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Discussion Starter #1
Ok so I have have a few drivability problems and I have been able to fix them so far. But I just put mbrp 4" with muffler and tip on my 01 and now I have a noticeable miss sound at idle and low rpms. So I had it scanned and the buzz test was good but it said #8 failed on contribution. So I knew that injector had been replaced before so I took the cover off and the wiring
Connectors was fine and running it flowed oil just fine out the discharge port but I noticed it was a AD injector instead of a AE. So will that cause the miss sound and will it harm that cyl. By continuing to run it. And the sound is a miss not a flutter. It almost sounds like a bad valve but the exhaust is smooth flow out no sucking back like and exhaust valve. But it runs fine and smooth through the rpm range. It just sounds bad. Thanks
 

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the #8 injector is a long lead injector it is different than the other injectors. it gets starved for oil so it is designed with a longer ttip.
i have a slight miss at idle as well. but no codes or anything ever.
and my truck runs great.
 

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I had a miss in the exhaust sound and it was a bad injector. Usually that miss sound is a bad injector. The only thing is cylinder contribution tests fail #3 and #8 a lot, has something to do with what cps you have. Buzz test it and see what it does.
 

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only thing i can come up with, for the #8 being replaced with the same as the others, is that the P.O. had a regulated return. If your system is deadheaded, i'd put the long lead injector back in.
 

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After market injectors don't use a long lead
 

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I'm saying after market injectors don't use a long lead, its not necessary. BTW after market injectors don't get a new code. Mine are ab codes (split shot) and they are single shots. The injector code doesn't mean anything if they have been changed over. The ae in the #8 slot is not necessary.
 

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Discussion Starter #10
I don't have aftermarket injectors they are stock. But for one reason or another the #8 was changed at around 80,000 mi. And when they did it they put in a AD, and I wasn't sure if the ECM have to be rolled back to pre 99 1/2 or if I was damaging the cyl. By leaving it. But would that cause a miss sound if the ECM had the wrong flash for the AD injector. And it has the flutter sound like the pre 99 1/2 7.3s. I spoke with the ford tech and he said he knew they changed it for the sound complaints of the earlier 7.3s but didn't think I had to reflash the ECM and it shouldn't hurt to run it. But if I thought it was going bad again to make sure I had no less than 400 psi compression and if I did have over 400 psi that the injector could be failing.
 

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Someone could have just tossed an ad. Never seen it cause any damage to the cylinder. Never seen it cause a miss sound either.
 

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Discussion Starter #12
I think they mistakenly put the AD in as well and I know several people have said it won't damage the cyl. So that's good but I guess now just check the comp. And see if it is good and if it is put in a new injector.
 

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Run a buzz test and cylinder contribution test, see whats up. I bet on injector is failing. The ad won't make a difference.
 

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Discussion Starter #14
The buzz test was good but it failed on the #8 on contibution. But the ford tech said if the compression is low it will fail as well so I need to get a Gage and check that next. Thanks
 

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cps has know to cause #3 and #8 to fail, that is if you have one of the gray one in there.
 

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Discussion Starter #16
i am not sure what color of cps I have I will look tomorrow. But will it show them both bad, and will there actually be a bad cyl. or does it just appear to be bad?
 

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Certain cps and bad cps have been known to show bad contribution tests. Will fail it, but will sometimes fail a random cylinder that will change with tests. Id leave the ad and run it. No need to worry.
 
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