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Rough idle at 1000 rpm

Discussion in 'PT Cruiser' started by Brenda, Nov 2, 2016.

  1. Brenda

    Brenda Member

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    Hi People!
    Once again I come to you for ideas on an issue my beloved PT Cruiser is having. I have 2005 regular PT Cruiser with only 83,000 miles on it and I kept it up really well. My issue is for about the past year when the engine is cold and mostly when it is cold out the car starts fine and the idle speed is a little over 1000 rpm. As the idle speed starts come down when it hits 1000 rpm I get a "shimmy" or a rough idle for about 5-10 seconds and when the idle goes under 1000 rpm it stops and idles fine while the car is warming up. I had a motor mount fixed two weeks ago so the car doesn't shake as much but I'm still having the rough idle issue The car used to run so smooth I had to make sure it was running. I've had the fan motor replaced (not sure if its related to this) and when I've had the car in they cannot duplicate it as it doesn't happen every day but most days when its cold out. No problems in the summer. I live in CT. Car is going in Friday. I googled it and it might be the IAC or throttle body sensor?? Any suggestions or help would be appreciated, I trust my mechanics but I'd like to get this fixed. Thanks again for any help, Brenda :)
     
    ImperialCrown likes this.
  2. ImperialCrown

    ImperialCrown Moderator Level III Supporter

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    Cooler weather may increase the possibility of fouling spark plugs. Higher spark voltage is required to fire a cold spark plug. It would be my first 'easy' thing to look at and fix.
    Worn or wrong type of spark plug and deteriorating spark plug wires can increase the possibility of cold misfire. Replace both plugs and wires at the same time if there are any doubts about them.
    Plug life is 30K miles and wire life is 60K miles according to the scheduled maintenance list in the owners manual.
    You want the correct Champion RE16MC or NGK LZTR4A-11 and a good brand of premium spark plug wires. Their best store brand wires should be fine.
    I see that back in April 2015, you were also having some cold running issues:
    Cruiser running really crappy after dying three times.
     
    Doug D likes this.
  3. Brenda

    Brenda Member

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    Hi Imperial! That was my fuel pump. This is a weird intermittent thing. Thanks for your input once again!
     
  4. Doug D

    Doug D Virginia Gentleman

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    I agree with Imperial. If the plugs/wires haven't been changed, I'd replace them first.
     
    Brenda likes this.
  5. Brenda

    Brenda Member

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    Plugs changed two years ago, not sure about the wires, I only put about 5,000 miles a year on it but I'll ask them to check them, thanks!!
     
  6. ImperialCrown

    ImperialCrown Moderator Level III Supporter

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    They are probably not worn out, but make sure that they are the plugs specified for your car. I have found that the wrong plugs can cause many driveability issues.
    Any Bosch, Autolite or Motorcraft, etc plugs are not meant for a PT Cruiser. Platinum plugs might also cause problems.
     
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  7. chuzz

    chuzz Active Member

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    I agree with IC. Champion copper core plugs work best in the PT's. My GT runs okay on the Champion platinum, but it runs best on the Champion coppers. Have you ever had the throttle body cleaned? If not, then you might try that. Even though you have low mileage, it IS 12 years old now and if you do a lot of short trip driving, the throttle body may be a little funky.
     
    Brenda likes this.
  8. Brenda

    Brenda Member

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    Thanks for the reply-I mentioned when I dropped off my car today what ppl on the forum were saying. I do do a lot of short trip driving, Its only ten miles round trip daily to work. Thanks for the suggestion!!
     
  9. chuzz

    chuzz Active Member

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    Short trip driving is rough on a car. I'd rather buy a used vehicle with a lot of highway miles on it than one with low mileage, short trip ones. Things need to get up to operating temp and stay that way for a while for all of the systems to operate properly and get all of the moisture out of the engine and exhaust.
     
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  10. Doug D

    Doug D Virginia Gentleman

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    That's better than the 1 mile commute my wife has with our Journey. Gauge isn't even off the cold mark. We do drive it everywhere else though. We live in rural county (no cities or townships). A trip to "town" is 35 miles one way so it does get worked out on occasion. On the other hand my '06 Ram 1500 (Hemi) gets driven about 120 miles per day.
     
    chuzz and Brenda like this.
  11. chuzz

    chuzz Active Member

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    Back in 1994 when I worked for Autozone, I lived about a mile and a half from the store. I used to ride my bicycle back and forth to work as much as possible. Helped keep me in shape and kept the wear and tear off my cars! Get your wife a bike, Doug. LOL
     
    Brenda likes this.
  12. Doug D

    Doug D Virginia Gentleman

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    I suggested that long ago but not advisable. She would have to cross a major 4 lane divided highway (US 301) and she works at night. Otherwise, yes, she would walk or bike.
     
  13. chuzz

    chuzz Active Member

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    Yeah, that sounds pretty risky. All I had to do was ride the back streets of the neighborhood where I lived. One hill was kind of a bear, but it helped keep me in pretty good shape!
     
  14. Brenda

    Brenda Member

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    Thanks for your help with this issue and as usual you were all right on pretty much!! Had the IAC cleaned/checked and they checked the throttle body which was fine. Had them change the plugs, they were at 46,000, supposed to be at 40,000. They said they weren't that worn but I said I didn't care just change them. The wires were fine. Now she's running like a champ again!! Idle is much better, stays more consistent if that makes sense. Thanks people!! :)
     
    ImperialCrown likes this.
  15. chuzz

    chuzz Active Member

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    Hey Brenda, thanks for the update. FYI, the recommended plug change interval should be 30,000 miles, not 40. I don't much think 10,000 miles makes all that much difference, personally.