high idle rich or lean

after a hard blast the idle is high 1k is this a sign of running rich or lean or none of the above. on start up its fine 750 or so rpm

My car does this aswell but settles after a minute, i think its just extra fuel getting burned up.

Also if your air con is on this will happen.

after a hard blast the idle is high 1k is this a sign of running rich or lean or none of the above. on start up its fine 750 or so rpm

most motors will increase rpm if they go slightly rich. if they are mapped to idle at stoich of lambda greater than 1..

youll most likely find that after youve been for a blast the inlet air temp is very cool.. as soon as you pull up the hoat will soak back into pipework etc.. and if your on the stock IAT sensor they response quite slowly..

so hot air (less dense) and a sensor thinking cold air (enriched fuelling) would be a rich running situation..

theres not much you can do about this situation unless you fit a fast acting IAT in the airflow path and some careful tuning.

think that makes sense.. lol

so a little rich as opossed to lean cheers

It won't be related to lean/rich idle, more likely a sticky ICV.

You really need to get yourself and AFR gauge Nigel!

Have you tried closing the throttle butterfly closed with your fingers when the idle is high?

If its a TT it wont have an IAT, i agree with Homer, more likely to be ICV, if the idle is high its more likely to be more air getting in, the the injection system will compensate due to the MAP sensor.

If you watch an AFR gauge at idle you will feel it slow slightly when the ECU adds more fuel, and then speed up slightly when it goes lean again.

If its a TT it wont have an IAT, i agree with Homer, more likely to be ICV, if the idle is high its more likely to be more air getting in, the the injection system will compensate due to the MAP sensor.

 

If you watch an AFR gauge at idle you will feel it slow slightly when the ECU adds more fuel, and then speed up slightly when it goes lean again.

the 2jz gte doesnt have an inlet air temp sensor?? are you quite sure.. its in the top plenum. it is needed as part of the fuelling calc for a MAP based system.

If its a TT it wont have an IAT, i agree with Homer, more likely to be ICV, if the idle is high its more likely to be more air getting in, the the injection system will compensate due to the MAP sensor.

 

If you watch an AFR gauge at idle you will feel it slow slightly when the ECU adds more fuel, and then speed up slightly when it goes lean again.

i would agree that if the ICV park position is quite "open" then a fall to idle would be higher than normal.. yet it would do it all the time in all situations

Always thought that the J spec TT doesn't (could be wrong)

the UK spec TT does as it also has AFM and so needs IAT.

The non VVTI engines have an IAT probe.

If its a TT it wont have an IAT

It's just in a different place, Ricky - stuck in the side of the plenum.

Heat soak The less said about that the better.

Easy first steps, the idle control valve is known to gum up, give it a clean. Also muck out the throttle butterfly mechanism as well, that can gunk up a bit over time. Doesn't take much of an opening to lift it to 1000rpm. Otherwise, as a MAP based system you may have an intermittent air leak causing the increase in revs, but do the cleaning stuff first as it's cheap and easy

Does the idle ever recover back to 750 by itself if you leave it idling? Does it recover if you poke the throttle a couple of times? Pushing on the throttle cam as suggested by 4packet is a good idea as well.

-Ian

after a hard blast the idle is high 1k is this a sign of running rich or lean or none of the above. on start up its fine 750 or so rpm

some cars hold the throttle open slighty after releasing so as to promote burning in the cat then reduce down to nomal idle, this might be the same on you supra?

ps i think this only happens when in closed loop mode, so only does this when the engine has warmed up?

does your car drop to normal idle after a short while?

as already said i dont think its rich/lean related,

hope this helps, regards chris

 

Heat soak The less said about that the better.

 

-Ian

really... you think this is not a valid issue with a slow acting IAT?

the revs are hunting a little but it does drop down to 750/800rpm. seems to take a while for it to drop after a good hard drive though. maybe my mix of toulene/xylene has something to do with it.the idle is just very rough. drives fine in every other way boosting etc is fine. think its a little harder on petrol plugs only 3k on them ik24s

Of all the TT's I've been in, they all hang around 1k after a good blat, then settle after a few seconds.

It's just in a different place, Ricky - stuck in the side of the plenum.

 

 

 

-Ian

Do you know i never actually took much notice, don't remember seeing the input in the ECU pin out, but yes its there,never used it when connecting piggybacks etc, just out of interest, just how much effect does it have on load scaling?

It seems to me that its going to have a narrow scale as most of the time the plenum is bloody hot! and the probe will surely, ( i hate to say it:innocent:) suffer a lot of heat soak and so give a somewhat spurious reading?

Do you know i never actually took much notice, don't remember seeing the input in the ECU pin out, but yes its there,never used it when connecting piggybacks etc, just out of interest, just how much effect does it have on load scaling?

 

It seems to me that its going to have a narrow scale as most of the time the plenum is bloody hot! and the probe will surely, ( i hate to say it:innocent:) suffer a lot of heat soak and so give a somewhat spurious reading?

the ecu uses it as part of the fuelling equation.. so there would be no need to connect to a piggyback..

air temp (density) has a great effect on resultant AFR's

so for the layman... if the car is tuned in with a summer IAT of 45degrees.. and no IAT correction is present then with a winter night IAT of 20 the fuelling would run considerably leaner than you might like...

the stock sensor position does suck.. and is subjected to incorrect readings sometimes and also the sensor is too slow reacting to facilitate accurate adjustment of the IAT fuel trim.

the IAT sensor also serves as an ign trim.. which again requires different values for IAT..

the only thing i can think of if you change the position of your IAT sensor and dont retune/ run a stock ecu is that the resultant values will change for the same IAT. this could play havoc with your existing tune..

the ecu uses it as part of the fuelling equation.. so there would be no need to connect to a piggyback..

 

Which seems a bit strange to me as if as you say it plays such a big part in fuelling calculation then i would expect it to be tweak able by a Piggyback, but i have yet to see one that has this ability.

 

air temp (density) has a great effect on resultant AFR's

 

As above.

 

so for the layman... if the car is tuned in with a summer IAT of 45degrees.. and no IAT correction is present then with a winter night IAT of 20 the fuelling would run considerably leaner than you might like...

 

Which in my books leads me to believe it doesn't play such a big part as the factory map calc would be done to an average IAT for that very reason?

Every engine that i have seen tends to run richer on a could day due to colder denser air being metered by the AFM or MAP sensor

 

the stock sensor position does suck.. and is subjected to incorrect readings sometimes and also the sensor is too slow reacting to facilitate accurate adjustment of the IAT fuel trim.

 

So again it seems the stock sensor is neither accurate or fast enough to react with any consistency.

 

the IAT sensor also serves as an ign trim.. which again requires different values for IAT..

 

the only thing i can think of if you change the position of your IAT sensor and dont retune/ run a stock ecu is that the resultant values will change for the same IAT. this could play havoc with your existing tune..

Strange as all the tuning i have ever done with piggybacks or PFC has not taken IAT into consideration and i have yet to encounter any resiting problems due to this.

a piggy back ecu alters final pulse width.. not the main fuel calc..

google "speed density"

as you know the supra system is speed density. so the main fuel calc is

manifold pressure vs engine speed.. = given air amount per stroke..

what this doesnt tell us is the density of the air.. hence an air temp sensor is introduced to allow air density adjustment as you know cold air is denser.. hence requiring more fuel to achieve same AFR

just because a supe runs rich on a cold night does not mean the this rule is bollocks.. it means the ecu tune in the stock ecu is not accurate.

the PFC has IAT cal table circled below.. as have all standalones..

not sure if this makes sense but the cars idle is a lot lower now and smoother all the time hard pulls etc. the only diff is the outside temp has gone way up.would the fact the car was mapped in summer 25 celcius have anything to do with it. should there be a switch for winter map and summer map. also the boost on high setting wont go over 1.4 were in the cold it was rising 1.55/ and spiked at 1.71bar

no you ndont need a switch bud.. its just that if the car was tuned in certain circumstances then it would have been hard to replicate the colder conditions a the time of mapping.. so in effect a knowledged guess.

just because a supe runs rich on a cold night does not mean the this rule is bollocks.. it means the ecu tune in the stock ecu is not accurate.

Which was kind of my whole point, which is probably why i haven't considered it, can't actually remember configuring the IAT in the PFC i had on my S14, long time ago mind, however the SR20 and the CA18 are also motors that would run pretty rich in cold weather.

I never said the rule was bollocks, just that the IAT measurement seems pretty inaccurate and made very little difference to these engines in real terms.

Which was kind of my whole point, which is probably why i haven't considered it, can't actually remember configuring the IAT in the PFC i had on my S14, long time ago mind, however the SR20 and the CA18 are also motors that would run pretty rich in cold weather.

 

I never said the rule was bollocks, just that the IAT measurement seems pretty inaccurate and made very little difference to these engines in real terms.

oh yeah id totally agree.. it depends on if the nissan ecus you had were djetro or not.. since the nissan motors dont have a stock IAT.

i must admit that most factory tunes afr stabilty is not that great.. then again they are so rich that it doesnt matter.