Announcement

Collapse
No announcement yet.

High idle in D4, idle will bounce when put into park w/ AC on

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    High idle in D4, idle will bounce when put into park w/ AC on

    I've observed this problem for the last couple months. Whatever the problem, it isn't observable at all when I'm not using the A/C. FYI just to cover my bases, I warmed the motor up and double checked my base idle and ignition timing (it was off. Thanks, expert Honda mechanics).

    Here's what I've found.
    1. The engine's idle speed is spot on when setting the base idle and after it's set. I also checked for any variances in RPM when load was applied per the 1991 service manual, page 11-86. When doing load checks, turning on the AC is one of them. I saw no change in idle speed. Note: trans is in park this whole time.
    2. If I go driving around and turn the AC on, once the car goes through the gears and I come to a stop, my idle is raised to about 1100 or so, enough to be noticeable. If I leave it in drive and turn the AC off, the idle will drop back to normal after a second or two. If I leave the AC on while stopped and put the transmission back in park, the idle will start to bounce up to about 2k RPM, drop, and go up and down continuously until I turn the AC off. As soon as I turn it back on, everything seems normal. I've verified this behavior many times.
    3. After the motor was warm, I did make sure to check the FITV and gently bottomed it out/tightened down. I think this is the correct way to verify it's adjusted correctly, not 100% sure since Honda just says to check the o-rings and replace otherwise. I'm planning on checking the airflow when it's cold and hot.

    As I don't have the special Honda test harness, I'm not sure how I could go about checking the items on page 11-69. I will say I haven't noticed any other malfunctions or idiot lights on the dash indicating problems.

    I'm going to report back later after I've checked the FITV, but I'm not confident it's the problem. I have a new Honda one ready if it is though.

    Anyone ever experienced this?
    My '91 LX build. Bought September 2017. Sold June 2020.
    http://www.cb7tuner.com/vbb/showthre...r /> t=209871
    Current mileage: 399450 5/18/2020

    My '92 LX build. Bought Novemeber 2019. http://www.cb7tuner.com/vbb/showthre...91#post3293791
    Current mileage: 422679 11/21/19

    #2
    Check all around for vacuum leaks. The FITV is a prime candidate, just replacing the o-ring on the pale yellow piston inside should be enough. If you really want to eliminate the FITV as the problem, remove it and put a piece of electrical tape over both holes, then reinstall. If that solve the problem, then you know the FITV is at fault.

    I also had idle problems with leakage past the o-ring on the idle adjusting screw on the throttle body. With age, it got really hard and no longer sealed (I could hear it leaking). Honda doesn't sell just the o-ring; I got one at my local hardware store that fit.

    If you've been messing with the IACV or FITV (taking them off, putting them on) without replacing the seal at the plenum interface, they could be leaking as well.
    90 LX 4dr 5 spd 396,014 (sold 1/1/2022) - MRT: http://www.cb7tuner.com/vbb/showthread.php?t=201450
    08 Element LX FWD AT 229,000 - MRT: fleetw00d : 2008 Honda Element LX - CB7Tuner Forums

    Comment


      #3
      That's an interesting tidbit about the idle screw! I didn't realize it had an o-ring! I've worked on Honda motorcycle carbs, I should've thought of that.

      I'll give both of those a try Paul.
      My '91 LX build. Bought September 2017. Sold June 2020.
      http://www.cb7tuner.com/vbb/showthre...r /> t=209871
      Current mileage: 399450 5/18/2020

      My '92 LX build. Bought Novemeber 2019. http://www.cb7tuner.com/vbb/showthre...91#post3293791
      Current mileage: 422679 11/21/19

      Comment

      Working...
      X