My car suffers from idle issues. I run S2 and idle is set at 1500rpm. Was set and professionally tuned by AMS Then when I pull up to the stop light, idle goes to over 2000rpm and then falls down to a stall. I went to AMS, they said IAC is faulty so I bought a new one. The same problem. Went there again, said my MAF might be faulty so I changed that as well. Problem the same. I came to the conclusion S2 cams are to big for stock head on the 8 cause of a overlap but I really don`t know.I found this info on EVOMOTO

"With more aggressive cams l (and more overlap), you will lose vacuum. How much depends on the cams themselves. With our cams, we went from about 17 in/Hg (0.6kg/cm2) at idle with the stock cams to about 14.5 in/Hg (0.5 kg/cm2). With the A/C and other accessories running and on the brakes, this could get as low as 11.5-12 in/Hg (0.40-.0.42kg/cm2). You can see how that could cause a problem with stalling. Since the stock vacuum is on the weak side already, you may find your Evo wanting to stall at idle with aftermarket cams, particularly when driving. Letting off the gas and immediately hitting the brakes is a prime example of the most likely time this will happen (power brake booster uses vacuum to operate). You may want/need to adjust the idle up a hair and possibly add some fuel in with a management system at idle to help "catch" it before it wants to stall when you let off the gas."

Now I`m thinking to switch to a smaller cams. Do you guys think that 274 CAMS are giving me a idle problem or should I look elsewhere to fix this.

 

I assume you are still on a flashed stock ECU? They are pretty solid in terms of idling, and I am surprised to see issues with stalling with those cams.

If your signature is up to date, I would blame the PTE 1000cc injectors. Not on Evo's specifically, but I tune all sorts of cars, and PTE injectors 850cc or larger, idles really poorly. I give them a 3 out of 10 for idle quality, and in comparison, I give ID1000's a 9.5 out of 10, for comparison's sake

Cams, multi-disc clutch, big throttlebody, etc.. these mods affect idle quality and stability. So another car with the same PTE injectors may not have an issue, but yours could, etc..

Another thing you can check is your battery voltage. Make sure it is not fluctuating. A weak alternator could skew up a lot on the injector response times, and even when properly tuned, it provokes idling and stalling issues.

 

were the cams dialled in .?? more timing in the idle area helps too

 

I'm running those cams on my 8..did u do springs too? Cam angle sensor? 180 off?

 

yeah im running s2's plus the springs and my car has never idled better. im on stock 8 ecu head, maf, 35r plus tripple disc clutch. maybe u should try another tunner. i would think ams would b on top of this but it something else to try since they r coming up with reasons that arent their fault.

 

If it didnt have the issue directly after leaving ams for the tune and it now does then it means something changed..maybe you have a boost leak somewhere? Have you added a VTA BOV or anything? Stupid question..is your defroster on when this happens?

 

I would check the obvious first like a boost leak. First thing I would check is the vacuum hose to the egr valve. This popped off on me before and the car would stall at idle.

 

I ran S2's in my car and the idle was fine (aside from the sound a cammed car makes), but it took some tuning to get perfect. off the top of my head some things I did were:

make sure there are ZERO boost/vaccum leaks
adjust the BISS in evoscan
adjust the ISCV tables
adjust the timing in the approporate cells

of all those I think the biggest difference was making sure the BISS was set correctly. that made the most difference. the other settings more or less just fine tuned the idle.

 

A lot of info guys. Thanks. I got NO boost leak did the test twice. I run stock ECU flashed, BOV is recirculated. My drivetrain is all GSC springs and retainers. If it come to timing, BISS or tables adjustment I thought good tuner will take care of it. I already bought new 800cc injectors and wanted to go back on a dyno to see if it helps but if it doesn`t I`d probably blame cams so I`m thinkin to switching to 264`s before I go but if you guys think, that is not the cams maybe first I should change the injectors and see what happens. I really like the sound and insane power of S2`s but now every time I pull up to the stop light I have to pump the gas and use my hand brake...... How crazy is that and is not acceptable. So should I go for another tune and just downsize injectors first before I jump into swapping cams ? What should I say to my tuner so he can make it right. I`m not as educated as some of you guys so I need some help. I just thought I put bigger turbo cams, inj. etc and tuner does the rest.

 

This should be able to be tuned out. A Tuner wont fix stuff like this unless you tell them you have a problem.

 

yea dont give up on the gsc's yet, if the cams were the problem then they wouldnt be the most recomended cams out there.(speculation but I think most would agree)

 

a lot of tuners aren't interested in investing the amount of time it takes to fully tune a car. Making a couple of WOT pulls and adjusting your timing/fuel maps isn't that difficult and that is all a lot of so called 'tooner' out there do. However, dialing in injectors to get the correct fuel trims, adjusting the BISS and/or idle settings so the car doesn't stall when it comes down from load and making the car drive like stock EVERYWHERE in the RPM range takes a considerable amount of time.

If the shop you go to just wants to throw parts at your car to try and fix a problem (at your expense) I would look elsewhere...

 

I think I`ll keep S2`s for now go back on a dyno by putting smaller injectors, explain the whole thing and maybe tell`em to adjust my timing properly. I heard by increasing lobe separation can help make a bigger cams more streetable, hopefully they can smooth out the timing for improved idle.

 

its not injectors man, im running 1250cc on my stock ecu. id go elsewhere for a tune and make sure they road test it afterwards.

 

There is a local shop in my state that is reputable and they are willing to take time and do a good job on your tune. BeyondRedline is expensive but worth it. It did some work there before but I come back to AMS only cause they retune your ride 50% OFF but it seems like when you are not dropping off GT-R with 50 grand mods in it, they are like blowing you off. I got that impression when I talked to them explain where I wanna go with my tune. I got adjustable cam gears so maybe playing with timing will help. Anyway I made my mind I`m keeping S2 I just gonna spend couple hours on a dyno till they make it right. Thank you guys, you sure influenced my decision. I`ll call`em in the morning to schedule an appointment and post the outcome of this