Guys
Can you help me with a problem i am having with my Pinto.
It is a 2.0 running the original fuel injection system. All was working perfectly but I am now having what appears to be fuelling problems.
The engine starts and runs fine at idle speeds and fuel pressure is steady but when I drive it once it has warmed up it stutters and misfires under acceleration and drops the fuel pressure. The fuel pump seems to be working as it should do and all other things seem to be working properly.
I am stumped as to what the cause is.
Help please.

I had a similar problem on an XR3i and found it to be a relay. Which i think was why i got it so cheap at the time.

What dizzy do you have if its got bob weights are they sticking ?
this would not explain the drop in fuel pressure though

Could be the airflow meter spring needs resetting. The only way to check it is with a CO meter up the exhaust and the engine running (HOT). Screw the mixture screw fully home and CO should rise to a maximum of 6.0.

If it is 6.0 return it to a setting of 0.5 and the meter is OK.

IF it is higher than 6.0. Turn off the engine, remove the meter and carefully lever off the wedge shaped black cover on the underside (it is held on by a thin bead of silicone sealer). Re-fit meter upside down and start engine. Rotate the big cog (by flipping it against the spring latch) until reading is 6.0. Turn off engine, remove meter, re-fit plastic cover after cleaning and applying a new silicone bead. Refit airflow meter, restart engine and adjust co back down to 0.5%.

Job done test drive and enjoy.

Blocked fuel filter maybe?

"When it is warmed up". Points to it being OK during cold start cycle running open loop, makes me think sensor problem.

I was also thinking it may be a sensor problem. I have ordered a replacement manifold temp sensor to try first and I will also swap the fuel pump relay to see if it's any better.

I've had similar problems when a fuel pipe was kinked and when the fuel filter was blocked. Check the basics first.
have you checked the pump connections and is it getting battery voltage to the pump?
How are you measuring the drop in fuel pressure?

[Edited on 24/3/14 by Grimsdale]

I replaced the fuel regulator with one that has a gauge I can read the pressure on. I have had a thought that the tank breather may be blocked which is causing a vacuum to build up and will investigate.