Vacuum/PCV/Engine mounts?

[angel_gen_01]

I'm no mechanic and have recently started working on cars myself. It's hard to find information or help without someone either trying to take over or take one look at me and think I can't turn a wrench cause I'm a girl (true story haha). That being said I apologize if I sound ignorant being in a car forum asking bad questions, but I really want to learn DIY for my car.

A little background..she's a 92' Subarau Legacy sedan 2.2L non-turbo w/207K, and I've owned her for 10 years. I've done most of the maintenance work myself as well as some more in depth fixes...I have recently done some work on my car so I know of a few things that not only have I re-checked but have had contact with in the last few months with the recent repairs/tune-up I've done. With the repairs I replaced my manifold gasket, spark plugs and fuel filter.

Here in lyes my question:
Yesterday, I let a buddy of mine drive my car. He claims everything went smoothly until he got to my driveway at which time it began to 'idle rough'. After test driving it myself it does in fact run/idle rough to the point that the car sounds a lil more 'throaty' and has virtually no power. It runs, but runs like crap! I've been watching my RPM's and although sitting in park RPM's seem normal and fairly stable though there is a slight fluctuation. However when you are driving and come to a stop it kicks the RPMs down to 1-150 RPMs (I don't honestly know how it runs that low) but it doesn't die and stays constant. Once I hit the gas the RPMs respond normally but the reaction time is definitely 'sluggish' to say the least. I've been reading this forum all day and although I have a lot of ideas of what could effect it. I have no real idea of where to start realistically speaking. I was wondering if anyone else has had a similar issue and knows where I could start? I've been told so far: 'Could be:' warn engine mounts (since this started the car shakes a lil from running so rough?), Vacuum leak (was my thought), possible PCV issue or fuel pump (I don't smell gas, no excessive smoke comes out of the exhaust and it doesn't smell any different than it did the day I bought it), as well as a head gasket/manifold gasket issue (I replaced the manifold gasket 4 months ago and no problems, doesn't seem that would be the culprit? Also all of my fluids are stable and look good..so now what?

Any help or suggestions would be greatly appreciated!! Thank you for your time and any effort!!

[vrg3]

Welcome to the board!

The shaking is a result of the engine misfiring at low speed; I doubt the motor mounts are the cause.

The engine can't idle at 150 RPM. The tachometer isn't super clear at low speed; the first tick mark below 1000 RPM is 750 RPM (which is the normal idle speed), and the one below (that's really close to the 0) is 500 RPM. So the engine speed isn't as low as you think.

The symptoms make me think it's likely to be either a vacuum leak as you guess or a sticky IAC valve. I don't understand why either of them would just crop up all of a sudden during a drive though. Do you trust that your buddy would have noticed if the engine was overheating? If it overheated it could have blown a head gasket.

You can test for a vacuum leak using starting fluid (the aerosol stuff used to help an engine start, not the stuff people use to light charcoal). Spray around the intake while the engine idles. If there's a leak, the engine will suck a little of the fluid in through that leak and it'll temporarily enrich the fuel mixture and also seal the leak, and you'll hear it as a change in idle speed. It may take a second or two for the change to happen, so wait a few seconds between sprays. Check all over the intake tubing and vacuum hoses and wherever there's a gasket. You say you replaced the "manifold gasket" -- if you mean one of the intake manifold gaskets, definitely carefully check that one.

You can clean the IAC valve by slowly pouring a solvent like Sea Foam into the IAC valve's hose while the engine's idling. It'll want to stall since it'll hiccup on the solvent and because the disconnected IAC hose will let in unmetered air, so you'll have to hold the throttle partly open to keep the engine running. Lots of crazy smoke will come out the tailpipe as all the crap burns off. Reset the ECU afterwards because the IAC calibration will be way off.

Let us know what you find. Good luck!

[angel_gen_01]

"Do you trust that your buddy would have noticed if the engine was overheating? If it overheated it could have blown a head gasket."

Well the temp was normal when I got in and he had literally just pulled in a few minutes prior. In addition (which I failed to mention) I replaced the radiator and the thermostat (and gasket) 4 months ago as well. So thankfully temperature was not an issue.

So here's my update..I kept 'scratching my head' and kept thinking it could possibly be that something's 'missing'. A buddy of mine suggest a quick way to dissolve that possibility was to do a 'dead cylinder check'. Upon which I found that in fact I was only running on only 3 cylinders. I pulled the plug from the non-working cylinder (remember I said I did a tune-up 4 months ago, so I did not recheck here..shame on me!) it did look like new still (thankfully). I swapped the wire with another 'known good working wire' and it seemed to smooth right out...HOWEVER.....as it runs smoothly at 750 RPMs it will frequently dip down below 500 RPMs and act like it's about to die then it kicks back up to 750 runs smoothly for a while and back down again..I haven't replaced the wires just yet as I'm also going to get a compression test done to be sure there is nothing else going on with that cylinder..is there something else I should check? I do not understand why it seems like the timing is off though I know that is not something that is adjustable? Could it still be that bad wire? Seems to me there wouldn't have been a change if the wire was not working, and to test it I pulled it and it did 'rough up' the idle like it was previously..

[vrg3]

Hmm. What's this "dead cylinder check" exactly?

Our cars use a waste spark ignition setup. The front two cylinders fire together and the back two fire together. If one of them isn't getting spark, its partner also won't get proper spark, since the spark will have to find another way to ground. So if you had a bad plug wire, you were probably really running on two and a half cylinders.

Did you reset the ECU when you swapped the plug wire? You should; all that misfiring throws off the IAC calibration and fuel trims so even if everything's correct the ECU might not behave.

Your posts would be easier to follow if you split your writing up more into smaller paragraphs.

[Legacy777]

If you pulled the spark plug wire and the engine idle didn't change, the problem is likely with that cylinder. As Vikash mentioned, our cars run a wasted spark ignition system, so cylinders 1 & 2, and 3 & 4 share a coil. I would think it is unlikely the coil is bad. I would focus more on the spark plug wires, plugs, or possibly fuel injector.

Test the resistance of the "dead" wire and compare it to the others. Also, pull the plug and see what it looks like, black and sooty or white and ashy looking.

[angel_gen_01]

If you pulled the spark plug wire and the engine idle didn't change, the problem is likely with that cylinder.

Yes I did that, and all changed the idle of the engine but the 1.

Test the resistance of the "dead" wire and compare it to the others. Also, pull the plug and see what it looks like, black and sooty or white and ashy looking.

The spark plug still looks fairly new, not black or white. You can view it at my photobucket link below.

http://i67.photobucket.com/albums/h282/ ... 001556.jpg

["vrg3"]"Did you reset the ECU when you swapped the plug wire? You should; all that misfiring throws off the IAC calibration and fuel trims so even if everything's correct the ECU might not behave."

So 'Vrg3', because I did not reset the ECU could that be the reason it's running as if the 'timeing' is off as previously described?

[vrg3]

Yes, maybe. The ECU's idle control has been trying to work around the misfire so it's likely to overshoot the proper idle speed and then overcorrect and so forth. Also, every time there's a misfire the oxygen sensor misreads a lean condition because of the unburnt oxygen and so the ECU's closed-loop fuel trims are way off, making misfires more likely.

[silence2-38554]

It would be worth checking your knock sensor. I've been troubleshooting VERY similar behavior on a '90 legacy (with the rough occasional idle) and that's going to be my next step. It's easy to see, if you lean over the motor from the front of the car & look down just to the right of the throttle body on the block, you will see a bolt going through the middle of a black round puck & 1 wire coming out. That's the knock sensor. if the black puck part has any cracks in it, replace it. It can throw a code & retard the timing, resulting in the loss of power...

[SiCkSTi04]

Wow that spark plug looks a little too new lol

[Legacy777]

If you pulled a wire and there was no change in how the car ran, you've got a dead cylinder. I would focus on that rather than the ECU. Find out why you have a dead cylinder and then once it's fixed, reset the ECU.

[angel_gen_01]

VRG3:

I reset the ECU yesterday, it did run a lot better..gave it a lil gas..still ran smooth..took for a test drive..if I give it a little gas it runs top notch..if I give it just smig more..it goes back to sounding like there's an issue with the cylinder again?

Silence2:

I'll do that, doesn't hurt to check on things I know I haven't replaced in the time I've owned my car.


SiCkSTi04:
It's cause it's about/less than 4 months old. Though the fact that it shows so little wear makes me question it a lil too. I am waiting on a friend of mine to help me do a compression test so I can rule out the cylinder being faulty instead of wires or sensors.

So the update so far is that I've reset the ECU (as stated above) it did help her run like normal..but under a load (when I'm driving) is when it begins to act up again. So then back to the cylinder or wires?

Doesn't seem feasible that the cylinder would be dead or not getting spark if I she idles and runs normally until under a load? What else could effect it? Is this where that knock sensor could be causing issues?

By the way everyone...I cannot tell you how excited and greatly appreciative I am for all the responses/advice you've all given me! I've learned quite a bit already and I'm still taking notes

[vrg3]

I wasn't suggesting resetting the ECU would fix your problem. I'm just saying to reset the ECU every time you try a fix or you might never know that you fixed the problem.

I'd imagine a spark plug would look new if it never fired and only ever saw air and raw fuel. The fuel would keep it clean, in fact!

Hearing all this, my guess is that an ignition system fault is making it so your car is actually always running on only 3 cylinders, and when you notice this rough running it's actually only running on 2.

Our little boxers run very smoothly even on only 3 cylinders. Several years ago legacy92ej22t felt like his engine wasn't running quite right but we didn't know what the problem was. Even after a day at the track we only thought something was a little off but didn't expect it to be a big deal. It turned out that cylinder 4 had no compression at all.

Whichever cylinder you found to be "dead" or whatever has a bad plug wire. It wasn't firing at all, ever. You're new to the car so you didn't notice. The spark found another path through ground, so that cylinder's mate was able to fire, but with only a weak spark. That spark is enough at low load but not at high load. At high load, both cylinders in that pair failed to fire and that problem was much more noticeable.

When you replaced the wire you didn't reset the ECU, so even though you made the ignition problem go away you still had the problem of the ECU's calibrations being way off, so it didn't look like the problem was solved. Even then, the problem may not be just a bad plug wire -- a crack in the coil or improper wire installation could cause this.

That's my guess.

[angel_gen_01]

VRG3:

The only thing is, I've had this car for 10 years...it's never acted like this and when I first got her I was not only surprised by the power she had but the fact she could make most turbos look like snails on the road (believe me I have the ticket list to prove it). She doesn't have the same performance these days but it's not too far off. So the problem is literally a very new thing for her (in the last 10 years that is..).

I am going to try to put the wire back where it was, reset the ECU and see if maybe it was just a connection issue. I've heard from several people that switching wires can cause more problems, I don't know if that's true for our lovely ladies though?

[vrg3]

Oh. Sorry, I already forgot that you said how long yo'd had the car in the first post.

Really, though, even if you're very familiar with the car you might not notice if it's running on only 3 cylinders, especially if that 4th cylinder has even the tiniest bit of spark.

What do you mean when you say "switching wires?" If you mean switching wires from one cylinder to another, I can't imagine what problems that would cause. I guess on other cars you may have the problem of the wires being very different lengths, but it's not a big deal on our engines. That might not do a whole lot to help you diagnose the problem though.

How old are your plug wires? What kind are they? What kind of shape are they in? They do wear out, and the low-to-moderate quality ones wear out a lot faster than the good ones.

Make sure you know what it feels like when a plug wire properly snaps onto a plug. Take a plug wire and a spark plug -- outside of the engine -- and push the plug into the wire's boot until it snaps into place and becomes hard to pull off. That's the feel you're looking for when you're pushing the plug wire boot into the valve cover.

Also, make sure you're putting a little bit of dielectric grease on the inside and lip of the boot. Not too much, though, or it will interfere with the proper fit.

[angel_gen_01]

vrg3:

It's ok, between all the questions and information flying around I could easily have over looked it myself too

I am getting new plug wires today, the other's were factory and 4 yrs old. I will let you know what the update is once installed.

[vrg3]

Hm, factory plug wires shouldn't wear out in 4 years but they may have had some kind of mechanical damage. Keep us posted.

[angel_gen_01]

Yaaayyy new spark plugs and reset my ECU all is well and running ggrreat!!!

So I have another question..

I have been toying with the idea of bringing my car some place to get the engine steam cleaned. I have been told that has been known to cause bad electrical issues down the road. The suggested method has been degreaser and a pressure washer? Somehow that seems brutal to the hoses and connectors in there? Have any suggestions on this?

[vrg3]

Awesome.

You should probably start a new thread to discuss the new question.