it up and either rev it at 3k until the fans come on or leave it for a good while until the fans kick in.

 

[El_Boomo]

I believe theirs a method to have the ecu relearn the idle point, I think you disconnect the battery for 5 minutes, then when car is completely cold start it up and either rev it at 3k until the fans come on or leave it for a good while until the fans kick in.

I'll give that a try. Tried pulling the ECU fuse whilst the engine was warm and then starting it up and leaving for 10 minutes but no joy.

 

[El_Boomo]

Ok so this still hasn't worked. However, I plugged in a bluetooth OBDII reader and, using Torque on my phone, found that the throttle position is showing 12.5% when closed. I haven't checked the voltages to see whether or not they're in spec yet, but would this fool the ECU into thinking the engine is not idling?

 

[Johngreen537]

TorquePro generally shows TPS around 10% when warm idling. If the engine was warming, I wouldn't be too worried on 12%. Does it achieve 100% on a run?

I normally tell it to datalog, rather than relying on refresh of screen.

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[El_Boomo]

TorquePro generally shows TPS around 10% when warm idling. If the engine was warming, I wouldn't be too worried on 12%. Does it achieve 100% on a run?

I normally tell it to datalog, rather than relying on refresh of screen.

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Cheers for that. Shows 97.3 with foot flat to floor so close enough for me. Starting to look like I'm going to have to try cleaning the IACV again.

 

[integraleo]

Tps sensor needing adjusting maybe?

 

[El_Boomo]

That's what the 12.5% on throttle closed led me to believe but John said it's about normal. I meant to check voltages at work but ran out of time.

Although reading back I should clarify that I was checking WOT with the ignition on but engine off. Closed throttle shows 12.5 no matter what so figure cold, warm or engine off won't be effected.

 

[Johngreen537]

Think it should drop to 9-10% when up to temperature mate. I'll put my scanner on later for a test to compare.

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[El_Boomo]

Cheers, I unplugged the TPS with the car running and it made no difference to the idea speed.

I also unplugged the IACV sensor which caused the idle speed to drop but pulse. Not sure whether this is meant to happen, but I'm guessing it means the IACV is good.

Checked for vacuum leaks with car cleaner aswell, can't find any. Vacuum reading with Torque Pro shows around 23 (not sure what that means).

Bled the coolant system again and did the idle relearn thing. Can safely say those aren't working.

I've got a couple of hour and a half motorway journeys in it tomorrow so maybe a good run will sort it out.

 

[El_Boomo]

I've finally fixed this after a few weeks of annoying the neighbours and scratching my head.

As it turns out, the IACV sensor is very slightly adjustable. When putting it back together I'd obviously screwed it in so that it's default position was slightly more open than it should be.

Now that I've re adjusted it, I have a nice low idle of 950ish again. Thanks for all the help and pointers.

 

[WalshDC5]

sorry to bump this thread but im having the same issue but i dont have a great deal of mechanical knowledge (im learning...slowly :xgrin: )
How do i adjust the sensor and get the idle back to a reasonable speed?