Hunting on idle???

[Matts-gen2]

My car seems to be hunting when running on idle, dipping in revs and a drop in tone.  

I recently had the heat exchange removed and a straight through pipe welded in.

Could it be timing needs adjusting or new plugs?

Any help appreciated.

Matt

[Prof]

If you mean the intercooler from on top of the engine, what did you do with the 2 small pipes that come off the back of the intercooler - these carry a quantity of metered air to 2 solenoids the AWS (warm up system) and the other one (can\'t remember the name), but this is basically designed to compensate for Power Steering pump load.
 
If you\'ve just left these hoses floating, then there could be unmetered air getting in.
 
Another possibility is a sticking or Faulty BAC valve (long 1" dia cylinder on the drivers side of the engine)
 
And it could also be the Throttle Position Sensors - particulary if it hunts up and down between 1000-1500 during warmup.

[Matts-gen2]

Ive got a non-turbo gen 2.  

The straight through pipe im referring to is in the exhaust, heat exchange removed (because it was blowing), and piece of straight pipe welded in.

I was told that theres a supply from the air pump, but when the exhaust was changed there was no such air supply pipe to be seen.

There isnt any free pipes hanging around.

Matt

[Prof]

Sorry - my bad !
 
That other pipe is to feed air to the cat\'s - if your decatted, then no need for it.
 
Person to speak to on EGI\'s is probably Brett - I\'ve no doubt his radar will be on this soon enough
 
TPS could still be a problem - does it hunt all the time on idle, or only when warming up ?

[Matts-gen2]

It hunts when warming up and when on idle.

Probly every 10 -15 seconds it will dip in revs then return to normal idle again.

I have had a problem in the past with the throttle cable being un hooked from the groove on the rear of the throttle body thingy (hope you know where i mean).

I have fixed this, but while trying to diagnose this problem abdjustments where made to idle, which i have returned to what it was on: 850 - 900 rpm.

Is there a ideal range setting for idle, and am i right in thinking this  idle setting should be done when the car is warmed up.

Is there a cold start adjustment? What does it need to be set at?

I get the feeling this may be a LONG step by step elimination process.

Matt.