ryeguy2006a

iTrader: (27)

Hi guys. New to the site, and new to tuning and looking for some help. I recently started up my project after doing my LS1 swap, and now it won't idle under 1200? I am unsure if it is a tuning issue or a simple vacuum leak. I haven't had enough time to out rule the vacuum leak, but wanted to see if anyone could point me in the right direction.

Background on the car: 1976 Pontiac Trans Am, that I recently have swapped in a 1999 Camaro LS1 and t-56. I modified the wiring myself with lots of help online. Other than the LT headers and a CAI the engine itself is stock. I plugged the egr hole in the intake with an expandable rubber freeze plug as a temporary solution until I can buy an LS6 intake. All my gauges are fully functioning and the only real issue I am having is getting the car to idle properly.

I have HP Tuners so I have the ability to make just about any change to my tune. So far I deleted the EGR, AIR, EVAP, Rear O2 sensors and I thought that I read all the proper ways to disable them from my tune. Essentially what I did was changed the egr to disable, and for the rest unchecked the boxes for the codes to be thrown. Is that all I needed to do? The reason I ask is because under DTC's EVAP is a code that keeps being thrown, but I unchecked it.

I am at work now, but I can upload my tune later if someone wanted to look at that.

Here is a link to my build and on the last page is a video of it running from this weekend. Not sure if that will help any?

http://transamcountry.com/community/...opic=24465.630

Any help would be great.

Thanks,
Ryan

Bilster

iTrader: (21)

Is this a drive by cable? If so, check the obvious first. Make sure the cable is not binding. Make sure your throttle body butterflies are shutting all the way.

bczee

iTrader: (12)

I would also check all of the sensor to make sure that they are secure and use HPT to scan to see if input is being received from the Sensors.

try unpluging the MAF and see the RPM change ?

ryeguy2006a

iTrader: (27)

I have checked all of the obvious things first, before I posted here. I am more concerned with the tune. I got a complete running/driving 1999 Z28 that didn't have any issues prior to using it as a donor for my car. I was able to start and drive with no issues.

i r teh noobz

iTrader: (4)

Watch the short term fuel trims and spray brake wash/carb cleaner onto anywhere that may have a vacuum leak. If the fuel trims move negative, you found a leak.

Check the CTS data. If the car thinks its -40 outside it might try to idle way high to compensate.

gofastwclass

iTrader: (2)

Agree. For a stock 02 WS6 6 speed the -40 degree idle is 1050 RPM and the idle speed is 800 RPM for every temp point above 133.

Another thing to check is to see what the "commanded idle" is for the temp you are at vs. what the current idle speed is in the scanner under VCM Controls.

onetype

iTrader: (6)

I had the same issue, spent a few days cheaking for vacuum leaks. Ended up plugging the .150 hole in my TB butterfly and no more high idle/rev hang.

hoopty

The "IAC motor" the idle air control motor is what controls your idle speed. It is mounted on the throttle body towards the top on the drivers side. It is held on with 2 screws. It has a plunger that moves in and out to open or close off a small passage to alow air into your engine at an idle to control the idle speed. I used to work at a GM dealership as a mechanic. We would use a Tech 2 scan tool to check to see how far open the IAC was at an Idle. If the IAC was totally shut and the car was idleing to fast it would tell us that it had a vacumme leak. The scan tool would also alow us to over ride and open and close the IAC to see if it responded to the command. I would remove and inspect the IAC motor and the check it's position and operation with the proper scan tool. I hope this helps.

ryeguy2006a

iTrader: (27)

Thanks Hoopty. Do you know if you can use HP Tuners to check the IAC position?

gofastwclass

iTrader: (2)

Yes, HP Tuners can monitor the IAC position.

ls1nova71

iTrader: (4)

If the engine ran fine in the donor car, and you didnt change much in the tune, then my guess is it's going to be a vacuum leak. Did you have the intake or throttle body off for any reason? There are only a couple of vacuum ports on an LS1 intake, the big one on the back for the power brakes is hard to miss, but there is also one that is smaller that provided vacuum for the HVAC system, make sure it isn't open. Also, check that plug you put in the EGR opening, if it doesn't fit well it could be causing a vacuum leak.

ryeguy2006a

iTrader: (27)

LS1Nova, thanks for the tips. I did have the intake off in order to clean all of the grease and grime off the car. I actually did what you mentioned and sprayed all of the vacuum ports with starter fluid, and it didn't raise the idle at all. I took off the IAC last night and cleaned everything and reinstalled. I also took the throttle body off and pointed it towards the driver while turning on the key. I verified that it was working and moving back and forth. I am unsure what the position should be at start. It was slightly cracked allowing more air to the car.

When I was doing this all, I remembered what onetype said about the hole in the throttle body blade. So, just to test it out I put a piece of tape over the hole, and it worked! The idle went down to around 850 where it should be. Although it worked, I don't think that it is the right solution. The car in the donor had no idle issues and I am thinking that it is a tune issue at this point. The only thing that I can think of is that because I am running no filter currently and 1 7/8" long tube headers, the MAF calibration needs to be adjusted since it is flowing much more air. Can any one verify that?

gofastwclass

iTrader: (2)

Some throttle bodies have a rubber plug in the throttle body hole, others don't. I'm not sure if any F-Bodies did but I have seen them on a lot of trucks.

I'm sure you could leave the hole open and tune around it but maybe the plug was accidentally knocked out during the swap which is causing your grief.