so have installed a skunk 2 alpha 70mm tb and now my idle jumps from 800rpms to 1200rpms any help would be great . ive set the tps from ecu wires ive also read that bleeding the cooling system could fix this issue but i doint think my b16a has a bleeder valve once again any help would be great

 

You dont need a bleeder valve to bleed the coolant. How do you think air is gotten out of the system if they installed no bleeder?

I would check for vacuum leaks around the t/b

 

ok so no vacuum leaks now what ppl ? the jumping idle is bugging the **** outta me,any other suggestions

 

Have you played around with the screws on the t/b at all?

 

Bleed the air from the system.

 

The coolant system is only for cold start idle. If the ECU thinks the engine is cold it will raise idle to get to optimum running temp faster.

This sounds more like the throttle air bypass screw. Bigger TB means more air which means higher idle.

 

He's not talking about a higher idle...his idle is pulsing from 800-1200 rpm

 

Right. Pulsing idle. Not high idle.

 

Copy Paste from Hondata

Idle problems and oscillation

Idle control valve characteristics vary between intake manifolds. When the ECU is swapped, it expects an idle control valve of similar characteristics. If it is different, more or less air can pass leading to a very low idle or oscillating idle.

The ECU has a 'target idle speed', which varies with coolant temperature and electrical load. When fully warm the target idle speed is 700 or 750 rpm. If the engine speed is different from the target idle the ECU will alter the duty cycle of the IAC valve to compensate. A combination of a duty cycle lookup table, the current duty cycle and the difference in idle speed is used to calculated the duty cycle for the IAC valve.



This is a closed feedback loop, and is dependent on the characteristics of the engine matching what the ECU has been programmed to expect. If any of the components in the feedback loop, or a combination of components are different from what the ECU expects, then the feedback loop falls apart and the idle will often oscillate. Don't confuse this with the oscillation which can happen if the TPS is out of adjustment and the over-run cutoff is operating. The idle oscillation is a good example of a lorenz attractor in non linear dynamics if anyone is interested is chaos.

For an example consider that the engine is idling at 750 rpm by using a duty cycle of 25% for the IAC valve. The engine speed drops to 725 rpm, the ECU calculates the difference of 25 rpm and calculates a new duty cycle. The tables in the ECU tell it that when the IAC is at 25% duty cycle and the idle is 25 rpm low, use 30% as the new duty cycle. This valve has been set by Honda as the correct duty cycle for the stock engine, and will return the idle speed to 750 rpm for a standard engine. If the engine has been modified it might be possible that the IAC duty cycle needs to be 50% in order to increase the idle speed again. Because the IAC duty cycle is too low, the idle speed drops, and eventually the ECU will give the engine a shot of fuel and open the IAC right up so that the engine does not stall. This will raise the engine speed to 1000 rpm or so, and the cycle continues.

The solution is to alter the behaviour of the idle speed components so the system is stable again. Usually adjusting the TPS, idle bypass valve, mixture and ignition will cure an unstable idle.

 

wow thank you for breaking it down for me it totally makes sense the way you break it down thats what i was looking for so i had the tps set to the right voltage now to adjust everything else accordingly,cuz iam running a stock p30 and ive got a big tb and a ctr intake manifold so i new when putting the 70mm tb i would have to tweek things here and there once again thanks for the info