HKS 264 Step 1 Cams - Vacuum lower?

[ka24det-power]

I just installed my HKS 264 Step 1 Cams. Went pretty smooth the only issue I have is that it wants to stall when I let the motor drop from high RPM's to idle. I am only getting about 14 to 15psi of vacuum at idle. Before the cams it was 19 to 20psi of vacume.

I adjusted the IAV to raise the idle (which it does) but it still wants to stall when I drop it from high RPM's. I did a vacuum check and I have no leak. I have a GReddy intake mani as well.

Is this normal what should I check?

[sdtouge]

this is because i believe now some vacuum at idle is leaking out because the valves are staying open to long for 1000 rpm or so. its fine

[RBS14]

yes, it's normal to have less vacuum at idle with aftermarket cams. This is attributed to valve overlap. However, your engine shouldn't die when you let the engine drop to idle from any rpm. I'd check to see you didn't install one (or both) of the cams 1 tooth off.

[sdtouge]

if the cam gears are a tooth off even, you car would suck, rev really slow shake alot have almost no vacuum etc, but it is possible. my exhaust cam was 2 teeth off and i was pulling 3psi of vacuum....

[ka24det-power]

I dont think the timing is off because I zip tied the cam sprockets before I took them off to make sure the stock timing didn't change.

When I rev it up to say 4 or 5 and let it drop it goes to 400 rpm and then bounces up to 900 rpm or so. Some times it tries to stall when it hits 400 most times it just bounces up.

Do you just deal with it or is there something I can do to smooth it out? Adjust the IAV or TPS?

[fliprayzin240sx]

did you double check your timing yet? Those cams are still drop in, there should be no ill effect of you running it on stock cam sprockets and stock timing. If you make the jump to stage 2s, then its time for cam sprockets.

[Mirage]

give it a week and see if the ecu smooths it out itself. When I did my 264 step 1's into my old fwd sr20de (b13 se-r), it idled rough for about a week, then idled rock solid at 800 with a nice lope. guessing the RWD ecu goes through the same process. That and make sure you dont have any leaks in your intake path.

[ledzeppelin240]

The lower vacuum is due to more degrees of valve overlap, did you break the cam in at all? Even though they are machined surfaces they are still rough and need to be worn smooth...