Little help with my 2001 Denali

[Labont865]

Ok new member first time posting.

I am having an issue with my 2001 Yukon Denali 6.0l. It is really having a hard time starting. Not everytime but I would say two out of every 5 times I start it.
It just sits there and cranks but takes a few seconds to actually fire up. Once its running it runs fine.
Its throwing a P0300 code. I replaced the spark plugs and did a seafoam treatment and no change what so ever.
Any ideas?

I have heard it could be a few different things. Bad Cat, bad wires etc.
What would be the most likely cause, as I dont want to throw away a bunch of money on unnecessary work

Thanks

 

[ATL]

how many miles are on the truck? if its still all oem stuff, id do a simple tune up, plugs and wires as well as clean mass air and throttle body. if that doesnt help, possibly check to see if an ignition coil is failing

 

[Labont865]

207000 kilometers on it so about 128000 miles.

The spark plugs were in pretty bad shape. Random Gap. So I was really hoping that was the issue. I replaced them all with new bosch iridium plugs .040 gap which is what was recommended in the owners manual. And nothing has changed.

I will move on to wires next I guess. And clean it all up. Hopefully that works.

 

[Clean_Yukon]

Might be your fuel pump, mine did the same for almost a year then one day wouldn't start at all. New fuel pump now and hasn't happened again.

 

[ATL]

fuel pump is easy to check, run to local parts store and borrow a fuel pressure gauge. go outside and take the plastic covers off the engine. screw the meter onto the fuel line on the passenger side of the intake and see what it says

 

[Labont865]

Fuel pump wouldn't throw the P0300 code though would it? I didn't think a faulting fuel pump would cause a random missfire. I will check it for sure though

 

[scottg918514]

Ok new member first time posting.

I am having an issue with my 2001 Yukon Denali 6.0l. It is really having a hard time starting. Not everytime but I would say two out of every 5 times I start it.
It just sits there and cranks but takes a few seconds to actually fire up. Once its running it runs fine.
Its throwing a P0300 code. I replaced the spark plugs and did a seafoam treatment and no change what so ever.
Any ideas?

I have heard it could be a few different things. Bad Cat, bad wires etc.
What would be the most likely cause, as I dont want to throw away a bunch of money on unnecessary work

Thanks

Any electrical upgrades, like HIDs or anything like that?

 

[ATL]

Fuel pump wouldn't throw the P0300 code though would it? I didn't think a faulting fuel pump would cause a random missfire. I will check it for sure though

not ideally, but ive seen weirder things happen. but itd be free to check it out. and theres still possibility of having a bad coil.

 

[Labont865]

Any electrical upgrades, like HIDs or anything like that?

Truck is stock with exception of rims and tires

 

[OHSIXX]

Anything can happen but I'd suspect a fuel pump especially if it is the original one. These trucks are known for failing fuel pumps...one of their few flaws....