Engine noise, run on?

[FourcannonZ71]

Hey new to forum, but not to GM's. Got a 2000 Tahoe Z-71 (obs) with 5.7. This week it started doing something strange. When I crank it there is a loud noise that sounds like an exhaust leak. This lasts about 2-3 minutes then it just instantly stops. It did this 2 days and only in the morning, not during the rest of the day when cranked.
Saturday I go to crank it and only needed to move it a few feet and while it was still whistling I cut it off, only it did cut off. Key in my hand it sounded for about 15 seconds like it was trying to turn over but would not fire. I could put key back in and turn switch and it'd fire instantly and begin to whistle again. Did this a couple of times and finally let it run long enough to quit whistling. Cut it off and it quit instantly, like it should.

This one has me stumped. Just bought a 2013 Sierra ccsb, Z71, maybe its jealous

Any suggestions would be greatly appreciated!

 

[83 Bimmer]

Sounds to me like you might have a faulty ignition switch or possibly a sticky starter relay that keeps the starter engaged even though you have taken the key out. Relay is easy and cheap to swap out, if you don't have any electrical diagnostic tools, that's where I would start

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---------- Post added at 08:52 PM ---------- Previous post was at 08:44 PM ----------

And actually it could be in the starter solenoid also...What needs to be done is to disconnect the small wire connected to the starter solenoid and put a test light or volt meter to it and see if the power goes away when the key is turned away from the start position.

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[SunlitComet]

Agreed. If you have the key out and your starter is running you have something wrong with your starter electric circuit or mechanical part in the system. Your starter and A/C compressor relays are the same so you can try swapping them to see if it goes away as a relay issue. That wont cost you any money at all. Unless you can offer more details of the problem. Then that might cost you something

 

[83 Bimmer]

Maybe it is just jealous and you need to take it out for a nice steak dinner to let it know you still care

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[SunlitComet]

Take me with you.

 

[FourcannonZ71]

Or maybe have to give it a synthetic oil change

Thanks for the tips. I did get a chance today to swap the relays, but surprise surprise after swapping the relays and then swapping them back it has started several times this evening with not a single issue regardless of which relay. This is gonna be fun.