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Thread: CNG Engin tune up - EFI corolla '92

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    Default CNG Engin tune up - EFI corolla '92

    HI

    I own a 92 corolla XE (reconditioned '05) and I strongly feel like its performance on CNG is just wrong in terms of acceleration. Even makes a few noises that are aren't observed when on petrol. Acceleration on Petrol has suffered VERY little, if at all. It's been like that for almost a year now and I'm just starting out to fix things!

    Here's a background & observations i think are relevant

    4EFE stock w/ EFI, auto tranny, landi renzo last serviced about a year back.

    ***This may not be important information so you may skip***
    Went to Enercon ISB about a month back and the guy changed the spark plugs (which had RUST on them) and added this blockage in the air intake to set it right for CNG. Then fiddled with the ignition timing a bit and asked me to test-drive it. There was absolutely no difference in acceleration and it was knocking badly on petrol. Told him and its got to be the piston rings etc cuz the engine tune up is at its best.

    So I got hold of a wrench and decided to retard the timing a bit (atleast to kill the petrol knocking) and surprisingly it even improved the acceleration AND mileage on CNG at the cost of about 15% drop in petrol mileage. (what a dick, that enercon guy). But I still feel like the engine needs some servicing from the inside because it's not how it used to be OR DO I?

    ***Optional read above this***

    -175,000 on the ODO
    -Engine oil has been depleting much much quicker than usual, over the last 3 months.
    -Cold starts are flawless
    -Spark plugs had rust on them (got em changed)
    -Recently got a few seals/rubbers replaced inside the CAM HEAD which has started to leak oil. ( Oil still depleting after the replacement)
    -a low volume tuk tuk sound from under the hood with acceleration (only on Gas)
    -Never noticed any smoke from the silencer but the enercon guy showed me how white smoke was coming when revved heavily ( implying that the piston rings are damaged)


    So basically, If someone could help me here with the major steps (in the the right diagnostic order) involved in restoring an engine that will help me figure out what all work this car really needs, I'd be really thankful. With the knowledge of that, I will start looking for an expert mechanic. Can't trust random mechanics!

    Isn't there a comprehensive guide or something that will help me diagnose with maximum precision what exactly is wrong, looking at the signs I mentioned above or some other DIY tests. Xulfiqar or someone must have put one together? Tried searching the forums but
    cudn't find any.

    Thanks alot!

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    Default

    *Bump*

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    Default

    agar ma aap ke help ker sakta hota to zaroor kerta ....
    Engineer + Car Enthusiast = Awais Jan

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    Default

    ok - here goes.

    you need to get hold of a nice decent multimeter (you'll know why)

    firstly - you start with the valve clearance adjustment and a compression test afterwards. Making sure the cylinders are pumping nice, I would suggest to replace the valve seals at this point of time - very easy when the buckets are removed for shim service (tappet/valve clearance) Replace/clean the PCV and assorted vacuum tubing to ensure no sludge or gunk is present.

    now remove the injectors and have them tested, if they are bad or too worn out/leaking get another set. reassemble correctly and install back. make sure the engine has a thermostat valve and the engine normally sits at half scale of the temperature gauge. If not your ECU will never go to closed loop.

    test the spark plug leads and replace as required, also test the ignition coil (replace if necessary)

    Whip out your multimeter to test the O2 sensor voltage waves, you should find a port on the diag connector called O2 - stick your probe in there with DC setting to the lowest and ground the other probe. When the engine is hot you should see it fluctuate between 100 and 800 mv, if you plot this you will see it make a wave form. test it by either spraying some fuel into the throttle body - your O2 should spike from the rich mixture, similarly leaning it out (vacuum leak) should make it go lean.

    If the sensor is lazy or dead - your ECU will not control the fuel trim and work off its base default setting causing high fuel consumption and also quicker engine wear as high fuel in the cylinders washes down the oil.
    ZRS - Zulfiqar Racing Systems ..... - professionals at work - at crackwheels.com

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    Thanks alot bro. I'll try to translate this to the mechanic and see if he can make sense of it cuz I'm quite zich in this area. Thanks!

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    Default

    Did u tuned ur card from Enercon G-8??

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