mikespeed95

iTrader: (1)

Hey guys,
Let some friends use the shop, and am a bit confused.

They have a LS6 z06 they put TSP Longtubes/Xpipe on, has intake and exhaust already, and subsequently it runs like poop.

Runs fine at WOT, but breaks up a bit at partial throttle and gets a misfire code. Put new plugs/wires on recently (has 100k) and I haven't really had time to help them and am a tad confused by what they coulda done. I helped them a little bit, mainly removing the manifolds and putting the headers in for them, they did all the plug/wire/02 stuff and I haven't had a chance to look over their shoulder yet on it.

Anways, is it possible it just needs a tune with no Cats/longtubes?

This may sound odd/arrogant, but I've never messed with a modded LS1 that was this simple. Normally whatever I'm playing with winds up on the dyno right off the bat. My logic says tell him to replace his o2's but again I may be ignorant to a normalcy of time to get a tune on these.

mikespeed95

iTrader: (1)

Correction, its a 2002.

That whole not having time to help look into it thing...yeah.

Higgs Boson

iTrader: (3)

for sure, it's probably pretty lean and the o2 sensors aren't working properly and need to be tuned themselves in the longtubes. outside an improper installation of course.

kenp

iTrader: (9)

Headers aren't going to cause a misfire. Something else is wrong. If you plug the front O2 sensors in wrong the car will idle very poorly. I believe the passenger side sensor plugs in on the driver side and the driver side sensor plugs in on the passenger side. Check that first & then move on to wires & plugs.

mikespeed95

iTrader: (1)

Which o2 sensors was he suppost to plug in?

Only had provisions for 2/4 o2, with removal of cats I would assume the pre-cat would be the one you want, and omit the post cat, since there isn't a cat.

Haven't had a chance to check which one he actually plugged in...

nandos_z28

iTrader: (5)

The rear sensors are deleted but I believe what Kenp was trying to say (which I agree with) is they have the front sensors connected backwards. Have them swap the connections and I'm almost positive that will fix the issues.

mikespeed95

iTrader: (1)

Alright cool, so tell him to run the front o2's, and make sure the drivers side harness plug goes to the pass side o2, and vice versa?

Thanks again for the help, I feel really kinda dumb but this is the simplest LS1 I've ever messed with and every time I used to play with these in the past we had a dyno and all kinds of pimpy diagnostic stuff to tell us what was angry at my disposal.

nandos_z28

iTrader: (5)

Yeah well I'm not exactly sure which o2 sensor gets plugged into which side but based on Kenp's advice that would seem correct. Just have him reverse them from how they are connected right now, then start the car and let it switch into closed loop and see if runs right.

And I don't know if you guys have access to tuning software or a handheld but the car is going to throw codes with rear o2's deleted until you turn the codes off. Or you can by o2 simulators which plug in where the rear o2's used to.

prochargedpony

iTrader: (6)

I just dealt with this exact issue on my ws6, he most likely cracked a spark plug. Mine ran like crap threw that code, I checked and poof number one plug was cracked.

mikespeed95

iTrader: (1)

That was my initial suspicion but he's replaced them. I can't remember when I had them pull the plugs out so they wouldn't get banged on, but I thought that, and also we were using 7 year old wires that have been sitting for 3 years off my racecar, and ruled that out by putting some new ones on.


So its gonna run like poop till we convince the PCM to omit the o2 or get simulators?

nandos_z28

iTrader: (5)

I don't think the rear O2's have much effect on the tune, More than anything, they are there to monitor the cats and ensure they are working right.
it'll just throw a code.

Once you reverse the front O2 connections the car should run better.

BLK02WS6

iTrader: (2)

And you are sure they didn't drop a plug or anything? Sounds like a cracked plug to me too...

Rear O2 sensors have no effect... unplug the fronts and see if it does it in open loop - if it does, then it isn't O2 related at all...

Slowhawk

iTrader: (12)

It is possible the 02's are switched side/side. Just make sure the driver side is plugged into the driver side harness ect.

jimmyblue

iTrader: (11)

Could be simple mistrimming from cold O2s. Headers ought
not to bother anything at idle as far as the open loop tune.

2xLS1

iTrader: (25)

Just look at the fuel trims. If one side is +25 and the other side is -25, the front O2 sensors are switched L&R. It happens a lot of Vette header installs because prople use the rear O2s with the longer length for fronts and because of the angle the rears thread into the stock exhaust, GM swapped the sides they plug into.

joecar

+1

opposite pegging LTFT's is a sign of crossed connectors.

kenp

iTrader: (9)

Correction: The front 02s do not cross over. The passenger 02 plugs in on the passenger side and the driver 02 plugs in on the driver side. It's the rear 02s that cross over on the Corvette.

I'd start with trouble-shooting plugs & wires. If you don't get the wire fully seated on the coil or plug it will cause issues.