Idle still a little rough

My idle is still not as smooth as it should be on my EJ22 with 93K miles. It generally idles at a consistent 650- 700 RPM and sometime the idle is fairly smooth, and sometimes the car vibrates a bit more when sitting at a light. Otherwise, the engine accelerates and performs like it should, as well as getting 26- 27 MPG in mixed driving. I never gotten any CEL's except when I pulled the IACV hose off while the engine was running one of the times I was trying to clean it..

So far I have:

-Replaced plugs & wires with NGK wires and NGK platinum plugs

-New fuel filter

-Replaced the more dried out vacuum hoses which led to breaking the fuel purge solenoid so that's been replaced too.

-Sprayed Seafoam through the IACV and put clamps on either end of the large vacuum hose as it wasn't fitting that tightly.

-Sprayed carb cleaner on all of the visible vacuum hoses but no signs of leaks.

-Checked and cleaned the MAF (it looked really clean anyway- also it's working as the engine died as soon as I pulled the power connector off).

-Run at least one bottle of Techron through- I just bough ta couple more as I suspect it can't hurt.

I was going to pull off the IACV to really clean it but mine just looks too hard for me to get to and I'm afraid I wouldn't be able to reassemble it and get it sealed to the manifold right (even with the new gasket)- don't want to create new problems. Also, since the idle speed is very consistent (not erratic like I've seen of some bad IACV's), I don't suspect the IACV is defective or very gunked up anyway.

I'm just wondering if there are any other likely places to check for vacuum leaks (that's been my suspicion as the old plugs looked like it's been running a bit lean), or should I look at motor mounts, or something else entirely?

Hello;

Check the EGR valve for function. If not closed all the way can cause a rough idle. Do not use any chemical cleaner on this, you can destroy the vacuum chamber. Clean the carbon off the seat with a bent scriber. Just a thought, Steven.

Actually now the idle seems a little high. I didn't remove the EGR, but disconnected one of the vacuum lines and applied a little suction to it and I could hear the valve open and close so I deferred removing it and cleaning it to another time.

It seems, however, in the past week that the idle has been running more between 750- 850 RPM when sitting a at a light. It almost seems a little fast now. I'm wondering if I happened to unstick the EGR valve, or does the ECU tend to increase the idle speed in colder weather (this AM- it idled 800- 850 RPM in 25 degree weather, but engine fully warmed up- I've also owned this car in warm weather until recently). I'll take this idle over the rougher 600 RPM idle any day of the week, but the change has me wondering what caused it, and will it return to the slow idle again.

Does anyone know why my idle would have increased approx 200 RPM from a couple of weeks ago...

I didn't remove the EGR to clean it, but disconnected one of the vacuum lines and applied a little suction to it and I could hear the valve open and close so I deferred removing it and cleaning it to another time.

It seems, however, in the past week that the idle has been running more between 750- 850 RPM when sitting a at a light. It almost seems a little fast now. I'm wondering if I happened to unstick the EGR valve, or does the ECU tend to increase the idle speed in colder weather (this AM- it idled 800- 850 RPM in 25 degree weather, but engine fully warmed up- I've also owned this car in warm weather until recently). I'll take this idle over the rougher 600 RPM idle any day of the week, but the change has me wondering what caused it, and will it return to the slow idle again.

Hello;

A couple of thoughts, the weather is getting colder. The heater and lights are being run more frequently and with the increased load, computer is raising the idle speed. The 4eat will slip to warm up the tranny fluid, Steven.

Lately I've noticed when the car is idling at a light, sometimes after 30 or 40 seconds of fairly smooth idle around 800 RPM, the engine will suddenly "shudder" (for a lack of a better word) and RPM's will drop to 650- 700 and the engine will feel continue to shake a little, like there's a slight miss at idle. As soon as I start to go, the engine runs fine, car accelerates smoothly, etc... It feels like the ECU is changing the fuel mixture all of sudden, or making some other change that makes the idle crappy. it doesn't always do this, but I've noticed it more lately. Weather here has been cold- generally running in 25- 40 degrees.

In summary- I've gotten no CEL's, new NGK plugs & wires, new fuel & air filters, cleaned the MAF & throttle plate, checked for vacuum leaks, etc...

Your chasing your tail. I've read multiple reasons why they do this NONE of which have anything to do with the engine itself. My old 96 L had this issue and when I owned it I replaced both front CV axles and it vibrated more after the axles. Last year I read on either this forum or another about using reman axles causing vibration issues at lights. Around the same time my now 99 LGT needed a LF axle so I wanted to see if this reman axle thing was true. I bought a reman cheap axle from O'Reilly Auto parts and right away I noticed the car had a definite vibration that was more apparent then before. Do to the design I believe our cars will have a slight vibration but with the reman it was more noticeable. I returned the reman axle bought a New axle from the same place, installed it and she went back to normal. Now if someone had replaced both front axles then I feel the vibration would be greater. The reasoning behind this is cause by the axle being worn and only the failed parts are replaced. In almost every case the CV cups aren't replaced and sometimes nothing but the boots are replaced. Check your axles to see if they're not the orgs I'd bet this is your problem.

To back this all up, my friends son owns a 98 LGT and I replaced his axles with remans and his also has a pretty good vibration as well. I told my friend about the vibration deal and he still insisted on the cheapest axles. His son complains weekly and I say everytime, I told you so. There's a thread all about this somewhere here just search.

Your chasing your tail. I've read multiple reasons why they do this NONE of which have anything to do with the engine itself. My old 96 L had this issue and when I owned it I replaced both front CV axles and it vibrated more after the axles. Last year I read on either this forum or another about using reman axles causing vibration issues at lights. Around the same time my now 99 LGT needed a LF axle so I wanted to see if this reman axle thing was true. I bought a reman cheap axle from O'Reilly Auto parts and right away I noticed the car had a definite vibration that was more apparent then before. Do to the design I believe our cars will have a slight vibration but with the reman it was more noticeable. I returned the reman axle bought a New axle from the same place, installed it and she went back to normal. Now if someone had replaced both front axles then I feel the vibration would be greater. The reasoning behind this is cause by the axle being worn and only the failed parts are replaced. In almost every case the CV cups aren't replaced and sometimes nothing but the boots are replaced. Check your axles to see if they're not the orgs I'd bet this is your problem.

To back this all up, my friends son owns a 98 LGT and I replaced his axles with remans and his also has a pretty good vibration as well. I told my friend about the vibration deal and he still insisted on the cheapest axles. His son complains weekly and I say everytime, I told you so. There's a thread all about this somewhere here just search.

Thank you. However, the car is stationary when the engine shakes a bit, so I don't believe the axles would have anything to do with it. The car has the original axles (which have the green paint on them) with only 94K miles so hopefully they're good awhile, but since the boots are 16 years old, they're likely to fail before the CV joint does. Not looking forward to replacing them as the cheapest Subaru OEM axles I've seen are $400 each.

Since I bought the car this summer my idle was first a consistent 650 RPM and a little rough, then as the weather got cooler (or after cleaning the throttle body, making sure EGR wasn't stuck,etc...) idle was a consistent 800 RPM and pretty smooth. Now I still have the 800 RPM idle but then something changes and it drops to 650- 700 RPM and feels like it has a miss at idle- anything off of idle is still smooth. It's probably not a big deal, but I wonder what's causing my idle to change like that (and why did it increase from 650 to 800 RPM in the first place).

In Contrast I have an '07 Corolla whose idle dropped a bit after 100K miles and is consistently a little rough, but I'm guessing I need a new intake manifold gasket as the factory ones dry out around 100K miles. I have the gasket- just haven't put it in. Wishing the Subie was that simple of a fix...

could it be the cooling fans turning on and a weak ground system? i know i have had that issue on a few different vehicles, and since i did the ground mod to my wagon the shudder from the ac or cooling fans coming on is almost gone. could be that and worn motor mounts in combo, too i guess.

It's worth checking to see if the fan is coming on when this happens- if so, looks like I'll try the grounding mod after all.