This is my first time posting. So thanks in advance for the help. I have a 98 Discovery 1 4.0 150,000 miles. I replaced the engine about 4 mo ago with a used one. 108,000 miles on that engine. It was running fine until it sprung a leak in the front cover. Replaced the cover and checked the oil pump. All was fine with that. However when it overheated due to the leak it now has a leak in the head gasket. Will fix that shortly. Now to the most recent problem at hand.

After reading posts about this topic and coming to no conclusion I’m posting here. Engine stalls immediately after putting it into a gear. Reverse or drive. At idle it purrs like a kitten and will never stall. I can give it gas and keep it running while in a gear but not drivable. As soon as you let off the gas Stall… Also when you put it into a gear it sounds like it is trying to suck in much more air. You hear it at the Mass airflow sensor.
I have changed Ignition coils, plugs, wires, Fuel pressure regulator, Relay module Main relay Fuel pump relay, Engine coolant temperature sensor, EVAP purge valve, Crankshaft position sensor, and Idle air control. Fuel pressure is at 28 to 30psi. At this point I’m stumped. Any advice would be appreciated Thanks

 

Throttle position sensor. Tells ECU butterfly throttle valve opening angle. You'll see resistance from it bounce all over, like a dirty volume control on an AM radio.

 

While reading your long list of parts guesses I noticed your fuel pressure reading. Have you changed the in-line fuel filter and pump strainer? When you measured the fuel pump was that with motor running or off? Stock fuel pump is rated for 40+ psi. If that is your running pressure it's on the low end and should be 32 - 38 psi for good performance. Once the throttle is open you need higher pressure to keep up with the longer injector pulse width, more fuel being added. If pump is original it might be time for a new one if over 100k on the clock.

How much did the Fuel Pressure Regulator set you back? Kind of an expensive guess......

 

I have changed the Fuel filter couple weeks ago.So I’m assuming that should be ok. Pump strainer? Where is that located? And noto checking the pump strainer ha ha. I checked the pressure with it running.Not real sure how good my gauge is so may not be too accurate. Side note whenyou turn the key on the pump pressure rises for about 20 seconds. Is thatnormal? Even if the pump is going or is bad would it stall immediately? Fortunately I had another pressure regulatorfrom the other engine!!! As far as the Throttleposition sensor I checked it and seems to be workingfine getting throttle % readings on the OBD reader.

 

Crimped fuel line? Bad fuel filter?

 

I know it is getting fuel. When I replaced the Fuel pressure regulator I didn’t get the o-ring in correctly and it was spraying fuel everywhere that was fun!!!!!!

 

vac leak? The IACV is a computer controlled one, but it can't compensate for leak past it.

 

I can't see or feel any vac leaks but also don'know all the spots to check. Another thing that I figured out is when theengine is idling the load is around 22% on the OBD reader and running smooth. WhenI put it in gear step on the breaks and give it gas holding the rpm at say900rpm the load goes up to 55 to 70%. Ideas???

 

Also I got it in reverse had my food on thebreak and could push the pedal to the floor. The RPM never got above 1500. Slowlylet go of the pedal and it would move. But if I take my foot off the gas stall.Still purrs like a kitten in neutral.

 

Something in the drive-line binding maybe, like a brake caliper. What color are the plugs?

The pump strainer/screen sits in the fuel well, directly mounted to the bottom of pump. Not an issue it seems.