I noticed since I switch to the BF272 cams, during deceleration in gear my car struggles to go extremely lean, like it use to.

I'm montoring it with my innovative wbw o2 and only about 10-20% of the time it goes past 20 to 1 when I let off the gas at any rpm.. It use to do this instantly with the hks272..

I wasn't sure if there was a setting in the ECU that could be adjusted to set a different threshold? Has anyone else has this issue, I was wondering it if was a vaccume leak or Idle control valve or something along those lines?

thx,
Freddy

 

If I am thinking correctly, this is the throttle hang issue that is a normal thing with the Evo ECU's.

 

You gotta slightly tap the throttle in decel to "shut off" the injectors.

 

Thanks for you help.. would adjusting the Idle screw have any effect on this? how should I try and correct it? thx

 

Bump for an old topic and a new problem on mine...

I tossed in some HKS 272's a few weeks ago and never had this problem until a few days ago, and it's exactly as the original poster mentions. During decel previously the injectors always shut off and my lc-1 would shoot to 22.4afr. Now I let off the throttle and it sits at 14.7 and gradually goes richer to near 11.3afr until I tap the throttle again, and then sometimes it goes to 22.4afr. Does anyone else have an answer or suggestion that I could try other than "it's normal", because it definitely isn't.

 

I have a suggestion, its not proven to work, but you might be the guinea pig.


go to your accel enrichment and take it down a few. let us know if it works.

your recent issue may be weather related.

 

Mine goes to 20 on my ZTX on decel every time. HKS 272's

I would say there is something wrong hardware related.

 

i remember even when i was on the stock injectors, when i was lifting the car would sit at the afr i had for a few seconds maybe and then will go lean, i guess around 20 because the plx stops reading there.

It does the same on the 780s that i have know...

 

I was just thinking that maybe there is a load variable map that requires load to be below a certain value before it will allow decel fuel cut. For my Evo7 I found the map that controls the RPM when the fuel is turned back on, but seeing how the guys with cams have issues it may be linked to load as well as TPS.

Sort of like: If TPS = 0%, RPM> "x"rpm, Load<= "y", then do the fuel cut.

I have the "x" map, just need to find the "y".

A way to see if this is the case would be to introduce a small "vacuum" leak somewhere between the throttle body and the MAF. In this way it will lower the airflow drawn through the MAF, fooling the ECU into thinking there is less load. If this activates the decel fuel cut then we know there is a setting somewhere for it. If it exists, we can find it.