Hesitation and backfire

[black_demon69]

OK 2.3l 93 ranger 5 speed

Hesitates and backfires occasionally when under hard acceleration

Done so far :
Plugs and wires
Fuel filter
Injector cleaner in the fuel tank

On the agenda :
Check fuel pressure
Check compression
Check valve timing

Any thoughts?

 

[RonD]

Yes, check compression first, 2.3l used a timing belt which could slip and lower compression.
Expected compression would be 150psi or higher

There is a TPS(throttle position sensor) on the throttle body, it has 3 wires connected, make sure connection is good.
TPS gives the Computer(PCM) a "heads up" to add extra fuel when you press down on the gas pedal, it serves same purpose as the "accelerator pump" did on a carburetor.
Faulty accelerator pump would cause hesitation and back fires when you pressed down on gas pedal, because fuel mix got too Lean.

You can test TPS with volt meter and a sewing needle, use needle to pierce wire for testing
Red wire should have 5volts with key on
Center wire should have .69-.99 volt(under 1 volt) with throttle closed
As you open throttle voltage should go up steadily, no jumping or dropping, at Wide Open Throttle(WOT) it should show 4.5-4.8volts

 

[tomw]

I would check the MAF for buildup of 'schmutz' on the wires. If the MAF does not detect the change in airflow coming into the engine, the fuel flow will tend to go lean until the MAF DOES detect the change. Air will accelerate into the engine faster than liquid fuel, as a gas is less dense than a liquid. MAF detects Air Flow(the name... Mass Air Flow), and if spudged, can cause hesitation on acceleration.
tom

 

[black_demon69]

Thanx for the responses

I am more familiar with the 4.0l lol

I will update as soon as I get some of it done

Currently rebuilding m5od for my 94 4.0l so time is limited until then

 

[black_demon69]

Thinking maybe egr valve
What do you think?

 

[tomw]

Not considered likely by me.
tom