My 94 TR 4 cylinder has a strange, possibly temperature related problem.

After driving for an hour (less if driving uphill), the engine will lose all torque when pressing the accelerator. It will continue to run fine with little throttle, the more I press the pedal the more it surges though.

This gets worse the longer I drive it (as in, less throttle required to make it surge).

Shut the engine down for a few minutes and everything is normal again, but after a short while, the problem will return.

There is no misfiring. Coolant temperature is fine, middle of the gauge.
On previous advice here, I checked for air leaks between the filter and the throttle body - all good.

That leaves fuel, doesn't it?
I'm thinking, check fuel pressure and fuel pump?

Problem is that this can't be reproduced without first driving it around for an hour...

Too much air and the engine cuts out, you probably have an air leak somewhere between the MAF and cylinders. Could be weak spark, or low fuel pressure.

Thanks -
I took the air intake hose off and can't find anything wrong with it. Rubber seems to be in good condition, all hose clamps are tight.

If it was ignition related, wouldn't I get some sort of backfiring or misfiring sounds?
Also, the problem seems to be triggered by the amount of throttle, independent of Engine RPM.

Hard to fault this one as it will only happen on a hot engine - not just warmed up, but driven around under power for an hour.


Edit: Injectors look good and clean. So do the plugs. Still clueless about the problem though, do I have to take it to a dealer after all?

Update:
I pulled the injectors last weekend, checked all lines in the engine bay and "tested" the fuel pump (by connecting 12V to the test terminal in the engine bay and listening for the sound, as described in the shop manual).

Car ran fine all week but I never drove it more than 20k, and it never had any issues on short drives previously.

Then tonight, coming home from a BBQ - 30k drive - it almost stopped. Speed was down to 40km/h at one point, and it felt like it was running out of fuel, except it never quit completely. Engine stuttering and not taking any throttle.
Eventually it picked up a bit of speed again and I got it home. I filled it up, 57L to the brim (60L tank) so I was quite low, but not out of fuel. After refuelling it ran fine again.

So now I am pretty sure that either my tank has got a few liters of water in it, or my fuel pump is stuffed.

- How does the fuel pump work anyways, does it take the fuel from a floating hose, or just from the bottom of the tank?
- is there a DIY way to measure fuel pressure?