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Discussion Starter · #1 ·
Here is an odd one for you guys. Started up my corrado G60 today and it started real funny. Started, idled around 1000 for a split second, then blipped itself to 1500 down to 800, up to 1500, down to 800 and did that a few times - almost like it was cammed - and then started to idle real rich because it was cold last night. Then while driving, every time i came to a stop the idle would come down, blip to 1500 and then come back down. Almost like the throttle got stock or something and continued to do this when i came to stops until it hit operating temp. I’ll add in a link so you guys can see it. In the video when it jumps from 1000-2000 is the car doing it itself. Not me at all. My CO Pot is set a little low - i think 350 or 400 OHM - so maybe in this colder weather it needs to be set higher because its compensating too much for fuel? I know my oxygen sensor is only a year old and maybe a couple thousand miles old.

https://youtube.com/shorts/9-a87OfGmkc?feature=share


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Discussion Starter · #4 ·
have your lambda probe tested. The wild swing in idle speed is often a lambda issue.
Apologies, I realize what you are talking about now. My lambda sensory is practically brand new. Maybe 1k miles on it and put in about a year ago if that. I did just check the lambda sensor not too long ago as well, and it still read just fine. I checked the wiring for it when I had done the bottom swap in the car and the wiring was also just fine from what I could tell.
 

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Discussion Starter · #5 ·
Also just for reference, the vacuum for the ECU from the intake manifold is brand new OEM spec hose that is one meter long. This issue did not start to happen until it started to get cold out again (freezing at night kind of cold) and the car had not been started for a couple of days which is what is leading me to believe that 350 ohm for the CO pot may be too low and need to be raised up to around 400 ohm or so. Would this be an accurate assumption? Or could it still be something else as well?
 

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One thing to try is to replace the throttle cable bushing that goes on the gas pedal and throttle cable. A common upgrade was to use the plastic style throttle cable bushing, but I see it is no longer available, or at least not as easy to get as it once was. The plastic bushing previously retailed for around $1. My rubber cable bushing was torn and it caused some weird throttle issues that went away with a new cable and bushing.
 

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Discussion Starter · #7 ·
One thing to try is to replace the throttle cable bushing that goes on the gas pedal and throttle cable. A common upgrade was to use the plastic style throttle cable bushing, but I see it is no longer available, or at least not as easy to get as it once was. The plastic bushing previously retailed for around $1. My rubber cable bushing was torn and it caused some weird throttle issues that went away with a new cable and bushing.
Thank you for the link sir! I just replaced my throttle cable probably around March of this year because of the fact that the bushing was going out haha
 

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Discussion Starter · #8 ·
Update on the blip. I resistance checked my ISV, and my CO pot. CO is at 410 ohm - yesterday was at 360 so i adjusted it up about half a turn - and the ISV was within spec as per the Bentley. I checked the Bentley on the blue CTS as well but found a different reading for what the resistance should be than what I was told it should be. The Bentley has a chart for what the cts should be at in correlation to the temperature. So now I’m confused as to what the CTS reading should be?

Some good news: I went for a drive today and it actually only did it one time in the middle of the drive. The car was already warmed up when it did it. Was coming to a stop and took the car out of gear - at around 2k rpm or so - and that’s when it did it but not one other time during the drive did it do it. Could I be on the right track with the CO pot adjustments?


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When the ISV start to go it will cause the idle to hunt when the a/c is off. If switching on the a/c controls the idle, it’s time for a new isv.

An ISV bypass kit will protect a newly replaced ISV by taking the boost off the internals. After I installed one It gave a better throttle response that requires less feathering of the clutch from a dead stop. It also removed a momentary hesitation on acceleration I’d gotten used to.


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Discussion Starter · #10 ·
When the ISV start to go it will cause the idle to hunt when the a/c is off. If switching on the a/c controls the idle, it’s time for a new isv.

An ISV bypass kit will protect a newly replaced ISV by taking the boost off the internals. After I installed one It gave a better throttle response that requires less feathering of the clutch from a dead stop. It also removed a momentary hesitation on acceleration I’d gotten used to.


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ISV bypass kit you say? Can you link one for me sir? Is this the same as a boost return delete or am i thinking of something else?


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Discussion Starter · #12 ·
When the ISV start to go it will cause the idle to hunt when the a/c is off. If switching on the a/c controls the idle, it’s time for a new isv.

An ISV bypass kit will protect a newly replaced ISV by taking the boost off the internals. After I installed one It gave a better throttle response that requires less feathering of the clutch from a dead stop. It also removed a momentary hesitation on acceleration I’d gotten used to.


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Apologies sir, I think I misunderstood what you meant. Did you mean an ISV bypass, or ISV reroute (same thing?) because an ISV reroute has already been done for mine.

By bypass, I thought you meant filtering the ISV with some sort of mini filter and basically venting to the atmosphere. But did you mean ISV reroute?
 

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Discussion Starter · #13 ·
Caught it pretty well on camera. The first blip was the car and the second time me trying to get it to stop. I had turned the car on for about five minutes to check for a coolant leak - fixed it thankfully - and then shut it off for a probably about ten minutes then decided to take it for a drive. First time the car was on it didn’t do it but when i turned it back on to go for a drive it did this after being on for a minute. ISV?


https://youtube.com/shorts/yLywgWbHeec?feature=share


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That looks like Digifant getting kicked in the nuts by unmetered air. Since there’s a replacement value for almost all of the sensors it’s a process of elimination. I’d start with the ISV, as mentioned.

You’ll have to keep your foot on the gas when first started, but it’ll idle fine once warm. Might need to back the idle screw off a tad if not.
- Bypassing it is just for diagnostics purposes because it’s much more pleasant drive with (a working) one installed.
 

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Discussion Starter · #15 ·
That looks like Digifant getting kicked in the nuts by unmetered air. Since there’s a replacement value for almost all of the sensors it’s a process of elimination. I’d start with the ISV, as mentioned.

You’ll have to keep your foot on the gas when first started, but it’ll idle fine once warm. Might need to back the idle screw off a tad if not.
- Bypassing it is just for diagnostics purposes because it’s much more pleasant drive with (a working) one installed.
Hi sir, I will bypass the ISV and give it a shot. I will see what it does when it starts today at first. It is not a constant issue, it is very intermittent. I did happen to notice that the AFR will shoot rich when this happens if that helps anything at all.

Can the ISV be bad and still resistance test good?

As for testing things: the CTS resistance checks fine, the o2 resistance checks fine, the wiring fro everything checks out fine, the ISV resistance checked fine. The only that made a difference so far was adjusting the CO Pot to take out some fuel.
 

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Discussion Starter · #16 ·
Not sure if this helps or not, but I have about 17 inHG at idle. I was thinking maybe vacuum or boost leak, but am unsure what a normal amount of HG looks likes when reading the boost gauge that I have in the car. I also just checked all of the connections for my boost hoses and it seemed like the most of them were loose for some reason...? Very unsure why those were loose, but I retightened them all down as well as checked all vacuum lines/caps for any sort of damage or loose connection as well.
 

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Discussion Starter · #17 ·
Update on situation:

Seems like there is a theme. It likes to do it when its colder out and when the AFR is lower than 12 starting. It did it today a few times upon starting until i opened the throttle and gave it a little gas then it balanced out. Seems like ISV is maybe getting stuck?


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Either style of one of these doo dads in conjunction w/ a new ISV. These often allow the ISV to operate normally for a while until you clinch a deal on a replacement ISV.


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Discussion Starter · #19 ·




Either style of one of these doo dads in conjunction w/ a new ISV. These often allow the ISV to operate normally for a while until you clinch a deal on a replacement ISV.


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Awesome. Good news is i already have that done to mine. Other news: the car did it both times starting it today and so i disconnected the ISV, started it, and it actually idled really well. No blips at all. I took the ISV off to clean it and see what it does after. If it does it again, I will try to source a new one. As far as i know they are only found on eBay mostly right?


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eBay & eBay in Europe is the best place for ISV. Shop for them by the Bosch part number not the VW part # and save a few $100


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