[Pinto EFI] Low MPG problem, question on sensors

[galingong]

Hey,

I've already tried passionford, but there's a significant amount of knowledge on Pinto engines here, so I guess I'll give it a shot.

I've owned a '91 Ford Sierra for more than two years now. It has a N4B engine (the one with ~100HP, O2 sensor, MAP sensor and a catalytic converter, mine is missing the cat.) I've been struggling to find the cause of relative low MPG (19-20MPG, 12L/100km instead of 23-24MPG, 10L/100km). It's likely that mixture is rich, no gas leaks or anything along those lines.

I've already had injectors cleaned, replaced MAP sensor, had sensors checked with a DVM, all seem to work fine. O2 sensor should be OK.

I've heard that N4B Pinto engines have different MAF sensor (the dreadful grey thing next to airbox), then earlier models. Mine is an N4B and has a MAF from an early ('87?) Sierra (N4A or something else, point is that donor had no O2 sensor and cat.), and it may cause issues with the mixture. Can anyone confirm that?

Other tips for solving slightly low MPG-issue are welcome.

Cheers!

[Miniliteman]

What is the partnumber of the MAF sensor?
Inside this part is an airtempsensor have you checked that also?
If you check sensor at the sensor itself then a wiring-problem cannot be found.
Use a breakoutbox between ECU and loom and measure there for voltages/resistances.
Have you checked the fuelpressure?

[galingong]

MAF is BOSCH - 0 280 202 063 ; Ford - 85GB-12B529-BA

I've checked sensors at ECU, loom is fine, I know it inside out.

Fuel pressure is a possibility, I haven't measured it, AFAIK I don't have a tool for it (but may find something in the "Dad's unsorted tools" section). I've checked fuel pressure regulator - disconnected vacuum line, waited a couple of minutes, no sign of fuel. That doesn't mean it's not faulty I guess, and I also have no idea if fuel pump is original. Where would I check fuel pressure and how?

[therealpinto]

Have you tried reading the fault codes?

The catalytic Pinto has the newer fault code system so it can provide a reasonable amount of codes.

I'm not sure about the MAF being different, it may be but there is no visual difference. I might still have an ECU for this engine, could be a last resort to try...

Gustaf

[r2vdh]

how have you got the MAF mounted? This will affect air flow through the unit.