CharlieB Posted December 28, 2020 Share Posted December 28, 2020 Hi all, I have a query regarding the idle control on a 14CUX system I am having the age old problem of sometimes stalling when going into drive or reverse. i have carried out all the usual stuff like air leaks/blockages, idle valve clean, timing, base idle speed etc. But I have noticed something odd. If I use Rovergauge to monitor the system, in Park/neutral the target idle is 700rpm, and when I select drive or reverse, the target idle drops to 600rpm, that seems back to front to me. If I break the auto box wire to the ecu and ground it so it thinks its in neutral, it works better. Any ideas? Regards Charles Quote Link to comment Share on other sites More sharing options...
teabag Posted December 28, 2020 Share Posted December 28, 2020 The RPM at idle will be higher without any load, move out park or neutral and the revs will drop, and a bit more with electrical stuff and A/C added to the mix. My 3.9 auto sits at around 730rpm at idle in neutral and anything between 650 and 675 when loaded, but all vary slightly sometimes not that I notice, I don’t look a the rev counter often. LRs workshop manual adds + or - 28rpm to their stated idle speeds, also all loads off in neutral 665 to 735 rpm. Base idle 525+-25rpm. Quote Link to comment Share on other sites More sharing options...
CharlieB Posted December 28, 2020 Author Share Posted December 28, 2020 Yes, I know, my query is that the ecu is calling for 700rpm idle in Park/Neutral, but it calls for 600rpm when I put it into drive/reverse. Surely it should try to increase the idle in drive to compensate for load? Quote Link to comment Share on other sites More sharing options...
teabag Posted January 3, 2021 Share Posted January 3, 2021 (edited) A breathing issue maybe? Checking the crankcase breather and hose are clear, remove the ‘flame trap’ from the rocker cover and soak it for 1/2 hour in petrol, or overnight, or replace it. Also is the air filter clean. Edited January 3, 2021 by teabag Quote Link to comment Share on other sites More sharing options...
CharlieB Posted January 3, 2021 Author Share Posted January 3, 2021 I've checked and cleaned all the breathers. My query is that the ecu is requesting a lower rpm figure in drive than in park, which seems back to front. If I activate the aircon input, I get a revs increase as expected. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 3, 2021 Share Posted January 3, 2021 The ECU is doing what the ECU is programmed to do, unless it's causing you a problem I'd find something else to worry about. Quote Link to comment Share on other sites More sharing options...
CharlieB Posted January 3, 2021 Author Share Posted January 3, 2021 That's the whole point of my post, it is causing me a problem. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 3, 2021 Share Posted January 3, 2021 It's the same thing it does in every other vehicle running that ECU so I'd be inclined to wonder if there isn't a different problem that's causing the stalling? Quote Link to comment Share on other sites More sharing options...
CharlieB Posted January 3, 2021 Author Share Posted January 3, 2021 FridgeFreezer, probably something else is causing this glitch, but I'm in the process of installing a Speeduino system now, so not really worth spending time on it! Quote Link to comment Share on other sites More sharing options...
teabag Posted January 3, 2021 Share Posted January 3, 2021 From P into R or N into D my engine RPM drops by at least 80 revs, there is a slight increases when AC is on, all controlled by the EFI ECU and idle control valve as you know. So with AC on and in drive my engine idles around 675 give or take and when for example stationary at traffic lights. Buts its not very i look a the rev counter. So from the RPM numbers you posted thats just 20 revs lower at idle than my engine in the selector P or N Quote Link to comment Share on other sites More sharing options...
CharlieB Posted January 3, 2021 Author Share Posted January 3, 2021 I don't have aircon, so as a quick fix, I will just put a feed on the aircon ecu input to up the revs a bit. I will be able to play with the revs as much as I want with the Speeduino installed. Quote Link to comment Share on other sites More sharing options...
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