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I’ve recently replaced all the injectors in my 3.9l rover efi v8 and it is constantly running very rich now. How can I fix this? The exhaust fumes are so over fuelled they make your eyes water!! Thanks in advance

bennyboy79 wrote: ↑

Sun Jul 25, 2021 10:04 am

I’ve recently replaced all the injectors in my 3.9l rover efi v8 and it is constantly running very rich now. How can I fix this? The exhaust fumes are so over fuelled they make your eyes water!! Thanks in advance

Assuming the same and correct injectors, have you disturbed the wiring elsewhere? For example, if the CTS is unplugged, it will run very rich when hot.

But are you certain they are the same injectors? Same part number stamped on them?

As above, replaced with what exactly ? and also why ?

Prett sure old old injectors were low impedance types, much less common these days, although later Rover's used highZ injectors

Either way, both fitment, electrically and flow needs to be exactly the same.

The 3.5 flapper had Lo-Z injectors fed from resistor packs. But Hotwire Hi-Z? However, Hi-Z used with resistor packs would result in under fuelling. Lo-Z used where they should be Hi-Z, burnt out injector drivers in the ECU, or burnt out injectors.

What EFi system are you running?

As 3.9 assuming 14CUX Hotwire.
Have you checked fuel pressure, both with and without plenum pressure applied. High fuel pressure will increase fuelling.

What map are you running? If it’s a closed loop map (with lambdas) the system should try to correct, if enough adjustment range is available. If it is a closed loop map and not self adjusting it it could be that the lambdas are not giving correct values or the trim values are maxed out.

Is there any possibility the coolant sensor has become disconnected/disturbed? An incorrect signal could cause the system to think engine is cooler than actual and add more fuel.


As already said, have you used like-for-like injectors. Green band for a 3.9.
If you have used injectors with different flow rate and/or spray pattern you will need to have the map changed, this may be simply a case of adjusting the fuel multiplier to give an overall adjustment up or (in your case) down.
There is now a lot of information available for the 14CUX so this is quite do-able.


Getting a copy of Rover Gauge and a cable would help you understand what the 14CUX is seeing/doing.

Thanks for all the info. I shall do some more investigating of the cables and see if i can get hold of rover gauge and a suitable cable. Yes they are the same injectors with the same number on them

and yes, 14CUX Hotwire but not sure of the map but sounds like it will need to be remapped

Assuming decent quality injectors, the difference in flow rate between examples is tiny. I'd first check for something you've disturbed/broken when fitting them.

That sounds like one injector is stuck open to me.

If you unplug them one at a time, the engine will still run. A normally operating one will be obvious as it will drop to 7 cylinders. A permanently open one won't make any difference.

Chris.

bennyboy79 wrote: ↑

Mon Jul 26, 2021 3:09 pm

14CUX Hotwire but not sure of the map but sounds like it will need to be remapped

If the injectors have not been changed then re-mapping should not be required, the problem must lies elsewhere.
Still a good idea to get Rover Gauge though so you can see what’s going on.

Has it gone into limp home mode? Disconnect the battery for 30 seconds to reset.

Ian