What I mean is at idle the engine revs rise and fall between 850 and 1150 rpm.

Is this a mixture problem? Its really only started since I installed th ST.

Inlet manifold doesn't match the head, there is a step up into the ports which again are much bigger than the last engine and are partly covered at the top. Could it be this??

Steve

i don,t know your engine set up but my guess would be airflow meter,
just my opinion but probably way off the mark

andy

[Edited on 30/3/09 by handyandy]

this used to happen on my old bmw 6 cylinder when the idle control valve was sticking and the revs would bounce when you came off the throttle. Taking it apart and cleaning it with carb cleaner would sort it, any help?? Or am I barking up the wrong tree??

Dan

That sort of thing is normally an air flow / air leak problem.

Id go for an air leak in the inlet. Spray some WD around the head flange and see what happens. Is it an st 170 engine if so have you got the VVT connected or removed.

Hunting at idle is a sure sign of an air leak somewhere....

Sorry, as mentioned there, its on carbs so no idle valve or MAF..

VVT is set to activate at 4K, pure stand alone triggered by aux output on the Megajolt.

The AFR meter goes up and down in time as well so as said will check for air leaks.... however engine is fine just off idle and runs close to 14.5 AFR at WOT, revs passed 8K (gauge stops there) pulling like a train.

Mental note: set the rev limiter, don't want to be the only April fool with bent rods!

Ta,
Steve

For peak power you want 12.5 AFR at full throttle...

If you only have a slight air leak you will only have a problem at idle, under power it wont make any difference.

David

Agree with what David Said.....First check the balancing - then look for air leaks.....

Sounds like you need larger main jets to throw in a little more fuel at WOT.....

Thanks guys, any where I can see what AFR I should be getting across the range?

14.7 at light cruise and under light acceleration ramping up to 12.5 at WOT.

I'll post my afr map up later.

David

This is my base AFR targets for the pinto TPS against RPM.
Rescued attachment afr.jpg

Cheers my man..