Grand Am Oil Consumption.....

I recently aquired a 1995 Pontiac Grand Am. Outwardly it looks like new. It only has 56,000 miles on it and appears to have been well cared for. I did buy it at an auction, so chances are there is something wrong with it. Since the day I brought it home, it's ran very well, although the "service Engine soon" light remains on almost constantly, it always appears to run fine. I guess my major concern is the amount of oil it consumes... I drive about 500 miles a week and it uses almost 2 quarts... It doesn't appear to be in the coolant and it's not on the ground, the car doesn't smoke, even at start up... Where the hell is it goin ?? It's got the 3.1 V6 Engine. I do tend to drive it fast( 75-80 ), could it be some sort of high speed blow by ?

Any ideas would be welcome, because short of paying someone to look at it, you guys are my last line...

Rich...

Reply to
Guess
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It's got to be either burning it or leaking it. The burning you might never see until the cat gives out. If it's leaking at fast speeds, then the underside of the vehicle it probably coated. My old G/A with the 3.3, 177k miles, burns/leaks 1 qt every 5k miles.

Reply to
« Paul »

Reply to
Paul

Thanks for the suggestions but, The Engine compartment is clean as a whistle, and the undercarriage is no worse than any other 9 year old car, certainly not covered the way

2 quarts a week would cover it... I'm lean>That is a lot of oil to burn. I would look for leaking gasket, valve
Reply to
Guess

I don't know what you mean by blowby. Engines have been sealed since about 1968. If it was not sealed it would be running really bad. Either the cat is cracking the HC or it is leaking out onto the road. Check the smog papers and see if the CO and CO2 is at high end of the scale. I would suspect your car has 256k miles or broken oil rings if it not dripping onto the road. It would not have passed the CARB with a CEL on. What are the CEL's?

Reply to
« Paul »

I meant Oil Blowing by the rings... And the SES Light is on "most of the time" usually when the engine is warmed up for 20 mins or so.. The smog shop is 3 doors down from my job, so I dropped the car there early in the AM before they opened and walked over a few hours later, so the car wasn't very warm when they placed it on the dyno ( planned it that way ) When I picked up the car at the smog shop it came on within 2-3 mins, any earlier and I would have failed. I was very fortunate. I'm certain the milage is correct, as the car is in just too nice of condition. 56k was what it had when I purchased it, now there's 68k. When I brought the car home ( the first day ) it had a miss, which turned out to be the coil pak. I was told by someone at the auction yard that it had sat in someone's garage for several years because it wouldn't run. It was trailered to the auction and to my home. Could the Rings by collapsed or stuck ? I did forget to mention the milage is not what I'd expect, I'm getting only 15-18 MPG. I don't know what the car should get but I'm guessing upper 20s. Even with wife driving (timidly) it still gets no better than 20. I was hoping if the rings were "stuck" that just keeping clean oil in it and driving it would free them up.. it that a feasable belief ? I sure can't afford a ring job...

Rich...

Reply to
Guess

Here's the Smog #s if they mean anything to you....

HC(PPM) = 40 Max Allowed = 87 (Average vehicles = 21 ) CO(%) = .25 Max Allowed = .51 (Average vehicles = .06 ) NO(PPM) = 196 Max Allowed = 701 (Average vehicles = 150 )

%CO2 = 14.7 %O2 = .2

???

Reply to
Guess

Great bit of info and especially in the previous post. It still sounds like the cat is doing it's job. A pre-cat exhaust analysis would narrow it down.

Since the car sat for X years, my first thoughts are the rings rusted to the cyl walls and one or more oil wiper rings broke when the engine was cranked. It could be as you suggested that an oil ring is stuck to the piston but I think that unlikely. Blowby is considered gases from compression or combustion getting past the worn rings into the crankcase... higher pressure to lower pressure.

I would have someone run a compression test dry and then with oil squirted into the cylinders.

Mileage on that car should be lower 20's around town and close to

30 on the freeway.

If possible, post back with the actual CEL codes. My guess is that one of them will be lean exhaust.

Reply to
« Paul »

Hello Guess,

Looks more like a high CO problem to me specially since you mention the bad fuel economy. There is the possibility of a rich fuel mixture. The diagnosis for this failure should include close inspection of your vehicle's fuel management and control systems. Check out

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I got most of this info from them.

CO stands for Carbon Monoxide. It is a by-product of incomplete combustion, more then often related to the presentation of too much fuel to the combustion chambers. The spark created at the sparkplug can only burn a small amount of fuel, the fuel it cannot burn is sent out the tailpipe and will normally contain high levels of partially burned fuel(CO) and raw fuel(HC). In a "Rich Fuel" condition diagnosis would begin with inspecting all possible mechanical faults, which could cause excessive fuel to enter the combustion chambers. This diagnosis would include inspecting your vehicle for high fuel pressure, intake vacuum leaks, air restrictions and/or leaking fuel injectors. NOTE: A dirty air filter may restrict ample air from entering the combustion chambers. The lack of air will create a rich fuel condition and result in high CO. If your vehicle has not had a tune-up in the last 15,000 miles, we recommend a quick service from a local smog stations.

As part of the mechanical system diagnosis, the vehicle's EVAP system would be inspected also. The EVAP system is designed to introduce gas tank and/or carburetor fuel bowl fumes into the combustion chambers. These gases (vapors) are just as combustible as the actual fuel in your gas tank. If they are not routed into the combustion chamber, the vapors build up within your engine's fuel system and eventual escape through a vent into the atmosphere. So in-order to eliminate this problem auto manufactures have designed the EVAP system to make use of this vapor. If your EVAP system is not functioning properly it can present these vapors to the combustion chamber at the wrong time and/or to often, causing a rich fuel mixture and increased CO in the exhaust.

Once the mechanical faults have been factored out, the focus would turn to the vehicle's electronic fuel control system.

Fuel distribution to your engine's combustion chambers is controlled by your vehicle's ECU(Engine Control Unit) and fuel injectors. In order for your engine to pass a smog inspection, fuel delivery must be preciously controlled to produce the least emissions. If the injectors do not present enough fuel to the combustion chambers, this would cause low CO emissions. In a situation where the injectors present too much fuel, this would causes high CO emissions. In order for the ECU to estimate the right amount of fuel to distribute, it needs to know how much fuel is currently in the system. This way it can always maintain a proper Air/Fuel ratio and keep emission levels at their lowest. The main component responsible for letting the computer know how much fuel is in the exhaust system at this moment, is the Oxygen Sensor. The Oxygen Sensor sends an electrical signal to the ECU, letting the computer determine exactly how much fuel it should continue to deliver to the combustion chambers. If for any reason the 02 sensor (oxygen sensor) does not send accurate information to the computer or it is "lazy" in sending the correct signals, the fuel delivery program can be altered. The computer may then present either too much or not enough fuel to the combustion chambers and therefore cause an emission failure.

In a computer controlled engine such as this, there are several components which also play a role in determining Air/Fuel ratio also. Along with the Oxygen Sensor, components such as the, TPS (Throttle Position Sensor), ECT (Engine Coolant Temperature Sensor) and the MAP (Manifold Absolute Pressure Sensor) sensors also send vital engine information to the computer which is used to determine proper air to fuel ratio. If any one of these components are defective they can alter the fuel delivery program. A smog service station can diagnose each component and report it's condition.

I suggest checking out

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They have great info onsmog failures.

Alec - The Smog Tech

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TheSmogTech

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