low power/ low acelleration?

[FordTruckJunkie]

Hey guys kinda new here but know my way around on here haha. well anyways i have a 1994 exploder limited 120.5k, thats been developing problems lately mainly the no power/acceleration problems. i can sit in park and rev it all i want the powers there when i need it( which isnt alot lol) but as soon as i drop it into drive creeps its way up to speed on a good day might hit 45 on a straight. what can be causing this? ive heard maf cat tranny fluid fuel filter ect but dont wanna waste my time on something i dont need to worry about. and oh btw, my modulator is bad is there any pics i can find bout removeand replacement? thanks guys

 

[Smaknu03]

to me it almost sounds like the cats.

 

[arco777]

Hey guys kinda new here but know my way around on here haha. well anyways i have a 1994 exploder limited 120.5k, thats been developing problems lately mainly the no power/acceleration problems. i can sit in park and rev it all i want the powers there when i need it( which isnt alot lol) but as soon as i drop it into drive creeps its way up to speed on a good day might hit 45 on a straight. what can be causing this? ive heard maf cat tranny fluid fuel filter ect but dont wanna waste my time on something i dont need to worry about. and oh btw, my modulator is bad is there any pics i can find bout removeand replacement? thanks guys

Do a search on the forums about the vacuum modulator issue and you may find pictures. It's pretty simple. There's an access panel in your floor if you pull up the carpet. From there the modulator is held in by a retainer with one bolt and then just pulls out (don't lose the pin!). Easy as that.

As for your power issues, check your throttle linkage is opening the butterfly all the way - just have someone floor it (engine off) while you observe the throttle butterfly with intake tube removed.

Run a KOEO and KOER test, see if it's throwing any codes.

Check the usual tune-up items for worn out stuff. Check your fuel pressure as well. If your trans is slipping you can re-adjust the bands. Check that the sensor wires of your MAF aren't dirty. Verify there are no airflow blockages to the intake.

To check if the catalytic converter is bad, it's as simple as disconnecting it and seeing what happens.

These engines, when running right, make plenty of power for the weight of the truck.

 

[FordTruckJunkie]

to me it almost sounds like the cats.

thats what i am thinking bc the exhuast rusted off right after the cat so its been running open cat but this problem was occuring before then

 

[FordTruckJunkie]

Do a search on the forums about the vacuum modulator issue and you may find pictures. It's pretty simple. There's an access panel in your floor if you pull up the carpet. From there the modulator is held in by a retainer with one bolt and then just pulls out (don't lose the pin!). Easy as that.

As for your power issues, check your throttle linkage is opening the butterfly all the way - just have someone floor it (engine off) while you observe the throttle butterfly with intake tube removed.

Run a KOEO and KOER test, see if it's throwing any codes.

Check the usual tune-up items for worn out stuff. Check your fuel pressure as well. If your trans is slipping you can re-adjust the bands. Check that the sensor wires of your MAF aren't dirty. Verify there are no airflow blockages to the intake.

To check if the catalytic converter is bad, it's as simple as disconnecting it and seeing what happens.

These engines, when running right, make plenty of power for the weight of the truck.

just dont feel like ripping my interior apart bc its like factory finish in there but thanks man deff will read up on it. cleaned the maf back probed the wires to make sure it was getting good voltage and singla and both were in range, getting good pressure to the rail. i know they have a problem with slack in the line to the throttle body but no slack at all and also no codes. could the modulator be causing my problem bc the diaphrams go bad wich would cause a vacuum leak right?

 

[arco777]

If the diaphragm fails it will suck tranny fluid back up the line, and eventually into the intake. It won't leak air, but the vacuum line that goes from intake to modulator can develop a leak if the tubing has gone bad.

The modulators do go bad without the diaphragm failing though. They seize up and you end up with a delayed 1-2 shift.

New modulators can be ordered as a stock replacement or as an adjustable one. A stock style one is fine for most people and adjusting it isn't really that convenient anyways.

 

[Smaknu03]

easiest way to find out if its the cats, pull the exhaust off manifold back and run it down the road one time. if u have full power and everything is good then you know its the cats.

 

[rhauf]

check codes

check fuel pressure (should be about 30-35psi, and when you rev the engine it should spike up a little)

check exhaust pressure (over 2psi means its plugged)

clean MAF

does it idle smoothly? when was the last time you changed the plugs and wires?

 

[rhauf]

oh and the modulator is really easy to change.

1. take off the heat shield on the pass side of the trans.
2. use a 10mm wrench (or socket) to remove the retainer holding the modulator in.
3. pull the modulator out.

reverse process to reassemble (duh)

 

[FordTruckJunkie]

If the diaphragm fails it will suck tranny fluid back up the line, and eventually into the intake. It won't leak air, but the vacuum line that goes from intake to modulator can develop a leak if the tubing has gone bad.

The modulators do go bad without the diaphragm failing though. They seize up and you end up with a delayed 1-2 shift.

New modulators can be ordered as a stock replacement or as an adjustable one. A stock style one is fine for most people and adjusting it isn't really that convenient anyways.

it already been sucking in tranny fluid through the tree in the intake and btw i am not missing any gears shifts smooth

 

[FordTruckJunkie]

easiest way to find out if its the cats, pull the exhaust off manifold back and run it down the road one time. if u have full power and everything is good then you know its the cats.

thanks man ill try that this weekend im 17 and still in school so not alot of time right now, but even if i pull the cats off just to test ill loose some low end power bc ik the 4.0 likes back pressure right?

 

[FordTruckJunkie]

check codes

check fuel pressure (should be about 30-35psi, and when you rev the engine it should spike up a little)

check exhaust pressure (over 2psi means its plugged)

clean MAF

does it idle smoothly? when was the last time you changed the plugs and wires?

im really leaning to that it might be my cats. it idles like the day it was assembled and i did plugs wires and coil pack 2 months ago the problem existed before i replaced them

 

[rhauf]

thanks man ill try that this weekend im 17 and still in school so not alot of time right now, but even if i pull the cats off just to test ill loose some low end power bc ik the 4.0 likes back pressure right?

wrong

no engine "likes" backpressure. back pressure is ALWAYS the enemy of torque, horsepower, efficiency, valve life, a cool exhaust system etc.

the myth surrounding backpressure "makes torque" comes from a misunderstanding of exhaust tuning, and from the notion that "there is always a trade off" such as, a bigger carb, bigger intake, or bigger cam will gain top end at the expense of torque, therefore a free flowing exhaust will do the same, not true.

 

[FordTruckJunkie]

wrong

no engine "likes" backpressure. back pressure is ALWAYS the enemy of torque, horsepower, efficiency, valve life, a cool exhaust system etc.

the myth surrounding backpressure "makes torque" comes from a misunderstanding of exhaust tuning, and from the notion that "there is always a trade off" such as, a bigger carb, bigger intake, or bigger cam will gain top end at the expense of torque, therefore a free flowing exhaust will do the same, not true.

thanks man big help

 

[Smaknu03]

wrong

no engine "likes" backpressure. back pressure is ALWAYS the enemy of torque, horsepower, efficiency, valve life, a cool exhaust system etc.

the myth surrounding backpressure "makes torque" comes from a misunderstanding of exhaust tuning, and from the notion that "there is always a trade off" such as, a bigger carb, bigger intake, or bigger cam will gain top end at the expense of torque, therefore a free flowing exhaust will do the same, not true.

+1. Think about it this way, have you ever been the the drag strip and seen anything fast with exhaust besides headers. Same with NASCAR. They virtually have no exhaust. They just have it so it's directed out from under the car

 

[FordTruckJunkie]

+1. Think about it this way, have you ever been the the drag strip and seen anything fast with exhaust besides headers. Same with NASCAR. They virtually have no exhaust. They just have it so it's directed out from under the car

true, the only thing im not fimillar with is exhausts just a rookie when it comes to that haha but true good point

 

[rhauf]

a quick google search and here's some interesting reading on exhaust science that every gearhead should know.

http://www.superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/viewall.html