supercharger swap now high idle

**jtackerman28** · 05-27-2014

I just put a new supercharger on my 2003 gtp, I ported the supercharger before i installed it and it also has a 3.5 pulley on it. For other back ground on the car it has a aftermarket down pipe with a highflow cat, a hot ait intake, 103's, and a 180tstat. I also have a scan gauge set up to read knock and the most i have seen on this set up is 2.5* with it about 90* out.

Now to the problem. The car is idling between 1000-1400 rpm in park ad down to 1000 even in gear. I've done a few things since the high idle to include spraying carb cleaner abound every vac line and around the supercharger and throttle body gasket. I also removed and swaped the iac off of a properly running 3.8 and still have the same problem. Also another thing that bothers me is that the evap purge is running like crazy, i also swapped this off the other properly running 3.8.

The only thing that i can think of so far is that there is an extra port on this m90 next to the air inlet at the rear of the supercharger and i capped both of those open ports off.

Any advice is greatly appreciated and would love to not have to take it to a shop

**REDCRAPGP** · 05-27-2014

Did u have it tuned for the ported sc?

**Fivefingerdeathpunch** · 05-27-2014

Originally Posted by REDCOMPG

Did u have it tuned for the ported sc?

What?

Why would you even need to do that lol.

Unhook your throttle cables and see if the idle returns to normal.

So you did a gen v swap? I assume thats what it is because you talked about a rear port on the case, and I know the 98-03 didnt have one, only the 3 line vacuum tree ontop.

**jtackerman28** · 05-27-2014

no its not a gen 5, ill try and find a picture.

**jtackerman28** · 05-27-2014

should work hopefully http://s1056.photobucket.com/user/jtackerman28/library/

**Scottydoggs** · 05-27-2014

you have a 97 blower there, cap those two ports on the tree. thats your vac leak.

**Fivefingerdeathpunch** · 05-27-2014

Oh, thats a 95-97 style superchrger with those silly vacuum towers.

Capping it should be fine, just make sure you have the map going to the intake, then over the FPR and to the boost solenoid and it looks like you do.

I'd still try messsing with the throttle cables.

**jtackerman28** · 05-27-2014

i have the ports capped because i figured thats all they were, it still has the high idle. and yes the map is routed to the lower intake. I dont know where else to go from here. I havnt messed with the throttle cables but i wil do that. it is showing 0 on the tps though. not sure how accurate that is.

**jtackerman28** · 05-27-2014

is it possible it can be related to the purge solenoid constantly purging? when i pull the connector for it the idle drops down and then climbs back up a few seconds later.

**BillBoost37** · 05-28-2014

Is it possible you can rule out the throttle and cruise cable before you keep asking us for potential items to cause it?

We like to start off with the easiest items that may be causing the issue and then work our way into the items that will cost you the most time and money. If you'd like to skip right to most money.. replace your motor and then we will diagnose the high idle on the new motor.

Please stop pulling connectors off when you have no idea what the reaction of the item should be. This will only upset the pcm and cause it to counter act you messing around with sensors etc.

**jtackerman28** · 05-28-2014

Okay will do the only reason for pulling the purge was I had read that it can cause high idle.
Today after work I will pull the cables and see what happens

**BillBoost37** · 05-28-2014

Things that cause high idle.

Vacuum leaks - however you said you checked for them with tb cleaner.
IAC - no reason this should have magically started having trouble with the swap
Cables - they do a loop on the strut tower and .. sometimes a slight move can cause them to cause this issue

Screwing around with something that you didn't change doesn't make a lot of sense. Typically if a car was just worked on, look to the areas in and around the work. Electrical items/sensors won't usually mess up from being unplugged and plugged back in. However if you unplug/plug in while the ignition is on.. it can get a reaction from the pcm.

**jtackerman28** · 05-28-2014

I didnt unplug anything while it was running until after the problem. It almost seems to be intermediate now. The car is staying in closed loop mode like it should and the upstream o2 is not even two weeks old. My gas mileage is also dropped by like 10 mpg I know there will be some drop with the smaller pulley but I am pretty sure it shouldn't be this much

**Scottydoggs** · 05-28-2014

post some more pics of your vac lines and the routing you have set up.

**jtackerman28** · 05-29-2014

okay i will tomorrow. im pretty sure its all correct but a second set of eyes is deffinitly worth a try. Its idling at 1200rpm right now and the vac at idle is -8.2 lbs according to the scan gauge.

**Fivefingerdeathpunch** · 05-29-2014

If you scanner can read MAP in/hgs, thats far better than trying to read it in lbs which is normally wrong.

Vacuum off the map sensor should be -19 to -20ish at idle, which is 700-800 rpms.