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Bad hesitation on acceleration

Discussion in 'FAST Support Forum' started by Timonator, Dec 30, 2017.

  1. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    My car was working great for the longest time but today on the way home from work it started running really poorly. It starts out ok but when I give it the pedal it stumbles really bad and sometimes dies on deceleration. Like I said it just started doing this all of a sudden. It is a Buick 455 with cam, headers ez efi 2.0, msd 6a, pertronix 3, manual transmission.
    I tried resetting the setup wizard but had no luck after that either.
     
  2. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Check the MAP sensor first. The reading should be around 100 with the key on and the engine off engine. Higher altitudes will show in the lower 90s. If the MAP is bad, use the FAST MAP adapter and the older GM style MAP. If the MAP isn't bad, check the exhaust for leaks and the O2 sensor.
     
    Last edited: Dec 30, 2017
  3. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    Map is at 103. It does sound like it has an exhaust leak on the side that doesn't have the O2 sensor. I will have to wait until I can get underneath it to investigate further.
     
  4. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    In the meantime, check for any errors or codes. Check for codes with the engine running. You can also do a Wizard reset - which may solve a possible fuel mapping problem.

    If you have any errors, check the rotor and inside the cap, and the plugs and wiring.
     
  5. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    A screenshot of your handheld master screen with the engine running would be helpful.
     
  6. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    Ok, will do tomorrow. Thanks for the help AA
     
  7. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    Here's that screenshot. It appears that my exhaust leak is one of my mufflers on the opposite side from the O2. Do you think that would cause this ? I'm guessing that's been that way for a while too. Haven't looked at the distributor cap yet.
     

    Attached Files:

  8. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    950 RPM is a high idle for your 2.0 TBI engine - even with a performance cam. The idle fuel is also fat. Your plugs are likely glazed.

    I imagine your timing may also be off. What compression and .050 duration are you running? Are you running a dual plane intake? The Pertronix distributors usually don't offer the timing adjustments needed for best performance with FAST fuel injection. Factory or aftermarket dual plane intakes also don't allow good cylinder fuel distribution with TBI. EZ EFI 2.0 also has no option for turning off the adaptive learning - needed for manual transmission vehicles. You really need the Sportsman ECU - which is a direct replacement for the EZ EFI 2.0 ECU. EZ EFI is best suited to automatic transmission vehicles.

    Here is an example of a low idle vacuum engine running a XR282HR camshaft (MAP 58 at warm idle):

    My EZ EFI 2.0 on a 406 small block with a turbo 400 trans makes just over 500 horsepower with 9.5:1 compression, and a Victor Jr. single plane intake. It idles nicely at 750 - even 700. My idle A/F is 14.3, cruise A/F is 14.7, WOT at 12.7, initial timing at 24 with mechanical slope all-in set 30 degrees at 4000. The vehicle with this engine is an '85 Trans Am and runs as well any stock engine will on the street. It just has much greater power and a louder exhaust.

    In any case, you will be better off using a locked rotor phased distributor and using the FAST ECU timing feature. If you have a dual plane intake, it needs replacement with a single plane intake for improved cylinder fueling. The RPM recommendation of single plane intakes only applies to carbureted engines.

    If your initial timing is too low, you will experience excessive exhaust manifold heat and early plug wire and boot destruction.

    Plug wires should also be 40 Ohm spiral wound to help prevent ECU interference.

    While you may be able to get good performance with the EZ EFI 2.0 ECU with your manual transmission vehicle, you truly need to replace the EZ EFI 2.0 ECU with the Sportsman ECU. The Sportsman ECU has no limitations for high performance low vacuum camshafts. It also keeps the fuel maps stable in manual shift vehicles by allowing adaptive learning to be turned off.
     
  9. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    Its 10:1 the intake duration is 230 while exhaust is 245. Yes it is a dual plane intake. I did intend to replace it with a single plane in the future when I do my head swap. I agree that it could use a little more timing.
    What I really want to figure out is what went wrong. It worked fine since April of 2016 (not daily driven) and yesterday this problem started.
     
  10. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Plugs and wiring plus oil build-up in the cylinders is the likely problem. You can't hear the pre-ignition that has been occurring. My 406 ran okay with a dual plane for a year of sporadic driving before it began acting up. I had to keep its idle at 950 also - to keep the vacuum high enough for decent performance. It was then I also had to change the MAP sensor and checked all the plugs - the MAP sensor gasket had gone bad due to fuel reversion in the intake. The plugs were also showing different coloration from cylinder to cylinder - indicating unequal cylinder fueling.

    The change to a single plane allowed me to raise the initial timing and to lower the idle. All plugs then ran clean after leaning the A/F and changing the timing. 230 duration at .050 causes a lot of fuel reversion. The deeper plenum of a single plane intake alleviates this problem. 10:1 compression will also mean you need to raise slope and limit total timing aggressively for the fuel used.

    The single plane intake also took my engine from 490 horsepower to over 500, and excellent drivability with much improved cold and warm starts.

    Don't wait for the head swap to make the intake, fuel and timing changes - unless you also have some bad valves. You're getting excessive wear the way your engine is currently running.
     
  11. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    Ok, thanks, it will probably have to sit a while before I can get a new intake.
     
  12. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    Also, what is the part # for the ECU upgrade that will work with my ez 2.0 ?
     
  13. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    There is an ECU only XFI Sportsman upgrade, but I don't know the current price or part number. I suggest contacting Richard at fastmanefi.com. He will provide you with a free ECU program designed for your engine if you purchase the ECU from him. His prices are reasonable and he won't try to sell you anything you don't need. He may see this and enter the thread.

    Some things to also consider:

    The EZ EFI 2.0 handheld doesn't work with the XFI Sportsman ECU. You will need the XFI handheld if you want a handheld with the Sportsman ECU. The handheld isn't a requirement as a computer is used to make changes to Sportsman.

    If you have a second vehicle the EZ EFI 2.0 would be more suited to (milder cam, automatic transmission), you might want a full XFI Sportsman with 2.0 throttle body kit - to be more cost effective.
     
  14. Timonator

    Timonator New Member

    Joined:
    Oct 22, 2015
    What bothers me about this is that I bought and installed this system less than 2 years ago . It took me a long time to save up for it and I was told that it would work fine with the way my car is set up. I really don't like the idea of having to re set up a new system in my car.
     
  15. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Yes, I was also disappointed - along with a lot of other folks. The advertising described the EZ EFI throttle body systems as directly compatible with everything - then the FAST techs (along with everyone else) began finding out different. That's why the first thread in this forum was started by a company employee concerning selecting the correct system for your application. They do all work, they just don't work as well as they should in all applications. It all boils down to only using the EZ EFI systems with automatic transmission equipped vehicles, and with engines making over 10 inches of vacuum at 700-750 RPM that also use a single plane intake. You can take solace in the fact the fellow that did the advertising is no longer employed by the COMP team.

    The two EZ EFI 2.0 systems, I have, worked out for me since I used automatic transmissions. But, the one engine with the larger XR282HR cam just barely makes enough vacuum for proper operation of the EZ EFI 2.0 ECU. The XFI Sportsman ECU would have made tuning that engine a lot easier - and wouldn't have been much more expense at the time.
     

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