Corvette Action Center - The ultimate online hub of Corvette news and information! Click here to go to the Corvette Forums!


Supporting Vendors / Dealers - Supporting Membership - Advertising Information - Corvette Amazon Shop
Results 1 to 8 of 8

Thread: Low RPM Miss

  1. #1
    Member Gorgon's Avatar
    Join Date
    Jul 2002
    Location
    Philadelphia, PA
    Posts
    1,386
    Corvette(s)
    None

    Default Low RPM Miss

    My engine has developed an odd miss at idle. This has been going on for some time and I thought an application of Sea Foam had help out but it's not totally gone.

    At idle the car has a random miss. When launching the car the engine stumbles when the RPM drops under 1000RPM. It almost seems like the clutch slips a but that's not the case. Once the car is launched and the RPMs are up the car is fine but this is getting worse.

    What's been done:
    Plugs and wires (AC Delco iridium tips)
    Sea Foam application as well as a GM top engine clean
    New air filter (K&N)
    New fuel filter

    There are no codes thrown and I'm looking for other options. I would think that the MAF or O2 sensors would throw codes. It seems like it might be a sensory since it normally happens in closed loop mode and not open loop mode. Any suggestions?

    Leon

  2. #2
    Member Ripp 73's Avatar
    Join Date
    Oct 2004
    Location
    Columbus, OH
    Posts
    534
    Corvette(s)
    1973 L82 Blue Coupe

    Default

    Well, I guess I'll be the first to throw out an idea. You would think with all the sensors on these cars that if anything was changing that a code would be thrown. You mentioned that plugs and wires have been changed. How long ago was this and did you have the miss and stumble at low RPM's before you changed them out? Also, how many miles are on your 99 FRC?
    I have known a few cars to miss at low RPM because of a cracked Spark Plug. All it takes is a small hair line crack on the porcelain and you can have a miss at low RPM. Eventually the porcelain will crack even worse and if you drive a standard you won’t be able to shift into 6th because the car will shake so badly. This is also something that does not always throw a code right away. This may not be your case at all, but just an idea to play with. If you have a chance to pull the plugs you might want to look at them. Then again, wait for some other responses.

  3. #3
    Member Gorgon's Avatar
    Join Date
    Jul 2002
    Location
    Philadelphia, PA
    Posts
    1,386
    Corvette(s)
    None

    Default

    This has been present for some time but just not this bad. The car has 122k miles on it and the plugs were done some time ago. The plug change was completed around 100k miles and did not affect this at all.

    Leon

  4. #4
    Member LLC5's Avatar
    Join Date
    Sep 2004
    Location
    Wa.
    Posts
    1,148
    Corvette(s)
    98 black 6spd convert.

    Default

    Start with the basics first if there are no codes. External vaccuum leaks should be checked, hoses, pcv valve, etc. Make sure the plug wires are clipped on tight to both the spark plug and ignition coils. Look for any burning, tears, or carbon tracks. Pulling the plugs and looking at them for any differences in burning patterns, and cracks, would be a good idea. If one plug looks different, then you know which cylinder is affected.
    Master Technician

    25+ year ASE Master Certified Tech

    22+ year Honda Master Tech

  5. #5
    Member bwing's Avatar
    Join Date
    Oct 2005
    Location
    California
    Posts
    500
    Corvette(s)
    03 Z06,66 coupe,99 Porsche Carrera

    Default

    Did you have this miss before you changed your plug wires? Check your plug wires because it sounds like you may have mixed 2 of them up. Just my humble opinion.

  6. #6
    Member zagger's Avatar
    Join Date
    Apr 2006
    Location
    San Diego
    Posts
    469
    Corvette(s)
    99 C5 Convertible

    Default

    What's been done:
    Plugs and wires (AC Delco iridium tips)
    Sea Foam application as well as a GM top engine clean
    New air filter (K&N)
    New fuel filter
    I'm reaching here but when you added the K&N filter did you check if there was an excessive amount of oil on it? To much oil on these type of filters could be sucked onto MAF or the IAT sensor and that could effect the engine performance without throwing any codes. I learned that lesson long time ago on my Jeep. now whenever I recharge any K&N filter or even when buying new one I dry it by ruining a shop vac over it. That does not degrade the filter but you would be surprised how much oil they can hold. There are several different types of aerosol MAF cleaners on the market, don't remember which one I used but they all should be good. Hope this might help you, good luck.
    Zig.

  7. #7
    Member Gorgon's Avatar
    Join Date
    Jul 2002
    Location
    Philadelphia, PA
    Posts
    1,386
    Corvette(s)
    None

    Default

    Quote Originally Posted by zagger View Post
    I'm reaching here but when you added the K&N filter did you check if there was an excessive amount of oil on it? To much oil on these type of filters could be sucked onto MAF or the IAT sensor and that could effect the engine performance without throwing any codes. I learned that lesson long time ago on my Jeep. now whenever I recharge any K&N filter or even when buying new one I dry it by ruining a shop vac over it. That does not degrade the filter but you would be surprised how much oil they can hold. There are several different types of aerosol MAF cleaners on the market, don't remember which one I used but they all should be good. Hope this might help you, good luck.
    Zig.
    I will try to clean the MAF but the filter I just put on was a brand new filter. I had cleaned and oiled the old one before but I honestly can't remember if the problem was there before I cleaned the filter last time.

    The problem was there before and after the plug change and, in fact, there was absolutely no change in this issue when the new plugs were installed. I had hoped that would have fixed the issue. This was part of the reason I was doing the plugs to begin with.

    Leon

  8. #8
    Member Willfulone's Avatar
    Join Date
    Nov 2006
    Location
    VA
    Posts
    232
    Corvette(s)
    2004 CE Coupe

    Default

    Quote Originally Posted by Gorgon View Post
    I will try to clean the MAF but the filter I just put on was a brand new filter. I had cleaned and oiled the old one before but I honestly can't remember if the problem was there before I cleaned the filter last time.

    The problem was there before and after the plug change and, in fact, there was absolutely no change in this issue when the new plugs were installed. I had hoped that would have fixed the issue. This was part of the reason I was doing the plugs to begin with.

    Leon

    My bet is you have a coil going bad...

    Good luck with your fix

    Peace
    Chip

Similar Threads

  1. Torque vs Horsepower - VERY impressive commentary
    By Fiddler's Gold in forum C4 Technical and Performance
    Replies: 55
    Last Post: 12-29-11, 10:03 PM
  2. Car cranks but doesnt start
    By Deusxmachine in forum C4 Technical and Performance
    Replies: 50
    Last Post: 08-14-09, 03:04 AM
  3. OK, now i'm baffled - high RPM miss???
    By BarryK in forum C1 & C2 General and Technical Discussion
    Replies: 31
    Last Post: 06-24-06, 08:55 PM
  4. Torque vs. HP - VERY interesting commentary.
    By Fiddler's Gold in forum C5 Technical and Performance
    Replies: 1
    Last Post: 09-09-02, 01:28 PM
  5. Horsepower vs Torque
    By JHL in forum General Automotive Discussion
    Replies: 7
    Last Post: 06-14-02, 04:36 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
© CORVETTE is a registered trademark of the General Motors Corporation & Chevrolet Motor Division.  Neither Chevrolet Motor Division nor any subsidiaries of GM© shall bear any responsibility for CorvetteActionCenter.com content, comments, or advertising. CorvetteActionCenter.com is independent from GM© and is not affiliated with, sponsored or supported by GM©.  Copyright/trademark/sales mark infringements are not intended, or implied.  All Rights Reserved