RockinWs6

O2 WS6 all stock, I bought it used with 40k on it. Car runs great BUT it runs a little on the rich side all the time. If I start it cold you can smell the exhaust is rich, once warmed up the exhaust has a constant sulfur smell to it. Sometimes strong sometimes just slight. The engine oil doesn't smell or look washed down BUT if you pull the oil cap off you can smell strong fuel smell in the cap.

Car has 47k on it and is all stock, what seems to happen is after a few 100 miles of normal driving the engine carbons up and starts to knock and ping at part throttle only.WOT its quiet and runs nice. If I add Lucas upper cylinder lube to the fuel and run its hard the knocking goes away and it quiet for a bit.

The car has fantastic power and doesn't miss a beat, no black smoke out the exhaust cold or hot start. I checked the fuel trims and everything was 0 except the driver side stft at idle was at 3%, as soon as you give it gas or drive it goes to 0.

I'm an experienced mechanic and usually know where to start but I just can't find anything wrong that's obvious. Intake is tight and no codes come up. PCV system is good and pulls good vacuum on the engine. No oil in the pcv system either, Its nice and clean. I've owned and driven quite a few LS1 cars over the years and this the quickest nastiest one I ever drove that was stock.


Someone shoot me some ideas, thanks

chopperb

iTrader: (1)

sounds like a clogged cat to me. Check the fuel pressure also.

RockinWs6

Fuel pressure is good, cats are clear...it runs like a raped ape.

Maxito628

I hate to suggest such a simple fix, but try seafoaming your engine. I did have a smell like that coming from my car a while back as well, even though it came at about 100k miles. Find the brake booster vacuum line and pour about 1/3 can into your engine and then let it stall. Let it sit for about 10min then take that girl on a hard run. Should see the culprit of the problem flying out your tailpipes as the residents of earth frown upon your great pollution.

RockinWs6

Thanks for the suggestion but I wouldn't put seafoam in your tank....IMO it can cause more troubles than it solves.

RPM WS6

iTrader: (3)

Has the MAF been cleaned?

I disagree. A clogged cat would cause more problems at WOT, not get better at WOT (in fact, once clogged, the engine may not even be able to reach high rpms under WOT).

RockinWs6

Yes the car had a K&N filter in it, 1st thing I did was clean the maf and all the dirt and K&N oil that was on throttle plate. I'm sure I found the problem after posting in the PCM section. I'm sure I have a injector on the pass side leaking a little. LTFTs are -8 on that side. Running some injector cleaner through it and see if it helps. If not i'm going to test each injector for leakage with my scanner and go from there.

I found a good test while looking online for checking injector leakage. Basicly you get the engine hot into closed look and watch the fuel trims, then one at a time pull the injector plug off. This will cause the PCM to add fuel and you will see the fuel trims change. You compare the change on each one and should be able to find the leaker. Example if you pull injector plug no1 off and it rises +10 and all the others rise +15 when you pull the plugs off, you know no1 is leaking some because the PCM didn't add as much fuel.


The fuel trim is only high at idle, driving its good.

Car runs fantastic! I'm talking really nice, I suspect its been tuned by someone before. It is all stock as far as I know.

lt1pwr1

iTrader: (1)

I would also take a look at the fuel pressure regulator. Those are pretty common to leak (on many GM cars).

RockinWs6

Its pulling fuel, not adding fuel. Pressure is good.

garygnu

MAF,O2 sensor,fuel regulator.you can test and data log O2 sensors.check Utube to learn about O2 sensors.

lt1pwr1

iTrader: (1)

Umm, you said it is running on the rich side. That would be burning excess fuel. The computer would be pulling fuel to compensate for running rich.

You have a scanner right? Can you read the coolant temp sensor reading? If that is reading too cold it will dump fuel.