codes and exhaust
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New User
Joined: Mar 2005
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codes and exhaust
Well i fixed my diagnostic port problems and it was just a fuse. Checked the codes and it has a PO402 EGR Flow Excessive. Is this a bad EGR valve or possibly something else? Also my truck has 2 what looks to be Cats on it, are they both cats or is one something else? Both pipes from the manifolds go into the first one and it comes out 3" and goes into the other cat and then comes out int 2 1/4" then goes to the muffler which is missing. I would really like to make this sound better because it is really quiet even with no muffler. What kind of exhaust systems have you guys put on? Thanks for all your help.
Postmaster
Joined: Jun 2004
Posts: 2,665
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From: B/CS, Texas!!
Could be a stuck EGR valve, bad EVP sensor, or bad EVR. Remove the vacuum line off the EGR valve when the truck is idling. THere should be very little to NO vacuum at idle.
As for exhaust, I took cats off and put 3" pipe with flowmaster. Sounds SWEET. Check my galler for pics.
As for exhaust, I took cats off and put 3" pipe with flowmaster. Sounds SWEET. Check my galler for pics.
Senior User
Joined: Nov 2004
Posts: 447
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From: Florida
Depending on where you live, gut one cat (taking the center out and leaving the case on), try it and if you still want it louder, gut the other one. Then with 3" pipe back to a flow master 40, with dual 2 1/2" pipe out the back or a single 3" pipe out the back, it will sound great either way.
Lead Driver
Joined: Nov 2002
Posts: 9,556
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From: Concord, NC
I wouldn't recommend messing with the cats on a '96 since it is OBD-II. It'll have a constant check engine light. I think that the OBD-II trucks used a differential pressure valve or something to that effect to view the actual egr flow. The valve is either stuck open or opening too much (or excessive exhaust back pressure as a distant possibility) when it is open. Start testing sensors with a multimeter and see if you can find one that doesn't act like it is supposed to.
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Thanks for the info guys. I don't have to worry about cutting cats off where I live so that is an option. as for the check engine light will it still come on if I have the o2 sensor still in the pipe after the y?
