Rough idle has me stumped.

Okay, I've been reading since I got my WRX, about the rough idle issues. Heres what my issue is like.

Starting, car starts right up and jumps to 2k rpms or whatever when starting, and when its settling back down sometimes it will just die, otherwise idle will drop extremely low to the point of it not registering on the tach, and then idle back up.

Sometimes coming to a stop, letting off the gas completely, will have the rpms drop to the point of it stalling, though rare. Car drives great and pulls hard. Isnt burning any oil, changed the oil not that long ago and it looked good. Its holding 14-15psi on the stock boost gauge.

So far, I've cleaned the IAC, changed out the plugs, cleaned all connections I can get to, cleaned the turbo inlet lines, vacume lines and T fittings, changed the air filter, cleaned the MAF, reset the ECU numerous times.

When hooked up to a code scanner, it said misfire on cylinders 1, 2, 3. Everything else checked out fine. At this point, could it be injectors? I dont have a ton of money, so taking it into a shop is pretty much out of the question. Car from what I can tell is stock, besides a catback exhaust that is way, way too loud.

Also I'm thinking intake gasket? Could that be something that would cause this, if it was leaking?

 

possible but highly unlikely. Is the cel flashing or lit? Is the rough idle pertain to the car only when its cold or is it when ever it goes to idle? Recent mods by you? Timing belt been done?

 

I've only seen the CEL flash 2 different times, from when I had the car, and it was from doing a hard pull, letting off the gas and it going back down to idle with the clutch in. Otherwise the engine light is on solid. If I reset it, I can drive probably 200 miles without it coming back on, until I let it sit and idle.

I havent done any mods, car has 89k on it now, no clue on the timing belt. Does it warm and cold, though worse warm I'd say. The car before I got it, was in an accident with a tree, and cracked the timing belt cover. Could it have skipped a notch? Would that cause anything like this?

 

yes it could have skipped a notch and yes that would cause this if your lucky.

 

What if I was unlucky? lol, something a bit more serious?

 

possibly valve issues.

 

Check that your cruise control cable isn't too tight, sounds stupid I know but my car was throwing IAC codes and idling really awkwardly and rough today when nuke showed up to tune it. Well 3hrs later, after swapping the iac and a number of other things, I disconnected the cruise control cable from the TB and it was fixed.

 

This or possibly the opposite....throttle cable too loose causing the throttle to be too closed at idle causing engine to choke??

 

I'll go thru that stuff and check it tomorrow. Cars perfectly drivable, just annoying, lol.

 

In my experience with an early style WRX, I had the same symptoms that were from two related causes:
1) a dead IAC valve. Cleaning it helps for some folks but for mine it didn't. I had to install a working valve.
2) an air leak. When I took off the dead IAC valve, the rubber-band gasket ripped and caused a small air leak. Being that your car is stock and you haven't taken off any intake piping recently, it could be a crack in the piping that developed over time.

You have an 02 WRX so this could apply to you. On newer Subarus and my 04 FXT, I haven't been able to locate the IAC valve so I'm thinking it has been integrated into the electronic throttle.

 

I had the same problem with my IAC valve. I had to clean and add a new rubber ring/ gasket whatever you want to call it. You have to clean it every so often. But when you get done cleaning it make sure you drive softly for a little bit so it can get seated properly

 

Bought a new gasket, cleaned valve and manage to reinstall the old gasket without any leaks a few days back, will install new gasket today. Going to look through all the piping and see what comes up. Cleared the codes today and still a misfire on cylinders 1 2 and 3.

 

I have the TGV gasket, large gasket set that looks like intake ports, read that they can leak over time, so bought two sets. I changed the fuel filter about a month ago. Cleaning the idle control valve helped the idle a bit, though misfire is still there. Ill check the cruise cable, though guessing whatever is causing the misfire was effecting the idle too.

What would I need for a proper tune? I have a Perrin CAI laying around, that I can't use without a tune also. How hard is it to get injectors out and flow tested?

 

What kind of tune? Well, stock I guess lol.

 

Well I have no clue what my tune is then, lol. How much does it cost to get a stage 1 reflash done?

 

Also checked every hose I could see, and sprayed some shots of carb cleaner at every clamp and joint, to see if anything effected the idle and nothing. Then I noticed the clamp and hose right after the MAF was completely loose... Lol. Tightened that up and reset the codes, maybe that will fix it.

 

Well, ran great for about 25 miles, then rode it up the RPM's doing some 2-3rd gear pulls, and after slowing down, it was idling about 1700 rpms steady, then all the sudden the CEL popped up after maybe 10 seconds, and it starting sputtering down to 1k RPM's. Then driving slow, it was really sputtery for the next mile, and it cleared up. Any thoughts? Injectors possibly?

After doing some more reading, it almost sounds like the injectors are giving it too much gas, maybe leaking? And its not burning all the fuel off, which is getting pushed into the IAC and causing some bad carbon build up and idle issues. Could the injectors be sticking after doing WOT pulls, and after I back off the throttle, its still dumping gas into the engine, even though the engine sent the signal for the injectors to close up?

 

Would flow testing the injectors tell me if they are good or bad for sure? If they are sticking? Pretty broke right now, lol.

 

Not true
Stock tunes can hit 14-15psi, especially colder weather and/or if they have a dp/tbe

List of mods please
And things you did right before all of this happened?

 

Check your grounds too, could have a loose or corroded one, even a loose battery connection.

 

Car from what I know is stock, besides a cat back exhaust. I've been having issues like this since I got the car, though didn't notice right away as I was pretty easy on it. It's kind of a mystery car, with some kind of custom made cat back. Could a bad ground cause a high idle like that and then a cel and sputter? What else could cause the idle to jump to 1700-2000?

 

Okay, spent the last 4 hours inspecting every little thing I could find, without tearing the car apart. Rerouted the cruise control cable back into the oem position, clipped into place, and loosened it as much as possible since I read it can cause high idle issues. Also checked all the grounds, theres one on each side of intake manifold, and one on each inner fender. If theres more then that, well I couldnt see them. This engine is like some hellish maze I did manage to find a small half penny size hole in the soft rubber boot, on the front side of the turbo, under the hose clamp. Not sure if its leaking, as its covered by the hose clamp or not, but that boot does look pretty beat up. Also is the TMIC boot that connects to the Throttle Body supposed to be an extremely thick, super hard rubber? Mine looks like its almost weather checked, its pretty odd looking, and bulges between the clamps. Not sure if its OEM or what, but it looks pretty rough.

Its unreal how cramped this engine bay feels, cars starting to drive me nuts. Its perfectly drivable, maybe I'll just have to accept it for what it is, a bruised up jimmy rigged daily driver, lol. Its almost comical how many zip ties I have holding things together on this car, lmao.

 

That hole in the turbo inlet is a massive post maf leak. DONT boost until its fixed, hell I wouldnt even drive it. This is likely the source of your idle problem.

 

very true, I wouldn't drive it, the one under the TMIC can look flimsy if have taken the TMIC off a few times, they are cheap fixed.

 

Well its the hose coming straight off the side of the turbo, facing the front of the car. Its called the turbo inlet hose I assume? Anyone know where I can find a diagram of all the intake parts? Seems a silicone one would cost me 200$+, ouch.

 

just a toss up. same type thing happend to me in school(auto tech student) a chevy truck was missing in only 2 cylinders. after tons of smoke tests and leak down tests and other tests i pulled the vaccum line off the fuel pressure regulator. gas was pissing through the vacuum line and into the intake causing a miss fire. this was found out 10 minutes before i was about to pull the intake off and do an intake gasket. so run the car and pull the vacuum line off the intake from the fuel pressure regulator. if gas is coming through that line that could be the source of your problem.

im in duluth and have a cobb AP also if your in need of throwing a base tune on the car and wouldnt mind trying to help out a bit! how ever im new to subaru to lol

 

I had something very similar to this kind of idle. I'd suggest its a vacuum leak. I would come to stop signs and the car would die but when I drove it just fine it would run flawlessly accelerating. I had my friend find the vacuum leak and it was fixed.

 

Yup, an airleak that small can cause a car to run like that. Glad you found where it was. I suggest you replace all odd looking hoses at the same time to rule out any other possible leaks.

 

You can usually find inlet hoses used for a cheaper price...check out the FS section or Nasioc.

 

Thanks! You guys rock, I'll get a new hose for in when I get some money, laid off again so be awhile maybe.

 

Really, you should hook up and watch what the Fuel Trims are doing. What kind of plugs did you put into it. I just fixed one that had an almost identical problem and after compression and leakdown tests and swapping injectors around I put a set of factory NGK plugs in and it fixed the problem.

 

I put in the recommended factory iridium plugs, from Advanced Auto. Was also having the same issue before swapping out the old set of plugs.

 

He had also just swapped out the plugs to try to solve the problem, The parts store sold him a set of "factory" iridium plugs. Problem was that they were autolite brand. From my experience I have found usually anything other than NGK causes misfire problems. If they sold you NGK then ignore my previous statement. Just putting it out there though. Either way I would try to find someone with a scan tool that can watch your fuel trims while driving. If I was closer to Duluth I would say I could help you myself. If your anywhere near the cities with your car in the future let me know and I would be more than happy to diagnose it for you.

 

Actually bought the NGK Iridium's I think it was, basically the most expensive plug Advanced Auto had for the car. And when gapping, I gapped the plugs between the lowest and highest number, like .030 or something? What should I watch for on the fuel trims? I can borrow the scanner from Advanced Auto, since i use it allllll the time, lol.

 

Anything greater that +/- 7% specifically on STFT (Short Term Fuel Trim) is a good indication of whats going on. If the number is + the ECU is adding fuel due to a lean misfire which could be a lot of things including, but not limited to, compression lost, ignition, or unmetered air leaking into the engine post MAF. If you are running a negative number then you are running rich. That can only really be caused by excessive fuel being burned. IE leaking injectors. With what your describing I am guessing you will see numbers between 15 and 30%. Also watch the A/F sensor reading. It may be listed as B1S1. Should be at 1.00 varying .2 either way depending on if you are on or off the gas while driving. If it stays solid at 1.00 and doesn't move your front A/F sensor is bad. Let me know what you find both for current codes and what you find on the readings.

 

Here's a pic I took while idling.

 

Ok, heres what I can tell from your readings... The ECU is compensating for a lean condition. This could either be the cause of the misfire or the misfire could be causing the lean condition... I am guessing more than likely the lean condition is causing your misfire. You said earlier that your turbo inlet pipe had a hole in it. Well that could be yout issue, there is something weird about it. I have done a couple dozen of the fuel line recalls on these cars and I would say at least 50% of them had a hole in the turbo inlet pipe with no running issues. I have never gotten a good answer to why, but I think its because well there is -20. in of vacuum in your manifold sucking away, the vacuum from the throttle plate to the MAF is very little. Usually the hole was about the size of a dime. Double check all hoses and clamps from the MAF all the way to the throttle body. Call a dealer and see if the fuel line recall has been done. If so, it is very possible that a hack tech didn't clean the intake manifold and head good enough before replacing the gaskets. If it hasn't been done, get it done. Only cars that were sold in cold weather states got the recall. So if yours is a car like mine that came from a southern state the recall wouldn't apply and you would either have to pay or do it yourself. No matter what, I would definitely do both compression and leak down tests. Mostly because it is fairly common for these engines to have burnt valves. No the ECU compensating by adding fuel doesn't necessarily mean your getting too much air, it just means the ratio of o2 to co2 too high. That ratio can also come from when the fuel is not completely burning(misfire). Long story short... Check all hoses and clamps, if good, with engine running spray brake clean around all manifold connections(block,TGV,brake booster hose,throttle body) and listen for a change in RPM. If there is a change in RPM when spraying somewhere, that's your leaking spot. If that is inconclusive, its time to do both compression and leak down tests.

 

I say I think its a slightly lean condition causing the misfire because that's what your fuel trims are indicating along with the fact that its idling about 100rpms high.

 

Okay, did a redneck data log (had my phone record the real time data from the scanner, using the camera). The low fuel trim, depending on throttle position, would be anywhere from -25 all the way to 24.5, and it's a misfire on all 4 cylinders, no other codes. I checked all the intake parts with electrode cleaner, which is extremely flammable and no change in idle. If you want I can upload the video of my little drive with the camera on the scanner, and u can see a bit if info. Timing changes all over the place, no clue if that's normal or not.