Griffith overfuelling and hesitating/ choking out once hot!!
Discussion
400 pre cat Having problems with the car since a mysterious event whilst travelling at 70mph. Sudden power loss and smell of fuel from exhaust. Car was running fine up to this point. Managed to drive the car home with intermittent loss of power but suddenly returning. After further investigation(plugs dizzy cap leads obvious air leaks found no problems except a vacuum advance unit leaking air. Faulty one replaced for a new one. Checked fuel and water temperature sensors both check out ok, both receiving 5V. Checked mass airflow voltages (0.3v engine stopped 1.75v at tickover)(co voltage 1.2v but other values tried with no real improvement). Problem is that as soon as the engine is hot it doesn't want to tick over and if you throttle quickly it chokes out and stinks of fuel. Will rev if throttle is pressed progressively but will lack power if under load. Once the airflow sensor is unplugged engine is very responsive doesn't choke out revs as it should do! Seems like an airflow sensor problem but readings suggest not! Tried a ebay reconditioned one £50 pounds but suspicious of its reliability/quality seems to behave like the original (better off unplugged!)without it plugged in engine seems fine no missing or hesitation. If anyone has any suggestions as to any other possible causes of the symptoms other than the airflow sensor. All suggestions welcome thanks.
"1.75v at tickover"
Bit high for a 4 ltr, this is what you expect for a 5ltr motor, but it does depend on the idle RPM obviously. Dont forget AFM's get cooked, so it could just be failing when hot. Second hand units from Range Rovers dont have the hard time they get in the TVR engine bay, or the oil contamination form the air filter. Watch out low cost 3AM / 5AM replicas now appearing on the market, they look genuine, but are not badged Lucas. Never thought one would be saying "Lucas is good" but compared to Chinese stuff it is!
Bit high for a 4 ltr, this is what you expect for a 5ltr motor, but it does depend on the idle RPM obviously. Dont forget AFM's get cooked, so it could just be failing when hot. Second hand units from Range Rovers dont have the hard time they get in the TVR engine bay, or the oil contamination form the air filter. Watch out low cost 3AM / 5AM replicas now appearing on the market, they look genuine, but are not badged Lucas. Never thought one would be saying "Lucas is good" but compared to Chinese stuff it is!
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