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  • Some cylinders running twice as hot as others.

    Recently installed the Pro Flo 4 on my 1939 Ford project car's Ford 302. Engine starts easy and idles but seems to have a slight miss or slightly rough idle. Sometimes on cold start it will have slight backfire through the throttle body and once in while coming off idle. This project car has not been driven, still sitting on the hoist.

    I noticed lately that two cylinders on each bank are running hotter than the other two at idle. Cylinders # 2,3,6,7 check out twice as hot at the headers as #1,4,5,8, when checked with a laser thermometer. I have used this method for locating a bad injector on a diesel before. The plugs colors are blacker on the hot cylinders which to me would indicate running rich. Cold plugs are a little on the wet side. All injectors are showing green on the diagnostics screen.

    This is my first experience with an aftermarket EFI. Seems like it would indicate a timing problem but I cannot come up with any problems. Checked TDC with a dial indicator and comes out right on the money. Static timing and actual comes out to 12' BTDC. Hot torqued manifold bolts. Rechecked valve lash.

    Baffled!

  • #2
    the mod's will need some info what cam shaft what map did you load what firm ware are using what fuel p.s.i . if you could post a vid of tablet while running these will help to get to the fix

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    • #3
      Here is some additional information on this issue and I have done some additional testing since my first post.

      This is a fresh long block rebuild. 1982 block, rear sump, bored .40 over, mild cam, stock heads except roller rockers and 140 AMP alternator. Compression 160-165 lbs across all cylinders. The firing order is 1 5 4 2 6 3 7 8. Cylinders 8 1 5 4 are cool, and 2 6 3 7 are hot. So it is only fully firing half the sequence.


      Noid light is dimmer at the bad cylinders than the good. Indicated voltage on the tablet is 14.2 to 14.4. As would be expected from the Noid light, my tester shows 11.9 to 12.0 V at the bad cylinders and 12.7 to 12.9 V at the good cylinders.

      I know the injectors get there pulse signal from the negative side so the engine block is well grounded.

      What am I missing or could I have a bad ECM?







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      • #4
        Swap over the injector leads from the hot bank to cold bank. ( for testing )
        See if there is any change?

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        • #5
          Great Tip.

          I did various combinations including L and R injector harness on opposite sides and same results. The engine ran almost the same which was surprising. I have a mid priced set of new MSD ignition wires. Changing out the plug wires is something I have not tried which is worth a try, Does not explain the voltage difference at the pigtail.

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          • #6
            Check all the pin connections of the Pro-Flo 4 harness......it has 4 wires that turn into 1 to fire the ignition coil.

            Replace all the spark plugs.
            See this a lot with to much idle time, and not enough road time.
            At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

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            • #7
              Do you have access to a set of noid lights? You plug them in place of an injector and it tells you if it's getting a signal.

              However, what are all your cam specs and what are the actual temps you are seeing and what it the finish on your headers? It's odd that only the 4 center cylinders with the shortest runners are running hotter than the outboard 4. How about if you go to 2500 rpm, same results?

              I am with BITE_ME though, check connections and replace plugs if funky, watch going too much gap, not a lot of benefit there. I probably wouldn't start fixing the problem until you can get it out and run it a bit to see if it is a problem

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              • #8
                Checked all the pin connectors and could find no visible damage. In general, I am very impressed with the quality of all the connectors on this harness.

                The car is sitting on a hoist with the front clip off at a comfortable height so very easy to access everything and work on. Changed out the plugs and plug wires, same results.

                I failed to mention I have the recommended Walbro in- tank fuel pump run through a relay. Fuel pump regulator set at 43PSI with the vacuum line removed. Vacuum line reconnected during run-up. All green lights on the diagnostics screen.

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                • #9
                  What is the Pn# of the camshaft installed into this engine?
                  302's have two firing orders.

                  Later model cams use the 351w order.

                  Just sayn ?????

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                  • #10
                    That was it! 2700 Cast was right on. The cam is a Melling MTF-5 that uses the 351 firing order i just discovered. Took a bit of digging to find that. Changed the firing order and that resolved it. However the engine did not like the 351 selection in the Setup Wizard and ran better when I went back and selected 289/302 firing order, which is still puzzling. Maybe a "heads up" but I think my situation is resolved!

                    Thanks for the help!

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                    • #11
                      Firing order in the app is for the fuel injectors.
                      The placement of the plug wires on the distributor, dictates the actual firing order.
                      At 43,861 MPH Elon Musk now owns the fastest car in this Galaxy

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                      • #12
                        Originally posted by tnormantt View Post
                        That was it! 2700 Cast was right on. The cam is a Melling MTF-5 that uses the 351 firing order i just discovered. Took a bit of digging to find that. Changed the firing order and that resolved it. However the engine did not like the 351 selection in the Setup Wizard and ran better when I went back and selected 289/302 firing order, which is still puzzling. Maybe a "heads up" but I think my situation is resolved!

                        Thanks for the help!
                        Smart catch 2700 Cast. FYI, I have run into this with EEC-IV tuning, it likely would only affect it at idle and maybe very low rpm, once you climb a little the injectors sort of continuously fog so it's not at critical, but certainly MUCH better to have the injectors firing when they should. In kits with injector timing inputs, you can even adjust for the specific intake lobe design and it really smooths things out, never mind afiring order error.

                        However,to the OP, are you saying you are running 302 with the 351W firing order selected? or you are now running 351W with 302 firing order? In the end, actual wire location and EFI has to match cam, regardless of what displacement

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                        • #13
                          At the moment I am running the 1-3-7-2-6-5-4-8 firing order on my distributor but selecting the 289/302 firing order on the AP which shows Ford 289-302 [1-5-4-2-6-3-7-8].

                          An interesting thing is page 6 in the User Manual that came with the kit shows SELECTING FIRING ORDER choices as: Ford FE [1-5-4-2-6-3-7-8] under item 7 in the Setup Wizard and Ford 289-302 [1-3-7-2-6-5-4-8]

                          So which is it?

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                          • #14
                            STAY out of Setup Wizard......

                            Go into ECU Settings > Load MAP > MY MAPS> Pro FLo 4 > " your current MAP # > MANUALLY SELECT 1-3-7 firing order & hit LOAD

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                            • #15
                              OK, I did that. Thanks.

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