2nd gear stall

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Trickflowed306
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2nd gear stall

Post by Trickflowed306 » Thu Jan 10, 2019 1:11 am

What would cause stalling in second gear from a dead stop? Car will just stall like its not getting gas no matter how much throttle is applied and rpms drop below 500 rpm, then conk out.1st gear starts are fine. Trying to get more heat in tires while doing burnouts at the track. I'm using the a9l2 with quarterhorse.

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cgrey8
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Re: 2nd gear stall

Post by cgrey8 » Thu Jan 10, 2019 7:38 am

I'm not sure I fully understand what's happening yet. I get that 1st is fine, but 2nd stalls. But you were saying something about 500RPM, but burnouts don't usually get associated with 500RPM. So I'm just confused about the scenario.

That said, stalls are most often caused by fuel problems. When the fuel is WAY too rich (not just a little rich) or just a little too lean, the engine can loose power and if the engine is also loaded, like during a take-off, it might be enough to stall the engine. In manual transmissions, this can happen faster than you can get your foot in on the clutch to relieve the load. And often when fueling isn't right, pushing on the throttle just furthers the lean condition until the throttle is deep in the stroke which causes the engine to way over-rev.

Although I've found this can also be caused at REALLY low RPMs, particularly on take-off, by excessive spark advance at low RPMs commanded by either the idle spark functions or by the spark table(s). When I first theorized this might be the case, I dropped my sub 600RPM spark advance for both idle and part-throttle to well below 10, particularly in the loaded range above say 15-20% Load. My theory was that when the engine is at that low in RPM on takeoff, starting the combustion too soon can actually build pressure in the compression chamber while there's still enough angle on the connecting rod to try and run the crank backwards. When the connecting rod is +/- 4 degrees of TDC, any pressure in the combustion chamber is just down-force on the crank and main bearings, but isn't producing any meaningful rotating torque (true at any RPM). However while the crank is say 12-15 degrees before TDC, there's a significant enough angle that too early of a combustion can cause the engine to loose it's rotational inertia and stall. The effects are exponential the slower the engine spins which is why this often manifests as a SUDDEN conk-out with no warning or sputter while trying to do a smooth low RPM take-off from a stop sign or traffic light. People with automatics and high stall converters would likely never find themselves experiencing this kind of problem.

But as it relates to your problem of stalls while trying to do a burnout, my guess is this is going to be fuel related, not spark related.
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89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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Trickflowed306
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Re: 2nd gear stall

Post by Trickflowed306 » Thu Jan 10, 2019 9:43 pm

Hmmm, thats interesting.
I have not attempted to do a burn out in 2nd gear yet. I have just been attempting regular take offs in second gear. It looks like there is a quick timing bump to roughly 26 degrees falls to 10 degrees. The Afr does super rich .65 for, I have attached to log the take off starts at about 13 seconds. I guess it would be helpful to have a log of a take off in first to see the differences.
Attachments
2nd gear start.csv
(221.5 KiB) Downloaded 5 times

motorhead1991
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Re: 2nd gear stall

Post by motorhead1991 » Fri Jan 11, 2019 12:42 pm

Starting in second is probably forcing it into lug mode, which has it's own set of spark controls.
1990 Ford Ranger FLH2 conversion. Ford forged/dished pistons, Total Seal file-fit rings, Clevite rod and main bearings, Clevite cam bearings, IHI turbo, Siemens Deka 60lb/hr injectors, Ford slot MAF in custom 3" housing. Moates Quarterhorse with Binary Editor, using the PAAD6 database.

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Trickflowed306
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Re: 2nd gear stall

Post by Trickflowed306 » Fri Jan 11, 2019 11:15 pm

If FN125 is all zeros would that disable the lugging tables? I tested it again tonight adding timing it did not help still conks out. Fuel is there. Something is causing the rpm's to slowly drop after the take off.

Maddox
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Re: 2nd gear stall

Post by Maddox » Mon Jan 14, 2019 6:37 am

Did this issue occur out of the blue or did you notice it after you changed/played around with something else?

Trickflowed306
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Re: 2nd gear stall

Post by Trickflowed306 » Mon Jan 14, 2019 6:44 pm

I can't for say for sure as I never tried to start in 2nd since the car was on the stock tune. Which from what I remember it did so without issue.

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Re: 2nd gear stall

Post by Trickflowed306 » Mon Feb 04, 2019 10:28 pm

After some testing I made some progress. I doubled the dasmin value and that allowed me to do normal starts in 2nd gear. However after attempting a burnout in 2nd gear the car immediately stalls, definitely not a fuel issue as I have to press the pedal to the floor to restart the car . After experimenting with every setting I could think of with no luck. I attempted a burnout in 2nd with the rpms above 4k not stall, and was able to repeat this. What in the tune would cause a stall in 2nd gear when the rpms are below 4k?

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cgrey8
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Re: 2nd gear stall

Post by cgrey8 » Tue Feb 05, 2019 6:17 am

The only things I can think of are flooding it out badly OR some electrical problem somewhere that's either cutting out a critical signal and causing the EEC to not control the injectors or spark correctly. I've heard of MAFs having bad connections and bouncing the EEC in and out of limp mode.

If it's a bad MAF connection, that would be seen in the logs by watching the MAFv value. There's probably also a flag to indicate limp mode or open loop, or something.

Also you can watch the injector PWs before and after the stall and see if there's been a noticeable change in them. Either they go way longer or shorter which would indicate it's either flooding or starving the engine of fuel.

If it's a bad coil or a bad connection to the coil, that's going to be more difficult to diagnose. That's almost a determination by elimination of other possibilities unless you've got something you can tap onto the coil wires (primary or secondary) and monitor the current draw to determine if it's consistent or fluctuating at the moment of stall.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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