2000 Yukon Denali misfiring on cylinders 1 and 7.

[Dd1994]

I have a 2000 yukon denali with the 5.7 vortec, that my dad stored outside for 5 years, I am trying to get it into running shape. When I first got it, I changed spark plugs and sprayed fogging oil into the cylinders, new battery, had to put in a new starter, checked the fluids, etc. At first it smoked a bit (most likely from the fogging oil), but now its good.

However I have a new problem, it is misfiring a lot on cylinders 1 and 7 (which are on opposite ends of the same bank). It vibrates alot. Its throwing P0300 and occasionally a specific cylinder code for cylinder 7 or 1. I used a spark tester, and cylinder 1 and 7 seem to be getting spark normally, inspected the new spark plugs and confirmed they are ok, checked fuel pressure, and according to the obd2 data the vacuum level is normal.

I am going to do a compression test next but I think that maybe the valves are stuck or sticky, because i'm not sure what else it could be.

One other peculiarity is that when I turn the key to the run position the fuel pump never shuts off, I have replaced the relay and it still does this. Not sure if it is related however. I am also getting a weird reading from the sensor TID: $07 CID:$0d in torque pro which gives a current voltage of 56,320 and a max of 197.

 

[skylark]

I would bet that the poppet injectors are gummed up. You can try a fuel system cleaning but I bet that you're going to be replacing the spider.

 

[Dd1994]

I guess a trip to the junkyard is in order then. They are quite pricey new.

 

[454cid]

I guess a trip to the junkyard is in order then. They are quite pricey new.

I would think that's false economy.... if your spider injectors are gummed up from sitting, why would a junkyard spider, that's also been sitting, be any better? Besides, you really want the updated one any way. Have you checked Amazon or Rockauto?

 

[Dd1994]

Is there any way to verify that my injectors are gummed up before I bite the bullet?

 

[east302]

Have the intake gaskets been replaced? They like to leak at the corners near numbers 2/8 and 1/7.

The injector inspection was called a fuel injector balance test and it measured the pressure drop across each injector.

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GM had a TSB for California market vehicles where they referenced a cleaning procedure to remedy sticking poppets. If that failed, they replaced them with the MPFI as part of a warranty repair for California vehicles up to 10 years or 200,000 miles.

The cleaning involved connecting a pressurized tank to the injector assembly and using a scanner to command individual injectors open, the pressurized cleaner forcing any stuck poppets open one at a time. Even if you found a dealer that still did it, the cost would probably be a couple hundred bucks. Book time for the cleaning was 1.3 hours.

You could instead pop the upper intake off and carefully remove the injectors in question to see what they look like...but by then you may as well just replace the whole spider. It’s around $300 for the Delco MPFI.






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[Dd1994]

I just ordered the felpro metal intake gasket kit, makes sense to do the injectors and the gasket at the same time I'm guessing. Looks like a pretty big job, but there are good videos on the internet so I'm sure I will be able to do it.

I would think that's false economy.... if your spider injectors are gummed up from sitting, why would a junkyard spider, that's also been sitting, be a

Have the intake gaskets been replaced? They like to leak at the corners near numbers 2/8 and 1/7.

The injector inspection was called a fuel injector balance test and it measured the pressure drop across each injector.

You must be registered for see images attach

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GM had a TSB for California market vehicles where they referenced a cleaning procedure to remedy sticking poppets. If that failed, they replaced them with the MPFI as part of a warranty repair for California vehicles up to 10 years or 200,000 miles.

The cleaning involved connecting a pressurized tank to the injector assembly and using a scanner to command individual injectors open, the pressurized cleaner forcing any stuck poppets open one at a time. Even if you found a dealer that still did it, the cost would probably be a couple hundred bucks. Book time for the cleaning was 1.3 hours.

You could instead pop the upper intake off and carefully remove the injectors in question to see what they look like...but by then you may as well just replace the whole spider. It’s around $300 for the Delco MPFI.






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Have the intake gaskets been replaced? They like to leak at the corners near numbers 2/8 and 1/7.

The injector inspection was called a fuel injector balance test and it measured the pressure drop across each injector.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

GM had a TSB for California market vehicles where they referenced a cleaning procedure to remedy sticking poppets. If that failed, they replaced them with the MPFI as part of a warranty repair for California vehicles up to 10 years or 200,000 miles.

The cleaning involved connecting a pressurized tank to the injector assembly and using a scanner to command individual injectors open, the pressurized cleaner forcing any stuck poppets open one at a time. Even if you found a dealer that still did it, the cost would probably be a couple hundred bucks. Book time for the cleaning was 1.3 hours.

You could instead pop the upper intake off and carefully remove the injectors in question to see what they look like...but by then you may as well just replace the whole spider. It’s around $300 for the Delco MPFI.






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ny better? Besides, you really want the updated one any way. Have you checked Amazon or Rockauto?

Rockauto has one for around 300 I think I'm going to go with that one

 

[east302]

It’s not a bad job, there are only a few things that can maybe trip you up: the RTV on the china wall, torquing it down in sequence (get an in-lb torque wrench) and resetting the CMP sensor offset when the distributor is replaced. There are apps that can read it (usually) so do a search for “CMP Retard” and some will pop up.

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[Dd1994]

Just curious but where do you find the manual you are referencing, it would be super helpful. I have been looking for one but so far haven't found one.

 

[east302]

Here you go...

http://67-72chevytrucks.com/vboard/showthread.php?t=700011

Alldatadiy.com subscription is pretty much the same thing and much easier to navigate (unless you print off the manual). It’s around $20-30 a year per vehicle.


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