3.5 hotwire bad misfire

Hi, Im in dire need of some advice. Over the past few days I've been converting my 1988 3.5 110 to hotwire efi, off of a early 90s 3.9 disco. I've now finished everything up and the moment came to starting it, and first issue the fuel pump wouldn't run, after a bid of looking, relay was fine but no voltage to the pump, so just to see if it would start I just hotwired the pump on and everything was fine, perfect pressure. It then started and immediately kicked rpm up to a little over 2000 where it held it, not sounding happy and misfiring and then tried to bring it down to 700 or so but was constantly trying to save itself from stalling. It honestly sounds like its running on 4 cyclinders, however it seems all injectors are firing. The car was quite healthy before I just wanted to go efi as I was fed up with sus and endless problems, but when I started the efi conversion it was good at the time, making me think that the issue relates to something I've done rather than ignition. I have a sinking feeling it's bad vacuum leaks where I changed the valley gasket.
Any ideas? Rover guage doesn't snow any codes.
Thanks

Has the 110 had Lambda sensors fitted.
The 14CUX ECU is expecting to see lambda signal returns, if it isn't getting them it'llwill throw out the correct engine fueling, if it's not getting them it'll run bad or not at all.

And of course a vacuum leak will cause it to idle high, and run like shyte..

Henry_b said:

Has the 110 had Lambda sensors fitted.
The 14CUX ECU is expecting to see lambda signal returns, if it isn't getting them it'llwill throw out the correct engine fueling, if it's not getting them it'll run bad or not at all.

And of course a vacuum leak will cause it to idle high, and run like shyte..

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I have the correct tune resistor in (470 ohm) but yeah I really think it's a vacuum leak tbh, just hoping I wasn't going to have to pull it all apart again.....

Burtie2904 said:

I have the correct tune resistor in (470 ohm) but yeah I really think it's a vacuum leak tbh, just hoping I wasn't going to have to pull it all apart again.....

Click to expand...

All part of landy ownership

Could be AIV stepper motor, at the rear of the plenum could and/or be sticking or dirty.

Also the hotwire airflow meter can play up it can be carefully cleaned. with Airflow meter cleaner of course

Burtie2904 said:

I have the correct tune resistor in (470 ohm) but yeah I really think it's a vacuum leak tbh, just hoping I wasn't going to have to pull it all apart again.....

Click to expand...

That tune resistor is correct if you don’t have catalytic converters fitted.

did you notch the intake ports before fitting efi manifold

jamesmartin said:

did you notch the intake ports before fitting efi manifold

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For a wierd reason, no idea when or why, it already had efi heads on, wasn't expecting that tbh.

If the base idle is set correctly, on starting from cold the engine revs will rise to something like 1100/1200 rpm but then very quickly drop to idle around 725/750rpm, do you have the 3.9 high pressure EFI fuel pump fitted in the tank along with the flow and return pipes to and from the tank.?

Try this, it was sent to me from guys that build and supply parts for V8’s.

Hotwire EFi setup

First things to do on a setup are as follows (and we normally do this in this order)

• Ensure there are no air leaks, these cause unmetered air which in turns gives a lean mixture.
• Check the throttle butterfly is at closed throttle open 0.5 to 1mm (so measure top and bottom from the plenum snout and you should have 1mm difference in the measurements and it should be in the open position (i.e not closing over centre)
• Set the Throttle position sensor to have an output of 0.35 volts at closed throttle - You should also achieve between 4.5 and 5 volts at full throttle
• If you have an adjustable fuel pressure regulator set this according to the instructions (prime to 40psi on most engines)
• Set the ignition timing to 6 BTDC
• Next warm the engine up.
• Adjust the CO trim on the air flow meter. (Non CAT vehicles 1.5 volts, Cat Vehicles 1.8 volts) (Voltage reading between Blue/Red wire and Red/Black wire)
• Now turn the engine off and remove the pipe that supplies the stepper idle valve with air. Blank off both ports that are now open. The stepper motor is now not in control of your idle. There is an idle valve adjuster on top of the plenum which you can now use to set base idle. Start the engine (you may need to hold the idle up initially) and then adjust a base idle of 550 to 650 rpm
• Next turn the engine off and re connect the stepper motor air feed pipe.
• Now drive the car down the road and advance the ignition timing until you find pinking under load. Then retard the timing be a couple of degrees so that pinking can not occur.