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Discussion Starter #1
Hey guys, I'm trying to track down this noise and I wanted to see if anyone here might have an idea what it is. I noticed while driving on the hwy that I had a kinda rattle noise coming from the firewall area. I first guess was that it was the bypass valve fluttering because the low vac can has no spring tension in it at all, and the valve wont shut on its own.

When I would accel or decel it would stop, but cruising it rattled/fluttered. I'm trying to get all the quirks worked out before I get this truck sent off to get tuned.
 

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I Miss My L
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Does your truck have cats on it, they could be falling a part.
Yeah one of my cats decided to start rattling after a WOT blast now when cruising it rattles a little....
 

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Discussion Starter #6
Good call everyone, Ill have to take a look at the exhaust this weekend.
I can only hope its something that simple.
 

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Discussion Starter #7
Update:

Ive been getting a tune done by Rick and the truck has been running amazing. Prior to that, I had just pulled everything off the top when I went back to my stock COPS. I ohmed COPS and injectors, everything was good and the the truck ran great with the new tunes. Now the problem is back, I can hear a type of lite rattle while cruising and the truck feels like it lost power.
I tried to pull each coil connector one at a time but its hard to tell a difference in idle since I have cams. Any suggestions?
I was kinda starting to lean towards my IAC since Ive noticed noise from that area, but its intermittent.
Also, I took my SC belt off and took the truck out around the block, it seemed to run a lot better and my exhaust tone sounded way better.
 

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Not Fast Enough
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Possibly could be the KB then giving you some issues.
 

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Discussion Starter #9
Possibly could be the KB then giving you some issues.
Its crossed my mind, but I think I found the problem.

I did some reading and decided to pull the green line off my EGR valve and plug it. Took the truck out for a spin and it seems like its back to normal. When I started the truck, it could feel pulsing from the line like it was pulling vac, but that would be normal if the engine is cold. I took it for a spin around the block to get it warmed up again and parked it while it was still running, the line was still pulling vac. I believe that would be my problem. I dont know its its my DPFE of EGR solenoid.
 

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Not Fast Enough
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Just delete the EGR all together.
 

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Its crossed my mind, but I think I found the problem.

I did some reading and decided to pull the green line off my EGR valve and plug it. Took the truck out for a spin and it seems like its back to normal. When I started the truck, it could feel pulsing from the line like it was pulling vac, but that would be normal if the engine is cold. I took it for a spin around the block to get it warmed up again and parked it while it was still running, the line was still pulling vac. I believe that would be my problem. I dont know its its my DPFE of EGR solenoid.
dpfe sends signal to pcm....pcm sends signal to EGR solenoid to put vac on EGR Valve...

many a DPFE has taken a shit.....also make sure the rubber hoses are hooked up correctly to the DPFE.....theiir is and Upstrem hose and downstream hose...if they are hooked up backwards it can skew the readings the DPFE is sensing and sending to the PCM
 

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Discussion Starter #12
Ill have to go double check but I'm pretty sure I hooked them up correctly, they are 2 different sizes, right?

I had my stock DPFE replaced under warranty in 06, so I dont know what I should change next. Ill ask my tuner if EGR is turned off in the tune, because it was pulling vacuum on that line.
I wonder if that has been my problem with the truck intermittently running great, then crappy, then great. By crappy I just mean, noticeable loss of power and that rattling at cruising hwy speeds.
 

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Ill have to go double check but I'm pretty sure I hooked them up correctly, they are 2 different sizes, right?

I had my stock DPFE replaced under warranty in 06, so I dont know what I should change next. Ill ask my tuner if EGR is turned off in the tune, because it was pulling vacuum on that line.
I wonder if that has been my problem with the truck intermittently running great, then crappy, then great. By crappy I just mean, noticeable loss of power and that rattling at cruising hwy speeds.
one hose is slightly larger than the other on the DPFE...they are also marked as upstream and downstream on the DPFE
 

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Discussion Starter #14
I don't think it's fixed, I'm thinking possibly an injector or coil. I'm not getting the typical miss when I drive, it just feels low on power now. Also my injectors or something is loud as hell, that's all I hear when the radio is off.
 
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