ele-blue95

iTrader: (10)

I have a 99 with a 408ci. its has a ls2 ported 90mm TB. 6-speed. Car was running great. Made a 3 hour drive to FL last night mostly interstate. Once I got into town the car acted like it wanted to drive itself. with foot off the gas the car is revving between 1500-2500 rpms and as high as 3500 rpms. It threw a (reduced power )when it happened. But the only code i have is a P0507 & P0151. but im sure i remember a p1516 before i cleared the codes. the only work ive done to the car as of late was a Fast 102mm intake... Could it be a vacuum leak from the long drive? I would think if it was a vacuum leak the idle would be constant, not a up and down on its own.

Any help would be great, as im only here for 3 days for a wedding.

Eric

ele-blue95

iTrader: (10)

OK...So i pulled the Fast 102 intake off and cleaned the TB...took the whole intake apart and resealed the whole thing, new o-rings on the injectors. put the car back together, and i can hear the leak from the driverside very well....but its still there and there are no codes at all this time. what is going to be the best way to figure this out....im running out of time to play with this thing.

Thanks, Eric

ele-blue95

iTrader: (10)

well ive taken the intake back off...made room where the ARP head bolts were hitting. took the guide pins out (incase they where to long) and reflashed the tune. Its running better, but the car still wont idle steady (jumps around like i have a really big cam).

feeder82

Try this C5 Idle Relearn Procedure
Purpose
This page basically shows you step by step how to do an Idle Relearn. You would want to do this if you have done any intake modifications. If you do not do this, you may have hesitation or other issues.
Tools Required
None.
Do the Job
Follow these procedures EXACTLY or you will have to start from scratch.
1. Insert key into ignition and turn to the "On" position but, DO NOT START THE ENGINE.
2. Pop open the engine fuse block box cover and remove the two 10amp fuses from position numbers 16 & 23.
3. Your DIC will now display "check" messages for ABS, etc...
4. Turn ignition to the "Off" position.
5. Re-insert both 10amp fuses for positions 16 & 23.
6. Start your engine
7. Allow engine coolant temperature to reach a minimum of 176 degrees F and run at this minimum temperature for at least 5 minutes.
8. Shut down engine
9. Let rest for a minimum of 30 seconds.
10. Restart engine - check for DIC error codes (there should be none).
11. Drive car for a minimum of 30 miles at varying rpm settings and speeds. PCM will now re-learn and adjust for the new air flow and air temperature at the intake.

slammedc5

iTrader: (1)

If you can hear the leak. That's no doubt the problem. Go back to the basics. The vacuum fitting in the back of the manifold.
Did you change the valley pan bolts to round headed low profile bolts? The intake will never seal with stock pan bolts. Some guys even crack their intake.
Did you use an ls2 water pump or grind down the front of the manifold? Double check that as well. Post your findings please. I'm curious.

ele-blue95

iTrader: (10)

I have cleaned the MAF, i did grind the water pump, changed plugs and wires, the valley bolts are the button head bolts and i have checked the lines at the back of the intake. Today i swapped the stock intake back out. cant hear the leak at all, but the car still wants to idle high when driving.....as i come up to a stop sign or light and put the clutch in, the car idles 1900 rpm and slowly drops to 1000 rpm....it does this even shifting all gears. I also did the idle re-learn and nothing different. the car runs strong, just need to figure out whats up with the idle thing.

35th SS

iTrader: (2)

check what those codes are before you cleared them and start from there.all else fail swap your pcm.

gregX10A

did you ever figure out the problem? im having the same issue with my ls swap on my 89 firebird. it wants to drive itself up to 30mph and drive down the road on its own

dreww

iTrader: (1)

I had a similar problem on my 2002 c5.
When I got the car, it had cel on but didn't surge. Eventually it started, and I learned the vararam was causing the issue.
had a full dyno tune and it fixed the problem. Its not drive by wire, so can't really adjust anything

one fast zo6

iTrader: (490)

good info