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2G Trying to fix this idle issue

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Talon Cooke

Proven Member
32
4
Jan 27, 2020
Winnipeg, MB_Canada
Hey guys ive been trying to fix this idle issue. My car has been idling funny since ive gotten it. I took out the iac valve, cleaned it and it sort of fixed it for a little while although it still idled high. Now its back to how it was but even a bit worse. The idle is not consistent at all and sometimes jumps up to 2500 then brings itself back down. Its always after i come to a stop at a red light or stop sign and put it into neutral it will jump around for a bit all willy nilly then stabilize at 1500 or 2000. I posted a video so you guys could see what im talking about. Any help is very much appreciated
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I am talking about the two small 3/8 inch coolant hoses at the bottom half of the throttle body, are those still connected?
 
touching that thing is what led me to create my original "I broke my car" post LOLol. i tried adjusting it before to fix this problem and for some reason it completely ruined it and i could not get it to run at all after. after adjusting it i got the idle down but then it would just stall out on me after revving it. Then it got to the point where it wouldn't even run any more and i had to take it in. I dont think this is the problem tho because of how erratic and inconsistent the idle is. It jumps around and after i give it a throttle blip it will fall down and nearly stall out but then jump back up.
 
Have you boost leak tested it? Does the throttle hit the throttle stop on the back of the throttle body? Make sure all of the barbs and fittings on the intake manifold and throttle body are connected to something or capped. A boost leak test would also tell you, but you can spray some brake cleaner or starter fluid around the throttle body gasket and intake manifold gasket to seti if they're allowing air past. You also want to make sure the oring for your iac is in good shape.
 
To troubleshoot this, a boost leak test is required to make sure you have no external leaks. High idle or idle surge is caused by too much air going past the throttle plate or air getting in after the throttle plate that’s not metered. Here’s a list:

1) throttle cable not adjusted correctly
2) IAC stuck open
3) throttle shaft seals leaking
4) BISS not adjusted properly
5) FIAV stuck open after warm up
6) throttle plate not closing all the way
7) TPS Sensor Not adjusted correctly
8) intake gasket leaking
9) fuel injector O-Rings not sealing in the intake
10) throttle body gasket leaking

most common with dsms is the FIAV and it’s hard to test. Rule everything out and if it’s the FIAV, pop the freeze plug out on the throttle body and turn the plate all the way in to bypass it or use a block off plate. Done.

hope that helps!
 
To troubleshoot this, a boost leak test is required to make sure you have no external leaks. High idle or idle surge is caused by too much air going past the throttle plate or air getting in after the throttle plate that’s not metered. Here’s a list:

1) throttle cable not adjusted correctly
2) IAC stuck open
3) throttle shaft seals leaking
4) BISS not adjusted properly
5) FIAV stuck open after warm up
6) throttle plate not closing all the way
7) TPS Sensor Not adjusted correctly
8) intake gasket leaking
9) fuel injector O-Rings not sealing in the intake
10) throttle body gasket leaking

most common with dsms is the FIAV and it’s hard to test. Rule everything out and if it’s the FIAV, pop the freeze plug out on the throttle body and turn the plate all the way in to bypass it or use a block off plate. Done.

hope that helps!
There is a very easy free way to test the fiav being the problem, unplug the mass air sensor assy, pull the intake from the throttle body, start the car (yes the car will run like this and can even be driven like this if you needed to, I have) and as its idling cover the fiav air bypass port in the throttle body with a finger, if the idle settles down, there is a problem in that area, the same can be done with the other port for checking the isc control of the idle.
 
update: haven't done much testing since this post aside from spraying carb cleaner around the throttle body/ intake manifold; Nothing happened. but, i recently noticed a small leak in the welds on my exhaust manifold. So i am wondering if you guys think that this could be the issue. I will be doing the fiav test that motomatt mentioned above in the mean time. Thanks!
 
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