Won't accelerate & got the shakes. We've owned our '97 Discovery I for 20 years - a real investment. We have over 260k miles on the original 4.0 engine. The latest problem is no acceleration under load. When trying to accelerate up a slight incline, there is a shake in the engine, no response on gas pedal and the RPM's go a bit hay-wire. Feels like an air-fuel problem or some type of governor, or the RPMs and transmission lost their mojo. Just last week put a new throttle cable in; replaced spark plugs; transmission fluid & such but had no effect. About 8 years ago, our mechanic suggested we put her down --- NO! We had the engine block heads repaired (pitted) with metal filler to keep the original engine, and new head gaskets. We've replaced or repaired much more since then to keep her climbing to So. Lake Tahoe. Any suggestions what is happening with acceleration? No engine light or signals - she starts and idles fine (no stalling). A grateful LR fan!

 

Any codes set?

My first thought would be a TPS (throttle position sensor)

 

Thanks ArmyRover. No codes are coming up. I'll research the TPS and give it a shot to replace.

 

 

I checked again and NO CODES are coming up. My research also leads me to think its the TPS as Discovery is acting the way its described.
I found this YouTube clip below. It says a P0121 trouble code should (or not?) come up on the scanner.
Do you (or does anyone) know if the TPS could still be faulting even w/o a CODE coming up? There is no engine light displayed either. But something air/fuel/RPM/throttle is out of whack. Please let me - thanks!

 

I would start with ignition and fuel.
possible the fuel pump is going bad and cant keep up under load
check the fuel pressure and the rest of the ignition system on the engine (if you havent)
check the grounds - they can cause weird Sh**

 

You might not have a code showing but there might be one pending. Have you hooked up an OBDII scanner? They not only show the current codes but pending as well.
I see that you changed the plugs but how about wires? If everything checks out with the spark, I would move onto fuel delivery. Vacuum hose to fuel pressure regulator look ok?

Mine has acted that way before, when the Crank Position Sensor got wet but it threw all kinds of codes at me.

 

Perhaps the u-joints are pooched? When is the last time all of the grease points underneath were checked and greased?

I had bad shakes with mine until I had the bushings and u-joints replaced (I went with the heavy duty u-joints), and there is no more shaking/vibration.

 

Get a cheap fuel pressure gauge. Mine was doing the same thing, turned out the fuel pump could only make around 18psi even with the return hose clamped. Went to O'reilly and bought a similar pump, stuck it in and runs better than ever. On Amazon a replacement pump is $35 and takes like 20 minutes to replace.

 

On replacing the fuel pump, any special tools needed, fluids, etc.? I may do this this weekend if it isn't a major time consuming event. When you say you bought a "similar" pump from O'reillys, was the replacement to spec?

Thanks