LSCha0s

iTrader: (4)

This is an LS swap in a 91 Corvette.
specs:

built/forged 5.3 347 iron block with 241 heads

MS3 cam
237/242, .603"/.609", 113 LSA

LS6 Intake


Wiring harness and PCM from a 99 Z28

The veh goes in and out of open loop at idle and the KPA is in the 90s all the time. I have checked the wiring multiple times and its all good. I'm running only 2 02 the front and the others have been deleted in the tune.

85MikeTPI

iTrader: (9)

Have you checked for Vacuum leaks? Does the KPA@idle change if you increase the idle RPM ? Are the heated O2 sensors getting good power to the heaters?

LSCha0s

iTrader: (4)

The 02s should be getting good power we had the wideband hooked up to the same fuse block as the 02s and it never failed. I think this may be 2 different problems. Would a vacuum leak also effect the veh staying in closed loop. My brakes are also hard so I could have a Vacuum leak at the booster. There is only a few possibilities here ..intake gasket, cracked intake or brake booster/line. There are not many vacuum lines on the LS. I have not checked for vacuum leaks yet. I need to replace my Valve springs first and will be doing that on Friday. I don't know if you saw my other thread but while we were tuning I broke a spring. It looks like the PO/builder only used one spring of a dual spring kit and I am replacing them all.

85MikeTPI

iTrader: (9)

I doubt the MAP/vacuum would affect closed loop, mostly O2 swing and coolant temp. Do you have the coolant sensor hooked up? Have you put a scan tool on the PCM to verify the sensor data? The O2s will function somewhat without heaters and give symptoms like you describe, probably wouldn't hurt to verify the O2 heaters are getting good power and grounds.


Since you replaced the factory brake booster vacuum inlet, have you vacuum tested it?

LSCha0s

iTrader: (4)

Ok, thanks mike you are always a big help. I will start some diag as soon as I get the springs in.

LSCha0s

iTrader: (4)

I found my leak. I was looking for cracks on the backside of the intake and found a nipple that I did not know existed.. I feel like an idiot.

85MikeTPI

iTrader: (9)

Good deal.. Don't beat yourself up, I'm sure it happened to many. I notice my LS3 intake has a nipple there too, but it's factory sealed until needed.. Hopefully that will fix the open loop issue too, but I'm a pessimist by nature...

LSCha0s

iTrader: (4)

the guys over at HP Tuners forum said a big vac leak can cause both problems. I'm crossing fingers toes and the rest right now is not a good time for extra expenses. Thanks for your help mike.

LS1MCSS

iTrader: (18)

Well, don't feel bad. You're not the first one to miss that nipple and won't be the last.

LSCha0s

iTrader: (4)

Thanks, I have new springs in it now and I'm waiting for the tuner to come over and flash me back to where I was before he tried to tune it with a vac leak. I'm afraid it will be way off if I fire it up now.