Black Spark Plugs / Stalls in a few secs

[Diablo4]

Originally Posted by ABM2SS

I had a similar issue on my son's '91 Firebird V6. It would fire-up and run great until it went into closed loop. Then it would run very rich to point of stalling-out on cold days. After much investigation, O2 sensor replacement, and other BS; it turned out that the O2 Sensor wire was bad, but not broken. Just had high resistance which confused the ECM, so it would try to compensate by adding fuel.

I just added a detailed reply just above, there was also a matter with the wire. Could you please let me know your oppinion ? My cats are deleted and downstream O2s are disabled

[Diablo4]

Originally Posted by FasNuf

See if a local autoparts store will lend you a scanner to plug in. Most lend tools on a deposit. Buying genuine o2 sensors aren't cheap so why not try to diagnose a little more for free? If you do decide to just try replacing the O2's, like Joe said, get the good O2 sensors, and stay away from Amazon or Ebay because there's tons of AC Delco counterfeits out there.

I always buy spare parts at rockauto and very rarely at ebay. some things are not on the rockauto, for example the washer behind the harmonic balancer on the crankshaft

I added a detailed reply just above, could you please write your opinion ))

[morepowerjoe]

Why do you have downstream o2's with your cats being removed? In my case I don't have cats either so my downstream o2 sensors are turned off in my tune.

[FasNuf]

^^^^This.
I don't have cats and my secondary O2's arent even plugged in and the ECM can't even report about them. The fuel trims look normal otherwise. I'd start to question something mechanical allowing enough oil into the combustion chamber to coke the plug but not saturate them.

[SlowLS1]

Originally Posted by FasNuf

^^^^This.
I don't have cats and my secondary O2's arent even plugged in and the ECM can't even report about them. The fuel trims look normal otherwise. I'd start to question something mechanical allowing enough oil into the combustion chamber to coke the plug but not saturate them.

I was hesitant to say this earlier because it would be a somewhat rare occurrence, but I have personally had an oil burning ls1 and his plugs looked like mine. OP didn’t mention oil consumption, but it would be notable with the way the plugs look. The small bits of white ash is very similar to what I experienced.

OP, do you have notable oil consumption between oil changes?

[FasNuf]

[QUOTE=Diablo4;11413029]Ok, i've checked something again.

Idling 530 rpm
Short fuel trim: it varies from -0,8% to -3,2%. Long trim -6.3%
Upstream O2s voltage varies from 0,10 to 0,8V.
Intake pressure 4,06 psi (0,28 bar)
Fuel pressure 57,4 psi (3,96 bar)
MAF readings varies 5,2 gramm/sec to 5,5 gramm/sec. I have the second spare one Delphi and the readings were the same.

So it seems you're saying these fuel trims are from idle. What are they at cruising? It could easily be different if the tune is off. I'm still leaning towards oil in the intake though.

[Diablo4]

Originally Posted by morepowerjoe

Why do you have downstream o2's with your cats being removed? In my case I don't have cats either so my downstream o2 sensors are turned off in my tune.

I also don’t understand why the previous owner, for example, left the rear sensors heated.

I will try to disconnect them physically and check for fuel trims again

[Diablo4]

[QUOTE=FasNuf;11413110]

Originally Posted by Diablo4

Ok, i've checked something again.

Idling 530 rpm
Short fuel trim: it varies from -0,8% to -3,2%. Long trim -6.3%
Upstream O2s voltage varies from 0,10 to 0,8V.
Intake pressure 4,06 psi (0,28 bar)
Fuel pressure 57,4 psi (3,96 bar)
MAF readings varies 5,2 gramm/sec to 5,5 gramm/sec. I have the second spare one Delphi and the readings were the same.

So it seems you're saying these fuel trims are from idle. What are they at cruising? It could easily be different if the tune is off. I'm still leaning towards oil in the intake though.

No, there is no oil consumption, about 0.2-0.3 lbs at 3000 miles and I change the oil at 3000 miles.

Spark plug was mate carbon-growth but it's not an oil, I am sure.

What are they at cruising? - I'll check it

[morepowerjoe]

Originally Posted by Diablo4

I also don’t understand why the previous owner, for example, left the rear sensors heated.

I will try to disconnect them physically and check for fuel trims again

Do you have a check engine light for your downstream o2's?

[Diablo4]

Originally Posted by morepowerjoe

Do you have a check engine light for your downstream o2's?

No No. No CELs.

2 codes P0430 and P0054 in the ECU but no CELs.

[morepowerjoe]

If your getting those codes that means that your downstream o2 sensors are still turned on in your tune and probably need to be turned off with hp tuners.

[FasNuf]

Originally Posted by morepowerjoe

If your getting those codes that means that your downstream o2 sensors are still turned on in your tune and probably need to be turned off with hp tuners.

It doesnt matter, because the downstream O2 sensors dont affect fueling.

They tell the ECU wether the cats are making a change from when the primary sensors control fueling to after the cats process the exhaust. He's getting the code because that portion of the tune wasn't turned off only the CEL.
.
.
.
.
.
.

[morepowerjoe]

How are you checking your fuel trims? HP Tuners?