2.8 stalls and dies under load


terramedi

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Hello all!
Its amateur hour here but I need help! HELP!

So I have a 2.8 or 2.9 out of a Ranger or Bronco II (not sure where the engine came from). When I drive on the flat it does fine as long as we are going 15mph or less. If I try to accelerate it dies, or backfires and dies. If I try to go up an incline it dies. I can put it in park or neutral and it revs just fine, step on the gas and the engine accelerates well, but put it into gear and accelerate and it dies.

So where to go from here???

Thanks in advance.
 


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PetroleumJunkie412

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Hello all!
Its amateur hour here but I need help! HELP!

So I have a 2.8 or 2.9 out of a Ranger or Bronco II (not sure where the engine came from). When I drive on the flat it does fine as long as we are going 15mph or less. If I try to accelerate it dies, or backfires and dies. If I try to go up an incline it dies. I can put it in park or neutral and it revs just fine, step on the gas and the engine accelerates well, but put it into gear and accelerate and it dies.

So where to go from here???

Thanks in advance.
Map sensor.
 

RonD

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Wrcabejr

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I'm having about the same thing as this guy but mine is a2.8 mine is sputtering and missfiring under a load. I have changed everything from fuel pump filters timing carb adjustments accelerater pump power valve wires plugs grounds and so on still can't find the problem
 

RonD

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I'm having about the same thing as this guy but mine is a2.8 mine is sputtering and missfiring under a load. I have changed everything from fuel pump filters timing carb adjustments accelerater pump power valve wires plugs grounds and so on still can't find the problem
Welcome to TRS :)

Whats the spark timing set at?

And are you using the TFI module spark system?

There are two spark advance/****** methods that need to be used on all gasoline engines, except fix speed/RPM engines
RPM advance/******
LOAD advance/******

14.7:1 air fuel ratio burns at a fixed rate, and its not instant, lets say from Spark to full explosive power takes 500 milliseconds(made up number)
So spark ignites the fuel Before TDC so full explosive power happens 10deg AFTER TDC so it can push piston down to add power to the crank, too far after TDC and little power it added, to close to TDC and damage can occur because there is no leverage to push piston down, so piston or rod can be damaged, before TDC and engine stops, lol

At idle 700rpms, a piston moves from 10deg BTDC to 10deg ATDC in say 500ms
So base timing is set at 10deg BTDC, spark happens then 20deg later full explosive power
But at 1,400 RPMs piston is moving twice as fast, so spark has to happen at say 20deg BTDC
At 2,800rpm 30deg BTDC
This is what RPM advance/****** does

RPM advance in a distributor setup was done with "weights and springs" inside the distributor
As the shaft inside the distributor spins faster with higher RPMs the weights move "out" away from the shaft and that advances the spark timing, as shaft slows the springs pull the weights back "in" retarding the spark timing
Weights and springs are changeable/adjustable to fine tune for best RPM spark timing



LOAD is a different kettle of fish
When you make the air:fuel ratio Richer the time from spark to full explosive power is shorter, so instead of 500ms its now 400ms
And RPM spark timing is now incorrect
Thats is what Vacuum Advance was for, when you accelerate more fuel is added, Richer mix, and intake manifold vacuum drops because throttle plate opens more
So Vacuum advance ******* the RPM advance for the shorter burn time of the Richer mix
If that doesn't happen then engine stumbles and misfires

When car makers went to computer controls for spark they dropped vacuum advance in favor of computer advance
RPM advance usually stayed as is until distributorless spark systems were used
TFI used a SPOUT wire between computer and distributor
This SPOUT wire needs to be disconnected to set base spark timing, RPM timing, at 10-12deg BTDC
Then reconnected so you have LOAD advance back
 

Wrcabejr

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The computer in this engine has nothing to do with the engine any longer it's a standalone engine is running the factory distributor everything is Factory on the engine except for the computer I never had a problem until I had to replace the head this past November then it's been simply one thing after another and now this has been the main problem I cannot figure it out I have been a mechanic for almost 40 plus years and can't figure out what I'm missing
 

RonD

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So you are using DuraSpark system with vacuum advance?

Factory was TFI and needs the computer

Duraspark was popular conversion for the 2.8l when going to a regular carb and dropping the computer
Even better is using HEI module instead of duraspark module, which had problems

And you disabled vacuum advance to set base spark timing

I can't remember if Ported or regular vacuum was best for the DuraSpark vacuum advance?

But one will cause stumbling on acceleration

Can you stall the engine by blocking most the the carbs air intake, so no vacuum leaks?
 

Wrcabejr

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No it's the factory distributor everything on the motor is Factory just bypass the computer setup and cutaway three-quarters of the wiring harness everything is still Factory except it's been match flowed
 

Wrcabejr

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No smog control no air condition pump just the basics
 

RonD

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If distributor doesn't have a Vacuum advance diaphragm then thats your problem

TFI module distributor has no way to detect LOAD for spark timing, it relied on the computer for that

Conversion info here: https://therangerstation.com/tech_library/2_8Duraspark.shtml

BUT.....................don't use Duraspark module, use an HEI module instead with the duraspark distributor
Cheaper and better

Info here: https://www.therangerstation.com/forums/index.php?threads/a-different-approach-duraspark-tfi-hei.117817/
 
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