This is doing my head in!!!, but I think I have worked out that the IACV is causing the 2000-3000 RPM idle after cold start.
Today I started the engine then slowly blocked over the IACV intake pipe inside the Carbon Airbox… as soon as I did this the idle dropped and was at 1000 RPM with it completly covered over.
When the engine was nice and warm, the idle was back down to 1000 RPM… however there was still vacuum suction from this intake pipe! Is this what should be happening? Surely all the induction should be through the throttle body direct?
I have tried resetting the IACV using the ‘5 press’ method but am still getting this fast cold idle. Will the lotus ‘reset tool’ do a better job?
At least I know there is unlikely to be an air leak anywhere else as the warm engine idles normally!
The I(dle) A(ir) C(ontrol) V(alve) is there to provide a stable idle regardless of engine temperature and load. On the Exige at idle there will be very little air drawn through the TB, most will be drawn through the IACV.
If the load on the engine increases (such as when the alternator loading goes up or the aircon switches) more air is modulated through the valve to prevent the engine from stalling. When the engine is cold the IACV is opened a lot more to facilitate a faster idle, this is programmed within the ECU and it will gradually decrease as the engine comes up to temperature. If you have a stock ECU this is unchangable, if you have an Emerald it is a simple fix to stop the engine soaring.
Yep! But I do have an Emerald and I have checked the idle speed settings/coolant temp are all sensible, ie: 1000 to 1300 ish max! But the bloody thing is going to 2-3000 about 15 seconds after start! I have tried the ‘5 press’ Lotus reset procedure to no avail!
Dont get it as all was ok? It is obviously sort of working as when the engine warms it does idle normally! Do you think a dealer with the correct ‘tool’ could re-set better?.. but HTF did it go off anyway!
BTW, do Jenvey DTH TB have the same pickup for an IACV or are they just straight thru?
It’s not the idle settings that you need to look at, these are just for close maintenance of the idle by ignition control, it is the IACV settings you need to look at> There is a table of values that indicate how far open the IACV should be at all operating temperatures, at low temnperature you will have a value of around 85-90 which gradually decreases with temperature, it is those figures you will need to reduce.
There is no correct dealer tool, the Emerald software is the only way you will change it as the dealer stuff is relevant to the original ECU. I any event, even if you had the original eCU most Rover/Lotus dealers only have the stuff for the regular 120BHP engine.
The 5 press routine is again for the original ECU and is a waste of your time with the Emerald. Every aspect of the ECUs aspect is programmabel, it is just a matter of understanding a little about waht is going on and the interplay between the various settings and their influence on the engine. I would review the IACV settings, that is probably where the problem lies.
Jenvey TBs dont use an IACV, but it is perfectly possible to disaable the current IACV and just use the airlfow through the TBs but you will need to change the airflow through the TBs to do this.
TBH all it needs is 10 minutes with someone who knows and understand the Emerald software and all would be well. The prolbem with programming a cold start is that the engine has to be stone cold to test it… not easy at a rolling road session…
On the face of it Pete, the IACV numbers look respectable, so it warrants some further investigation, maybe the IACV is faulty… Either way it needs a glance from someone with Emerald experience, when the engine is cold.
If the IACV is set to manual (fixed) and you have an air leak somewhere (the engine is still running with the IACV intake blocked) you may have high idle levels when the cold enrichment is operative. Once hot, the engine will run too lean and idle levels will drop.
Not the definitive answer, but might be a possibility…
If the IACV is set to manual (fixed) and you have an air leak somewhere (the engine is still running with the IACV intake blocked) you may have high idle levels when the cold enrichment is operative. Once hot, the engine will run too lean and idle levels will drop.
Not the definitive answer, but might be a possibility…
This is very interesting… thanks!
SO, let me get this clear pls!!
If I completly block over the IACV intake pipe with the engine cold, my engine still does run (rough) at about 1000 RPM.
So, does this mean I do have an air leak somewhere else, or are the TB’s allowing just enough air past the butterflies to allow this slow idle?
(once again once the engine is warm the idle is 1000 RPM)
I have replaced all the vacuum pipes…
…that is running from the centre ‘ballast switch’ (one of 3 located on the left hand side diagional engine brace) and then to the 4 small bleed intakes on the top of each TB, and then onto the fuel rail vacuum with a ‘T’ piece feed to the vacuum ‘bubble’ over the right hand side wheel liner.
Since I have fitted an Oil Catch Tank, I have removed the oil vent pipes from the top of the rocker cover, (these used to have 4 bleeds feed back into the TB’s). So, I interconnected each pair of TB bleed valves with a ‘hoop’… (Perhaps I should actually block these off totally?). In any event all these junctions are tight. The TB’s also have a new inlet gasket.
I’d thought about the possibility of an air leak, because I have seen exactly that situation when a hose slipped off the IACV, it also gives a shedload more symptoms, especially when the throttle is opened with leaning off and engine stalling. Also when the engine went past idle, it would be virtually impossible to get it to fall back as it would operate on a different part of the map.
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