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    Thread: g60 rough idle when cold/ runs rich

    1. Member jetta-j2's Avatar
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      Jul 30th, 2007
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      1991 Jetta GLI, 95 Jetta GLX, 04.5 Jetta GLI 1,8t. 1990 Corrado G60 Karman
      10-05-2012 04:29 PM #1
      My g60 Corrado has 98,000 on it. i just did the following :
      Fuel Filter
      Spark Plugs
      Wires
      Cap
      Rotor
      Timing Belt
      Water Pump
      Thermostat
      ISV Reroute


      Im running a stock airbox with the K&N Drop in.
      I had this problem prior to doing all of this work and i did all of these things because of mileage. When the car starts say first thing in the morning or when its been sitting a while, It idles really rough almost to the point of stalling. Also i can smell and see that the car is running really rich. Once the car warms up, it idles beautifully and drives good with no issues. Doesnt over heat or anything. I noticed that my supercharger is slightly leaking oil so i got a Rebuild kit that is on its way but this wouldnt cause a rough idle..

      1. I noticed that when i unplug my ISV, nothing changes ( possibly a sign that the valve isnt working?)
      2. I was going to pull my plugs to see which cylinder is running rich ( if any )
      3. I replaced the vacuum line going to my FPR because it blew. Possibly damaged the FPR?

      Like i said earlier once the car is at operating temperature it runs great. Could it be that something is keeping the engine at open loop?

      These are the next things im going to check:
      -Coolant Temp sensors
      -PCM Grounds
      -02 Sensor
      - Ignition Timing? although i dont see how this could change with the temperature.
      - ISV
      - Vacuum lines

      if anyone has any input on whats going on please let me know because this car runs great. i just want it to run great all the time especially with winter on its way.
      Thanks!

    2. Member crazynorweegian's Avatar
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      Portland, OR
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      1990 Corrado 1.9L G60-ST5 Black, 01 stage 3 allroad 6MT
      10-06-2012 03:06 AM #2
      Quote Originally Posted by jetta-j2 View Post
      My g60 Corrado has 98,000 on it. i just did the following :
      Fuel Filter
      Spark Plugs
      Wires
      Cap
      Rotor
      Timing Belt
      Water Pump
      Thermostat
      ISV Reroute


      Im running a stock airbox with the K&N Drop in.
      I had this problem prior to doing all of this work and i did all of these things because of mileage. When the car starts say first thing in the morning or when its been sitting a while, It idles really rough almost to the point of stalling. Also i can smell and see that the car is running really rich. Once the car warms up, it idles beautifully and drives good with no issues. Doesnt over heat or anything. I noticed that my supercharger is slightly leaking oil so i got a Rebuild kit that is on its way but this wouldnt cause a rough idle..

      1. I noticed that when i unplug my ISV, nothing changes ( possibly a sign that the valve isnt working?)
      2. I was going to pull my plugs to see which cylinder is running rich ( if any )
      3. I replaced the vacuum line going to my FPR because it blew. Possibly damaged the FPR?

      Like i said earlier once the car is at operating temperature it runs great. Could it be that something is keeping the engine at open loop?

      These are the next things im going to check:
      -Coolant Temp sensors
      -PCM Grounds
      -02 Sensor
      - Ignition Timing? although i dont see how this could change with the temperature.
      - ISV
      - Vacuum lines

      if anyone has any input on whats going on please let me know because this car runs great. i just want it to run great all the time especially with winter on its way.
      Thanks!
      To be perfectly honest, you should be doing the temp sensors, cleaning the grounds, adding grounding wires, and replacing the vac lines with all of the other stuff you did anyhow.

      Also, ignition timing is PART of the timing belt change procedure... so why are you trying to troubleshoot before you finish your timing belt job? Adjusting the idle screw is also technically part of this.

      Unplug the o2 sensor and see if the idle changes. Also, it is safest to unplug or plug in the ISV with the battery disconnected as far as I have heard (though others have told me that the key just needs to be out, but do you really want to gamble with the ECU)?

      A bad G60 could add drag or reduce the air in the mix and create a weird idle until the computer kicks in after it reaches temp... I suppose. It would have to be pretty shot though.

      Keep in mind the computer is basically blind and deaf on a cold start, so it takes certain conditions for granted. It is programmed to be generous in order to get your car the fuel, etc that it needs on a cold start, even if your car is a bit off or you are in a weird climate. However, it is still assuming that you are not going to exceed those maximum or minimum variable values that are programmed into the mapping for the cold start. If something is pretty far off, it might have a hard time on a cold start but then sortof recover once the sensors are all working together to make adjustments, though they are maxing out their adjustability so to speak. I just had this type of situation happen with my AFR, it would only normalize once the sensors were warmed up and the computer knew to basically open everything up all the way.
      Stephen
      Portland, OR
      Black 1990 1.9L Stage 5 G60 - keeper
      Corrados decay in a way that can only be measured using quantum physics
      http://sites.google.com/site/corradoproject/

    3. Member jetta-j2's Avatar
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      1991 Jetta GLI, 95 Jetta GLX, 04.5 Jetta GLI 1,8t. 1990 Corrado G60 Karman
      10-06-2012 08:03 AM #3
      the timing belt job has been done and i didnt move the ignition timing. I checked it with a light ( through the hole in the trans ) and the ignition timing is on. As for the G-Lader i dont have any issues with boost or low rpms or anything like that, once i get moving it runs fine. Its just at cold idle and sometimes when i come to a stop ill get hit with the smell of rich, unburned fuel. Since im working today and there isnt **** to do ill pull my car in and check the grounds and vacuum. It doesnt help that the people that owned the car before me tried turning it into a race car and hacked the hell out of it. This car has come a long way since i first bought it. Also im going to pull my plugs. Thanks man, ill def check out/ do what you suggested.

    4. Member jetta-j2's Avatar
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      1991 Jetta GLI, 95 Jetta GLX, 04.5 Jetta GLI 1,8t. 1990 Corrado G60 Karman
      10-06-2012 08:04 AM #4
      Also, I did adjust the Idle screw in the back of the throttle body.

    5. Member jetta-j2's Avatar
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      1991 Jetta GLI, 95 Jetta GLX, 04.5 Jetta GLI 1,8t. 1990 Corrado G60 Karman
      10-06-2012 09:51 AM #5
      so i just cleaned and relocated the ground strap going from the ignition coil to the block, i rewired the ISV because the white wire leading to the ISV was attached by a strand and i adjusted the throttle valve again and its idling better ( at about 1,000 rpms ) and it doesnt hesitate quite as much but it still has a slight studder and the rpms will surge between 800-1000. If im not mistaken, when the engine is trying to " hunt " for a clean idle it could be the ISV.

    6. Member G0to60's Avatar
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      1990 VW Corrado, 2002 Audi allroad
      10-08-2012 03:50 PM #6
      Along with what was mentioned above (blue temp sensor, O2 sensor, vacuum hoses, wiring) one thing that helped me with a similar situation was cleaning out the ISV. Disconnect the battery and remove the ISV from the car. I ran some carb cleaner through mine and some nice black junk came flowing out. It didn't totally fix my problem (it was the BTS) but it did help.

    7. Member jetta-j2's Avatar
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      1991 Jetta GLI, 95 Jetta GLX, 04.5 Jetta GLI 1,8t. 1990 Corrado G60 Karman
      10-08-2012 04:35 PM #7
      awesome, yeah ill try that as well. thanks

    8. Member
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      Corrado G60 1989
      08-24-2014 05:31 AM #8
      This is a bit out of topic, but this thread was close as I got for my prob/question.

      When you start the G60 cold, it will push out more fuel then when warm.
      Is this time adjusted or temp adjusted ? I guess temp.
      If so; where is the temp limit for this function ?
      Mine uses way more fuel then normal and I´ve tried alot of things, but this resently crossed my mind..
      I have a new radiator and cooling parts, so when cruising on higway and stuff my engine temp is just above 70 degreese celsius !
      Do the ecu think that I have cold start all the way, causing it to pump out much more fuel ?
      It´s hard to imagine; Picture me rollin´
      Im BANKRUPT ! - A G60 owner

    9. Member mateok's Avatar
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      90 G60 (since new) 93+VR 13 GTI
      08-27-2014 12:21 PM #9
      Quote Originally Posted by Oekern View Post
      where is the temp limit for this function ?
      60*C - 140*F
      Up to that temp, that is. It controls 100% of injector duration at start-up, but it's authority is quickly revoked as the temp rises.

      It's never completely out of the picture, though. It controls acceleration and after-start enrichment over the entire temperature range. It's cold start function ends at the above stated temp.

    10. Member
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      Corrado G60 1989
      08-27-2014 01:33 PM #10
      Quote Originally Posted by mateok View Post
      60*C - 140*F
      Up to that temp, that is. It controls 100% of injector duration at start-up, but it's authority is quickly revoked as the temp rises.

      It's never completely out of the picture, though. It controls acceleration and after-start enrichment over the entire temperature range. It's cold start function ends at the above stated temp.
      Thank you Sir !
      It´s hard to imagine; Picture me rollin´
      Im BANKRUPT ! - A G60 owner

    11. Member G60 Carat's Avatar
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      1982 BMW 320i, 1986 Jetta Carat 1.8/ABA Turbo
      09-09-2014 06:22 PM #11
      Check the grounds for the ECU using a volt meter and, make sure they are not broken or really high resistance. The one ground on the ECU when broken, or suffering a weak connection will cause it to way overfuel at idle and generally idle like garbage.
      | Rust | Zip-Ties | JB Weld | Bad Idle | Scrapes Ground | Rubs when Turning | Busted Ass Door handles |

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