LGT rough Idle and other issues

**wheelsbreakloose** · #1: 10-14-2011, 01:56 PM

So, this is my first post ever!! But, here's the story.
Last Year My girlfriend and I purchased a used 2005 Subaru Legacy GT.
I've always been a Subi fan, I currently own a 98 legacy GT Limited and I used to have another one years ago.. Always loved Subaru's and dream't of having a Legacy B4 Blitzen one day. But see as in how they are not available here in the states, and probably never will be, that will probably never happen>

So, I decided to get this car instead.
Anyway, we purchased the car at 58,000 miles or so, and love it, except for one thing. This damn rough idle!!! I noticed it when we test drove it, but thought (screw it!) Its probably just due for a tuneup or something.. no biggy right?!...... WRONG!!!
The Idle isn't extremely bad or anything. But very noticeable when coming almost to a dead stop, and Once at a stop of coarse. the car will kind of just chug like it has a small missfire until I start moving again. The CEL isn't on and has never come on, except for when the little vacuum hose behind the intake manifold came off the little blue T-fitting. which I repaired with a ziptie.

The CEL hasn't come on since!!!.
Anyway! The first thing I did after purchasing this magnificent machine, was take it back to my shop, and pull the spark plugs. They seemed ok, but I replaced them anyway just for safe measure. That didn't change anything. I then cleaned the MAF sensor, thinking that it just had contamination on it. Still no change.
I've read posts saying that the VVT solenoids might be gummed up and need to be cleaned or replaced. I pulled those out, cleaned the SHIT out of them and checked the ohms or whatever. They checked out ok, re-installed, and Still no change!!
So I went back to reading posts!!
I read things saying faulty or gummed up fuel injectors, vacuum leaks, coil packs, and even CV shafts!! LOL!! WTF!!?
How CV shafts have anything to do with how a car Idles is beyond me, but hey whatever.. So after spending countless hours pulling Fuel injectors, checking for vacuum leaks, doing ohm readings on coil packs, checking compression, staring at My Snap-On Solus Scanner, looking for any indication of faulty sensors, and sucking down cans of Seafoam. I'm about to give up!! This car is pissing me off!! And I've just about had it!!

I don't want to spend a bunch of time throwing money and parts at it, but it seems like its the only thing left to do!!!

The other things that I've noticed about this car, is I have to change the oil very frequently. It seems to go through a quart about every 1000 miles, and gets dirty around 1,500 miles. I change the oil about every 2,000 miles and use Valvoline full synthetic 5w-30. the oil also often smells like fuel and is very watery when I drain it.. I have considered purchasing a Cobb AP, some post I have read say that it will take care of the issue I am having.. Something to do with The stock Map being screwed up or something. But I'm not sure for certain . $600 is alot of money to spend on something that may or may not fix the problem..
Sorry for the long post.. I tend to ramble I guess.

any Advice would be greatly appreciated!!!

**ehsnils** · #2: 10-16-2011, 11:51 PM

Use some carburetor cleaner and spray where the manifold connects to the cylinder heads and see if there's a change in the idle. Some vehicles has a problem with the gaskets there.

Also have the injectors checked, you may have a bad injector. There are some workshops that has rigs where you can test the injectors.

And the O2 sensors also have a tendency to decay over time.

**Max Capacity** · #3: 10-17-2011, 04:40 AM

I'm thinking you need to replace the o-rings at the intake to TGV's. When you see the old ones next to the new one's, you'll understand.

I also had my Tuner adjust the idle when he last tuned the car.

The other day I wiped the MAF and Air temp sensor with a Q-tip and that seemed to help it run better when cold.

**compsurge** · #4: 10-17-2011, 05:43 AM

Get a leakdown or compression test as well.

Check vacuum

Have you done any logging? If not, get a $15 VAG-COM cable and read up on live view, ECU Flash, and RomRaider and do some logging.

Also pressure test the system - you may have a silly leak.

Also, if you can post a video without any commentary (just car sounds) that might help as well.

**wheelsbreakloose** · #5: 10-17-2011, 11:50 AM

Wow! Thanks for all the speedy responses!!.. I was away for October fest this last weekend, so I didn't get a chance to respond until now. But anyway!! I did actually try testing for vacuum leaks, but I used starting fluid instead of carb cleaner...
Should i have used Carb Cleaner instead?
I figured that it would have been just as good?.. i dunno though.
There was no changes in the idle, and I used just about a full can. Pretty much just soaked the engine.
I sprayed it all around the TMI, TGV O-rings, all the vacuum lines, and throttle body gasket.. As ehsnils and Max Capacity had mentioned, I suspected the O-rings at the TGV after reading some other posts. But didn't get any changes in the Idle when I sprayed starting fluid around and on them. Maybe I need to use carb cleaner instead?

When I had The scanner hooked up, I did notice that the front O2 Sensor didn't seem to be Cross counting very much. The readings looked strange to me but I figured if there was a problem with it, then the CEL would have came on though. right? (shrug)
I'll hook the scanner back up today, and write down the exact readings to show you guys.I'll also try and get a video of the Idle.

As Compsurge mentioned, I actually just downloaded Rom Raider and ECU flash last week. I was hoping that I could have used it with my ELM327 Donger. but unfortunately its unsupported. So I guess I'm going to have to purchase the cable.

There's also one thing that I forgot to mention in my original post.
It seems strange that if I give it full throttle when taking off from a stop, the car seems to Lag really bad, and feels as if the turbo isn't even working. But If I only give it part throttle and take off from a stop, the car hauls ass and the turbo kicks in nice.
WTF?!! has any of you experienced this? A car being faster when only give part throttle, over full?
I'm assuming it has something to do with my idle problem I'm experiencing.. Least thats what I'm hoping.

**wheelsbreakloose** · #6: 10-17-2011, 04:31 PM

Kay! so, i was able to do a few things today. I sprayed Carb cleaner around all the mentioned trouble spots on the engine. I didn't notice any change in the Idle, so I'm going to Assume that Its not a Vacuum leak that I'm dealing with.
I did hook my scanner back up and wrote down all the info that it was able to gather off the ECM though.

all these readings are with the car completely warmed up and in Park. with the Climate control turned off. The temperature outside is 59 degrees and clear.

IDLE () 749 to 763 RPMs
TP (%) 12.9
IAT (CEls) 29 to 34
ECT (CELs) 90 to 93
MAF (g/s) 2.98 to 3.42
MAP (kpa) 36
SparkADV (degrees) 15.0 to 18.5
shortFT1 (%) 6.3 to7.0
LongFT1 (%) 14.8
O2S12 (V) 0.755 to 0.760
EQ RAT11 0.968 to 0.979
O2S11 (V) 2.608 to 2.662
EQ RAT11 (10) 0.968 to 0.979
O2S11 (MA) 127.910
Load PCT (%) 1.6

So these are all the readings that I got.. The O2 sensors are very suspicious to me. I have never seen an O2 sensor that didn't fluctuate from lower numbers to higher numbers.. usually they're suppose to drop down to about 0.127 Volts and then back up to 0.676 or so. these hardly even change.

Does anybody know if these numbers look messed up?

**compsurge** · #7: 10-18-2011, 06:20 AM

carb cleaner = starter fluid AFAIK

**compsurge** · #8: 10-18-2011, 06:31 AM

Read up on the datalogging thread in the tuning section of the forum. There are a few recommended logging parameters. I don't think the ones you provided will be useful. Once you get your VAG-COM ($15 shipped from ebay) you can do some runs. I would caution agains running WOT until you can get it resolved.

A few things could be going on here: you could be sensing knock, and running a dynamic advance multiliplier (ignition advance multiplier) of 0.0, thus running in limp mode, and will only boost wastegate pressure ~8psi. Another cause could be bad/burnt valves or bad rings. I recommend a compression or leakdown test be performed, especially since you are finding fuel in oil. If you have the tools, it's very straightforward to perform. If you do not, it may or may not be cost effective to buy a kit (if you have an air compressor, buy a kit off Amazon or make a DIY setup). If not take it to a trusted mechanic.

**GTTuner** · #9: 10-18-2011, 06:54 AM

Those O2 sensors do not work like traditional 0-1V sensors. I had a cold start issue last year, this summer it developed into a rough idle warm engine, logged cyl 4 misfire intermttent. I had a bad injector.

**compsurge** · #**10:** 10-18-2011, 07:23 AM

Also check your plugs for signs of cracking, once you can isolate what cylinder(s) the issue is occurring on, you can begin to swap coil pack and injectors to see if it follows.

Also forgot to note: if you have a laptop, you will only need the ECU Flash, RomRaider, and vag-com for tuning purposes.

**wheelsbreakloose** · #**11:** 10-18-2011, 10:09 AM

Thanks guys.

It had occurred to me before, that maybe the O2 sensors were just different then traditional O2 sensors. I was just uncertain of this though. I hadn't been able to find any information on them prior to GT tuners post.

The thing I can't understand is why the ECM hasn't never detected a missfire.
Thats actually the only reason why I have never done a compression test on it.
My friends WRX had just the slightest missfire on cylinder #1 at Idle, and his CEL came on almost immediately after we cleared the code.

So, anyway. guess my next step is to check compression like compsurge said. Just so I can rule out a bad motor. BTW. I do have a laptop, so I'm gonna get that cable, and take your advice.

I will let you know how the Compression test turns out.
I almost don't wanna know. LOL!!!

**Max Capacity** · #**12:** 10-18-2011, 10:30 AM

I have new O2 sensors on my 05, a few weeks back it had a little stumble when the air was cold. I wipedthe MAF and air temp sensors with a dry Q-tip and now the car seems to run better overall.

Just a thought...

**wheelsbreakloose** · #**13:** 10-18-2011, 10:40 AM

Yea..I've cleaned the MAF sensor numerous times, but never swiped it with a Q-tip or anything before.. The car did seem to run better overall after ward. But not 100% I'll give the Q-tip thing a try today as well. thanks Max

**Max Capacity** · #**14:** 10-18-2011, 10:52 AM

Quote:

Originally Posted by wheelsbreakloose

Yea..I've cleaned the MAF sensor numerous times, but never swiped it with a Q-tip or anything before.. The car did seem to run better overall after ward. But not 100% I'll give the Q-tip thing a try today as well. thanks Max

I also should say I got 2 cel codes after I started the car, I used my AP to read and clear them. Car runs fine. If you don't have a Cobb AP or code reader you can just pull the negative battery cable for a few minutes.

Both codes dealt with the MAF and air temp sensor.

**ehsnils** · #**15:** 10-18-2011, 10:59 AM

Another thing that have been seen is that bad valve clearance can cause strange things to happen, so if you have bad compression figures that can also be the culprit.