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bry21317

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mmmikkke Senior Enthusiast

mmmikkke

Posted
Posted
I didn't want to Double post so I am placing a Link to the spot where I posted under the GM TECH forum.  Here is the Link http://www.gm-trucks.com/forums/index.php?showtopic=45593

 

The car is misfiring, it is a 2000 Yukon Denali and does this about 2000-2500 RPMS.  5.7 Vortec with 82k on it.

 

Thanks,

Bryan

 

 

 

Your truck seems to have a misfire-under-load problem.

 

Too bad you just changed the plugs. You should have kept track of which one was where, because the misfiring cylinder would probably been apparent by its plug.

 

But at this point you might still be ok. Take out the new plugs right after making the engine misfire. (Shut the engine off first. :banghead: ) The misfiring plug will have a different look from the rest, probably shiny, or black, or both. Then run a new, temporary, "plug wire" outside the normal loom, for that plug. If that fixes the problem, replace the real plug wire.

bry21317 Enthusiast

bry21317

Posted
  • Author
Posted

Now that I have been running it with better gas for 2 days now, it seems a little better. Now I really am only getting it when I put it in 1st gear instead of drive, it will do it very bad then, almost like maybe a tranny issue to. It will really buck and sputter.

 

I have also noticed this a few times, but not near as bad when driving the Highway at 70+mph. It is getting really annoying.

 

Brand new plugs AC DELCO Platinum as Recommended- 2 days old.

Fuel Filter is about 6 months old, 5k miles on it about.

Cleaned the Throttle body, 2 days ago

Cleaned K+N Air Filter 2 days ago

Distributor cap is only about 4-5 months old and rotor

Tranny Fluid Changed and new filter 2-3 months ago. Maybe 3k.

 

I now tried revving the engine with it in 1st gear while my foot is on the break again, as I did before, and now it doesn't seem to misfire. It does do it very badly when driving in First gear and going any speed, as long as the RPM's are up to about 1500 or more it will do it in First bad.

 

Is this a Miss or could the Tranny having an Issue? I might take it by a tranny shop that I trust and have them see if that could be it, but I don't think so. It seems to have been perfect and then all the sudden started doing this.

 

Thanks,

Bryan

bry21317 Enthusiast

bry21317

Posted
  • Author
Posted

After driving it a little bit more. I have noticed that it does not do this hardly at all now. I can now only make it really do it when I put it in 1st gear and drive, even just barely giving it gas it will start to buck. Not sure if this could be the Tranny also, I am thinking of taking it to have the Tranny checked just to make sure, as I have 4k left on the warranty.

 

Where is the Knock sensor and the Cam Sensor located?

 

Thanks for all the help, as I will get it working, I hope.

 

Thanks,

Bryan

  • 2 weeks later...
04-silver Enthusiast

04-silver

Posted
Posted
Take out the new plugs right after making the engine misfire. (Shut the engine off first.  )
:eek:

 

Reminds when a buddy from work went to check the oil in our Honda EM 5000 jenny (generator) that we use on our service truck.

 

He let the jenny run and unsrewed the oil plug....... :rolleyes: duh......needs oil now :wtf:

 

:cheers:

John

 

 

edit: sorry but had to throw this in

Wingnut Senior Enthusiast

Wingnut

Posted
Posted
....I have 4k left on the warranty.

 

Where is the Knock sensor and the Cam Sensor located?

 

Thanks for all the help, as I will get it working, I hope.

 

Thanks,

Bryan

 

 

 

 

You have a warranty? Take that sucker in man! :rolleyes:

 

 

Not 100% sure on that truck...But the knock sensor on my '92 is on the block, down by the starter.

 

But on my '02, the knock sensor is under the intake manifold. :cheers:

  • 2 weeks later...
05HD Enthusiast

05HD

Posted
Posted

I'd spray the plug wires down with water while the truck is running. A bad one will start arcing like mad once it has a nice ground path from the water. Salt water seems to work better.

trever1t Enthusiast

trever1t

Posted
Posted
I'd spray the plug wires down with water while the truck is running. A bad one will start arcing like mad once it has a nice ground path from the water. Salt water seems to work better.

 

 

 

 

Joking, right? :chevrolet:

05HD Enthusiast

05HD

Posted
Posted
I'd spray the plug wires down with water while the truck is running. A bad one will start arcing like mad once it has a nice ground path from the water. Salt water seems to work better.

 

 

 

 

Joking, right? :rolleyes:

 

 

 

 

 

No, really. It works like a charm. A misting is all it will take. Please don't use anything flamable to spray them down with though, unless you are ready to burn it to the ground. :chevrolet:

05HD Enthusiast

05HD

Posted
Posted

Trever, I guess I'm just used to salt getting all over vehicles since I live in an area where the roads are salted in the winter. It has to stay on there a while to do any damage.

trever1t Enthusiast

trever1t

Posted
Posted
Trever, I guess I'm just used to salt getting all over vehicles since I live in an area where the roads are salted in the winter. It has to stay on there a while to do any damage.

 

 

 

 

Oooh! Salted roads suck, sorry. I lived in Vermont for a while, they also salt ther roads. Average life before rust is 5-6 years!

I lived in the Carribbean for 15 years and a new car would be a rust-bucket in 3 years.

The first thing i noted when i moved here to California was all the OLD CARS!!!! Not classics, mind you but just old cars driving about. No salt no corrosion. More burned out motors here than rusted bodies!

 

Yes, salt water is a much better conductor of electricity. But i would reccommend taking the wires and haveing them checked for resistance before doing that. Most auto parts stores have little wire resistance displays that you can use.

Trever

SS Crew Enthusiast

SS Crew

Posted
Posted

The misfire sounds like a bad plug wire. I had an '85 Monte Carlo SS that would go through #8 plug wires. It would only misfire under a load. Check your wires like 05 HD said, I'll bet that's where your problem lays.

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