Engine Shake - ABS Related or?

[mastervexx]

Great website you have going on here, so much useful information.

I recently picked up a 94 Legacy Turbo, 5mt, ABS with 142,000 km on it (like new!). Run's pretty great considering. 1st gear and reverse is a little hard to get into sometimes but that seems normal on these transmissions...

The issue I was hoping someone could enlighten me on is when I first start the vehicle and put it into 1st or reverse it shakes pretty bad like whole car bad. I'm not sure if its the engine itself knocking because it doesn't really make any noise except bad vibration. That is until I hear the ABS make a "shhhhhh" sound and the vibration seems to settle down and eventually disappear. I'm not sure if they're even related or not... other things I think it could be are:

1. Bad knock sensor maybe?
2. Sparks/Fuel Related?
3. Drive-line Related?
4. Power-Steering Related?

Should be noted it doesn't shake at any road speed, just that first initial get and go, and even then it doesn't happen all the time... Just want to make sure its not wrecking anything, which anything mechanical shaking that much probably will.

Thanks in advance!

[Legacy777]

Welcome to the BBS.

Can you describe the shacking a little more. Also, you can you elaborate whether the shaking occurs when you initially put the car in gear 1st or reverse, or when you let off the clutch? Also, if you rev the engine in neutral before you start off, does the shaking occur? Do you let the car warm up before going, or just drive away?

Where are you hearing the "shhhh" noise from? Any particular reason you believe it's the ABS?

Any other details you can provide would be helpful.

Thanks

[mastervexx]

Starts shaking like its gonna stall out, and it happens when I let off the clutch while its in gear. I normally let it warm up for about 30sec or so... I'll try the reving thing before I leave work today, maybe the injectors don't work so well on the first go of the day?

The shh noise comes from the engine compartment I'm pretty sure, I can hear it to the front passenger side... havn't tried listening for it with the hood off so I should try that too.. I was thinking the ABS because in the manual it says you should hear a noise coming from the ABS because it checks itself out everytime you start the car up.

[mastervexx]

Well I tried listening for the noise, but I let it idle with me scrutinizing the engine bay for 5 minutes with no sound except the motor itself.. but when I went to pull away it made it... to me the sound is like air being evacuated by something... is the ABS run off of a vacuum?

I also noticed that the idle seems a bit shakey, goes between 600-400, is this normal?

As well as I'm looking to get the following components can anyone comment on the worthwhile of this?

1. New Knock Sensor (haven't checked the old one yet, but I figure since its a common failure)
2. New spark plugs/wires
3. New air filter
4. New coil pack (is this recommended or only if its failing?)
5. New fuel filter
6. New PCV valve

I want to try sea-foaming it too, should I do this before or after the new parts?

Thanks again!

[Legacy777]

If you let the engine warm up for 5 minutes, and still heard the noise, it would not be related to the ABS unit. The ABS unit does a self-test upon startup, but typically you don't hear it, and it is done upon key on.

You may have a vacuum leak somewhere, which would explain the poor idling/shaking. How are you reading the engine RPM? The tachometer on the dash is a little misleading. The big mark just above 0 rpm is actually 500 rpm.

I think the list of parts you have is probably a good general tune up start. The coil packs typically are fine, so unless you have an issue with it, I wouldn't bother replacing it. You can spray a fine mist of water around the coil pack with the engine running. Do this at night with little/no light. If the coil pack insulation is cracked or bad, you should see some small sparks/arcs.

You can seafoam before or after, it shouldn't matter too much.

I would suggest using some starting fluid or other similar and spray it around the intake manifold gaskets and other sources for intake leaks to determine if everything is sealed up good.

[mastervexx]

Well I did the following:

Plugs, Wires, Oil (Fluid and Filter), Fuel Filter, Manual Transmission Fluid, Rear Diff Fluid and Air filter.
The plugs were champion (wouldn't put those in a lawn mower!) but in generally good shape when they came out. The only fluid that was showing wear was the rear diff.. I'm pretty sure it has never been changed as the fluid was not good looking coming out as well as how rusted shut it was. Didn't end up changing the Knock Sensor and Coil Pack (didn't them in stock) or the PCV valve since it still looked fine.

Car runs noticeably better, no surprise there I suppose.. Still likes to chug/shake though.. Couple people told me it was probably the clutch with a wear spot or the like.. Others said it could just be bad engine/tranny mounts.. Some people just told me I should just forget about trying to roll smoothly at idle and race around since it doesn't shake at high rpm

The more I think about the ABS being at fault seems silly, a vacuum issue seems to be more logical.

Are there any vacuum lines usual to suspect? I've looked for leaks before because my turbo likes to make a loud whistle before giving boost (still gives solid boost though) but I haven't found any. Due to the ludicrous placing of the boost gauge (previous owner put it beside the Parking Brake...) it's hard to see how it all reacts with engine speed. Also likes to make a little rattle on hard acceleration to boost in town (doesn't do it on the highway though so i suspect bolts/firewall) Should probably take a video for example.

Also the car needs to be cranked more in the morning after sitting overnight or longer, if its been started that day it starts like a flashlight otherwise. I've heard coil pack can be to blame for this?

And I found out the fuel tank level indicator doesn't work after about half a tank, so from what I've read gotta change the sensor on the one that measures the bottom level... some good write ups on it so I should be okay.

Sorry for all this blabbering on about the seemingly minor issues, I just got to say I really love this beast. Just want it to be running as good as possible. At this rate I should just change the title of the thread to "A quest for perfection"

[Legacy777]

I'd suggest using starting fluid around the vacuum hoses to see if you can find a leak.

Regarding the extra cranking in the morning, you may want to replace the coolant temp sensor as it controls the amount of enrichment when cold. If the ECU thinks the engine is warmer than normal it'll start fine warm, but have issues cold.

Due to the hump in the middle of the tank there is actually two fuel senders, and each measures the full tank depth. You'll have to do some testing to determine whether the main or sub sender is bad. I had intermittant issues with my fuel gauge and ended up having to replace both of the senders to get it to start working correctly again.

[mastervexx]

So.. I obviously have a vacuum issue.. If I had used my brain earlier I would have realized that my boost gauge (as old as it is) is only showing about 14/15 -inHg at idle when warm.. from everything I've read.. it should be around 19/20... would explain my shaky idle/engine and poor city fuel economy...

Did a couple of the pressure tests she only climbs to about 18/19, after going to 0, when spiking the throttle and goes back down to 14/15. And when holding the throttle at 2k RPM it sits at about 16, release it and it jumps up and then back down. (so I know its not a cat/plugged exhaust)

I pulled out the old PCV valve hoping it was the issue but it still sounded good (had the happy rattle), changed it anyway but the vacuum is the same.. I did a quick spray of the easily accessible hoses from the top with no such luck of an audible change.. Will give at a more thorough run down this weekend.. One thing I do notice is I can hear air being released when I stick my head near passenger side of the intake manifold (imagine my forehead on the turbo resonator) after feathering the throttle cable and releasing, not really sure if that's something turbo related doing its job though..

I'm guessing it's either one of the hoses underneath or according to the Subaru repair manual (thank you Josh) its a intake or throttle body gasket. How much of a pain would it be to change those? I could also guess it could be a fuel injector or spark plug air leak. Or at the very worst the piston rings starting to wear.. but that doesn't seem too likely since the idle vacuum is steady albeit low..

I have a OEM coolant temp sensor on the way though, so I'm gonna change that when it comes in and if my issues go away I know the gauge is junk/not calibrated right. It s teed in the right location though (in between the factory tee and intake manifold)
Hilariously enough it was only 33$ CAN shipped from one of the online vendors (11$ shipping) and the damn dealer here wanted 60$... they also want 170$ for a knock sensor... damn you Subaru of Canada.

[vrg3]

When you were spraying the hoses, did you try spraying starting fluid around where the intake manifold attaches to the heads? That would help you figure out if it's one of those gaskets. My old Legacy had an idling problem when I got it and it turned out to be the driver side intake manifold gasket. It sounds like your leak might be the passenger side one.

[Legacy777]

Hilariously enough it was only 33$ CAN shipped from one of the online vendors (11$ shipping) and the damn dealer here wanted 60$... they also want 170$ for a knock sensor... damn you Subaru of Canada.

I had a similar run in a couple years back, a local dealer in Houston wanted $90 for a coolant temp sensor. I bought it online for $20. Some of the markup the dealers do is ridiculous.

[mastervexx]

When you were spraying the hoses, did you try spraying starting fluid around where the intake manifold attaches to the heads? That would help you figure out if it's one of those gaskets. My old Legacy had an idling problem when I got it and it turned out to be the driver side intake manifold gasket. It sounds like your leak might be the passenger side one.

Tried spraying the intake ports, didn't make any audible difference.. but I imagine it would be worth changing them anyways. Is there an easy way to go about changing them? Other then removing the whole intake manifold, because I don't know how much I want to do that in my apartment stall in the winter...

[vrg3]

I've heard of people replacing the intake manifold gaskets on newer Subarus by just undoing the eight (I think) bolts holding the manifold down, slipping out the old gaskets, putting the new ones in, and tightening it down. I think the gaskets are made of a different material though. When I did the job on my Legacy Turbo, I had to scrape the old gaskets off with a razor blade, which I couldn't have done without removing the manifold.

I guess you could try just removing the manifold bolts to see if you can simply remove the old gaskets, and then only remove the manifold if you need to.

Removing the intake manifold isn't as hard as it may seem, even outdoors in the winter. Some notes:

One thing that might not be obvious is that the power steering pump can be unbolted through holes in its pulley, and after it's loose you can just rest it on the side of the engine bay without disconnecting the hoses. Also, there's a PCV hose right behind the alternator that is a little awkward to get loose. It may be helpful to run the engine a little bit first, so all the rubber and plastic is warm, so it's more flexible and less likely to break. There are also coolant lines going into the IAC valve and out of the throttle body that you have to loosen. It might be easier to cut the fuel lines than to slide them off the hoses; if you do that, you'll need 5/16" fuel injection hose to replace them. In either case, it'll be much less messy if you relieve fuel pressure first by unplugging the fuel pump and running/cranking the engine for a bit.

[mastervexx]

hmmm.. I'll have to print this thread off when I actually get time to attempt this.. any other gaskets worth changing while I'm at it? Throttle body maybe?

Also I checked boost at 4250 RPM and it was at ~9 PSI which seems right, would a intake gasket show a greater boost loss?

[vrg3]

I guess you could change the throttle body gasket, but that's pretty easy to do later on too. I can't think of gaskets off the top of my head that you'd expose in this process that is much harder to get to with the manifold on... I would carefully examine the PCV plumbing on the underside of the intake manifold; both the plastic pipes and the rubber hoses can get brittle and rigid and they'd be a pain to replace in the future.