1998 540 v8 fuel trims issues and rocky idle, where is the fuel pressure regulator?

[Eriklane]

200k miles, car taken care of well. Prior owner new plugs, fuel pump, cats, maf, coils. Check engine codes p0100(maf malfunction), p0111 (intake air temp) and p0443 evap purge valve.

Is it possible the maf is causing all this or the p0100 and the p0111? Was told it was replaced. When I unplug it, it blips but does not change idling.

Fuel trims are negative on one bank I think (cant remember). Think I remember an 02 sensor issue also.

[jclausen]

I would smoke check the intake system or while it's running spray carb clean around all sides of the intake manifold, ifthe idle goes up you have found a vacuum leak. Plus I would clear the faults and see which one comes back first

[Eriklane]

Discconn the maf, started it cold, hardly started. Finally got it going but rough. shut off, reconnect, restart, back to more normal but still somewhat rough.
Have a P0100-maf malfunction, also have a P0111-intake air temp issue and a P0443-purge valve (unlikely source of problem?).

Will do a fuel pressure test also asap.
Just curious where the pressure regulator is-by the fuel filter or IN the fuel filter?

[JimLev]

A few 98's came with the tu drive by wire engine, those had the regulator in the fuel filter.
The non tu engines (cable driven throttle) had the regulator on the end of the fuel rail.
IIRC it also has a change over valve that our tu engines don't have.

[Eriklane]

Mine is Cable driven. I've looked everywhere in the engine bay and can't find it...what's IIRC

[wagons ho]

97 is on the fuel rail. 98 is under car, under drivers footwell, behind the plastic underbody tray.
How handy.

[jclausen]

Well if the purge valve is not closed it's a vacuum leak

[Eriklane]

Got a new intake temp sensor and now the p0111 and 0100 are gone. Tackling the p0443 next. Still think the car lags when I stomp the gas-may replace the crank sensor.

[Eriklane]

Fuel trims was the throttle body gasket-it was leaking. Did a simple cigar smoke test (blew smoke into the iac port while covering the throttle body opening)