Newbie - 3.9 EFI Transplant into '87, hot idle issues

[AndyB]

Hi to you all. HELP after some advice!
A mate fitted a 3.9 Serpentine '94 disco engine and auto tranny in my '87 Ranige after she died, he's very knowledgeable, but not on the EFI electrics so much. It has the full loom and computer from the 3.9. Ever since fitting it wont idle when once engine is up to operating temp. Once off idle the engine runs fine, although I reckon a bit rich (heavy on fuel) I've cleaned the stepper motor, dissy, sparkplugs, upped the idle a little, but still no good. I'm wondering if, because of the old cable driven speedo, there is no speed sensor, as this was removed to fit the cable unit, whether this is the cause of the problem? Anyone have any ideas on what to look for/at? I'm assuming its electrical. I replaced the water temp sensor for the EFI aslo. the only thing it doesnt have under the bonnet I can think of is the disco Charcol cannister, all else is from the 3.9. If anyone has done this mod before, or has some ideas, that would be great, before I give up and send her to the doctor and most likely part with lots of my hard earned!! Cheers, AndyB

[justinc]

Andy,

The speed sensor has no effect on the idle speed, I have done 3 of these conversions and another one next week and haven't worried about it yet. I would recommend fitting the charcoal canister AND purge valve etc to the '87 from the serp engine donor vehicle. I seem to remember this was a problem for an earlier conversion I did that suffered from poor idle etc.
JC

[AndyB]

Andy,

The speed sensor has no effect on the idle speed, I have done 3 of these conversions and another one next week and haven't worried about it yet. I would recommend fitting the charcoal canister AND purge valve etc to the '87 from the serp engine donor vehicle. I seem to remember this was a problem for an earlier conversion I did that suffered from poor idle etc.
JC
G'day Justinc. thankyou very much for the info! Will get one to fit. From other threads I've read, I will check the TPS readings also........I saw in another thread someone had put a pic up of their idle Stepper unit on the back of the plennum chamber. it looked like it screwed into another unit, which then screwed into the the chamber. Mine is just screwed into the chamber. Is this correct? thanks again. Andy

[BigJon]

Don't expect anything marvellous on the fuel consumption front. My 3.5 used to regularly do 15 litres per hundred on the highway without trying, the 3.9 does more like 17 :eek:. I have checked almost eveything in the EFI system to improve it, nothing has helped yet.

[AndyB]

Bugger...I hoped it might run a bit better. Oh well, dont use it everyday. Cheers. Ex Beulah boy..

[Grumbles]

Heavy on fuel.......okay but can you expand on this please? What does this mean in actual fuel consumption figures over what sort of travelling?

[AndyB]

Hi Grumbles. I havent actually sat down and worked out the figures, but my wife drives the RR LSE 94' softdash, and its certainly much thirstier than the LSE. I havent driven it much as yet, cause of the idle issues, maybe it'll come down a bit once I sort that out. I'm thinking in the mid 20's/100 at the moment.