Rough idle, P0300, Help!

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wiscomick

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Yeah, I was super disappointed. Paid much more for the Delco stuff and still screwed me in the end. What I still don't know is what the exact problem with the stuff was. It looked perfectly fine. No wear, no buildup, nothing. Looked pristine. Idk. In the trash it went.

I too am always disappointed in the end when trouble threads don't have an ending and a posted solution. Made sure that didn't happen here. Thanks again guys. You were a huge help.
 

98 Nitro

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I have the same problem. Truck ran great, then out of the blue just went to crap in an instant and had the misfire code. Noticed a few days later it lost a little coolant and found the intake gasket leaked externally. So I fixed it and it runs better but not great. So I have a new Delphi cap and rotor that I hope will fix it, but it does say Hecho en Mexico.
 

Scott Martin

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Well, swapped the distributor out. Much less play than my old one. Before I put it in, I put the new ACDelco cap and rotor I purchased in March on the new distributor. Plugged it in, set timing, no difference. Same misfire.

At this point I was absolutely furious. Only thing I could possibly do that wasn't 'go buy head gaskets' was put the old GM distributor cap and rotor that came with this junkyard distributor on and see if these 'new parts' were already trash. The OEM one on the replacement distributor looked fine when I pulled it off but I figured why not put the actual new Delco stuff on that I just bought.

Put the old OEM stuff on..... Misfire completely gone. It was the new ACDelco cap and rotor the whole time.

Don't regret putting the new spider on even though it was expensive, was clearly leaking and was super brittle when I pulled it, but wasn't the problem.

Thanks for all the help guys. This one is solved.
They need to get their **** together on the quality of these parts, I literally lost count of how many caps I've put on mine.
 

JonFerron

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Thank you for following through with this thread. As i am in the same predicament, changed everything around my brand new distributor, telling myself it cant be the problem. I guess i just have too much faith in humanity......or automation.
 

HotWheelsBurban

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Thank you for following through with this thread. As i am in the same predicament, changed everything around my brand new distributor, telling myself it cant be the problem. I guess i just have too much faith in humanity......or automation.
Man y'all have me nervous now with all these crappy distributors. Knock on wood mine is behaving. Have a Blue Streak rotor and an Accel cap ,both with brass contacts. Used the white rotors before and they didn't last a year. No problem with the Blue Streak; just do not drop them!
Back in the day, the Blue Streak caps and rotors for the old style HEI were lots better than the factory style, even Delco. And on the coil in cap style, replacing the rotor periodically will save your coil and module.
Just had a thought: wonder if these defective caps / rotors are getting dropped somewhere in the supply chain? Or molding/ manufacturing issues with lighter gauge plastic? Make it lighter so it costs less to make and ship?
 

stutaeng

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Glad OP figured it out. I was going to recommend testing power to injectors, but that wasn't the issue.

I just did my injectors last weekend on my 5.7. When I reinstalled the spark plug wires at the distr. cap some of the plastic plugs broke a bit. They seem to be original. I checked on the local parts store and was shocked at the price: almost $60 for a cap and rotor. I hesitated and just reinstalled the original cap... mostly because of the sometimes questionable quality of aftermarket parts.
 

HotWheelsBurban

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Glad OP figured it out. I was going to recommend testing power to injectors, but that wasn't the issue.

I just did my injectors last weekend on my 5.7. When I reinstalled the spark plug wires at the distr. cap some of the plastic plugs broke a bit. They seem to be original. I checked on the local parts store and was shocked at the price: almost $60 for a cap and rotor. I hesitated and just reinstalled the original cap... mostly because of the sometimes questionable quality of aftermarket parts.
Yes I was shocked to see that the Accel cap was close to $50, but it's still doing great after 4 years of driving every day. Plastic things are made from oil, and when oil prices rise, plastic gets more expensive and never gets cheaper. Also the caps are not as common as the old fashioned HEI caps and that also makes them more expensive.
 

1998OBS

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Update. Swapped out the old spider for the new one. On opening the upper intake, it looked pretty obvious what was going on. Half the intake was black and sooty, the other wet and greasy. Pretty clear we had an internal fuel leak. Got everything buttoned back up, and the son of a ***** is doing the exact same ****. I'm at wit's end. Seems the only options left are either distributor, or a blown head gasket as far as I can tell. If anyone has a known good distributor laying around for sale, let me know. Pic of inside the manifold below.

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I have one I pulled if you want it… did you find out what it was? I’m going through your same issue…
 

Schurkey

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Good to hear you got it sorted.
ACDelco now isn't like the old ACDELCO imo, now made in China too.
I bought some "AC-Delco" spark plugs for my Trailblazer from an "Amazon Partner" in Texas. (i.e., sells through Amazon, but is an independent business.)

They didn't look like the AC-Delco plugs I took out. Had legitimate-looking Delco logos on the box and on the plugs, though. I understand that companies sometimes update their products, so I was concerned but not worried.

I took photos of the two styles of plugs, and sent 'em to GM. GM says the new plugs are not genuine. (i.e., fookin' counterfeits)
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The Amazon dirtbag wanted to do all the negotiations via telephone, so I'd have no record of what he offered, and if he didn't follow through I'd have no proof. I refused.

In the end, Amazon, not the dirtbag, gave me a full refund.

Point being--New doesn't mean good, and a well-known logo on the box doesn't mean they're not Chinese counterfeits.
 

1997

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^ nice, detective work!

I read a few articles on it happening big time in plane replacement parts, got the attention of the NTSB big time.
 
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