93 Explorer Acceleration Problems

[BlaccMagik28]

Hello All,

I'm a tech in training and I have rain into my first roadblock. I have a 93 explorer and I can't go faster then 35 mph and over 2000 rpm. The truck starts and idles just fine. Once I start driving it accelerates fine until I reach 35 mph and 2000 rpm then it just sits there. It never shifts and after a minute or so it will just lose all acceleration. Then it will act as if can't breathe and just putt and spudder until I cut off the engine. Then it will start just fine and repeat the same process I just explained. Someone please lead me in the right direction.

New fuel filter, transmission filter,ignition coil,spark plug & wires,cleaned MAF,removed converter

 

[Maniak]

Sounds like fuel starvation to me..

My guess is the fuel pump is getting weak and can't put out the volume.

When the pump started to go bad on our '92 (last time) it had a similar symptom. Things were fine and then slowly (over a few weeks) you couldn't get the rpms up past 4000, then 3000..

When I checked the fuel pressure it was fine at idle, but if I tried to hold it at 3000-4000 (in neutral) the fuel pressure would drop.. Not enough to replicated the issue but enough to tell me it was starving for fuel..

~Mark

 

[BlaccMagik28]

thanx for the reply

The fuel pump is old but did it prevent you from shifting gears and did u have the same spudder

 

[murkinstock]

If you are more on the gas since you're trying to get it to go, the TPS might be saying you're under load or trying to speed up faster than normal so it's not trying to shift until say 3500 rpm. so that might be why it won't shift.
I'm not sure but that might be why it won't shift.

^^^ My bad I wasn't thinking about how they actually use vacuum not Throttle position or anything. You get what I'm thinking though.

Would overdrive actually use the TPS and Speed sensor for shifting though? Since it's controlled by the computer?

 

[Maniak]

At the end, it was tricky to get going fast enough to have it shift. If I was on the throttle trying to go faster (which it wouldn't do) it wouldn't shift. If I gave up and let off the throttle it would shift and the same would happen again.. If I tried to go faster than it could it wouldn't shift. If I was fast enough that I could be in the next gear (light to no throttle) it would shift.

Shifting on the 1st gen is hydraulically controlled. There is a vacuum modulator which lifts the shift point when you are under load (less to no vacuum) and if you don't have vacuum because you have the throttle open trying to go faster than it can it may have pushed the shift point up high enough to not shift.. Is the vacuum line to the modulator on the trans still connected? If not, that will make it want to shift at higher rpms/load which it sounds like you may not be able to achieve.

It is also possible you have multiple issues... Delayed to no shift out of 1st gear can be caused by the governor in the transmission. If the weight sticks it won't shift.. Normally that happens until the trans gets warm but if it is bad enough it just wont' shift out of 1st.

For now, I would double check vacuum lines for anything disconnected and any vacuum leaks and I would do a fuel pressure test. Both are simple to do and won't cost anything (assuming you have a Fuel pressure tester)

~Mark

 

[murkinstock]

At the end, it was tricky to get going fast enough to have it shift. If I was on the throttle trying to go faster (which it wouldn't do) it wouldn't shift. If I gave up and let off the throttle it would shift and the same would happen again.. If I tried to go faster than it could it wouldn't shift. If I was fast enough that I could be in the next gear (light to no throttle) it would shift.

Shifting on the 1st gen is hydraulically controlled. There is a vacuum modulator which lifts the shift point when you are under load (less to no vacuum) and if you don't have vacuum because you have the throttle open trying to go faster than it can it may have pushed the shift point up high enough to not shift.. Is the vacuum line to the modulator on the trans still connected? If not, that will make it want to shift at higher rpms/load which it sounds like you may not be able to achieve.

~Mark

Yes! That's what I meant! I knew the trans was controlled by vacuum I just wasn't thinking about it. For some reason I was thinking electronic shifting.

 

[BlaccMagik28]

Where would the vacuum line be that goes to the transmission and the governor