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Can't Rev past 6500rpm

Discussion in 'General Tech and Maintenance' started by unix4linux, May 3, 2006.

  1. unix4linux

    unix4linux Senior Member

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    Hello All,

    Need some help here with my rev limit issue. I have a 1994 Civic EX...here are the only things I have done to the car:

    18 inch rims
    Apexi catback exhaust
    short ram air intake

    Problem:

    When I rev the car up to redline, it cuts off at 6500rpm. If I redline while driving it (under load) it still redlines at 6500. It should redline at 7200 and cut off at 7600 if I am not mistaken.

    What I tried so far:

    I checked to make sure I have a p28 ecu and I do

    I told my buddy to bring his 1995 civic ex over and so that we can swap ecu's to test. I put his in my car and still limit at 6500 (that's what the tach is showing)

    I put my ecu in his car and he can go up to 72-76k with no problems. His car feels noticeably stronger and climbs up to 72 much much faster than mine.

    Pined the ecu and all I have is a cel for 41 which is primary O2 sensor.

    Checked my oil pressure and thats fine

    No other cel lights. Don't know why his can rev up so fast and higher than mine while mine just cuts off at 6500.

    I got this car from a lady as a gift as is so I am assuming I inherited the problem.

    I changed the cap, rotor, wires, and spark plugs but still cutting at 6500. The engine is not producing the power I think it should have. My buddy's civic is stock with exhaust and intake just like me.

    At one poing I thought it was probably the 18 inch rims because of the speed changes on the bigger wheel radius but that shouldn't stop it from going up to 7200k

    Check the timing as well and it's fine at 16

    What can you guys suggest?
     
  2. VTECin5th

    VTECin5th Administrator

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    o2 sensor...
     
  3. unix4linux

    unix4linux Senior Member

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    Do you really think my o2 sensor will stop me from reving past 6500k...not calling you a liar but I have had other cars with o2 sensor problems and this has not stopped the car from reving to it's peak point

    Just trying to make sure...thanks for the help though
     
  4. VTECin5th

    VTECin5th Administrator

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    Every car is different man.
    My VSS stopped my fuel pump.
    My old prelude had 2 o2 sensors and it ran like shit until 4k rpms where it was like i had VTEC then cut out early and jerked really hard.
    Obviously if you have a code, i'd start there before trying to troubleshoot anything else.

    The short answer: yes i do.
     
  5. unix4linux

    unix4linux Senior Member

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    Well, I def. respect your answer. I will try that out because the way I see it, it still has to be fixed. I am still open for more suggestions as well...thanks a bunch
     
  6. wanderinman

    wanderinman Senior Member

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    First, stop hitting quote, this post is longest ever.

    Second, make sure your tach is reading correctly. You can either rent a gauge from a parts store, or just see what RPM's in what gear at what speed your at, then compare to your buddy's car. They should be the same as far as gear ratio so the RPM's should come out the same in a similar cruise setup.
     
  7. bcivicsi

    bcivicsi Member

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    Its the distributor!!2 of my friends had the same problem both were the distributor.Check that its most likely your prob. :thumbsup:
     
  8. jjraw85

    jjraw85 Junior Member

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    YEAH internal parts inside dizzy/sounds like
     
  9. unix4linux

    unix4linux Senior Member

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    I am not hitting the quote button. When I hit reply it automatically quotes everything...anyhow, I took the time to delete the quotes everytime it does that :p

    As for an update, I changed the o2 sensor and that didn't fix anything...but at least I don't have my cel light complaining about the primary o2.

    Today I will test with my buddy's distributor and see what happens. I think you guys might be right about the dizzy. I will let you know what happens. Thanks for the help and sorry about the quotes :-D
     
  10. VTECin5th

    VTECin5th Administrator

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    Yeah, i lost track of this thread, but when whoever suggested dizzy it made sense...my prelude acted fucked up on bad o2s, but- dizzy was a better diagnosis.
     
  11. vtecsir1

    vtecsir1 Senior Member

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    how about bad tach? my tach is off about 400 rpms; how do i know? because my ecu is set to redline at 8k but on the tach its more like 8400-8500
     
  12. wanderinman

    wanderinman Senior Member

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    How do you know its not the ECU? [​IMG]
     
  13. vtecsir1

    vtecsir1 Senior Member

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    2 diferent ecu's with chips set at 8k i hardly doubt they are both programmed wrong from phearable.
     
  14. unix4linux

    unix4linux Senior Member

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    ok guys,

    I think I found the problem. I swapped dizzy's with my friend and still the same problem. Then, we both decided to go for a ride and I told him to hold his car in second gear at 3krpms while I did the same. I did 31mph's and he did 25mph's

    So, I am positive it could be my 18 inch rims throwing the engine speed off. The tach is made for 14 inch tires and I am now running 18's.

    I eliminated the ecu, distributor, oil pressure, o2 sensor, basic tune up, and timing and still the same problem. When we both took that test drive his car was reading a different rpm than I was...looks like I have more rotation now with the bigger rims...

    What do you guys think?
     
  15. VTECin5th

    VTECin5th Administrator

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    tires would affect mph not rpm.. your tach is teh broked.
     
  16. unix4linux

    unix4linux Senior Member

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    [/quote]
    tires would affect mph not rpm.. your tach is teh broked.
    [/quote]

    I guess in that case I can go out and spend a little money on an aftermarket tach

    The only weird thing is that my friends car idles at 750rpms and so does mine...oh well..not sure but I guess I can go out and get a new tach and see
     
  17. HatchSpeeD

    HatchSpeeD ...Hi...

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    put the stocks back on & feel da VTeK y0!

    [​IMG] for puttin 18's on a civic anyways...sorry but just my opinion
     
  18. unix4linux

    unix4linux Senior Member

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    Well, what can I say, they are $1500 with tires and got them for free from a friend...can't turn that down ;-)

    so i guess i can [​IMG] u cause only a foo would turn that down ;-)

    just kidding...yeah...i might just get some Si's and call it a day...thanks for the help all
     
  19. HatchSpeeD

    HatchSpeeD ...Hi...

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    As long as it wasn't your choice to go out & put 18's on a civic :thumbsup: for you. It just urks the hell out of me when I see people do that. Throw them up on ebay & get some nice light weight 15's & hopefully you should be golden :)
     
  20. unix4linux

    unix4linux Senior Member

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    yeah, they were free and nice so I did take them. I would never go past a 16 on a civic but in this case, I didn't mind...I'll see if I can trade/sell them for some Si's or GSR Blades...

    Once again thanks for all the help guys...
     
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