sore

I have a 09 Pontiac G8GT with the 6.0. I've had it for over 2 years and its ran great. Only mods are headers, full exhaust and KN cold air intake. All of a sudden it started throwing codes...so now the car has been sitting up now for 3 months cause i can't seem to figure out the problem.

At idle it surge, and while driving it will periodically hesitation when accelerating and when just cursing at constant speed. I do notice a few things.

When i turn the key on, the IAT will read -13 degrees. After the car runs for 10 or so minutes it will read the correct temp.

When idling, the stft will seem fine (+/_) 5%, but then all of a sudden they will jump high sometimes lean, sometimes rich 25%

Also when driving and i notice hesitation, i notice the STFT are either 25-27% positive or negative. Both banks seem to be consistent..

So far i have changed..


MAF
Throttle Body
O2's
Tested a different map sensor
Intake gaskets
TB gasket

Is there possible grounds that i could check? Could the tune just screw up?

thanks!

Jeff

Darth_V8r

iTrader: (4)

Almost sounds like it might be a bad ECM

sore

Any good sites to buy one from or should i just go to the dealer and pay top dollar?

Darth_V8r

iTrader: (4)

I do t know if I would buy a brand new ECM just to test a fix. Maybe grab one from a junk yard.

Nicelysedate

iTrader: (3)

Can you log your O2 voltages? See if your STFT jumping around horribly agrees with your O2's. Could be an exhaust leak somewhere letting fresh air in near your O2's.

And what codes is it throwing?

sore

The codes have been all over but now after changing the throttle body, i've gone into limp mode frequently, and had codes

P0507 - Idle air control system revolutions per minute higher than expected
and a rich code, i don't remember the number.

I'm thinking i'll need to buy the HP Tuner software and learn how to use it..I don' have a way of seeing the voltages..but if both o2's seem to be reading consistent, i wouldn't think its an exhaust leak, right?

when all of this first started i was getting the following
P0101 - Mass or volume air flow circuit Range/Performance
P0106 - MAP Baro Sensor Range/Performance
P0121 - Throttle/Pedal Position sensor A Circuit Range/Performance
P1133 -Ho2 Insufficient switching Bank 1 Sensor 1
P1153- Ho2 Insufficient switching Bank 2 Sensor 1
P0068 - MAP/MAF - Throttle position Correlation

sore

Wait...i think i can log live data with the handheld Innova Scanner that i have. I'll check it out tomorrow and compare O2's to the STFT.

Nicelysedate

iTrader: (3)

Log your throttle position sensor too. I would also check your fuel pressure at the rail and check for vacuum leaks. You might have inadvertently caused more problems trying to solve your original problem (ie. caused to vacuum leak when swapping gaskets).

sore

Check out the video i posted. I'm uploading another one now. This is a cold start. I didn't touch the throttle the entire time. You can see the o2's and stft in the video. This is the car trying to idle on its own until it died. I know i need to get a better means to data log, but this is what i have at the moments..Check it out.

sore

Here's the video when i restarted it.

Nicelysedate

iTrader: (3)

Check your plugs and wires. Your O2's are switching like they are supposed to. Does your stft drop to below 5% when it's warmed up?

sore

I've changed the pulgs., not wires though. When its warmed up it will go to -25 % and ive seen it go to +25% or higher.

Nicelysedate

iTrader: (3)

In the video it sounds like your car is fighting a vacuum leak. That's my best guess without seeing a log.

Your STFT's pulling that much gas out or adding that much gas makes me think its not measuring air mass correctly or getting unmeasured air. You can see on the scanner where both O2's are reading a rich condition and your STFT's go negative in response.

This problem started suddenly correct? Not after any type of modification?

sore

Yes it just suddenly started. I didn't do any modifications. Where are common locations for vacuum leaks.

Intake
Throttle Body
Vacuum tube that goes from passenger side of throttle body to PCV (drivers side head near firewall)

I just don't see where else it could be coming from. Could it be a bad ground?

I did have someone data log it with HPT but that was before i changed the TB. i'll see if they can email it to me.

Nicelysedate

iTrader: (3)

You can rule out the vacuum line going to the pcv tube by disconnecting it and putting a finger over it and see if anything changes. You can also try spraying starting fluid around the throttle body and manifold whiles it running and see if your fuel trims spike suddenly.

On a newer car I doubt it's a ground. Grounds usually go bad from corrosion.

Try disconnecting the battery for an hour and reconnecting it. It will clear all your trims and might help.

LilJayV10

iTrader: (39)

Do you have cat's and/or 02 extensions?

LilJayV10

iTrader: (39)

1. If it was a vacuum leak his trims would be positive not negative and his 02 voltage wouldn't be rich.

2. That's not correct.

3. Edited, yes it will clear the trims but it's not going to help his problem.

LilJayV10

iTrader: (39)

If your STFT's are swinging that much it will definitely feel it. If your shorts are +25 I'm going to take a guess and say the longs are + too.

Look at the LTFT, it will give you a better idea of what's been going on with the car not just at the moment w/ STFT.

Check to see what your LTFT are at idle, 1500rpm, 2k and 2500.

That will give us a direction to go in.

By the videos you posted it's getting way too much fuel and the PCM is pulling the injectors back trying to get some of the fuel out of it.

It "could be", I know you've replaced some of these parts. I'm going off if I was looking at the car for the first time.

1. MAF
2. bad injector(but both sides seem to be about the same so I'm not sure on that one w/o further diag
3. clogged cats
4. bad/leaky MAP
5. bad 02 grounds, melted 02 extensions or water intrusion into the connectors.

At one point an 02 sensor showed over a volt. The only time I've ever seen an 02 read over a volt is a bad/damaged 02 ground and water intrusion into an 02 extension connector.

If the ground is bad/weak/damaged the voltage will be higher than it should be, that goes for any circuit because the ground isn't strong enough to pull the voltage back down.

Nicelysedate

iTrader: (3)

The video show his O2 voltage switching on both banks pretty much together.

There is a point where you can see the maf measurement and it's moving.

Bad injectors would have to be one on each bank.

O2 extensions or ground problems usually prevent the O2 from cycling and lock it in at a voltage.

Clogged cats is a possibility.

Nicelysedate

iTrader: (3)

After watching the second video again it show your spark advance going down to zero. Spark is all over the place it looks like.