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2003 GMC Sonoma P0302 4.3l


whinis

Question

I have 2003 GMC sonoma throwing p0302 code intermitantly under 2000 rpms and almost constantly above 2000 RPMS, after replacing the coil, plugs, wires and fuel pump over the last 6 months or so due to various failures at high milage I have to assume that its the fuel injectors. I can't find the entire spider at any local shop and only at places like rockauto do they have a complete kit with all 6 injectors and the body kit. My question is do I just replace the one injector to see if its causing the problem or can I buy one of these spider reman kits and assume it will work in my truck. My understanding is these kits are technically the SCPI to MFI conversion kits.

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Can you not just swap the injector for that cylinder with one from a different cylinder and see if the miss moves with the injector? Seems to me that would be a free test. Have you ever run injector cleaner through it?

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Without knowing your experience with the older type ignition systems I will offer this, take the rotor off and turn it over. If you can see any discolouring on the underside of the rotor, change it. By discolouring I mean any burnt type colour on a white rotor, and any rainbow type colour on the black rotors, replace it. Actually for the cost (or at least the cost last time I changed one) it is likely best to just replace it if you went to all the trouble to remove it for inspection. GM HEI ignition systems have a well known issue of the spark going from the coil button on the cap right through the rotor to the mechanical advance weights, and down the shaft to the engine. Usually shows up as misfiring, eventually not even starting in the right conditions, only to start 5 minutes later.

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Yes I have run injector cleaner through it and have done compression test so by process of elmination I can think little more than the injector or the fuel body. Also swapping the injector is a little more pain than its worth because if I do tear it apart to test it then I have to get all new gaskets for now and if its bad all new askets again. I was wondering if replacing 1 injector is the "right" thing todo as I have been told that it can cause more problems then its worth and to replace the whole spider. This leads to the delima, there is no whole spider kit from GM that I can see.

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Doubt changing one injector will cause issues. That being said, what it will do is point out the differences in flow between a new injector and the old injectors with lots of miles on them. It is not really causing issues.

 

You need only change the new gaskets on the second tear down if you damage them. Do not use a sealant on them when you install them, put gaskets in dry. The reason for testing the injector by moving it is to make sure that you are actually going to be addressing the correct issue, and not just throwing more money at it.

 

BTW, second tear down is always a lot faster than the initial one was.

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Sadly If I had known it might be a problem I would have fixed it whenever I replaced the intake manifolds gaskets about 2 months ago due to a rather large coolant leak. If its not the injector what else could be causing the misfireing, as I said fuel pump, filter, plugs, wires, and coil have already been replaced and compression test and fuel pressure has been tested.

 

EDIT: also going with a spider such as GB 833-22105-6 would actually save me money which is why I am asking the question, single injectors cost as much as the entire kit it seems from the only people that make the kit.

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Sadly If I had known it might be a problem I would have fixed it whenever I replaced the intake manifolds gaskets about 2 months ago due to a rather large coolant leak. If its not the injector what else could be causing the misfireing, as I said fuel pump, filter, plugs, wires, and coil have already been replaced and compression test and fuel pressure has been tested.

 

EDIT: also going with a spider such as GB 833-22105-6 would actually save me money which is why I am asking the question, single injectors cost as much as the entire kit it seems from the only people that make the kit.

 

Spray something all around the intake port where it meets the cylinder head and see if the idle changes. This may be a vacuum leak at that port due to a gasket failure, or maybe even the manifold is corroded enough at the coolant port that it is hitting the number 2 cylinder port. Number 2 port should be the first cylinder on the side that is NOT the furthest forward. Sorry, do not know the layout of the engine, but, furthest cylinder forward is almost always #1, so, on almost all except Ford, the other bank starts with cylinder 2.

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Alright, the rotor looked completly fine and ok no discoloration, spraying starting fluid on the intake ports at all the cylinders did nothing. We ended up replacing the spider today and checked all of that while we did this. entire top of engine looked good and clean from whenever we replaced the manifold gasket due to a coolant leak. However now it seems to either not be misfiring or misfiring less. However now its nolonger throwing a p0302 after replacing the spider and a more general p0300, but as I said we can nolonger feel the truck missing at high RPMs so we have no idea why its throwing a misfire code. Maybe the missing will be more appearnt on load rather than just reving the engine to check for misfires.

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The Cap is new and the rotor looked good whenver I changed the cap (The cap and intake manifold gasket were changed at the same time it failed, one morning started up without coolant pressure test squirted from the manifold gasket in the back). You are correct that Cylinder 2 is the forward most cylinder on the passenger side, I will attempt the spray tomorrow however I find it unlikely as it started a couple months after I had replaced the manifolds gasket.

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