Gearhead-GM

Hey Guys,

I'm new to this forum but I posted some info in the fuel section due to a repair of a buddies vent solenoid in his 1999 3.8 V6 Camaro.

"Fuel Tank Not Accepting Gas" Thread

I have a new issue that I have never seen in a GM.

The ignition timing gets mysteriously advanced for no reason once the engine warms up. It was running great and then as I was driving it the timing jumped like 12 deg advanced and stayed (I actually watched it happen on the EFILive dashboard). Then it starts running like crap and missing and pinging as the knock retard shots up to like 15 deg!!!!!

He mentioned it to me when he gave me the car ( I drove it when it was already warmand noticed the occasional missfire) but I just thought it was a tired V6. It actually had some good power when it was cold after the vent solenoid repair.

Cold before issue 9deg advance at 795 rpm



This is idling with over 23deg timing



In this shot the car is in neutral and revved up
39deg! at 2300 rpm NO LOAD



Any ideas ???
Crank sensor?
Cam sensor?
Does the 3.8 have an ignition module or is it in the coil packs?

SweetS10V8

iTrader: (4)

LS3s run 50 degrees of timing free reving them, i dont think thats a big deal.

Your timing is retarding if its going from 30 to 15. False knock? What have you checked?

Gearhead-GM

50 deg. sounds like alot for any engine, but maybe with no load, i guess.

The timing went from 9 deg advance at idle to 23.5 deg at idle, it is definately advancing the timing alot. The knock is not false it sounds like a hammer on the block when it does it (it's loud) and the car runs like crap and looses like 30% power as the timing is jumping all over the place (knock retard up to 15 deg).

I drove it to my office this morining to return it to my buddy, and it wnet like 15 - 20 miles of city and highway driving and then it started doing it. It was long after the engine had gotten up to operating temp.

BTW - you can actually fill the fuel tank now!

SSpdDmon

iTrader: (10)

A4 LS1 cars idle around 28* when warm. M6 LS1 cars will idle around 18~22* IIRC. What happens is...on cold starts, timing is pulled and other tables compensate to help the catalytic converter(s) warm up faster. Once the car gets up in it's operating temp range, the idle timing is restored to normal. That's why you see timing shoot up to 23*. If you pull down the tune and look at the timing map, you'll see the low load timing is higher than the rest of the table. This is the same prinicple as an oldschool distributor with a vacuum advance. When load is low, vacuum is high. LS1s from the factory can command 38~42* of timing IIRC depending on the RPM and load (load being measured as grams per cylinder in the timing map).

If your friend's car is relatively stock, the stock timing map should be fine. I'd look elsewhere for your source of pinging, missing, and knock retard. What do the fuel trims show? Are they pulling fuel when they shouldn't be? Did something get in his gas tank (bad gas, sugar, etc.)? Might be something mechanically deffective...knock sensors, dirty MAF, etc.

Gearhead-GM

The car is stock and I have not modified any tables (haven't even locked his VIN to my OBD cable). This apparent shift in timing is long after it "warms up" It occured about 10-15 miles after the engine was up to operating temp.

The weird part is that it drives great and has plenty of power before it happens.
I definately agree it some kind of mechanical or electrical fault. Not a tuning issue, has anyone seen a crank sensor do weird things like this. may not even be the same style for a V6.

Thanks for the input!