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Help! We have to get this car fixed! Major idle trouble.

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8.4K views 30 replies 12 participants last post by  BadlandsRacer  
#1 · (Edited)
Alright. I've been working this crappy idle issue for awhile. Here's the scoop: The car pulls like a monster under boost, no issues. At idle, the RPMs bounce up and down, AFR is all over the place, and it gets so bad that many times, the car sputters out (really embarrassing when it happens at a stop light or the starting grid of an autocross.)

At first I thought it was a post-MAF air leak caused by a vented-to-atmosphere hose off the top of my Crawford air-oil seperator. Rerouting the hose back into the turbo inlet, post-MAF, made no difference.

I contacted my tuner and sent him a datalog taken from AccessPort, and in return, he sent me back a map. I flashed to this new map, and there was no difference in idle quality. The local Subie dealership also hosed the motor with brake cleaner looking for vaccuum leaks, to no avail.

I also thought for awhile that unplugging the MAF sensor smoothed the idle out and made the problem go away. And truly, for awhile, it did. Today I unplugged the MAF and drove the car around...HARD. I took datalogs with my AccessPort and kept a close eye on my AFR to make sure I didn't jack up the engine racing around with no MAF connected. I don't feel as though disconnecting the MAF made any difference in how the car behaved under throttle at all...and before this lovely drive, my idle was smooth and perfect. Afterward, however, idle was just as rough and crazy as before.

I recorded a couple videos of the car at its worst...and one that was JUST taken today, of the car idling after my hard drive, still with the MAF unplugged. I also have numerous datalogs from AccessPort, but according to forum rules, cannot post them as attachments, but I would love to get these out here. Also, when hooked up to Romraider, the AFR correction gets as bad as -25.

The mods I have that may possibly affect idle (but I don't think would affect idle this drastically) are Brian Crower stage 2 camshafts, oversized valves, TGV deletes, a KSTech air intake with 83mm MAF housing, and the Crawford Performance air-oil seperator.

Please, guys, give me a hand in resolving this issue. I can't imagine what would be causing such terrible trouble, but it's embarassing to have my car die at nearly every stoplight I pull up to...and 3 times in the starting grid on Saturday's autocross! We've got to resolve this. :(



 
#3 ·
knucklehead said:
is there any bends before the MAF? my guess is yes. a straight shot of air may help, you can achieve this by putting in a screen to straighten airflow or relocating the maf.
Click to expand...
Here's a shot of the intake.

Image
 
#4 ·
try this for ****s and giggles....take the elbow off
beat the snot out of it then check the idle

reason i say this is: i had a custom intake that i made that looked like it flowed well but it had so many bends in it that it was messing my idle up BAD...i took it off and put my old intake back on and the problem went away
 
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#5 ·
Intake calibration is way off assuming there are no leaks anywhere. You really need to replace those worm clamps with some good T-bolt clamps as well. Worm clamps are often the source of alot of irritating issues like this. May also need to experiment with bumping the idle up a little although thats not usually needed with 850s. My .02 without being able to see some logs.
 
#6 ·
Turbineguy said:
Intake calibration is way off assuming there are no leaks anywhere. You really need to replace those worm clamps with some good T-bolt clamps as well. Worm clamps are often the source of alot of irritating issues like this. May also need to experiment with bumping the idle up a little although thats not usually needed with 850s. My .02 without being able to see some logs.
Click to expand...
I believe the tuner's other map adjusted idle settings, doing no good, and I started pulling post-catalyst fuel trim too lean CELs on the highway, so I flashed back to the original map. I've got logs, if you've got an email address.
 
#7 ·
After some PMing with Crawford Performance, they don't feel that the AO seperator is at fault here.

Could the intake timing position sensor, or anything else to do with the AVCS, be causing this? And how would I check that?
 
#8 ·
Update: Switched MAF sensors out with another STI...and it did nothing. I didn't expect it to, I just wanted to make sure I had "bad MAF sensor" crossed off my list of possibles.

Also, I made a list of all the codes that the car throws. I get my Barometric Pressure Too Low CEL regularly, so that one is not a big deal...but here are the four I occasionally see (once a week, or less.)

P0021 - 'A' Camshaft Position Timing Over-Advanced or System Performance (Bank 2)

P0011 - exact same as above, except (Bank 1)

P2089 - OCV Solenoid Valve Signal 'A' circuit short (Bank 1)

P2093 - Intake Camshaft Position Actuator Control Circuit High (Bank 2)

Anyone else got some ideas?
 
#10 ·
The air sucked by the air intake must get pretty hot, the filter is hidden and very close to the uppipe. You must have a leak somewhere.
 
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#12 ·
bluedemon_II said:
After solving your idle issues I would change to a blow threw maf setup or a Stand alone speed density. That intake placement is way bad in so many ways.

Check timing belt timing. Check for leaks before the turbo.
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I just want a different intake, period. I'll see if I can check the timing belt timing on Monday...and the sensors for the camshafts.

It just seems to me that both of those would be something that would affect the whole band of the motor, at all revs, not just idle.

The car gave me two additional CELs tonight:

P0301, P0304...Cylinders 1 and 4 misfire detected. The car didn't feel like it was misfiring, and once the ECU reset, the codes never came back...same as ALL of the above codes for camshaft and timing, etc.
 
J
#13 ·
When did the crappy idle start happening?

with all the codes you are throwing something definitely seems off. I'd go over the entire install with a fine tooth comb and check everything that everyone already mentioned in this thread. You wouldn't throw all those codes if it was just the intake...

Are Brian Crower cams proven in our engine? I ordered some brian crower valves recently and the valve stems were two thousands too large. I won't touch anything Brian Crower after that...

If you weren't throwing all those codes, and assuming no post MAF leaks, it would be all MAF scaling and injectors and I would blame the tuner. I would say that the tuner probably scaled the MAF correctly for the diameter but probably has the wrong latencies for the PEs so the fueling didn't respond linearity and caused a lot of issues down low which takes a lot of time to log and correct. Get rid of the crappy Power Enterprise 850s and go Deatschwerks or convert to topfeed and go InjectorDynamics. You can get as good or better than stock idle with the IDs.

give us a screenshot of your learning view:
RomRaider • View topic - Learning View (version 0.6a 03-21-09)
I want to see your learned fuel trims...
 
#14 ·
I don't have a Tatrix cable, no RomRaider stuff available yet.

I've been getting all of those camshaft and OCV solenoid codes again though. Could a sensor be going bad and causing all this ruckus?
 
#16 ·
The P0011 and P0021 are most likely the source of your problems. You need to fix those codes first and get your cam timing back to normal.

With big cams I was able to improve the idle a lot by tweaking the DBW Requested Torque maps to keep the throttle slightly open at idle. It gives the same result as the old domestic trick where you drill a small hole in the throttle body flapper.
 
#17 ·
I got the car to stop sputtering out by using the AccessPort to turn the idle up a bit. But it still definitely idle hunts, and runs REALLY rough at start-up.
 
#18 ·
Is the car even tuned right? I saw thoes same problems while i was tuning injectors on a wrx. It would help a lot if you had logging capabilities to see how are your fuel trims doing. When the cams where installed, did the installer remove the screws that allow oil to travel to the AVCS system? My installer forgot to remove them and I got thoes codes but non of the idle or drinving isues that you state, just the code. Broght the car back and in 20 min the problem was solved.

You want something diferent for an intake even if it plain sucks? I bet that your problems lies with a badly tuned intake and or injectors. Take it back to the tuner, if that dosnt help take it somewhere else for a second look.

Again, that intake will only cause problems.
 
#20 ·
Just a long shot but I had a similar idle and it came down to two blown fuses. One in particular that controls idle if I remember correctly. My problem stemmed from a loose connection I had to the power output on the alternator. $10 for fuses later, idle was perfect.
 
#23 ·
I'll check it. I'm up for anything at this point.
 
K
#22 · (Edited)
have you rescaled you maf for the intake you are running. Big maf means more air flow and the computer will still think it is the same amount of air flow and it gets all ****ed up. my did the same thing it took about a day to get the idle good and it still bumps on hot days and when you come down from a hard pull.
 
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#26 ·
Figured out what's up with the intake. It's installed incorrectly...it's meant to work with the factory afterMAF elbow, which I do not have. SO...I'll try working that out.

Much thanks to Matt @ KSTech and Spider96 on these forums. They were great help. I don't know if the incorrect installation is what's causing this problem, but we'll see!
 
K
#27 ·
well thats good but you do know a big intake is no good if you still have the little stock elbow on there its like pissing in the wind. I know on my car the stock elbow under full boost (27psi) was collapsing. We tested it with the stock and then i made a custom hard elbow and it made at 25whp just bc of it collapsing. But you need to talk to your tuner some more about rescaling your maf in you maps bc even with your stock elbow it will still act funny in idle bc the car is still not going to know how much there is really coming into the inlet pipe and the cams is going to change all that too due to the more air flow the though the heads.
 
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#29 ·
kiyanichenko said:
See if the vacuum hose on the BPV is connected correctly. Check both ends. It solved my problem. Like you said though, it runs strong at open throttle so im just throwing what I have experienced out there.
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No problem...I don't mind suggestions at all. I'm willing to take a look at just about anything to get this problem figured out.
 
#31 ·
Yeah....I'm waiting for them to come back so Subaru can pull the engine data at the time of CEL.
 
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