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P0302 for my 1996 Tacoma

Discussion in '1st Gen. Tacomas (1995-2004)' started by SmogSUX, Oct 12, 2015.

  1. Oct 12, 2015 at 8:23 PM
    #1
    SmogSUX

    SmogSUX [OP] No Money. No Love.

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    96 Tacoma Manual 2.7L 4x4
    Wheelers 5-Pack w/ AAL, ToyTec 1" Shackles, 10" 5125's, 5100's w/ ToyTech Springs, Braided Steel Brake Lines, AFE Filter, BAMF Sliders
    My truck was idling slightly rough for about 4 months, so I finally decided to change the plugs, wires, cap, and rotor. The CEL came on with the dreaded P0302 right before I decided to do the job.

    Here's a video of the idle before:
    https://www.youtube.com/watch?v=wC9hG8B4DaU

    Here's a video of the idle after:
    https://www.youtube.com/watch?v=unOV0gSX8fA

    (I know the videos are upside down and sideways...didn't have time to mess with them)

    Since the idle sounds the same like it's missing on 1 cylinder, does this mean the only thing left for me to check is compression? The engine still feels the same and gets the same gas mileage as it did a year ago. It actually just passed CA smog a month before the CEL came on too. I can post that sheet if it helps. My numbers were well below the MAX levels, but above the AVERAGE.

    Truck is a 96 2.7L 4wd with about 218k on it. Oil has always been changed, never overheated, never towed anything, etc..
     
  2. Oct 12, 2015 at 8:32 PM
    #2
    SmogSUX

    SmogSUX [OP] No Money. No Love.

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    Wheelers 5-Pack w/ AAL, ToyTec 1" Shackles, 10" 5125's, 5100's w/ ToyTech Springs, Braided Steel Brake Lines, AFE Filter, BAMF Sliders
    Forgot to mention I cleared the code and it came back. Also plugs came gapped at 0.043...I had an issue trying to push them to 0.038 so left them at 0.043. Old plugs looked uniform
     
  3. Oct 12, 2015 at 8:44 PM
    #3
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    skim through this post to start.

    a jist of that post is that ultimately it came down to 1 bad coil. it was cracked.

    he was also given the wrong plugs and sent on a wild goose chase between about 4 mechanics trying to figure out what was going on.

    he said though that after changing that 1 bad coil and getting the right type of plugs, his truck is no longer misfiring and the CEL hasn't come back on after so far 50 miles.

    and get some fuel system cleaners or guaranteed to pass and run higher octane fuel through your truck for a while. try and get the whole thing cleaner.
     
  4. Oct 12, 2015 at 8:51 PM
    #4
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    your 96 should have a distributor right? im sure that's where the issue lays. but you should really gap those plugs properly (NGK 2087 BKR5EYA, right?). if you have a compression tester, or one available, go ahead and do it. you'll be removing the plugs to gap them properly anyways :-D

    main thought is that the gap is so large, the voltage drops dramatically and isn't enough to properly ignite the fuel in the chambers.
     
  5. Oct 12, 2015 at 9:50 PM
    #5
    SmogSUX

    SmogSUX [OP] No Money. No Love.

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    It has a distributor, not coils since it's old :p

    I opted for the NGK BKR5EGP (7090). I guess the gap was supposed to be 0.032, so my gap is pretty wide..by the way I was using a feeler gauge. 0.043 was snug, so I'm assuming that meant the gap was at 0.043. I'll try to bend the damn plugs down to 0.032.

    I also used NGK spark plug wires and for the distributor I used OEM (Denso) brand cap and rotor. I can always run a can of seafoam through the motor to clean it up. I know the oil is clean as hell since I had to reseal to the oilpan when I did my clutch job, so I drained ALL the oil and what's in there now is super clean.
     
  6. Oct 12, 2015 at 10:27 PM
    #6
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    there may be issues with the distributor though. condensor, magneto, stator, lol even maybe a vacuum advance! ok maybe not. .. but still. ignition control module could be bad for 1 cylinder. cam or crank sensor could be damaged/dirty.
     
  7. Oct 13, 2015 at 9:51 AM
    #7
    frizzman

    frizzman Well-Known Member

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    running an injector cleaner probably wouldn't hurt but if there is no clog then you won't see any improvement. also there is no reason to run higher octane as it will have no benefit if the brand of gas you buy has the same amount of "cleaners" in it. if you were s/c or turbo then ya but more over it's just a waste. could possibly be the knock sensor?
     
  8. Oct 13, 2015 at 11:10 PM
    #8
    SmogSUX

    SmogSUX [OP] No Money. No Love.

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    Wheelers 5-Pack w/ AAL, ToyTec 1" Shackles, 10" 5125's, 5100's w/ ToyTech Springs, Braided Steel Brake Lines, AFE Filter, BAMF Sliders
    Plugs are properly gapped now. I will say though that I had to get around some traffic, downshift ed to 3rd, and gave it about 80% throttle and felt the power die off around 4k rpms...not sure if that's a sign of something. This weekend I'll have time to rent a compression tester.
     
  9. Oct 17, 2015 at 7:45 PM
    #9
    SmogSUX

    SmogSUX [OP] No Money. No Love.

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    96 Tacoma Manual 2.7L 4x4
    Wheelers 5-Pack w/ AAL, ToyTec 1" Shackles, 10" 5125's, 5100's w/ ToyTech Springs, Braided Steel Brake Lines, AFE Filter, BAMF Sliders
    Yep...it's the head. I just checked the compression: 175-75-150-170 ...I added a little oil to cylinder #2 and it didn't help the compression at all, so definitely the head. How the hell did this happen??

    Does this mean I need to replace the head? I don't have the time or skills to replace valves, so if I do I would most likely have to buy a rebuilt head ($500) and swap them over a weekend. I have never had the valves inspected or adjusted...only now have I read that they should have been done.

    Is there a chance that it's a stuck valve and that I should just seafoam it and see what happens or is it most likely a burnt exhaust valve and I need to replace the head?
     
    Last edited: Oct 17, 2015
  10. Oct 18, 2015 at 6:01 PM
    #10
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    FFFUUUCCCKKKKKK!!!!

    welp. it's not as bad as you think if you are willing to do all the work to get this stuff fixed. mainly because it would be so rewarding if you did it on your own! hopefully you have a service manual to help you.

    Yes, there could be an issue under the valve covers causing you to lose compression!! I've personally found an issue like this on my buddies 82 supra (non turbo :( ) L6cyl. one of the exhaust valve lifters was stuck in permanent position and somehow caused the valve to be stuck open or open too early i can't really remember, but it caused this exact issue. fortunately his valve cover was not obstructed by any other components of the engine, so we easily swapped the lifter without really any issues (didn't even have to remove the camshaft :-D). unfortunately, you have to tear down your intake manifold to get to your valves for #2 :(

    So you have 2 options at this point. either way you have to tear down your intake to get to the valve covers for inspection and repair. or tear down half the engine and replace just the head.

    if a new/rebuilt head costs 500 bucks, it's probably better to go that route. rebuilding your current head may cost half, but could take up to 2 weeks for rebuilding if the shops are busy. Which doesn't matter if you have another vehicle :-D. my shop was backed up as far as a month when it was busy and only had a 1 man crew. then i came in and now it's about 3 days.

    So the first option is to do just that, tear down the intake to get to the driver side camshaft and inspect for issues and repair. hopefully that's all it is.

    second option is much more difficult. after tearing down the intake you'll have to drain and/or disconnect the coolant and hoses, fuel injection, ignition, exhaust, AC compressor, power steering pump, fan, pulley, valve covers, timing covers (upper and lower), and disassemble/replace the timing components just to take off the heads.

    Once you remove the head, remove the camshaft because machine shops may charge extra for something you can simply do. you may want to take it to them though to see if anything needs to be polished.

    god speed.....
     
    Last edited: Oct 18, 2015
  11. Oct 18, 2015 at 6:10 PM
    #11
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    after thoughts. I told you what to do for a 6 cyl. much more complex than your 4 cyl i think.

    i doubt there's a stuck valve from anything that is lubed by oil (in the valve area). the valve springs put some immense pressure to keep them closed. like, 200 lbs of force or more. something wrong physically like a bad lifter is more likely.

    it's more likely that you have a very dirty intake or exhaust valve, and carbon buildup has coated the valve seats, causing a slight opening. less likely is an actual broken/burnt valve.

    If you want' to try and put something in the oil to clean any of the oil passages, try using dexron 3 ATF. but do your research first, as i've never experienced stuff like this, only heard about it.
     
  12. Oct 18, 2015 at 9:36 PM
    #12
    SmogSUX

    SmogSUX [OP] No Money. No Love.

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    96 Tacoma Manual 2.7L 4x4
    Wheelers 5-Pack w/ AAL, ToyTec 1" Shackles, 10" 5125's, 5100's w/ ToyTech Springs, Braided Steel Brake Lines, AFE Filter, BAMF Sliders
    Hmm I guess I can always run a thing of seafoam through it for shits and giggles. I found that the burnt exhaust valve was semi-common on the 2.7L engines when you don't have the valves adjusted. Btw my valves have never been adjusted...ever lol

    By the way just today the CEL flashed at me and when I ran another scan I had the code P1300 in addition to my P0302...I'm assuming it's all related?
     
  13. Oct 18, 2015 at 10:29 PM
    #13
    CodeSeven

    CodeSeven LOC: 33.781461, -115.867251

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    nah. you did a compression test and it showed there was a serious issue. the p1300 is something else.
     

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