Car idles rough when hot, wants to stall, VAC jumps up
I had the same exact symptoms on my car. After the car was warmed up, car idled like crap, but was fine during the warmup period. After a long time I eventually narrowed it down to something in the EGR system.
It might not be the same problem in your car but thankfully it's something really easy to test. Just loop the two vacuum lines going from the EGR system to the top of the throttle body back on itself, essentially cutting off the system from the throttle body. Drive it for a couple days to see if it solves anything. (You will throw a CEL for EGR insufficient flow, but for the sake of this test you can ignore it for now)
It might not be the same problem in your car but thankfully it's something really easy to test. Just loop the two vacuum lines going from the EGR system to the top of the throttle body back on itself, essentially cutting off the system from the throttle body. Drive it for a couple days to see if it solves anything. (You will throw a CEL for EGR insufficient flow, but for the sake of this test you can ignore it for now)
I've been having a new problem with my car. After it gets up to operating temp, it will occasionally start to idle really rough when I come to a stop, it almost sounds like it has cams (which it doesn't) or sort of like it's running on 2 cylinders which I experienced when I was making my COP setup (pins were not pushed all the way into the plugs, fixed it though). Again, this only happens when the engine is hot. When this is happening, it seems to run OK at highway speeds and under boost.
Ok one issue...the IAC pulled out of my car looks like the first file attached (the one with the red evo behind it) and my replacement looks like the other one with the exposed spring....my car is an 03 if that matters. Will the new one work? And yes I ordered the right one...
TOO BAD it didn't fix your problem though.
Have you checked your plug wires for any cracks or signs or age?
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Evolving Member
iTrader: (6)
Joined: Dec 2011
Posts: 162
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From: Central New Jersey
Okay big findings today.
I tested every sensor on this car and everything was fine. I got the car to start doing its thing running rough, then got under the hood. I pulled the hose off of the top throttle body on the nipple labeled "E" (it goes p, e, a). The minute that hose came off the car went back to normal!! When I put it back on, problem came back, instantaneously.
I'm assuming these are connected to the egr system? All the 2 hoses on the egr are connected and the ones to the solenoid are as well So I'm thinking at this point I'm just going to remove the egr completely from my car. Unless there's something I can fix with the egr that would be less work than removing it completely?
But anyway that hose is the source of my problems.
Also just a little tip to save every one some money- the iac valve I ordered was from eBay, cost me $24 shipped. It was brand new and came with an O ring. Worked flawlessly. If any one would like the link I can provide it.
I tested every sensor on this car and everything was fine. I got the car to start doing its thing running rough, then got under the hood. I pulled the hose off of the top throttle body on the nipple labeled "E" (it goes p, e, a). The minute that hose came off the car went back to normal!! When I put it back on, problem came back, instantaneously.
I'm assuming these are connected to the egr system? All the 2 hoses on the egr are connected and the ones to the solenoid are as well So I'm thinking at this point I'm just going to remove the egr completely from my car. Unless there's something I can fix with the egr that would be less work than removing it completely?
But anyway that hose is the source of my problems.
Also just a little tip to save every one some money- the iac valve I ordered was from eBay, cost me $24 shipped. It was brand new and came with an O ring. Worked flawlessly. If any one would like the link I can provide it.
Thread Starter
Evolving Member
iTrader: (6)
Joined: Dec 2011
Posts: 162
Likes: 1
From: Central New Jersey
I had the same exact symptoms on my car. After the car was warmed up, car idled like crap, but was fine during the warmup period. After a long time I eventually narrowed it down to something in the EGR system.
It might not be the same problem in your car but thankfully it's something really easy to test. Just loop the two vacuum lines going from the EGR system to the top of the throttle body back on itself, essentially cutting off the system from the throttle body. Drive it for a couple days to see if it solves anything. (You will throw a CEL for EGR insufficient flow, but for the sake of this test you can ignore it for now)
It might not be the same problem in your car but thankfully it's something really easy to test. Just loop the two vacuum lines going from the EGR system to the top of the throttle body back on itself, essentially cutting off the system from the throttle body. Drive it for a couple days to see if it solves anything. (You will throw a CEL for EGR insufficient flow, but for the sake of this test you can ignore it for now)
Ugh I WISH I HAD SEEN THIS EARLIER TODAY!! That's what I figured out doing by my self hahah but it took me all day to come up with it haha ugh thank you!!! Now my next question, trying to save some work/time that I really don't have these days...can I loop these hoses or just seal them off somewhere to fix my problem but still drive the car safely? Trying to avoid the egr removal or rather just push it off for a month or two. While it's something I plan to do, just right now I don't have the time.
You're technically not supposed to loop the throttle body ports. I ended up buying some cheap vacuum caps at Autozone and sealing all four ports. I would just take a look at them every few months, because they are kinda crappy quality, and make sure they aren't corroding. You can drive this way without an issue as long as the CEL doesn't bother you.
I went one step further and disabled the EGR completely through ECUFlash, and disabled the the EGR tests that cause the CEL along with it. If you search the ECUFlash forums there is a ton of info available on how to do it, it's pretty straightforward.
I hope this works out, this problem drove me nuts until I found what was causing it! Eventually I'll remove the intake manifold and clean out the EGR port of all the crud that's causing the system to function poorly.
I went one step further and disabled the EGR completely through ECUFlash, and disabled the the EGR tests that cause the CEL along with it. If you search the ECUFlash forums there is a ton of info available on how to do it, it's pretty straightforward.
I hope this works out, this problem drove me nuts until I found what was causing it! Eventually I'll remove the intake manifold and clean out the EGR port of all the crud that's causing the system to function poorly.
Ugh I WISH I HAD SEEN THIS EARLIER TODAY!! That's what I figured out doing by my self hahah but it took me all day to come up with it haha ugh thank you!!! Now my next question, trying to save some work/time that I really don't have these days...can I loop these hoses or just seal them off somewhere to fix my problem but still drive the car safely? Trying to avoid the egr removal or rather just push it off for a month or two. While it's something I plan to do, just right now I don't have the time.
Thread Starter
Evolving Member
iTrader: (6)
Joined: Dec 2011
Posts: 162
Likes: 1
From: Central New Jersey
You're technically not supposed to loop the throttle body ports. I ended up buying some cheap vacuum caps at Autozone and sealing all four ports. I would just take a look at them every few months, because they are kinda crappy quality, and make sure they aren't corroding. You can drive this way without an issue as long as the CEL doesn't bother you.
I went one step further and disabled the EGR completely through ECUFlash, and disabled the the EGR tests that cause the CEL along with it. If you search the ECUFlash forums there is a ton of info available on how to do it, it's pretty straightforward.
I hope this works out, this problem drove me nuts until I found what was causing it! Eventually I'll remove the intake manifold and clean out the EGR port of all the crud that's causing the system to function poorly.
I went one step further and disabled the EGR completely through ECUFlash, and disabled the the EGR tests that cause the CEL along with it. If you search the ECUFlash forums there is a ton of info available on how to do it, it's pretty straightforward.
I hope this works out, this problem drove me nuts until I found what was causing it! Eventually I'll remove the intake manifold and clean out the EGR port of all the crud that's causing the system to function poorly.
Thank you so much to every one. This was so annoying haha but I'm glad it was an easy fix in the end!
Glad it worked 
Just double check you're all set with your emissions before going for inspection next time.
Just double check you're all set with your emissions before going for inspection next time.
So I searched this morning and found the egr disable peripheries and the other egr disable tables and flashed them all. Didn't touch the egr or hoses, left everything on. This fixed my problem!!!
Thank you so much to every one. This was so annoying haha but I'm glad it was an easy fix in the end!
Thank you so much to every one. This was so annoying haha but I'm glad it was an easy fix in the end!
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