Misfire when warm (1990 3.9 EFI)

So it goes a bit like this:

Starts willingly, idles very fast, runs fine.

Fast idle can remain unless I stop, turn off just for a moment and restart after which it sorts itself out.

When warm, idle might drop further and engine becomes hesitant between approx 2,000 and 3,000 rpm.

Under 2,000 or on wide open throttle after 3,000 it's quite happy ... but in between it's being a pig, but only when warm.

When I had a TVR with a 4.6 Rover V8 I did things like the stepper motor but before I start cleaning / replacing things aimlessly I wondered if the above was enough info for anyone to recognise something specific?

I'm removing the Rover for a Chevy soon but would ilke it running right in the meantime.

Cheers,
Sam

Sounds awfully like an air leak....

Check the ignition amplifier (mounted on side of dizzy) they tend to breakdown internally when they get warm causing ignition issues.

Is it a lucas hotwire

ukadamwest said:

Is it a lucas hotwire

Click to expand...

It will be. Sounds similar to your problems, Adam.
https://www.landyzone.co.uk/land-rover/misfiring-at-2-3000rpm.309292/

ukadamwest said:

Is it a lucas hotwire

Click to expand...

It is ... and having read your thread from start to finish I'm not sure I have much hope! Well, temper that with knowing that an Overfinch(like) conversion is on the way, the time I put into fixing this will be limited.

Added to your woes, I have an LPG system so that could be affecting things / making things run in a non-standard way. That said, my misfire is similar on both gas and petrol. Symptoms are remarkably similar down to sooting plugs.

I will try a few of the basic tests but am not going to spend much on sensors etc as the engine is coming out anyway - it would just be nice if it ran well in the meantime as I like driving the car. Then again, it's a good impetus to get the conversion done!

cooltide said:

It will be. Sounds similar to your problems, Adam.
https://www.landyzone.co.uk/land-rover/misfiring-at-2-3000rpm.309292/

Click to expand...

Thanks for replies chaps, following your thread now Adam and will chip in if I fins anything useful on mine.

Regards
Sam

I have yet to try the replace fuel pressure regulator.. maybe the diaphragm has collapsed with age.. maybe we've found the life limit of such