discostew38

discostew38

Active Member
Long story short
Got a 1997 4.0 p38 with a dead engine so I've just fitted a 4.6

All runs nice but idles fast between 1500/2000 drops down to 1000 when in drive

The engine came complete so I'm using the ECU and AFM from the 4.0
So the question is do I need to fit a ECU or air flow meter from a 4.6 or are they the same

I've swopped the stepper motors over and no change
Or am I looking in the wrong area

Thanks for any help
 
ecu different..cos the engines are different...doooh (afm may be the same,do a part number check)....(though fault you have maybe totally no related.BUT YOUR FUELING WILL BE WELL OFF..expect slipped liner/s tomorrow, running tooooooooooooooooooooooooooooooooooo lean)
 
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zen said:
ecu different..cos the engines are different...doooh (afm may be the same,do a part number check)....(though fault you have maybe totally no related.BUT YOUR FUELING WILL BE WELL OFF..expect slipped liner/s tomorrow, running tooooooooooooooooooooooooooooooooooo lean)
Click to expand...

Ok so you don't know the answer
If the ECUs are different why is it that some I've seen for sale are listed for both engines and some are only listed for one or the other
and what part number would be the right one if they are different
 
If it was 4.0, wouldn't it be Bosch Motronic, rather than Gems? I thought the Gems engine was classed as a 3.9 (although the displacement is identical). You can tell by the air intake: the Gems had a box on top, the Motronic had curved air intakes.

If you replaced a 3.9 Gems with a 4.6 Motronic, that might be your problem.
 
I think you have to have the ecu connected up to something like rovercom and there is a setting in the software to change it from 4.0 to 4.6
 
discostew38 said:
I did find something on Google that said that was possible
Il have a look into that
Click to expand...

and re so you dont know the answer..what are we all psyhic then and can see into your engine from our computers??


so if you doing this why am i wrong???best you leave as is then???

the main reason for slipped liners is the fueling map lr use..ie really lean foe mpg and emmisions..as you now running 4.6 on a 4.0 map dont you think the worst could happen??
 
Ladies ladies ladies

The internal fuel map provides about 30% less fuel for the 4.0 than for the 4.6 and so it needs to be adjusted - GEMS does have some learning and self-adjust capabilities but not enough to compensate for the difference in this case.

Mark Adams of tornadosytems.com will unlock it and do the neccessary map for you for about 100 quid plus VAT

For 500 he will fit his bespoke Tornado chips inside(fuelling and ignition) which will get the best out of your engine and give you the economy of a 4.0. Throttle response is amazing.

He also re-writes THOR software and of course flapper and his hotwire tornado chips are fitted to about 2000 TVR V8s.

We have just fitted a John Eales 4.6 with ported heads and a Kent H180 camshaft into a 50th anniversary defender - it now runs superbly with the tornado and correctly-programmed 4.6 ECU.

When you talk to him tell him the spec of your engine and he will get the best map for it.

Mark's own 4.6 RR goes like the clappers and achieves 25mpg on the motorway
 
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on a less snooty note..dont bother getting your 4.0 ecu played with , even if its possible..i dont think you can,but may be wrong here..i thought you changed the eprom..ie to get uprated one costs 600!

reason...(s)

cost...how much to get it reprogrammed??atleast 1hr on test book..if possible..so atleast £50

you have to drive to dealer..risking killing engine...plus fuel costs and time

so buy another correct ecu..ie from pooh bay..£25..there are 2 or 3 on there for that..

you need part number..err6645..thats a 04/97 gems ecu number from mine.

yes that may not be your problem..but aving the wrong ecu and looking for another cause is silly..you need to start with atleast the correct parts for your engine and go from there.

ps see my boosted 4.6 thread...
 
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no not ladies..i am correct here..

it may not be ecu..but one has to sort that first...just has too...can you imagine speaking to lr dealer and telling them story and mentioning ohh running wrong ecu...what would thier reply be???besides..dont want to see gents engine die...that would be just mean!
 
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zen said:
on a less snooty note..dont bother getting your 4.0 ecu played with , even if its possible..i dont think you can,but may be wrong here..i thought you changed the eprom..ie to get uprated one costs 600!

reason...(s)

cost...how much to get it reprogrammed??atleast 1hr on test book..if possible..so atleast £50

you have to drive to dealer..risking killing engine...plus fuel costs and time

so buy another correct ecu..ie from pooh bay..£25..there are 2 or 3 on there for that..

you need part number..err6645..thats a 04/97 gems ecu number from mine.

yes that may not be your problem..but aving the wrong ecu and looking for another cause is silly..you need to start with atleast the correct parts for your engine and go from there.

ps see my boosted 4.6 thread...
Click to expand...


I got a ECM from a 4.6 with that part number and as it happens it's the same part number as my 4.0
So I'm guessing they are the same ECM but programmed differently for the two engines
But the replacement ECM don't run the engine "no crank" and if you by pass that and crank it there's no spark or injectors
I've had a look about on line and found a on line workshop manual the says
(If the GEMS ECM is replaced, TestBook must be used
to input the code to the new ECM.)
So it looks like I have a choice of coding the 4.6 ECM to my becm
Or getting my 4.0 ECM re-set/re-coded to become a 4.6 ECM
No quick fix what ever way I look at it
 
ahh rave..read it more..there are a few sections that need reading..look at the pin out/in for the ecu this tells a story

as i understand it, thats to allow the becm to switch on the power to coils and injectors..no correct code no switch on..the ecm does not control the power relays the becm does..gems is not canbus, it is quite simple the ecu will work on its own..

dont forget too that the fuel pump is controlled by becm..no fuel pump no injection..

so work around this and power up the power relays for above..and see what happens??
i am not sure on the alarm fuctions however, as i not using becm atall, just the ecu and autobox ecu..

anyway and i thinks for you cheapest easiest route is....30mins on test book is only 25..not a bank breaker..and hardly a long fix??so indy dealer or call out if close??
 
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