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Ez efi surging at certain Rpm range only

Discussion in 'FAST Support Forum' started by Algamotorsports67, Mar 4, 2018.

  1. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Remove the MAP sensor and check its gasket, and that its port is open with nothing blocking or clogging it. Sometimes the gasket degrades and partially clogs the port. You also need to use a vacuum gauge to measure the intake vacuum at idle. The vacuum gauge reading will help confirm whether or not the MAP is good. Your intake vacuum at idle should be greater than 10 inches. Looking at the screens will not pinpoint your problems. You have to eliminate causes and find what is not a problem, and then look elsewhere.
     
  2. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
  3. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    106 for the MAP reading on the coast is normal, but it doesn't mean the MAP is working properly.
     
  4. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    IAC looks better, but the MAP and Load are still high - need the idle vacuum reading. O2% looks better also. Take a look at the fuel pressure with the key on engine off. It should be at 43 PSI. Check your injectors are set for 75 Lbs. per hour.
     
  5. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    Fuel pressure test says 43
    74lb injectors
    Vacuum is 12-14”
    Headers and collectors are tight and show no signs of exhaust leaks
     
  6. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
  7. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    Don't disassemble the throttle body to remove and replace the MAP sensor. There is an Allen head screw that can be loosened to remove the MAP sensor. It just takes some dexterity. It's also easier to do with the throttle body turned upside down, but can be done with the throttle body still on the intake.
     
  8. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    Map looks good I had replaced it before with a Delphi unit, clean, seal looks good and the port it goes in on the throttle body is clean as well
     
  9. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    I have a spare map from fast I’ll put in tomorrow and see if there’s any change
     
  10. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    What should my map reading be my research shows it should be in the 60s for 12” of vacuum, which it is.....
     
  11. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    With a warm engine, your engine MAP should read lower than 65 in drive at idle. With your combo, you should be seeing 43-47 warm in neutral. Cold engine should be in the fifties.
     
  12. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    If nothing changes with a known good MAP, you need to check for vacuum leaks and the camshaft timing.
     
  13. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    Checked all the vacuum lines and tightness of throttle body and intake and everything was up to par. Camshaft was installed dot to dot with no advancing or retarding of the cam timing as comp had recommended I do. When the rain lets up I’ll install the new map and let you know
     
  14. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    I understand you used dot to dot with the cam gears, but you need to see the actual valve opening and closing degrees. Cam gears aren't always centered. If you have power brakes, temporarily plug the booster line and watch for any vacuum improvement. Sometimes the booster will still work but will be leaking. Two other things will also cause low vacuum - leaking valves and over tight lifters - cylinder compression testing will spot this. Your lifters will actually have some clatter due to the ramp design of your cam - if there is none, the valves are likely set too tight. Incorrectly set up valve springs will also cause the problems you have. Your hydraulic roller has to have correct springs set up as called for.
     
  15. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    I actually reset the valves yesterday and I had noticed a little more valvetrain clatter with this set up then previous smaller cams. It’s a hydraulic flat tappet, heads were worked when I had the block machines and are set up to handle 575 lift. Going out now to dry the new map then I’ll try plugging the booster. Thank you
     
  16. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    New map no change plugged booster now change still mid 60s map .
    Load low 60s high 50s
     
  17. A A

    A A Well-Known Member

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    Jun 22, 2014
    Hydraulic flat tappet explains some things. Looking at this cam, there's an easy solution for the better vacuum needed - just drop back to 1.5 ratio rocker arms. Using 1.6 rocker arms has the duration higher and that is keeping vacuum lower. Still, as is, warm engine MAP in neutral should be 58-60 - and average no more than 62 in gear.

    But, first, bring the initial up to 22 degrees and see if MAP improves. What stall speed converter do you have? It should be at least 2500 to 3000.
     
  18. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    I currently have 1.5 rockers never had the 1.6 that they speck the cam at, I will bump
    Up the initial timing and take her for a cruise

    Have a b&m torque converter rated at 28-3200 stall
    Th350 tranny
     
  19. A A

    A A Well-Known Member

    Joined:
    Jun 22, 2014
    With the 1.5 ratio rocker arms, you should have much better vacuum. The stall speed range with the TH 350 is no problem.

    What intake gaskets did you use and were the heads milled/how much?
     
  20. Algamotorsports67

    Algamotorsports67 Member

    Joined:
    Aug 11, 2014
    Heads weren’t milled.
    2.02/1.94 valves
    60cc combuston chambers
    Felpro gaskets not sure on the part number off my head maybe 1206
     

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