Rough idle just had the fuel pump and mass air filter sensor replaced in my 95 Jag xj6. Now when in drive the car idles rough at 7-8rpms.

set the fuel pressure on the regulator. its in the fuel line in the engine compartment

TPS sensor and IAC sensor.

It sounds like your Fuel Pump is failing once it get warm.

fuel filter or mass air flow sensor. do a tune up

White smoke is usually coolant that went thru the cylinders,
such as a failed head gasket or other reasons

Could also be fuel- but that wouldn't be a continual visual
site when driving

STOP USING IT ---get it fixed Don't ruin a nice car

Check the idle fuel pressure. Load the electrical with headlights and heater defrost etc and see if problem gets worse. Attempt again with all accessories off. Could be fuel pump is getting low voltage at idle or fuel pump is failing. Bad fuel pump would definitely be a problem high fuel demand. Check vacuum line between pressure regulator to intake manifold.

Check for a air leak in the intake manifold. Gasket/hose etc. The P0171/P0174 is an indication that not enough fuel or tow much air. You can sometimes hear the air leak during idle.


Best solution is to use a graphic capable scan tool and watch the fueling trim/idle.

Get a full tune up, how is your gas millage? if your gas millage is bad then you should suggest changing your o2 sensors.

I had to replace the mass air flow sensor. $ 150. the engine would shut off when driving too.changed fuel filter only worked for a day. The sensor is just after air filter.

check the actual fuel line. Also is it fuel injection or carberator