My 97 EL is quite old (158k), 4 litre auto with after-market dual fuel ULP/LPG. Acceleration on both fuels is just fine
but it misfires at idle on ULP (hence my interest in checking the timing). I replaced the plugs WR9LCX with no change to symptoms.
So I've just tried this technique to check the timing but found that after the STI and ground pins are interconnected, the engine starts at 500rpm, hesitates, rises to about 900 rpm for about ten
seconds and then reverts to 500 rpm where it stays.
According to all the manuals, in the it's supposed to stay at high revs for over a minute. Any ideas why it's not behaving like it should - it's not enough time to get around to the timing light?
In addition, the timing light is showing chnages in timing during that period just after starting the engine with STI grounded - not sure whether I should expect that with the change in revs mentioned above?
Without STI and ground connected (ie normal operation), the engine starts OK, idles at 750 rpm and stays fairly steady apart from the random misfires.