Forum » General Tuning Discussion » Idle control

Idle control

General Tuning Discussion

Discuss all things tuning in this section. News, products, problems and results. 

Page 1

Hi i'm having trouble adjusting the idle control so when i'm driving and have to press the clutch in, the rpm drops almost

Stalling then takes a little to come back to the idle target, also when idling and you rev the engine dipping the gas pedal it stutters a little like leaning out, how do you adjust this?

It sounds like your base idle control tables are set a little too low which is causing the dipping engine rpm when you come off the throttle. What ECU are you tuning? The settings are very specific to each ECU and this will determine what you need to do.

It's the stock ecu just reflashed with cobb tuning

Ah sorry I hadn't connected the dots from your other post. Given the range of issues you're having I'd be very doubtful the real issue is anything to do with the idle. Unless your engine is very heavily modified it's normally not necessary to mess with the factory idle control at all - This is one of the advantages of reflashing as the idle, cold start and cruise generally don't need to be touched.

Out of interest are you using a stock blow off valve? You will see the sort of issue you're explaining with a blow off valve that vents to atmosphere.

The idle doen't have anything to do with my problem, i'm just building a map of my own so i can tune the car myself while i'm learning from these courses, sorry about the confusion, i have a front mount with a tial 50mm bov,

Ok if you're using a Tial 50 mm BOV then this will have a huge effect on your ability to achieve a stable idle. When you clutch in or back off the throttle, the BOV will vent air that's already been metered by the MAF. This air doesn't make it to the engine though so the engine runs super rich briefly until everything stabilises. Atmospheric BOVs are not a match made in heaven for any engine that's running a MAF sensor unfortunately.

You may also want to check that the BOV is closing completely at idle and cruise. There are a couple of springs available for these BOVs and if you have the soft spring then it's possible the BOV can be held open under high vacuum situations (idle and cruise) which makes it hard to tune the engine and can result in weird driveability issues.

Maf sensor was eliminated using the cobb maf to sd conversion, so i'm running the car on sd with a aem intake tempereature sensor, idle just needs to be set on the map to react fast when i press the clutch in, also when on idle and i dip the gas to rev the engine it stutters a little, what do i set to let it rev smooth

Hi, sorry for hijacking this thread, but i have almost the exact same issue with my car. It happends when the engine is up to operating temperature. When revving in neutral the rpm drops down so low that it stalls. Same thing happends when driving and disengaging the clutch. It also stutters a bit when dipping the gas pedal from idle.

My engine is a RB25DET with a Vipec V44 Plug in ECU. Stock longblock with ID1000 injectors and GT3076R turbo, stock idle control valve.

I would start by raising the idle base duty values. It sound like your idle speed control base values may be too low and the ECU is then relying on the feedback to raise the idle duty and then achieve your target idle speed.

A good tip is to watch the actual idle speed duty cycle when the engine is idling at your target rpm and compare this value to the duty cycle in your base map. The numbers should be pretty close to the same value.

Thanks Andre. The duty cycle was set up starting at 55 cold and gradually decreasing to 25 at operating temperature in the base map. I tried raising it and that helped. The dip in the rpm is still there to a certain degree but not nearly as bad as before. It seem to hunt at little more at idle when I raise the duty cycle though. At least for a little while until it stabilizes.

Sorry for the stupid question as I am still an amateur in this field, but where can you see the actual duty cycle besides the rectangle circling around in the table? I cant find it in neither the logging parameters nor the gauge parameters.

If you press 'R' of 'F12' to bring up the runtime values screen, you can then cycle through to the 'Auxiliary' tab and on the left you will be able to see the current Idle Speed target and the Idle Position duty cycle. This is very useful in tuning your base position table. I'd also recommend setting up idle ignition control if you're not using it. There is a webinar about configuring that here -