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  • 99 civic rough idle

    My '99 Civic is having idle issues. When I start up it is usually fine but when I put it into gear with the brake on it idles really rough.. I can feel the engine shaking in my seat. It isn't a motor mount issue and I have already changed the PCV valve and reset the ECU by taking off the negative battery cable. The throttle body is clean of course and the idle is fine when it is not in gear. Any suggestions?

  • #2
    Re: 99 civic rough idle

    Evaluate the following;
    Spark Plug wires - OEM only for sure fix... aftermarket is a crap-shoot

    Spark plugs - same as #1. This car is picky about the plugs you use.

    Valve adjustment - every 30k recommended

    Fuel Filter/s - for oil removal. CNG injectors are extremely sensitive to the slightest amounts of oil. If you're not changing them as recommended (and most don't) all it takes is using an old compressor that blows oil past the rings to ruin your day.

    Fuel injectors - if all else checks out. Due to replacement price being the highest of previously mentioned items/services... test them first, replace them only after all other potential problems have been eliminated, unless they prove to be the problem right away. It's usually the injectors though.

    I'll add that running a car with this bad a miss will take out the O2 sensors and Catalytic Converter pretty quickly, so don't drive it (unless you have to) to keep a moderate $ repair from turning into a major $ repair.

    anyone want to build on that?
    Last edited by Curtis; 06-16-2010, 09:56 PM.

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    • #3
      Re: 99 civic rough idle

      [QUOTE] reset the ECU by taking off the negative batt.......QUOTE] Why did you do that ???? Was the check engine lite on?

      Get a code scanner and see what codes are stored.............Rare, but a bad distributor base can cause rough idle...........How many miles on the car , and when was the timing belt last changed? - 6 years or 90k miles. Honda is an interference engine type valve train, and timing belt failure makes the valves go Bye Bye$$$$$$

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      • #4
        Re: 99 civic rough idle

        Thanks for the input. I reset the ECU because it was recommended on a Civic forum; didn't make any real difference in fuel economy or rough idle. The car has 79,000 miles and has had the High pressure NG filter changed in the last 2500 miles and the timing belt and water pump changed in the last 5000 miles. I just bought a bosch distributor cap, OEM spark plug wires, and NGK platinum alloy spark plugs to put in; do you think that maintenance will help?

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        • #5
          Re: 99 civic rough idle

          Maintenance can never hurt. If it needs doing, or has been done egularly, it tends to eliminate some potential sources of the problem, but not always. We've seen members use after market plug wires (thinking he'd eliminated the source for a miss) only to do tons of other stuff before figuring out it was one of the new wires. As I said, this is very often an injector problem. Identifying the cylinder/s with a miss, then moving the injectors around and see if the miss moves.

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          • #6
            Re: 99 civic rough idle

            A note to all, the NGK application chart from NGK has an incorrect gap spec. for the 01-05 GX engine and I'm pretty sure they have the wrong gap on the '99 chart also. All '01 and later GX engines have a gap spec of .030 . This is much smaller than the gasoline engine. I'm pretty sure the '98-2000 is also a smaller gap. Check with the Honda dealer , because as I said before, the NGK supplier chart is wrong. A larger gap will change engine performance and CNG vehicles are very sensitive to ignigtion issues.
            Last edited by Lakewood90712; 06-18-2010, 08:15 PM.

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            • #7
              Re: 99 civic rough idle

              I will lay money down on a bad injector. Probably number 3. Make sure that you do your pgslugs, wires, cap and rotor if you haven't done them in a while. Partsgeek.com has great prices on the plugs. I posted about it a while back.

              Get a code scanner and find out what is causing the check engine light. And make sure that you aren't driving it unless you want to replace a catalytic converter (which is NOT cheap).

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              • #8
                Re: 99 civic rough idle

                So what is the correct gap for a 99 GX and what are the best spark plugs to buy? I went to an auto store and they didn't have a listing for honda GX so are the plugs compatible with another model in the 99 year? They gave me NGK ZFR5FGP plugs; are they even the right ones?
                Last edited by danaman; 06-29-2010, 08:39 AM.

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                • #9
                  Re: 99 civic rough idle

                  And can you let me know if there is any validity to this from EDMUNDS from someone with a similar problem????
                  *
                  He again attributed my rough idle to non-OEM parts (I guess Bosch doesn't know how to make Platinum plugs, or automotive spark plug wires). When I was ready to take the plunge and buy the Honda parts, the guy at the parts counter had seen the rough idle problem in the past, and knew it had been fixed by changing the distrubutor base plate. This is the main housing which carries the spindle, and the dist cam sensor. He didn't know whether it was bearing wear causing spindle wobble, sensor position, or sensor failure, but he was pretty sure it would work.
                  *
                  HE WAS RIGHT! $225 USD later, my rough idle was gone. This was great info from a guy who does not diagnose car trouble, but observed what worked to solve this problem in the past. He also agreed with me that Honda parts makers don't have any proprietary pixie dust to make their parts work better than other equivalent parts from alternate suppliers.
                  All the best,
                  Jerry

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