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Engine stalls when put into gear

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  • Engine stalls when put into gear

    I’ve got a 1978 Dodge RV with a new Pro Flo 4 setup. 5.9L 360 V8 small-block. Install went well and idle sounds good. Got some help from phone/tech support on an initial tune. Gauges are looking good (short FT, IAC, etc.) but it always stalls when going into gear (hot or cold). I can two-foot it into gear and then go driving, but can’t seem to get the system to “learn” to keep it from stalling when going into gear. Once driving, cruising around is good and I can one-foot it, but engine runs rough and has some misfiring > 2500 RPMs.

    More tuning/configuration needed?

    Not enough self learn miles yet? (only 10-15 miles so far)

    Something mechanical, perhaps ignition related?

  • #2
    A quick follow up question: Could an aftermarket voltage-triggered tach connected to the negative terminal of my ignition coil be the potential culprit here? I saw in a few threads for older ProFlo systems that this may cause some issues.


    • #3
      See here for discussions on stalling: of those other threads have questions - if you can answer those same questions here we can better help you.

      Doubt the tach is a problem but it's pretty easy to check. Just disconnect to see if it makes a difference.


      • #4
        Kit is 35900. AFR is about 13.9 and steady, short FT in low single digits, IAC at around 5% at 950 rpm target idle (hot). Vacuum at 19-20. No jump in short FT when putting into gear, just an instant drop in rpm/vacuum as the engine dies.

        Coil is MSD 8202 w/8.5mm MSD spark plug wires.

        Very tight torque converter (RV) so dialed vacuum advance back to 0 in initial tune. Just can’t seem to get the engine to stay running when shifting the automatic transmission into gear.


        • #5
          Having a very tight converter doesn't make things easier and is definitely one of the more challenging aspects to dialing the system in. I'm a little surprised that at such a high idle speed that there isn't enough oomph to keep the engine running when going into gear. What cal are you running? Cam specs? Idle ignition timing value? When you say the Short FT are low single digits, are they mostly positive or mostly negative?

          The two most common tactics to try and prevent stalling when going into gear is to dial in more idle timing and add in some idle fuel. More timing will give you more torque and should help keep the engine running after a whole bunch of load gets dumped on it when going into gear. As for fueling, we already attempt to counteract this problem by fattening up the fuel maps in the load areas above normal idle load so that when the engine loads up going into gear, we attempt to keep AFRs from leaning out. You can add in more idle fuel using the Fuel Modifiers. Ideally, the system is always having to remove a little fuel instead of always having to add fuel as this will give you richer base fueling which is always better than leaner base fueling. When you add in more fuel, the system will likely just trim it back out at idle but the extra fuel will still be there in the higher load area.

          BTW the system can't really "learn" to fix this. The system relies on a consistent Short FT value in order to populate the secondary Long FT fuel map. When this stall occurs, it happens in quick blip so there's no relevant AFR data the ECU can capture to learn from. When you operate the engine through its normal operating range of rpm and load, the system will easily learn but quick, nearly instant blips through a non-normal load spot aren't going to give the ECU any AFR feedback. I would not expect the system to fix this problem by learning - you'll need to try making some changes to help it.

          Not sure I follow the reasoning on having no vacuum advance - can you better explain your thoughts on this? Not having any vacuum advance is leaving torque and power on the table. One thing to keep in mind is that vacuum advance has no influence over idle timing. Idle timing is separate from vacuum advance and vacuum advance only becomes active once you come out of idle mode which is any time TPS is >1%.

          I suggest focusing on gear engagement only when the engine is fully warmed up for now. Address the problem at full operating temp first and then once that's resolved, you can start addressing the problem when the engine is cold and warming up. Your misfire problem is a separate issue. You'll need to troubleshoot that a little further. Is it misfiring in light load or heavy load? What's the ignition timing when it misfires? Have you tried changing the timing? Maybe try dialing in some vacuum advance. What's your spark plug gap? What are your AFR and Short FT values when driving? Have you verified the base timing so you know that the commanded timing in the tablet is what's being delivered at the engine?


          • #6
            Really appreciate the helpful explanation. Here's a quick recap of where I'm at so far:

            Vehicle: 1978 Dodge RV with Pro Flo 4 #35900 setup. 5.9L 360 V8 small-block (LA)
            App: v4.0.1.7 - Firmware: 65 - Map: 5011_v65
            Cam is stock

            Idle spark: 15.0 degrees
            Advance start: 1200 rpm
            Total spark: 36.00 degrees @ 3000 rpm
            Vacuum advance: 5.0 degrees
            No fuel modifiers
            Idle AFR 13.4 - Cruise AFR 13.9 - Accel AFR 12.8

            With this setup, here's where I'm at:

            Manifold: -19.1
            RPM: 905
            Coolant: 183
            Battery: 12.6
            Throttle: 0
            Air Temp: 129
            Fuel Press: 41.0
            Idle Target: 900
            IAC %: 2
            AFR: 13.3
            AFR SP: 13.4
            Short FT: 1
            Long FT: -6
            Injection: 3.05
            Inj Duty: 2
            Spark Adv: 15

            With this setup, I'm running into 2 core issues:
            1. The engine immediately stalls any time I put it into gear (but not N)
            2. I get a lot of backfiring over 2000 rpm (thus my prior 0 degrees of vacuum advance, I misspoke when I mentioned it in relation to the idle issue).

            Thoughts on where to go from here? I had tried some different AFR values (13.9 - 14.0 - 12.8 - 0 vacuum) and that cleared up some backfiring but made no different to the stall issue. When I reset this morning to the base cal to just focus on the stall issue at first, I tried walking up the idle spark 2-3 degrees at a time (up tp 25) but didn't find anything that kept it going when moving into gear. Also added in some idle fuel (up to 10) but I didn't find the right combo of fuel/spark to get me over the hump.



            • #7
              The test process I ran this morning was:
              1. Start engine
              2. Reach Temp
              3. Put in to Reverse (engine dies)
              4. Restart engine
              5. Increase idle spark 2 degrees, hit FInish
              6. Put engine into Reverse (engine dies)
              7. Restart engine
              8. Repeat...

              Maybe I'm missing an important step here re: to how the ECU functions, stores values, needs time to dial in the new idle spark value, etc.


              • #8
                Ah, sorry. Once engine died each time, I'd put it into Park before restarting (probably obvious since it won't start in reverse, but wanted to clarify).


                • #9
                  In case others run into a similar issue, wanted to share a bit of progress. Originally the map here calls for around 750 rpm idle (which makes sense for my 360 v8/727 torqueflight setup. When I initially set things up I noticed voltage was in the mid-11s and worried that maybe the idle rpms needed to be higher to support the RV charging both chassis and house batteries, etc. so I recalibrated idle to the 900s and things looked good...until going into gear. The setup wants to idle in gear at around 750 and the setup couldn’t support it.

                  Dialed the setup back down to 750 idle rpm with the appropriate IAC and throttle position screw setting, and now I have no issues going into gear.

                  Now to take a look at why my voltage is at 11.5 when idling in park...


                  • #10
                    Excellent news and thank you for the follow up. Thinking about it now, perhaps the idle speed was too high and was already stalling the converter which introduces a lot of load onto the engine.

                    For the voltage, I would double check the battery voltage at the battery with a volt meter. Many times old charging systems meant for a carb aren't up to snuff when converting to EFI. Alternator output may be too low and the alternator to battery cable may be too small. Late model cars with lots of electronics will use something like 6 gauge wire for the alternator charging cable.


                    • #11
                      I had the same issue with a "single wire" alternator on my SBF. It didn't want to charge below 900 RPM. When I increased the idle setting it hit the torque converter stall threashold which added load and basically negated the change. I was able to get a higher idle RPM by setting it just below the TC stall. I recently upgraded to a 2400 stall converter and it's no longer an issue.