Oil Consumption Questions

[burijon]

I think there is a consensus that the 3.5 Liter motor is thirstier than most engines. That being said let me explain my symptoms and have some of you give me your best answer.

I have the exact same issue as LittleHoov
http://www.automotiveforums.com/vbul...d.php?t=767948
We both have oil in the top left cylinder when facing the car looking at the motor.

If the valve cover is leaky and oil is coming into the spark plug area, does that oil leak past the threads onto the piston causing excessive burning?

If the above question is true would it blow out the tailpipe as black smoke?

Would it by itself cause excessive consumption having to add a quart every week?

If the above is not true, am I looking at a rebuild?

I have a hard time believing the "oil rings" theory building up gunk. At least with the way I drive it the rings should be sparkling clean if that is true.

I have noticed the oil consumption around 40k. It now has 125K. I still get great gas mileage(28+highway) and it idles smoothly and has plenty of power(for a V6) and starts quickly(clean throttle body always). Plumes of black smoke come out on anything harder than moderate acceleration.

I have put in 20w-50 as a test. It takes a whole lot longer to burn if it burned at all. The engine didn't rev at all and was very very sluggish. I hated it so switched back to 5w-30 after about 1500 painful miles.

Somebody give me some practical ideas/insights and some tests if possible.

The car isn't worth anything to anyone else. I have had it since 13,500 miles.

[LittleHoov]

The 3.5 does actually consume/burn some oil as part of NORMAL operation. The cylinder walls of the 3.5 are more porous than most engines, the same is true of the Northstar engines, the reason is to allow more oil to "stick" on the walls longer provide better lubrication needed for higher revving engines, some oil gets burned in the process.

I still have yet to tear into those valve cover gaskets, the parts are sitting on the shelf, but ive been waiting for better weather as I have to work outside, I believe that will at least stop some of the loss in my application.

I also know that carbon_02 (or something like that) had some issues with his balance shaft gaskets leaking some oil.

[Jimmy Olsen]

Sounds like your engine is burning the oil instead of leaking it since you didn't mention anything about seeing oil spots after parking your car. I would switch oil to 10W-30. I would change brands of oil. I would add some boosters to the oil like Tufoil or Lube-gard. Tufoil increases oil pressure and fills in the micro-pores of the engine, something that could reduce your oil burning.

Probably your engine is either (1) worn out or (2) your oil rings are sticking. Change your oil when the engine is HOT. Add some Marvel Mystery oil to the crankcase 100 miles before you change oil. In 2nd gear run the motor up to 6300 rpm and hold it there for 15 seconds. Keep repeating every day.

Doubt if any one rebuilds the Intrigue Northstar engine. Better off getting a used one from a salvage yard.

Hope that helps..

[phewop118]

Black smoke doesn't sound like oil burning, but rather a too rich fuel/air mixture. When oil is burning, generally a blueish smoke is seen. Occasionally I'll get a puff of blue smoke when I start my Intrigue after its been sitting for a few days (very rare).

Unlike most here, my oil consumption has not increased with miles. In fact, it almost seems to have decreased. Back when I got the car when it had 43,000 miles on it, I was adding between .5-1 quart of mobil 1 between oil changes (5-6k miles), mostly during the last 1500 miles. Now, at 101,000 miles, I usually add less than .5 quart during oil change intervals of the same length. Sometimes, I don't even need to add any oil. Perhaps this is a product of my rather aggressive driving (flooring it and holding it several times during my 140 or so miles/day drive).

[burijon]

I hadn't thought about it running rich. As I mentioned I have noticed the oil going rapidly around the 40k mark. Since the car has gotten older I need to replace the Secondary Air Injection pump. Right now I have it unplugged as it runs all the time(headlights don't flicker ). Perhaps this is contributing to running rich as well as possibly needing to replace my 02 sensors? Most of the articles I read about running rich indicate bad MPGs. I just drove 12 hours straight and the car got 29.x on ethanolized gas.

Would a TechII be able to reliably diagnose bad 02 sensors?

I have also read that a malfunctioning PCV system(not just the valve) can cause oil consumption issues. Does anyone have a schematic they can post of the PCV system route? What would I need to check? Is there an EGR valve on the 3.5?

Thanks

[phewop118]

You may want to try some simple things first, such as cleaning your mass airflow sensor. If it isn't reading properly, it could cause your vehicle to run rich. Replacing your O2 sensors could help, especially if they've never been replaced. Your best bet would be to get your car hooked up to a reader than can give you fuel info and readings for various sensors, so that you can diagnose the problem more clearly.