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94 Altima. Rough idle that's inconsistent. Most of the time it's around 800-900 RPM, going back and forth every 1-2 seconds. Then it will start to randomly drop to 400-600 RPM, there have been times I have to give it gas to keep it alive.

I have a EGR Valve code and a knock sensor code. I plan on replacing them both but I'm wondering if that could cause such a rough idle. I think it's more then that. I also have a hose going from the charcoal canister to the intake that is definitely leaking. I can't look at it right now but I will update tomorrow after I check more hoses, I'm just wondering if anyone thinks that rough of an idle could be caused by maybe like a IAC valve, or something more serious.
 

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I have a '98 Altima, 84k original miles, 2nd owner, and very recently had the same issues. I had the codes for the EGR valve and knock sensor 1, as well as a rough idle; sometimes I would put my car in neutral at a light to feel 'still'. I had the EGR valve/assembly replaced as well as the knock sensor and an oxygen sensor. Car ran better, then I had a stalling problem after stopping at a red light. Check engine light eventually came on after getting gas a few times and a few more stalls, and it was the MAF sensor and fuel pump/assembly unit. So to answer your main question, yes, those codes can/do cause a rough idle. You may also notice that your gas burns faster. All of those things I mentioned work together and it seems that one going bad can cause a horrible domino effect, especially in our older cars. I felt like my bad parts were so used to working together, that when a piece was fixed, the rest didn't know how to act so they messed up too! I say all this to say that if I were you, I would immediately get that EGR valve/assembly and knock sensor replaced so that it doesn't lead to more serious problems such as a shot engine and wasting gas.
 

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I have a '98 Altima, 84k original miles, 2nd owner, and very recently had the same issues. I had the codes for the EGR valve and knock sensor 1, as well as a rough idle; sometimes I would put my car in neutral at a light to feel 'still'. I had the EGR valve/assembly replaced as well as the knock sensor and an oxygen sensor. Car ran better, then I had a stalling problem after stopping at a red light. Check engine light eventually came on after getting gas a few times and a few more stalls, and it was the MAF sensor and fuel pump/assembly unit. So to answer your main question, yes, those codes can/do cause a rough idle. You may also notice that your gas burns faster. All of those things I mentioned work together and it seems that one going bad can cause a horrible domino effect, especially in our older cars. I felt like my bad parts were so used to working together, that when a piece was fixed, the rest didn't know how to act so they messed up too! I say all this to say that if I were you, I would immediately get that EGR valve/assembly and knock sensor replaced so that it doesn't lead to more serious problems such as a shot engine and wasting gas.
Thanks for the reply man. I changed out all the hoses and now when I start my car it revs up to 2000rpm and stays there for a few seconds, then it drops to 1000rpm and then dies almost immediately. I'm not sure what happened, I'm smelling gas like crazy also. I've inspected all my hoses and none are leaking. I disconnected the idle air control valve and the car acts exactly the same, I read online that if your car acts the same when you disconnect the idle air control valve, that it means its gone bad, but it's $200 and I'm not wanting to change it if its not the problem, so I want to be sure.
 
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