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Engine runs richer and richer, I get poorer and poorer

Discussion in 'FAST Support Forum' started by Fast 1.0 383, Jul 31, 2017.

  1. Fast 1.0 383

    Fast 1.0 383 New Member

    Apr 17, 2016
    I have an ez efi single, with the fast efi system. its sitting atop a chevy 383 (very mild) with a stage 2 intake, lonng tube headers and 2.5 in exhaust flow master muffler. That all sits in a 93 chevy truck... if that matters. ;)
    What I Know?
    Didn't run reliably, fixed electronic interference, removed tac, everything was already running to negative, isolated system further, now electronically seems to run well
    Didn't have enough back pressure. fixed that, got my low end torque back.
    Learned exhaust leaks can fool the system into a ultra rich condition, replaced all my exhaust gaskets(I knew they leaked, thought i would address after I got the truck running better)
    I cant get the idle target to settle in the little block, as to do so I have to adjust my engine to run at a ridiculous idle (above 2 grand somewhere)
    took it for a test drive tonight. Having learned that the more times you key off the quicker you will notice a problem... did this. was back into the ultra rich no power zone I reach after several long drives.
    What I don't know
    How to fix my truck.
    Am open to suggestions
  2. A A

    A A Well-Known Member

    Jun 22, 2014
    Check the fuel regulator pressure with the key on (engine off), and that the vacuum line to it is getting fulltime vacuum with the engine running.
    Check the MAP is reading close to 100 with the key on, engine off. (varies some due to altitude)
    Check for any vacuum leaks around or on the intake.
    Initial timing should be 15 to 20 degrees, slope above 2400 - 4000, total mechanical 28-34 degrees.

    What compression, what fuel, what are the camshaft specs (.050 duration and lobe separation), and did you degree the camshaft?

    What sparkplug and wires are you running?

    Once this is sorted, plan on installing new plugs of the correct heat range.
  3. Fast 1.0 383

    Fast 1.0 383 New Member

    Apr 17, 2016
    no vacuum to fuel regulation, after talking to tech they suggested that the controller cant keep up with the change so I disconnected that. Running 93 octane @ 60PSI currently. 8mm wires, auto lite platinum plugs I think. I've checked and re checked for vac leak, but will confirm the rest when I get home again. Timing is as close as I can get it, checked it with the light and confirmed with vac.
  4. A A

    A A Well-Known Member

    Jun 22, 2014
    Wrong, the regulator needs full-time vacuum connected. Assuming you have the 1.0 TBI, fuel pressure should be 43 PSI. Too much fuel pressure causes rich running. Not connecting the vacuum will cause fueling issues regardless - as the vacuum regulates fuel pressure according to engine load.

    The intake needs to be a SINGLE plane intake with a TBI unit. If it isn't, there will be uneven fueling and plug fouling from cylinder to cylinder. This will also cause rich running. There will also be eventual MAP sensor loss from fuel reversion problems. Any backfiring will also ruin the MAP sensor in the TBI.

    The Platinum plugs are also wrong, you need a regular extended tip type plug - like NGK BKR-5E for 9:1 compression and BKR-6E for 10:1. Do not change the plug gap from the gap set by the plug manufacturer. Correct plug type, gap, and heat range is necessary, or fouling and rich running will occur. It is critical the timing is set correctly, or good correct plugs will foul and/or glaze quickly to become useless.

    The plug wires also need to be spiral wound, 40 Ohm per inch, Pro wires like MSD offers. The correct wires will substantially lower electrical interference that will confuse the ECU and prevent proper fuel map setup - and will fire the plugs better.

    Timing - Your distributor needs to be set up with heavy springs for a 4000 RPM all-in slope. Depending on your compression, set total mechanical timing at 28 (for higher compression)-34 degrees (for lower compression). If you have a vacuum canister, you want no more than 7 degrees of vacuum advance - and you want the vacuum advance set for early vacuum timing fall off during acceleration. This will stop the detonation and pre-ignition you have going on.

    Fast fuel injection needs at least 15-20 degrees of initial timing. You find the exact amount by getting all the above done, resetting the ECU and providing the correct input to the handheld, and checking the idle vacuum at 750 RPM. You set the initial timing for highest stable vacuum. If the initial is low, engine heating will be wrong with high exhaust temps - that will cook the plug wires and boots from rich running (also caused by retarded initial timing). Once you find the correct initial timing. You will likely need to limit the distributor total mechanical advance. Not doing this correctly will cause engine destruction.

    Note: the correct MSD distributor will make distributor timing adjustment much easier.

    "after talking to tech they suggested that the controller cant keep up with the change so I disconnected that." That tech was lame.

    You have multiple mechanical issues.
    Last edited: Aug 1, 2017
  5. Fast 1.0 383

    Fast 1.0 383 New Member

    Apr 17, 2016
    Checked the MAP as directed and am getting a reading of 97-98 steady. my cam is a comp cam:12-314-4 duration @ .050 212 lobe lift .2960 separation 112.0.
    i am running a msd distributor, with no vac advance, so re setting the springs shouldn't be too much of a problem. My intake is a summit stage 2 intake on stock vortech steel heads.

    as to the second post..... that may take a bit, as time is tight, i'll report back how she runs with the changes.
  6. A A

    A A Well-Known Member

    Jun 22, 2014
    Sounds like the MAP sensor is still good. Your cam supplies good vacuum and should be no problem unless you have 10:1 or higher compression (it doesn't have enough .050 duration to blow off excessive compression at higher static compression ratios).

    The intake is a problem on possibly two levels. First, what I found Summit offering now as stage 2, was not designed for Vortec heads. Second, and very important, what I did see is not a single plane intake design. This means you have a serious mismatch for your TBI system at either point. If you do have Vortec heads, you can find a single plane that works here - https://www.ebay.com/sch/i.html?_nkw=single+plane+vortec+intake

    One inexpensive ones that will work fine with Vortec heads -


    I actually run a Hurricane Plus in my '81 GMC and it runs great with my EZ EFI 2.0 system - even with my higher compression and larger duration camshaft. The difference is my Hurricane Plus is the different model for old style 23 degree heads. The Hurricane Plus is the height of a Victor Super, and I can't find any difference in performance between them - but a huge difference in price. It also easily fits under the hood of a pickup truck.

    The intake change to a single plane style will immediately clear up some of your problems. The single plane will also improve torque and horsepower from idle to high RPM.

    The replacement sparkplugs will also need to have the correct reach for your year model Vortec iron heads. So my earlier supplied numbers may be off. The NGK heat range will still be 5.

    With your MSD distributor, install the two silver heavy springs and use the black advance stop bushing. This will give you 18 degrees mechanical advance with slope at 4000. You can then set the initial timing to 16 degrees for a total of 34 degrees advance. Any further changes will only involve changing springs and/or possibly increasing the initial timing - if the engine can safely handle additional timing changes.

    Edit: Wow, I finally found the Summit intake for Vortec. That is one over-priced puppy. It has a Chevy part number and it is still a dual plane.
    Last edited: Aug 2, 2017

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