My son has a 94 Z71 4 wheel drive with a 5.3 Vortec engine with 54,000 miles, when he starts it up in the mornig it knocks for aq couple of minutes then quits and runs fine. He says it does not use oil and he takes care of it. Any ideas what it could be? Thanks

My wife's expedition did that on cold mornings, as soon as she started it, it would make this knocking sound almost like the starter was still engaged, I took the ford dealership and they checked everything and couldnt find about thing wrong with it, they replaced the starter and it still did it. It was and still is a mystery to this day....

I know this doesnt help but thought I would throw it out there for you anyways...

Might check the see if the stater is sticking.....

Rick

just fyi the chevy's have had this knock for some time,you can have someone do a top engine cleaner on it and that might help it some but for the most part,if it last for less than a minute then i would not do anything to it,these engines have had that noise for a long time now and i know of several with over 200 thsd miles on them with the same noise.

ask Fool4Fishing in the Belton Bunch.
he owns a shop and i think works on mostly Chevys

I had an 02 6 liter that did it. My mechanic called Chevy and they recommended a bottle of (I think) Lucas with every oil change. They also said it would take a few hundred miles to change. It quitened down some but did not go away.

the 6.0 liter had a problem with the pistons they had a recall to replace them.the 5.3l we had some that we replaced pistons on but the noise came back even on those after a few thsd miles.

Thanks guys