Service Engine Light

**SSNAKEATER23** · 03-15-2014, 05:15 PM

Hi guys,

I have a 99 SS, 114k miles, stock LS1. No upgrades to the motor. The weather here in Chicago has been hell, but was warmer lately. I went to take my car for a spin, and the service engine light popped on. The car had a little bit of a knock but went away and there was a little bit of white smoke from the exhaust but that too went away pretty quickly. And the white smoke isnt consistantly happening. The exhaust sometimes smells funky, I dont think its sweet. I checked the oil it looks ok, but I.took of my oil cap and it had a milky white residue under it.

My low coolant light was on but I wasnt leaking at all on the ground. Its since stayed off its been 3 days. I have 3 codes...P0307, P0405, P0102. The first code is the most alarming #7 misfire. I have been reading up here and I havent changed the plugs, wires, injectors, or coil packs. I have no power loss, but im afraid it may be a head gasket. There is a strange hissing coming from the front of the engine as well. Im at a total loss, since im not over heating, and my temp is normal. Any thoughts or help would be great thanks!

**pajeff02** · 03-15-2014, 05:19 PM

Check where the EGR attaches to the intake -- sounds like you may have a gasket leaking there. That could cause all of the issues you have described.

**SSNAKEATER23** · 03-15-2014, 05:28 PM

Could that be the hissing sound im hearing? Is it easy to get to the EGR?

**pajeff02** · 03-15-2014, 05:31 PM

The EGR itself is located on the front passenger side of the engine, and the tube I am referring to goes right into the top of the intake just behind the throttle body.

**SSNAKEATER23** · 03-15-2014, 05:43 PM

Im going out to the garage now, ill update when I get back in. Fingers crossed.

**SSNAKEATER23** · 03-15-2014, 05:53 PM

Ok I found it thanks!! But when I started the car it sounds like a knocking, but it went away. Im ready to puke on myself

**pajeff02** · 03-16-2014, 11:16 AM

The milky white residue under the oil cap is not uncommon. Both our Trans Am and Suburban exhibit that to some degree and is simply the result of moisture in the engine - could be from short cycling and not warming up all the way. White smoke out the back is normal with the engine not fully warmed up, especially in cooler temps. It should go away though after the engine and exhaust system are fully up to temp. If it is antifreeze, then it will stay white and you'll smell it.

The knock... well, that might be another issue and you may need to do some diagnostic work on that one. Let us know what you find.

**Too Fast** · 03-16-2014, 11:24 AM

Yes our oil caps are located in one of the coolest parts of the engine, and the (normal) water vapor there can mix with the (normal) oil fumes internal to the engine and condense there. I don't think you have to worry about any head gasket engine.

And you know our engines have some piston slap, especially when cold, and that may be your knocking sound since it goes away when warm.

Is your hissing sound your air pump? It only comes on usually after a cold start.

**pajeff02** · 03-16-2014, 01:38 PM

That's a possibility - but with the codes he posted the EGR makes the most sense. He said he "found it" but not sure if he checked it for a leak yet.

**Too Fast** · 03-18-2014, 02:42 AM

Wondering what OP found. I found some stuff in my garage yesterday, and it wasn't good.

**pajeff02** · 03-18-2014, 08:27 AM

And what did you happen upon?

**Too Fast** · 03-18-2014, 02:34 PM

The usual after winter sludge fest. Our garage is at the bottom of a slight slope, so when we get heavy rainfall, over about an inch in about 2 hours, rain flows in. The quick snowmelt with rain does the same. I've thought for years to make a drain just before the entrance, but that's all I've done lol.

Wonder what's happened to Ssnakeater?