c1500 5.7 Vortec using oil
Hey fellas, new member here.
Here's my problem:
Girlfriends truck (98 C1500 5.7 Vortec) has been an excellent truck. It now has 220,000 miles, mostly highway. The truck developed a small coolant leak about a year ago, it is from the intake manifold gasket (pretty sure it's original). Found it was leaking externally, to the front of the engine. No leakage to the oil, the oil stays very clean, no sign of contamination. I have been putting off the intake gasket replacement but now I think I need too...
The truck until recently used about a quart of oil in a thousand miles. Totally acceptable by my standards for something with this many miles. The last few months, the oil consumption has gone way up, probably a quart in 300 miles. It has also developed a misfire and I get a PO300 code (Cylinder 3 misfire). When I checked the spark plug in cylinder 3, it showed ashy deposits consistent with oil burning. I put in a hotter plug (one step up) and it didn't help much. Recently tried a spark plug non-fouler, it also didn't help much, still throws the code.
It does not smoke on startup. If it did it would make me think a valve seal on cylinder 3. My question is...could the intake manifold gasket have gotten so bad that it is the cause of the oil consumption? I have read where the original gaskets are so awful that they basically fall to pieces. I know I am going to have to replace the gasket but am hoping that I won't have to pull the heads also. Money is tight right now. Any thoughts or experiences with the intake causing oil consumption?