I have a larger 74mm IPD Plenum and TB and the car has a very strange idle issue, when started from cold the car behaves perfectly in fact IMO it tick over a little low as it has a LWFW, just before it hits running temp on the guage (80) it idles perfect on 900rpm, as soon as it hits 80 the idle goes up to 1500 but a quick blip on the pedal normally sees it back to 1000 after its been driven hard (and presumably slightly warmer) when coming to a junction etc the idle climbs quickly to 2000 and drops back to 1500 where it stays no matter what!
Any ideas? we dont seem to run these larger plenums and TB's much in the UK and my mapper has never mapped with one before on a DME, the only ones he has had an experience of have been with standalones. Its making the car horrible to drive and if stuck i traffic its unbearable. Any advice woould be welcome as it definatly seems temp related and not mechanical, the only fault codes are a missfire which will be new coil packs needed now we have turned the boost up.
Spec is 35,000 mile motor, bigger ex manifolds and hybrid K24's, IPD 74mm plenum and TB, de cats and 3" Ti X pipe system, agency power twin entry air box, uprated intercoolers tested to 900hp, silicone pipes and iridium plugs.

 

first thing i would do is a boost leak test ..i would double check everything ... can be some calibration to cuz you say before 80deg car run fine...

 

Have done a smoke test and a boost leak test and car holding 1.2 bar boost, afaik we do not have a leak either pre or post turbo.

 

can you fit your old TB with the plenum ? i would do that and see how she does!

 

Was hoping to avoid that LOL but will try throttle body first, I was hoping one of the mapping gurus may chime in, I should have added that this engine was converted by another tuner in the UK from new and has run like a watch, when I got it there were a few vacuum pipes missing along with the DV's and crank sensor, all of which I swapped from my original motor and since then we habve had this tick over issue.

 

My thoughts were a boost/vacuum leak would effect it all the time not just when its on temperature, under boost fueling etc are perfect.

 

yeah before exchange TB wait for expert in these stuff maybe some calibration in your tune ! aniway TB is a 30min job to do very easy

 

I dont mind the TB its the plenum I wont enjoy !!!! Hopefully a stock body will go on the 74mm plenum ok. AFAIK its the idle is controlled by a set voltage signal to the TB so I need to know what may change at approx 80 degrees to increase the idle, thanks for the input so far guys!!

 

Check valve flows or bypasses too much air by the throttle plate. You can put a restrictor in the check valve to stop this.. to check if this is the case, take a durametric and log TB position (%) something like 1.x-2% should be ok, if more than this should be the problem

 

my maestro software has some feature to deal the idle controlled by temp ! i bet your tuner can fix this

 

I would have thought thats the first thing he would of done if he had that facility! But Ill forward this to him and see what he says, we also are struggling to get over 1.2 bar boost. But the car seems to fly, had a little dudel with a F355 on one of our freeways late at night and he was a little tricky at a set of double lights we have and pulled like 75 yards on me straight away but I still caught him at the top of third gear and flew past and just kept pulling away, did it 3 more times and I was shocked how slow the 355 was compared to my car, in fact my passenger said 'you didnt just beat that you *** raped it' !!!! So its going well but just not as well as it can.

 

355 still is a fast car and trap 110mph+ but no mach for your modded P not even if your car was stock!

 

750/800 is proper idle not 1000. so maybe replacing check valves and maybe tb not closing fully? or boost leak(s) and/or bad maf. also check valve(s) could be bad at top of plenum.

all just wag's on my part. gl.

 

Im thinking there may be a check valve actually missing as I had to replace some of the hoses at the top that were missing and I didnt realise the IPD plenum is slightly different to the stock in respect of one way valves etc. But I still cant figure why its fine until operating temp is reached !!! I dont like it ticking over at 700-800rpm with the LWFW as you lose all the inertia of the dual mass.

 

^^ i would begin there. my bad check valve(s??!) resulted in a minor boost leak. that coupled with a failing maf all contributed to idle "hunting". the valves are so cheap i would just replace them all and the maf same time. gl w it.