I have a 07 Scion MT, I bought it about 1 year ago with a Turbonetics kit already installed. The dealer claimed it was profeesionally tuned, but I later found out that there was no tuning computer in it. The ECU wires were hacked up and sodered back togather, so there was one at some point, just not when I got it. Anyways, I installed a AEM FIC, and hardwired it, and street tuned it. It runs good except...

For as long as I have had it it idled bad, very lumpy, like a muscle car, and the rpms bounced, and it flet like it was going to stall. I have been data loging and noticed somthing. My spark advance varies alot at idle, from about 5 to 15 advance (if im reading my computer right). I just read that it is supposed to be:

SERVICE DATA
Standard ignition timing 5 to 15° BTDC at idle
Standard idle speed
A/T 610 to 710 rpm
M/T 650 to 750 rpm

See the attached screen print from my data logger..

SO it seems right, but why is it wandering so much? It seems like the car shakes in rythem with the spark advance. Every few secs there is sharp drop in spark advance, along with a drop in idle speed, a shake, and the idle jumps up to 1000 for a sec, then back to normal. This happens over and over again.There is also a poping sound from the exhaust.

See attached image #2

Any ideas?

 

Manipulating timing is a quick response way to affect idle, Im assuming the stock ECU uses this strategy (I know the AEM EMS, and various other ECU's do). Basically when the idle rpm moves away from the target the ecu quickly advances or retards timing to correct it. Alot of the time this can be used to save the car from stalling, but youll often see a quick spike in rpm. So I think you may be looking at this wrong. Its not the change in timing causing the rough idle, its in fact something causing it not to stable idle and its manipulating timing to try to correct it.

 

ok, so its a sign of a problem and not the problem. What could be the problem? The fuel trims look good, so does the o2 readings. So i wouldnt think its fuel related. So maybe, air related? maf? vac leak?

 

Could be vac leak or maf issue. I had some weird issues like that with the FIC to be honest. Never really did figure it out, it idled well enough that it didnt die, so I was ok with it haha.

 

The turbonetics kit came with a unichip piggyback tuner I believe, you could get an authorized tuner to fine tune it further for your car, the previous owner probably yanked it out and sold it separately.

a turbo tC with larger injectors will idle surge since no piggy back tuner has any affect on the cars idle tune.

 

it doesnt die, its just annoys me. Buts its good to know that Im not alone... haha

Since I do have an 07, and the intake tube is 3", i have a 2.75" slide in adaptor from spectra, which keeps my cel off, but maybe its just not good enough at idle. I just bought some Fujita intake pipes for an 07, 2.75" dia. Maybe I will try to cut off the maf section and use that instead.

Another idea is that since I hardwired it, all the grounds go to frame, including the signal ground. Maybe it is picking up interfearance from the other grounds. I could try connecting it to the ecu signal ground, which I belive is isolated.

 

Since it came with the turbo kit on it, I dont have a stock air box. I wish I could get one cheap and just toss it in, so that I could rule out maf problems.

 

Also, if you have the ability, convert it to a blow through MAF set-up to help smooth it out more, if the BOV is after the MAF sensor, it'll have a harder time.

 

what tuning changes are need for a blow thru set up? maf map? fuel map?

 

Not sure, I had P-tuning convert my Turbotoyotas kit to a blow through set-up. Most of the tuning was mainly because the intake plumbing was larger, but the car made smiliar power and then came back to idle in a much more stable manner with the blow through set-up.

 

I have an 06 with a custom turbo setup with the FIC and I have the same exact problem.... mainly when I decelerate or clutch in when coming to a stop. Ive tried manipulating all maps and it still does the same thing. Fortunately it doesnt drop so low it dies but it does the same thing as yours. I think its a fairly common problem with the FIC

 

Get the AEM EMS2, I have it and have zero driveabilty. I used the FIC for maybe 6 months, hated it.

 

Easier said then done Haha that piece is not cheap but that is my next upgrade and wouldn't expect anything less coming from a standalone at that price. Overall I like the FIC other than the idle issue. Does everything you need it to do for a good price but of course inferior to the ems.

 

i think I paid like $2500 but if you want that stock feel from your car back, you have to pay to play.

 

Clutch in and decelerate is working fine even with the draw thru. The idle issue doesnt show up untill after your sitting for a few seconds, like at a traffic light.

The problem also doesnt show up untill operating temp. On a cold statup its just fine.

A standalone is never gonna be in my budget, and I have concerns about passing inspection with one. I have emissions testing that I need to pass every year. Lucky for me that PA only tests this through your ecu, and not at the tail pipe. So its not to hard to slip through, with the turbo.

I tried adjusting my 02 map this morning, it seems that IF I idle just a tad rich (3V) the spark stabilizes, so now we will see how long it lasts, or how long till I get a CEL...

 

so making the car run slighty rich only worked for a day. The timming went right back to how it was and the car still shook. So... gotta think of somthing else...

 

After more reading I see that some people changed their MAF map from voltage to percent and filled it with "0" and just set the MAF max voltage.

With the MAF in voltage mode you can see the MAF volts in and out on the FIC window. The out doesnt seem to match in the in at idle.. Its close but always just a little off. With the MAF in percent mode, the volts in and out match perfect... But..

For some reason it throws my fuel trimes way off... from +2% LT to like +25% LT...

Any ideas?

 

So the MAF is back to voltage mode...

I also cut up my fujita intake so that I have 2.75" maf tube, instead of a 3" with an adaptor...

Still my idle was no good,

After searching through some quite old posts if found a very usefull one..
https://www.scionlife.com/forums/sho...d.php?t=175197

B_REAL45
"Just for a reference, My 630cc's liked .931 and my 840cc likes 1.32

I would try about .600 at first and see if the car likes it. Set the response time, adjust your map to idle with STFT near zero - then use that number for the rest of the map at low load.. hold a rev of around 2000rpm - see if it is steady. If not, you will need to play around with the setting a bit more. "

Also good info on injector response here
http://www.injectordynamics.com/LowPulseTech.html

SO it seems my issue is with my injector response time. I think im in the non-linear response range of the injector pulse at idle. So after setting my injector response time to 931.5 and adjusting the fuel map untill I get fuel trims near 0.. I now have a much better idle.. I just need to re-adjust my fuel map in boost range..

I tried other repsonse times but..
If I lenghten the response time and re-adjust the fuel map, I go way rich at anything above idle, and I have to change the map alot before anything happens, then its a very dramatic change. SO its too hard to tune.
If I shorten it then I get my lunpy idle again..

SO.. a 931.5 injector response time on Siemens Deka 630 injectors seems to the magic number on our cars to get a good idle.

See attached data log

 

Does your FIC have the resistor mod?

 

Yeah I did the resistor mod. It made no noticable change. Also I belive that is for a high rpm stumble.

Update:
Since I changed the injector response time, the idle has improved, although not perfectly smooth the lumps seems much smaller...