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car stumbles at first when cold?

This is a discussion on car stumbles at first when cold? within the General Help forums, part of the LSx Technical Help Section category; Update I Still can’t take car apart, jeep is not back together. I did reset my TPS just for kicks ...

  1. #21
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    Update I Still can’t take car apart, jeep is not back together. I did reset my TPS just for kicks and the problem has almost gone away, it’s nowhere as bad, very low level now. Any thoughts? Bad TPS?

  2. #22
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    definately! when a engine stumbles as your's has it is mostly the tps.

  3. #23
    Smiles for 9.5 Years cammed goat's Avatar
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    Yep. I'm glad I replaced mine.

  4. #24
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    Well I replaced the TPS and cleaned my IAC. Problem still there…..Now the rest of the story, ever since I put the new cam in this car (just last winter), even with a tune, it would through a code about once a month for my bank 1 sensor 1 O2. I mostly ignored this and thought that it was because of the new cam.
    But was thinking both bank 1 and bank 2 should be doing this. Anyway the car has just shy of 80000 on it so maybe one was getting weak, so I replaced both for kicks. Problem with stumble gone, I don’t understand this, but glade its fixed. Thanks for all the help from everyone.

  5. #25
    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Quote Originally Posted by SuperSSguy View Post
    Whats the best way to do this? remove the maf and clean it out or do it while still hooked up?should you un hook the sensor too?
    Rule of thumb: Never leave an electronic componet connected to it's power source when cleaning.

    Yes, remove it, spray with the proper cleaner, and never use compressed air to clear/dry the MAF after spraying, let it air dry.

    You don't really want to pool cleaners in your intake manifold.

  6. #26
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    Quote Originally Posted by seweber View Post
    Well I replaced the TPS and cleaned my IAC. Problem still there…..Now the rest of the story, ever since I put the new cam in this car (just last winter), even with a tune, it would through a code about once a month for my bank 1 sensor 1 O2. I mostly ignored this and thought that it was because of the new cam.
    But was thinking both bank 1 and bank 2 should be doing this. Anyway the car has just shy of 80000 on it so maybe one was getting weak, so I replaced both for kicks. Problem with stumble gone, I don’t understand this, but glade its fixed. Thanks for all the help from everyone.
    Stock rear 02's should be replaced @ ~ 70-80k. Glad to hear you got her going again.

  7. #27
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    Quote Originally Posted by seweber View Post
    Well I replaced the TPS and cleaned my IAC. Problem still there…..Now the rest of the story, ever since I put the new cam in this car (just last winter), even with a tune, it would through a code about once a month for my bank 1 sensor 1 O2. I mostly ignored this and thought that it was because of the new cam.
    But was thinking both bank 1 and bank 2 should be doing this. Anyway the car has just shy of 80000 on it so maybe one was getting weak, so I replaced both for kicks. Problem with stumble gone, I don’t understand this, but glade its fixed. Thanks for all the help from everyone.
    Bank 1, Sensor 1 is your upstream (before the cat) driver side O2 sender. These are the sensors that control your engine fueling during closed loop operation. As the PCM does not accept feedback from them until it switches over from open loop to closed loop (I believe somewhere between 120 and 140 degrees coolant temp), it is probably not the cause of your cold stumble. This being said, you should diagnose the sender and replace it, or the wiring, whatever turns out to be the problem. Like Smittro said, an O2 sender has a service life of around 80,000 miles, after which their performance degrades. There is also a heater circuit in the sender that brings it up to temp faster. This is usually what goes bad and you can use a simple continuity check to determine if the heater circuit has failed.

  8. #28
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    Quote Originally Posted by Smittro View Post
    Stock rear 02's should be replaced @ ~ 70-80k. Glad to hear you got her going again.
    Quote Originally Posted by pajeff02 View Post
    Bank 1, Sensor 1 is your upstream (before the cat) driver side O2 sender. These are the sensors that control your engine fueling during closed loop operation. As the PCM does not accept feedback from them until it switches over from open loop to closed loop (I believe somewhere between 120 and 140 degrees coolant temp), it is probably not the cause of your cold stumble. This being said, you should diagnose the sender and replace it, or the wiring, whatever turns out to be the problem. Like Smittro said, an O2 sender has a service life of around 80,000 miles, after which their performance degrades. There is also a heater circuit in the sender that brings it up to temp faster. This is usually what goes bad and you can use a simple continuity check to determine if the heater circuit has failed.
    I'm sorry I meant to say front 02's not rear..Derp!

  9. #29
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    I thought that may be the case and knew what you meant to say. It all good.

  10. #30
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    I always let the car idle until it smoothes out (stops chopping) usually about 3 minutes or so then I pull out and it will stumble when given gas some just before the gauge hits 160. After 160 pretty good to go, it was getting bad gas mileage but I blamed that on all the upgrades (cam, gears, and stall). The car is not stumbling at all now and gas seems to be better. I’m going to check the o2 that I removed.

  11. #31
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    Quote Originally Posted by Blue28 View Post
    It's probably a dirty/sticking or bad IAC. Unplug the IAC and remove it and clean the plunger on it along with the hole/passage it fits in on the side of the throttle body. I'd also look over the plug and wires for the IAC also.
    I second this idea bad iac or dirty

  12. #32
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    What does IAC stand for?

  13. #33
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    Quote Originally Posted by blackcar View Post
    What does IAC stand for?
    Idle Air Control.

  14. #34
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    Quote Originally Posted by blackcar View Post
    What does IAC stand for?
    It isthe idle air control valve.is located on the side of your body close to the throttle position sensor. Looks like an electric motor.comes of taking of two screws and just spray the heck out of it with brake cleaner and let it dry a couple of minutes.

  15. #35
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    Once the IAC and port are clean, go for a drive. About 5 miles at 35-40 mph. I believe that is required for the relearn procedure.

    - - - Updated - - -

    Also inspect the O-ring around the IAC for wear.

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