Used 1998 K1500 engine problem?

Hi,

I'll appologize up front, I'm a real newbie! My problem is, I just purchased this 1998 K1500 5.7 V8 with 83,000 miles. I'll list the problems:
1. Engine knocking at very slow speeds (It almost sounds like a cheap 4 cyl)
2. After the engine warms up there is a continuous high pitched "whistle" when you are at slow speeds, ie in town.
3. Poor gas milage and slow starts.
4. Metal shavings on the oil plug, it was very black. I'm guessing that the previous owner did not change it very often.

I just changed the oil, air filter and fan belt. I'm wondering if I might need to change the fuel filter and spark plugs? Also, if I continue to have metal shavings, I heard you can bring your vehicle in somewhere like autozone or something and they will do a free computer test?

Thanks in adavance for the help!

Well the metal shavings may be a problem, or the oil may not have been changed for a long time. As engines wear, there will be metal that is worn off. If there are large quantities however, then that will indicate a major mechanical problem. Check the plug on the next oil change. If there are a lot of metal shavings on it you may have a problem on your hands.

High pitched whistle used to mean that a head gasket is blown...but you seem to hint that it only occurs at slow speeds so that may not be the cause. Potentially you could have a vacuum hose loose somewhere somehow causing the whistle. Vacuum leaks can cause poor idling and hard starting as well. You did not say if the "piston" knock was only at startup or continues. If it is only for a short while after startup and goes away then it probably is loose tolerance of specific piston to cylinder specs that are in the Chevy engines...some of them have it even new. My 2000 Silverado K1500 developed it after 80,000 miles and was getting severe. I use Mobile 1 synthetic oil and it still occurred...then recently at an oil change I put in a bottle (1 qt) of "greased lightning" additive with teflon...seems to have stopped the problem and it is now very quiet on startup...so far. I do not recommend additives so I was somewhat surprised af the fix. Obviously you need to change the oil/filter from conditions you mention. Probably should not wait 3000 miles for the 2nd time either...maybe change the oil/filter again after perhaps a few hundred miles to get all of the metal out of the system. Also, I suspect the air filter is clogged and needs changing...can drastically affect gas mileage. I found I got better mileage with the synthetic oil mentioned. Change PCV valve also. You may also be due for change of oxygen sensor but before doing so you might go to Auto Zone or other place that will run a scanner for free to detect this...why replace it if it is still ok.

Thanks for the reply!!! To answer your questions. The knocking is just at start, until the engine warms up. I changed out the air filter, pcv valve, fuel filter and ran seafoam through the engine manifold. I'm wondering if it's a loose hose like you are saying? I'll have to check them all. Thanks again!

The whistle you are talking about, is it coming from the engine compartment? My 97 has makes a high pitched sound from the fuel pump that you can hear standing beside the truck when it idles. Before i had my exhaust put on i could hear it driving around town with the windows down. I'm pretty sure it is normal.

Concerning the whistle you hear. I think you say it was coming from the engine compartment...but...the Silverados are known for wind whistle caused by loose windshield molding. I have it but have been too lazy to fix it...but there are many mentions of it and various ways to take care of it...some use double sided tape slipped under the molding, some use silicone caulking under the molding etc. With the other engine issues you mentioned though I would sure look closely at any bad rubber hoses, tubing, etc. in the engine compartment that use vacuum plus are they all connected at their ends.