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iomlt

rich on idle (increasing)

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Hello all.

Cut a bit of along story short, havent used the truck for 6months, (under going a bit of a change of use rebuild) 3.9 / auto on MS.

Been used for 4 years or so and 3 years on MS never really touched it since i got it going like a scolded cat of a red hot tin roof (or a similar known saying) its been upside down more times than i care to remember, Boiled far too many times in comp use and still runs as sweet as a sweet thing.

But the last couple of times i have tried to fire up because quite honestly its more fun listening to the v8 than boring rebuilding stuff and making good, i notice its near impossible now to start unless you take all the plugs out heat them up and then it fires up fine. (try new plugs i hear you say - yes i will and thats not my main concern at the mo)

Ok get her running again runs beautifully. but looking at the pretty gauges on MS it looks like shes (on idle) getting very rich, hold her in the high revs ort bounce of rev limiter for a few seconds (rough i know but to be honest i have a 4.2 sat in the garage but i'm refusing to change it till this 3.9 dies) and the air to fuel ratio drops back to around 14.

Attached is log file and map. like i say it goes very well idles great (for what i want it too for a auto and for what i do with it challenge truck etc) but why is it getting very rich at idle, is it normal? Like i say i havent really touched in a couple of years (if it aint broke not try and fix it attitude)

I will be moving the truck away from serious challenge events now, it was a tray back now a full bodied hardtop again so a change to a more economical running V8 would be best so any tips on my set up please feel free to throw them at me.

Cheers in advance.


Al

rich.xls

2015-04-25_10.56.21.msq

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Al, as you know I'm know great expert at any of this but could it be one of your injectors is sticking open? This caused mine to run rich but I never revved it very hard so can't say if the problem is exactly the same as yours.

By the way, do you recognise my profile picture?

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Hello,

Good to see/ hear from you. Great Pic! you should come over and we do that again!

The truck will be fine! I just havent used it for a while. so never been a problem in the past so a good run on the road and she'll be rite. or i just though the 4.2 in or to be very naughty i have a OM606 engine...... be a shame to "bin" the megasquirt and the V8.... I just need to finish her and get it used! even if that means red lining her more often (joke)

Speak soon

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I'm no expert either and it's nothing more than a stab in the dark but;

It it set to closed loop? Maybe it's getting a faulty reading and adjusting itself richer? Maybe an exhaust leak is letting air in and making it think it's lean but when you rev it theres enough flow for this not to matter?

Is the temperature accurate? Maybe the cold start part of the program is staying on?

Is there some sort of air leak at the top of the engine thats moving it to the wrong part of the fuel table that again is less noticable at high RPM. I assume it being ok at high rpm is without load?

I've had injectors stick closed before, I guess they could stick open too?

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Start with the basics, are all the sensor readings reasonable? Does it SMELL rich, not just reading rich? Any issues such as stuck injectors / FPR, air leaks, split hoses, that sort of thing?

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