Hamish Grundy Posted July 30, 2018 Share Posted July 30, 2018 Hi all. Firstly apologies as I’ve not been on here for so long! First time in a while and. I need some help. 😢 I have a 4.2 which I have fully rebuilt. It is running on megajolt and 14cux injection. All runs fine except the idle speed. I am monitoring everything on rover gauge and it is asking for a target idle speed of 600rpm. I have set the base idle to 540ish rpm. I have used brake cleaner to look for an air leak around the plenum and trumpet base but all is fine. I would like an idle speed more like 750. It is quite lumpy at 600!! I will try to upload a few pictures. Any help is greatly appreciated Quote Link to comment Share on other sites More sharing options...
Hamish Grundy Posted July 30, 2018 Author Share Posted July 30, 2018 I should also add that the stepper motor gets to the point that it’s reading 0% at 600rpm. Hence I went down the air leak route. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 30, 2018 Share Posted July 30, 2018 Does sound like air's getting in somewhere if it can't hit 600rpm with the valve closed - have you checked the other hoses, throttle stop, servo, etc.? Quote Link to comment Share on other sites More sharing options...
Hamish Grundy Posted July 30, 2018 Author Share Posted July 30, 2018 Throttle is fully closed, have adjusted stop as plenum is new. Have checked every hose to do with the air intake. Most other v8’s I have had have idled about 750, but I have never checked the target rpm before. I do have a fault to do with the gearbox but would that cause the target rpm to be lower?! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 31, 2018 Share Posted July 31, 2018 I'm not familiar with the Rover gauge thing, I'd say it's a good idea to clear obvious faults before hunting for others. Quote Link to comment Share on other sites More sharing options...
mickeyw Posted July 31, 2018 Share Posted July 31, 2018 Hamish, you're running auto aren't you? IIRC the neutral gear signal comes via the round plug that also has the reverse light switch wires. Is this connected/damaged/etc?. As a test or "cheat" you could connect the orange/brown wire on the 14cux through 510 ohm resistor to ground. This tells it you have a manual gearbox, and bypasses the neutral switch circuit. The fault you have shown will then be ignored. As an auto setup it wants to know when you're in gear so it can adjust the idle speed. Hope that makes sense. Quote Link to comment Share on other sites More sharing options...
Hamish Grundy Posted July 31, 2018 Author Share Posted July 31, 2018 I am running auto yes. I have found that 600rpm is the target idle for an auto when in gear. So if I sort the switch problem then that should sort it. I will have a look at fixing the fault properly first Micheal then see where I go from there. It’ll be out laying out for the majors this weekend so it’ll have to stay as it is for now. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 1, 2018 Share Posted August 1, 2018 600rpm in-gear would explain it as there's a drag on the system when it's in-gear that's not there in neutral, hence why it' can't get it that low. Quote Link to comment Share on other sites More sharing options...
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