diagnose my idle problem please!

chumpsteak · 09-15-2007, 08:07 PM

I've spent the last couple of weeks searching for an explaination for my idle problem and can only find threads about high idles or low idles or vacuum leaks or dirty MAF sensors. My problem doesn't seem to fit any of these scenarios and it's frustrating me.

My '05 STi is stage 2 and has been for about 6 months. Idle was fine before and after going stage 2 and the car ran great for a couple of months. About 2 months ago I noticed the car idling rougher and stop lights for no apparent reason. With the windows down you can actually hear what sounds like a miss but I don't get any CEL's and the engine never comes close to dying. The sound it makes when idling rough is kind of a "pup" sound.....

I know it's semi normal for it to do that once in a while, maybe every 15-20 seconds, but my car is now doing it about every 1-2 seconds. The best way I can describe it is "idle idle idle pup idle idle pup pup pup idle idle pup idle pup pup pup" it just sounds really lumpy and not very smooth at all. The entire engine vibrates and makes the car shake. You can also feel a sudden poof of air at the exhaust tip when it makes the miss sound.

Other than the idle the car runs great...very strong throughout the power band with no noticeable hesitation. I make full boost (up to 18psi) in 5th and 6th gears and it holds with no problems.

Should also mention that the car sometimes idles at about 800 rpm and feels pretty good with only the occassional miss sound. Most of the time though the idles settles in around 700 rpm and gets really lumpy.

Things I've tried to remedy the problem:

spark plugs, grounding mod, Techron injector cleaner, inspected vacuum lines and checked for boost leaks. Also cleaned the MAF sensor.

Current mods are Cobb turbo back exhaust w/cat, K & N typhoon intake, and AP V1. The rough idle was happening well before I installed the intake and I've also got a PDX e-tune for the intake. Idle problem was also happening when I was just running the Cobb OTS stage 2 91 oct map.

I'm seriously thinking about removing the exhaust and putting the car back to stock to see if it still happens, but I really don't think it has to do with the mods since it just started within the last couple of months.

Anyway, sorry for the long winded explaination. Hope somebody can help.

Thanks in advance.

itr_1211 · 09-16-2007, 04:19 AM

Notice the colour of exhaust smoke at startup? like white/black?

chumpsteak · 09-16-2007, 05:16 AM

No white,blue,or black smoke at startup. Exhaust tip gets a little black around the end but it's always done that.

2MANYCARS · 09-16-2007, 06:47 AM

What kind of plugs did you use? Did you gap them properly?

chumpsteak · 09-16-2007, 07:17 AM

Replaced the plugs with the same as stock. gapped them to .028. The plug change didn't seem to make any difference good or bad.

I just got done pulling the intercooler again to check the turbo outlet and see if I could find any vacuum lines off under it, but after I put it all back together I still get the same crappy idle.

I popped the hood and watched the engine while it was idling and the engine seems to shake in sync with the "pup" noise, but I don't hear any pinging or any mechanical abnormalities....just the noise from the exhaust. I pulled a couple of vacuum line off while the car was running and it definately made it worse, so if it is a vacuum leak it must be really freakin small. I can't hear any vacuum leaks either.

***Draco-REX*** · 09-16-2007, 07:57 AM

This might be way off base, but it might be worth checking out anyways: Have you had a Compression/Leak-Down test done yet?

chumpsteak · 09-16-2007, 08:04 AM

No, haven't gotten to that point yet. Mainly because the car runs great once the rpms get over 1000 and I would think that the car would be burning more oil than usual if it was something like that wouldn't it? My oil consumption actually seems to be going down since the last oil change.

srt42sti · 09-16-2007, 08:18 AM

hmmm, i think a protune will correct the issue, sounds like youre rich at idle

chumpsteak · 09-16-2007, 08:22 AM

Quote:

Originally Posted by srt42sti

hmmm, i think a protune will correct the issue, sounds like youre rich at idle

Would I be able to see that on a datalog? I was thinking about borrowing a laptop so I can datalog at idle and see what's going on. Does anyone have an experience with datalogging? Can I just use my Accessport cable and get some free software or something?

20sti07 · 09-16-2007, 09:33 AM

i actually have the same exact problem, but have'nt realyl had time to start tearing into it. mine is on a protuned stage 2 07. it was fine up until about 3 weeks after the protune then this started so i have no clue yet to what it is. i checked all the lines on the engine and there dont seem to be any leaks but i'm thinking about taking it back up to the tuner to check it out.

chumpsteak · 09-16-2007, 10:58 AM

Glad to hear I'm not alone with this problem.

I just got done removing the K&N intake and flashed the car back to stock with the Accessport. The idle problem is still there. I'm really not thinking it's a tune problem at this point.

Anybody else have any ideas?

Thanks for the input so far!

itr_1211 · 09-16-2007, 11:15 AM

Quote:

Originally Posted by chumpsteak

Glad to hear I'm not alone with this problem.

I just got done removing the K&N intake and flashed the car back to stock with the Accessport. The idle problem is still there. I'm really not thinking it's a tune problem at this point.

Anybody else have any ideas?

Thanks for the input so far!

Try resetting the ECU

chumpsteak · 09-16-2007, 12:18 PM

It's gone through many ECU resets since this problem started...most notably the negative battery terminal was disconnected for several hours while I replaced the plugs.

twigg107 · 09-16-2007, 03:53 PM

maybe injector's??? IDK.... just throwing some ideas. :/

chumpsteak · 09-16-2007, 05:28 PM

I thought about this, but wouldn't I get a CEL if there was an injector or coil pack problem? I almost wish it would throw a CEL so I would at least have some idea of WTF is going on.

On another note I started pulling vacuum lines while the car was idling today and watched the boost gauge when I did. If I pulled small diameter lines the vacuum would drop a little, and when I pulled larger lines it would drop a lot. Obviously the engine ran like crap when I did this, but pretty much ran the same as my normal crappy idle, just intensified. Using this logic it would seem that I might have a very small vacuum leak. Does anyone have any good ideas on how to find a very small vacuum leak? I tried spraying some electronic cleaner around the different lines but didn't hear any change in engine rpms.

Also, can someone tell me what their stock boost gauge reads at idle? Mine pretty much sits at -.07 and fluctuates slightly.

09-15-2007, 08:07 PM	#1
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	diagnose my idle problem please! I've spent the last couple of weeks searching for an explaination for my idle problem and can only find threads about high idles or low idles or vacuum leaks or dirty MAF sensors. My problem doesn't seem to fit any of these scenarios and it's frustrating me. My '05 STi is stage 2 and has been for about 6 months. Idle was fine before and after going stage 2 and the car ran great for a couple of months. About 2 months ago I noticed the car idling rougher and stop lights for no apparent reason. With the windows down you can actually hear what sounds like a miss but I don't get any CEL's and the engine never comes close to dying. The sound it makes when idling rough is kind of a "pup" sound..... I know it's semi normal for it to do that once in a while, maybe every 15-20 seconds, but my car is now doing it about every 1-2 seconds. The best way I can describe it is "idle idle idle pup idle idle pup pup pup idle idle pup idle pup pup pup" it just sounds really lumpy and not very smooth at all. The entire engine vibrates and makes the car shake. You can also feel a sudden poof of air at the exhaust tip when it makes the miss sound. Other than the idle the car runs great...very strong throughout the power band with no noticeable hesitation. I make full boost (up to 18psi) in 5th and 6th gears and it holds with no problems. Should also mention that the car sometimes idles at about 800 rpm and feels pretty good with only the occassional miss sound. Most of the time though the idles settles in around 700 rpm and gets really lumpy. Things I've tried to remedy the problem: spark plugs, grounding mod, Techron injector cleaner, inspected vacuum lines and checked for boost leaks. Also cleaned the MAF sensor. Current mods are Cobb turbo back exhaust w/cat, K & N typhoon intake, and AP V1. The rough idle was happening well before I installed the intake and I've also got a PDX e-tune for the intake. Idle problem was also happening when I was just running the Cobb OTS stage 2 91 oct map. I'm seriously thinking about removing the exhaust and putting the car back to stock to see if it still happens, but I really don't think it has to do with the mods since it just started within the last couple of months. Anyway, sorry for the long winded explaination. Hope somebody can help. Thanks in advance. This ad is not endorsed by this member. Please register or login to hide this ad.

09-16-2007, 04:19 AM	#2
itr_1211 STI Driver Location: Toronto Posts: 243 Join Date: May 2006 Trader Rating: (0)	Re: diagnose my idle problem please! Notice the colour of exhaust smoke at startup? like white/black?

09-16-2007, 05:16 AM	#3
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	Re: diagnose my idle problem please! No white,blue,or black smoke at startup. Exhaust tip gets a little black around the end but it's always done that.

09-16-2007, 06:47 AM	#4
2MANYCARS Junior STI Driver Car: 2007 Subaru Impreza Fav Mod: Cobb AP Location: Tri-State & Overseas Posts: 99 Join Date: Aug 2007 Trader Rating: (1)	Re: diagnose my idle problem please! What kind of plugs did you use? Did you gap them properly?

09-16-2007, 07:17 AM	#5
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	Re: diagnose my idle problem please! Replaced the plugs with the same as stock. gapped them to .028. The plug change didn't seem to make any difference good or bad. I just got done pulling the intercooler again to check the turbo outlet and see if I could find any vacuum lines off under it, but after I put it all back together I still get the same crappy idle. I popped the hood and watched the engine while it was idling and the engine seems to shake in sync with the "pup" noise, but I don't hear any pinging or any mechanical abnormalities....just the noise from the exhaust. I pulled a couple of vacuum line off while the car was running and it definately made it worse, so if it is a vacuum leak it must be really freakin small. I can't hear any vacuum leaks either.

09-16-2007, 07:57 AM	#6
*Draco-REX* Black Dragon STI Car: 07 OBP STi 03WRB WRX Fav Mod: My whole suspension Location: Columbus, OH Posts: 1,638 Join Date: Jan 2005 Trader Rating: (0)	Re: diagnose my idle problem please! This might be way off base, but it might be worth checking out anyways: Have you had a Compression/Leak-Down test done yet?

09-16-2007, 08:04 AM	#7
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	Re: diagnose my idle problem please! No, haven't gotten to that point yet. Mainly because the car runs great once the rpms get over 1000 and I would think that the car would be burning more oil than usual if it was something like that wouldn't it? My oil consumption actually seems to be going down since the last oil change.

09-16-2007, 08:18 AM	#8
srt42sti Professional STI Driver Car: 06 STi CGM Fav Mod: what you cant see :-D Posts: 420 Join Date: Jul 2006 Trader Rating: (3)	Re: diagnose my idle problem please! hmmm, i think a protune will correct the issue, sounds like youre rich at idle

09-16-2007, 09:33 AM	#10
20sti07 Amateur STI Driver Posts: 32 Join Date: Mar 2007 Trader Rating: (0)	Re: diagnose my idle problem please! i actually have the same exact problem, but have'nt realyl had time to start tearing into it. mine is on a protuned stage 2 07. it was fine up until about 3 weeks after the protune then this started so i have no clue yet to what it is. i checked all the lines on the engine and there dont seem to be any leaks but i'm thinking about taking it back up to the tuner to check it out.

09-16-2007, 10:58 AM	#11
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	Re: diagnose my idle problem please! Glad to hear I'm not alone with this problem. I just got done removing the K&N intake and flashed the car back to stock with the Accessport. The idle problem is still there. I'm really not thinking it's a tune problem at this point. Anybody else have any ideas? Thanks for the input so far!

09-16-2007, 12:18 PM	#13
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	Re: diagnose my idle problem please! It's gone through many ECU resets since this problem started...most notably the negative battery terminal was disconnected for several hours while I replaced the plugs.

09-16-2007, 03:53 PM	#14
twigg107 Spec C Club Car: 08 DGM STI Fav Mod: Me..... Location: Vancouver, Wa Posts: 1,518 Join Date: Jun 2006 Trader Rating: (1)	Re: diagnose my idle problem please! maybe injector's??? IDK.... just throwing some ideas. :/

09-16-2007, 05:28 PM	#15
chumpsteak Amateur STI Driver Posts: 41 Join Date: Mar 2006 Trader Rating: (0)	Re: diagnose my idle problem please! I thought about this, but wouldn't I get a CEL if there was an injector or coil pack problem? I almost wish it would throw a CEL so I would at least have some idea of WTF is going on. On another note I started pulling vacuum lines while the car was idling today and watched the boost gauge when I did. If I pulled small diameter lines the vacuum would drop a little, and when I pulled larger lines it would drop a lot. Obviously the engine ran like crap when I did this, but pretty much ran the same as my normal crappy idle, just intensified. Using this logic it would seem that I might have a very small vacuum leak. Does anyone have any good ideas on how to find a very small vacuum leak? I tried spraying some electronic cleaner around the different lines but didn't hear any change in engine rpms. Also, can someone tell me what their stock boost gauge reads at idle? Mine pretty much sits at -.07 and fluctuates slightly. This ad is not endorsed by this member. Please register or login to hide this ad.