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Ask Chris (aka- Moose) Your Own Question
Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 44527
Experience:  16 years experience
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I have a 98 ranger 2.5 manual truck runs fine but if i snap

Customer Question

i have a 98 ranger 2.5 manual truck runs fine but if i snap the throttle it will die following what sounds like spark knock or backfire from intake
Submitted: 1 year ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 1 year ago.

Are you behind on any maintenance including:

Plugs

Wires

Throttle body, intake, EGR, and combustion chamber cleaning

MAF sensor cleaning

Fuel system cleaner

Filters

Do you have a loss of power while driving, from a possible valve seat or valve spring failure causing intake or exhaust backfires?

Do you have coolant temp issues causing high head temps, which causes spark knock?

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Chris also known as Moose

Customer: replied 1 year ago.
Spark plugs and wires have been changed idle air control valve has been changed mass air flow sensor has been changed EGR valve has been changed PCV valve has been changed throttle body has been cleaned and there are no vacuum leaks truck starts fine and idles fine no loss of power or noises while driving . Problem only occurs if the gas pedal is snapped off idle
Customer: replied 1 year ago.
I also forgot to add that there have been no trouble codes
Expert:  Chris (aka- Moose) replied 1 year ago.

So if I understand right, your in park or neutral idling. You rapidly accelerate and when it returns to idle is stalls?

Customer: replied 1 year ago.
It is manual transmission so typically only happens at idle for taking off in first gear if I press the throttle to quickly it will shake hard almost as if it were backfiring from intake or knocking but if I accelerate slowly once I am in motion going through the rest of the gears is not a problem
Expert:  Chris (aka- Moose) replied 1 year ago.

Thanks, ***** ***** hook up a fuel pressure gauge and monitor the fuel pressure while doing exactly that scenario to see if the pressure is dropping down?

Customer: replied 1 year ago.
It has already been done it has been checked for pressure and volume. I have a lot of experience working on older vehicles the way it acts is as if the timing were advanced to far but just for a split second. It sounds and feels as if a premature spark stops the motor abruptly
Customer: replied 1 year ago.
But as I said before if I accelerate slowly there is no problem it is just the very first eight inch of pedal I have to be careful with
Expert:  Chris (aka- Moose) replied 1 year ago.

Can you monitor the cam and crank sensors when doing this and capture it on freeze frame data to see if they show a steady increase or a hiccup? Especially the crank signal, this engine is known for balance failure.

Customer: replied 1 year ago.
Can you explain to me what you mean by balance failure. I would like to relay that information to the mechanic who has looked at it it has not given me any crank or cam sensor codes
Expert:  Chris (aka- Moose) replied 1 year ago.

Sorry its missing an (R). Balancer failure, the harmonic balancer/crank pulley. If yours is failing it can interrupt an accurate reading of the crank sensor and cause the spark to occur at the wrong time.

Customer: replied 1 year ago.
Okay I guess that is where I need to go next I know about the gear behind the balancer but other than broken teeth am I looking for anything else for example looseness? Is it possible that the crank or cam sensor could be giving a delayed or premature reaction/ signal
Customer: replied 1 year ago.
why would it not throw a code for something like this
Expert:  Chris (aka- Moose) replied 1 year ago.

The CMP nor CKP will provide to the PCM a delayed reading, but they could report back a wrong or inconsistent reading. If the tone ring they read from moves in any way other than just spinning, then the reading will be off.