strange roughness at highway speed

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  #1  
Old 06-26-11, 04:43 PM
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strange roughness at highway speed

Hello:
I have a 2000 Honda CRV with 168K on it. I encounter intermittent rough performance at speeds of 50 – 60 mph. This is likely connected to stumbling when the engine is cold. The idle is smooth and I don’t feel any decrease in acceleration or MPG. I say “intermittent” because unlike typical missing it is not a steady vibration. It feels as though it is missing at those speeds but not around town where the speed is typically 45 mph. It feels as though the car is being buffeted by winds as though on a plane. The tach (automatic trans) does not show any RPM fluctuations. I thought perhaps the motor mounts but seems unlikely since it is not present at all speeds, though I could be wrong. I have tuned the car with no plugs, wires, distributor cap, rotor, coil. The TPS, ELD and MAP sensor have the recommended voltage per Hayne’s manual.
I have never heard of this type of problem, normally a miss (or something like that) is noticeable at idle and worsens with acceleration.
What the heck could this be?
 
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  #2  
Old 06-27-11, 04:20 AM
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Is or has your check engine light been on? This does sound like an odd problem. One that may not be able to be diagnosed here. Are you sure it is coming from the engine and not the suspension? Does this vehicle have a Mass Air Flow Sensor?
 
  #3  
Old 06-27-11, 03:05 PM
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re intermittent problem

Has a MAP sensor which checked out OK per digital multitester and Haynes. Check engine light is not on. Possible also that the slight one-time hesitation when the engine is cold is not connected to this issue. Will also check motor mounts and do more research.
 
  #4  
Old 06-27-11, 07:07 PM
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how about we read error codes first?
 
  #5  
Old 06-28-11, 04:43 AM
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error codes

Can I get an error code with no check engine light on?
 
  #6  
Old 06-28-11, 04:44 AM
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There can be stored or pending codes that have not yet set the light. Does the light come on for a bulb check when the key is turned on?
 
  #7  
Old 06-28-11, 08:34 AM
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might be a lot faster to simply drive to any parts store and have them read codes, instead of banging on messages door. they do not charge for it and it's a 5 minute job.
 
  #8  
Old 07-07-11, 06:28 PM
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REplaced ECM, same problem

Once check engine light came on, headed to A-zone which showed misfire on all cylinders and bad ecm. I replaced that with a junkyard one with a 6 month warranty (Amazon). I had the same problem as before and no codes will show up as of today. I pulled the 5 amp radio fuse as per some other websites and still have the same problems, although it also misses at low speeds as well. Appears I have either
1. two bad ECMS in a row
2. bad wiring, connecter(s) somewhere
3. ?
I will let you know what's next. Still runs but intermittent as before on the roughness.
 
  #9  
Old 07-08-11, 03:55 PM
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solution found

Problem was the small screw that Honda puts on distributor rotors. Screw came loose and was rattling around in distributor cap. One lead in the tower was bent and the cap had a crack on the bottom. Off to the parts store...
 
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