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My M20B25's Characteristics

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    My M20B25's Characteristics

    I've tuned this engine but it still lacks the power that I expect it to have. For one thing, its an A/T, but I still doubt that its just the tranny. Now that I'm using it as my DD, the increased driving time has made me notice a few things about the car:

    1. Idling hovers 800-950 rpm. Sometimes, when seating in traffic, on a very hot day, it would go up to 1k rpm. But when I flick the gas, it goes back. Does ICV need lubrication, or vacuum leak?

    2. Sometimes, especially when its cold, tachometer is steady, but the idling is not an even "voooo" sound... It has this rhythmical sound like it has racing cams... blug, blug...blug, blug...

    Clogged injectors? AFM? Distributor cap? Rotor? Plug wires?

    3. Also, I can hear a whizzing sound outside of the car (left rear) that sounds like the fuel sending unit. Its intermittent though. Dirty tank? Fuel filter is new. Gas is more than 1/2.

    4. Bumper-to-bumper traffic, and on a very hot day, temp gauge goes over 1/2. Is that normal? It does not reach 2/3 though. Both fans working well. Had the system cleaned for a few hours, using a high-pressure water pump system to take all the rust out. Gingerly cleaned the thermostat by hand too. All hoses are new. No leaks.

    5. In neutral, you can rev it to high RPMs with ease, but under load it takes forever even to take it to 3k RPM. It feels "heavy," or sluggish.
    a. Is this the AFM? I haven't gotten my refurb unit yet, so no way to test.
    b. Valve clearances are too tight? I'm waiting for my parts to arrive as my valve cover gasket (VCG) is leaking into outer portion of cylinders (checked the plugs; black outside, clean inside), and will adjust it & replace VCG.

    4. Intermittently, left fog light goes off, and then without doing anything, goes on again. I've checked this, and even replaced the left bulb after checking the fuse and relays. Nothing. And then it suddenly switches on the next day. At one point, the low beam (HID) on the left went out too, and I just switched off the lights, and switched it on again. Voila! Lights on!

    Is it grounding? Where is this ground found?

    5. Tranny tugs. It does not smoothly upshift sometimes. Sometimes I feel a "kick" when the gear changes, and its not funny especially with a wife who has lower back problems. Could it be just the kick down cable?

    I noticed that there is no kick-down / Bowden cable connected to the throttle? For an A/T, shouldn't there be one? Only one cable is connected to the throttle. I have no Cruise Control.

    6. Steering whizzes when I reach the end of a full-turn to either side. Looked at the PS reservoir, and it looks "moist" with its own fluid. Opened it, and fluid level is ok. However, its brown and not clear. I think its due for a change, and its hoses too. Anyone who has DIY'd a PS steering system? I'd want to flush the system and change the hoses. Would appreciate some tips / links of the helpful kind.

    Would appreciate inputs and feedback. Thanks in advance, R3V.
    Last edited by Quinthirty; 07-17-2012, 03:30 AM.

    #2
    #1 and 2 sound like a vacuum leak.

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      #3
      It sounds to me like there are a number of things wrong. You can try to nibble away at the problems, which will lengthen the amount of pain, or do the whole thing at once. In the end it will cost the same in parts.

      1) Replace the ignition wires, distributor rotor, cap, and plugs. Use NGK ZGR5A plugs.
      2) Adjust the valves
      3) Replace the O2 sensor
      4) Remove and clean the ICV
      5) Test (electrically) the TPS and replace it if either of the switches isn't working
      6) Replace the entire cooling system (radiator, expansion tank, cap, all hoses, thermostat, fan clutch). If you don't know when it was last replaced or if not within 60k miles, replace the water pump, timing belt and tensioner.
      7) On a guess that this is a car with the two fuel pumps, pull the in-tank pump and check for rust in the tank. If there is rust, drop the tank and acid clean and seal it or replace the tank with a new or rust free tank. Also replace both fuel pumps, the filter and FPR.
      8) Remove the injectors and have them cleaned, rebuilt, and flow tested.
      9) Have a proper smoke test run and fix the leaks it reveals.
      The car makes it possible, but the driver makes it happen.
      Jim Levie, Huntsville, AL

      Comment


        #4
        Thanks, Jim. Just waiting for the parts to arrive... I'll keep you posted.

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