: engine stumble at red light after highway run



ponyboyt
11-05-10, 09:33 AM
98 STS; 120,000km on car, ~35,000 on engine (new from dealer)

short trip @ 110km/h. Lots of throttle on the onramp, cruise @ 110km/h. about 8 km trip to offramp. Came to red light, sitting still engine is stumbling, car shaking. Put in neutral and touch the gas, feels like it might stall. Back in drive, pull ahead and its stumbling. Feels like a stuck EGR... i snap the pedal to about 25% and it free's up, lurches forward and i see a huge cloud of blue smoke behind the car. The remaining 6 km to home (50km/h-70km/h) are uneventful.

I get home and check a couple things. PCV seems ok, PCV hose seems a bit hard to blow through, so i swap it with one that seems easier to blow through. (Edit: there really wasnt much difference between the 2 hoses, one just seemed easier than the other)

NO CODES

I still keep thinking EGR, but why would it smoke? Seems like something got clogged and then released whatever was clogging (oil??) and burned it up and was done puking after that.

Whatever caused that stumble, is probably what is causing my oil consumption. But i cant think of any reason why a bad EGR would cause oil consumption.

Edit 2:

Hummm. Hot topic at the shop today :)

Theory: Stuck or dirty EGR causing lean condition. Hot spots in the engine? Burning off oil, hot spots under valve covers or in crank case, smoke gets fed through PCV system = =oil consumption. (oil consumption started VERY suddenly. My first oil change to my next, the oil only went down one notch on the stick in 4500km. A week after i changed the oil ~700km i had to add a litre and a half.

This tells me something BROKE, not normal wear down of parts). If i plug the PCV hole in the valve cover and take off hte oil cap, run the car warm, its quite smokey at the oil filler cap. Smoke is a bit greyish in color. Its not blowing out like a mushroom cloud, its a slow, consistant, light flow, like you would see coming out an idling car's exhaust on a cold day. With the PCV in place and the oil cap off, it smokes a bit, add a bit of throttle and it stops, i imagine because that smoke is getting sucked up the PCV with the added RPM's.

Other than oil consumption, the car runs great. Ive had a few hard starts (warm and cold), i'd say maybe 6 times in the last month. Ive noticed a bit of power loss, (this car used to break traction when you floor it at 40km/h, to the point traction control would kick in. It doesnt do that any more, but still pulls like hell.. maybe my tires are just worn a bit) but that could be due to bad plugs as they are quite corroded (and oil in the threads). Not sure why it would be due for plugs at 35,000km. They are delco plugs, then again the car sat and did not run for a year. MPG around town is very yucky, but im a bit hard on the throttle. Highway MPG is great, it at least matches or is better than any of my other northstar cars.