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CIS tuning - slight roughness?

Discussion in 'Technical Q&A' started by Jagbuff, Sep 5, 2008.

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  1. Jagbuff

    Jagbuff Formula 3

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    Franck
    #1 Jagbuff, Sep 5, 2008
    Last edited: Sep 5, 2008
    My "new to me" 88 TR has some slight engine roughness that I am trying to tackle. At constant throttle the car does not run smoothly - ie I can feel some slight lurching and hesitation . Under throttle at Low RPMs there is slight roughness/hesitation which makes the car quite sluggish off the line, once it passes the 3.5K RPM mark things clear up. The idle is even at 1000 RPM with no surging and the car cranks right up from cold. It takes a little more cranking when hot but no hot start issue.

    Going back through the records, the injectors where replaced in 2003 (probably varnished from not driving), as were the O2 sensors and cats. I pulled the plugs and they look OK - if not a little lean - gap set at 0.6 mm, the CIS sensor plates look like they are correctly positioned and move smoothly. Pulled the distributors; no pitting, no play on the rotors. Tested the ignition wires and plug extender - resistant ranged from 800K ohm to 1400K ohm - tested extender separately all had 0 Ohm resistance.

    Things I haven't done yet - suggestions in terms of priority?
    Check timing
    Check cylinder bank balance
    Reset idle (if balance off)
    Replace fuel filters...just in case
    Check fuel system pressure
    Check injector flow and opening pressures
    I don't have a gas analyzer - but may be able to locate a scope for the O2
    Take it to the shop...

    Anything else?

    BTW, is there an external way to do a visual check (ie. alignment marks) of the cam timing on the TR w/out pulling the engine?
    TIA
    Franck
     
  2. 2NA

    2NA F1 World Champ
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    #2 2NA, Sep 5, 2008
    Injectors could use a cleaning.

    They might be squirting more than spraying which atomizes poorly at low air velocities but can smooth out when you speed up.
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #3 Steve Magnusson, Sep 5, 2008
    You say it has O2 sensors, but please confirm if it a US version TR (F113A040 engine family marked on top of cyl #6 at engine block) or not.

    Does it exhibit the exact same symptoms when cold (water temp less than ~140 deg F) as when warm?
     
  4. Jagbuff

    Jagbuff Formula 3

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    #4 Jagbuff, Sep 5, 2008
    It is a US car - 88.5 MY with all the emission stuff in place - exhibits problem regardless of engine and oil temp.
     
  5. Jagbuff

    Jagbuff Formula 3

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    #5 Jagbuff, Sep 5, 2008
    The other thing that I just noticed (driving the car back from the Inspection Station where it passed emission with a hitch!!) is the popping sound in the intake when accelerating - like a backfire in intake manifold...
     
  6. 335s

    335s Formula Junior

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    #6 335s, Sep 5, 2008
    disconnetct o2 sensors, ck co-OPEN LOOP, re-atttach o2 leads....does co value GO UP????!!!!
    from where to where
    If so, there is a harness ground open for the lambda propogation circuit....
    there will be an easy fix, depending on the aforementioned co testing...


    the popping is a lean issue....1.2-1.5% co pre cats no sensors attached...this pre-supposes all else is in proper order/tune/adjustment....

    this is a known "quirk issue"....

    if NOT, then there is something else afoot.....
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #7 Steve Magnusson, Sep 5, 2008
    Last edited: Sep 5, 2008
    Sort of good news and bad news:

    The good news is, since it also does it when cold, it is probably not related to the Lambda portion of your KE-Jet system -- i.e. cold-running (with the water temp less than ~140 deg after an overnight cold start-up) is the same as having the O2 sensors unplugged during warm-running. However, it wouldn't hurt to put a scope, or just a DC voltmeter, on each O2 sensor output wire and see what they're doing during warm idle when plugged in and unplugged as 335s suggested.

    The bad news is, since it has the problem while operating cold as a "dumb" K-Jet, it has to be related to the basic fuel delivery -- either being mis-tweaked or uneven fuel delivery.

    Good hunting!
     
  8. smg2

    smg2 F1 World Champ
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    #8 smg2, Sep 5, 2008
    adding to steves input, I'd use a infrared temp gun to locate the lean cylinder and check the fuel delivery rate of that injector. otherwise the fuel distributor needs a re-build and I get it over to Lary Fletcher 251-929-3771, the fuel distributors that is.

    then again is the WUR operating correctly? If you call Larry he'll talk/walk you thru a system check on the CIS.
     
  9. Jagbuff

    Jagbuff Formula 3

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    #9 Jagbuff, Sep 5, 2008
    Thanks guys for the suggestions, I will go hunting.

    I went I pulled the emissions report. Not sure if this provides any clue other than the cats appear to be working well!

    High Speed (2500 RPM) - no load
    HC(PPM) 21
    CO% 0.04

    Low Speed (1000 RPM) - no load
    HC(PPM) 51
    CO% 0.95
     
  10. Rock

    Rock Formula 3

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    #10 Rock, Sep 6, 2008
    your not running on twelve cylinders. check ignition
     
  11. spirot

    spirot F1 World Champ

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    #11 spirot, Sep 7, 2008
    Sounds to me like its electrical... coil, or plug wires? could you have some arcing? the symptoms to me are usually in the ignition, before you get to FI...
     
  12. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #12 Rifledriver, Sep 8, 2008
    If your cats are in good order those are not very good numbers. It should be almost that at idle when tested before the cats. With good cats and in good running order it should read near 0-0 at idle.
     
  13. fletch62

    fletch62 Formula Junior

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    #13 fletch62, Sep 8, 2008
    This sounds like a lean running cond. You need th look at differential pressures in the fuel distributors and cerrent draw on the EHAs. After that I would test the airflow meter position sensors.

    Call me it is not as bad as it sounds.

    Larry Fletcher
    CIS Flow Tech Llc
    251-929-3771
     
  14. Jagbuff

    Jagbuff Formula 3

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    #14 Jagbuff, Sep 15, 2008
    Ok - I guess the passing levels are quite easy here in Texas!
     
  15. Jagbuff

    Jagbuff Formula 3

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    #15 Jagbuff, Sep 15, 2008
    Thanks Larry, I will drop you a line, appreciate the help.
     
  16. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #16 Rifledriver, Sep 15, 2008
    My point is if it is running well it will pass easily. I tune cars to run correctly and never give a thought about passing emissions because they will pass by miles.
     
  17. Jagbuff

    Jagbuff Formula 3

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    #17 Jagbuff, Sep 15, 2008
    Understood, recently spoke with another owner of an 86 TR - apparently the cats are gone (other than housing) yet the car passes!
     
  18. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #18 Rifledriver, Sep 16, 2008
    There has to be cats in place, either precats or main cats. At 2500 with .04 C0 the HC would be through the roof.
     
  19. Jagbuff

    Jagbuff Formula 3

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    #19 Jagbuff, Sep 16, 2008
    I'll ask, he was with his mechanic and they were being coy about the whole thing... Oh well, there goes my dream of putting on a Euro exhaust and hoping to pass!
     

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