marshall2j

Fellas,

Ever since I changed my valve cover seals on my sc3, the car started dying everytime I quickly let off the throttle coming to a stop. I'm suspecting it's some sort of vacuum line issue. And I think I know where it's coming from. Can someone please take a picture of the vacuum lines located behind the intake manifold near the firewall? I'm almost sure I criss crossed something.

Thanks
Jeremy

fried_rice

iTrader: (20)

What's the car idling at? If it's idling high, most likely a vacuum leak. If it's low maybe you need to raise the idle screw on the throttle body.

marshall2j

It's idling perfect when you don't touch the throttle. I'm not sure if you guys have seen this before, but it's very similar to running a maf with atmosphere-vented blow off valve... If I'm driving then coming to a stop, and put it in neutral, the idle drops very low... sometimes it dies. Which is weird because I'm running map with my AEM v1.... and I haven't changed my map or messed with the idle screw. I'm thinking I messed up the vacuum lines when putting the car back together

Ali SC3

iTrader: (10)

did you tune the idle maps yet on the aem? sometimes your idle settles on an idle learned positive number, and when driving it gets cleared to 0 so when it tries to idle again its too low and stumbles before it has time to raise the idle up which takes a few seconds. I would take a look at the idle maps. If you have a valve cover leak it would only be sucking air through the PCV if you still even have that on, and since you are on a map sensor Its safe to say thats not the issue cause you can suck air from anywhere and a leak would raise your idle. you could have crossed lines somewhere affecting it, this normally will show a different vacuum at idle than normal, does it look different now?

you want the idle learned to be a few percent negative number when idling with the engine warm, so when it clears to 0 and the engine tried to idle, its actually a few percent higher than it should be and then works itself down the last few hundred rpm's to the negative learned idle again. its all in the tune.
likely whatever you did could have also caused it to be a few % off now and that is why its doing it, do you have the vacuum diagram under the hood?

marshall2j

I haven't messed with the idle with AEM with the map I got with the car originally. In fact, that was probably the only good thing with the car lol. The only thing I've changed is the valve cover seal before there were any issues so I was thinking it was related to vacuum lines. I've done valve cover gaskets before on my Supra so I'm pretty confident I did it right. Only issue is that the car still has the stock IM which makes it a PITA to assemble. I'm sure I missed something.

Thanks for the advice on AEM, I'll take a look at those settings. We all know that the AEM is not the most reliable piece of hardware...

Also, I now remember fixing a giant leak that connected the iacv, so I'm guessing you're right, the map is all confused now

Ali SC3

iTrader: (10)

moving to performance and maintenance.

yeah it could very well be it was tuned with the leak before and if you fixed it likely it will need some adjustment in the software now. if its driving fine and idling otherwise expect for the dip after you let off then its probably the tune.
yeah the stock intake is a pain but if you take it off in sections its not too bad to put the lines back together, I have done it lots of times. what hoses are you confused about, maybe post a picture. I don't have a pic of all the vac lines anymore but I did have a pic of the vacuum diagram somewhere, that helps alot.

edit* this would make sense cause if you fixed a leak you would have less air so it would have to idle up more which means your % learned value likely changed.
as I said just take a look at the % learned value when its warm and idling at the right rpm. if its a positive value then you will get the dip, its as simple as that.
If its positive, just highlight the whole idle map and bump it up with the "+" key until idle learned is like -2 % or so.
that 2% added in there for the aem to slowly remove after it starts idling is what cures the "dip".

Think of it like an 02 sensor, you tune the car rich and you use the o2 to pull fuel generally.
same with idle, you tune it a little high and let the aem pull some out.

marshall2j

Thanks, I'll definitely take a look. I don't have the car with me -it's at my buddy's- he's building a brand new single outlet, turbo back exhaust using real stainless steel instead of whatever the previous owner used that resulted in a giant 2" rusted hole exhaust leak *shakes head* but he too commented on it stumbling once throttle is let off