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Subaru engine vibration / shake

01-22-2005, 01:25 PM
[Also posted in Cars in General, Engineering/Technical Section]
Hi all,
Have a question for anyone with some Subbie experience. Car is a 1998 Legacy Outback, 2.5L, Auto trans, 113K miles. Timing belt was SUPPOSEDLY replaced at 90k(I'm not sure). No maintenance history available. The engine has some light vibration (not enough to spill your coffee, but noticeable) when idling, and this vibration / shaking increases noticably with rpm especially in the 1500 to 2500 rpm range. The vibration is not readily apparent while driving, though with snow tires on all fours it's somewhat difficult to tell. The car is also quite difficult to start when very cold - it kind of chuggs to life after prolonged cranking. I have read other threads here and on other BB's with the following answers:

1) Camshaft timing off
2) Injector fouled / fuel management problem
3) Ignition, plugs, wires, coil...
4) Head gasket leak
5) Short skirted piston design
6) Broken/bad motor mount
7) Some subbies simply vibrate and some don't (yeah, BUT WHY?)

Any help appreciated. I'm thinking of starting with ignition components, and perhaps moving towards the injectors / fuel system and then timing belt(properly positioned?


01-23-2005, 05:15 AM
I don't buy into the theory"some shake or some don't. Anybody that would say that probably is in a state of denial that something is wrong. Probably too broke,like me, or just hate,for what ever reason, to take they're car to a dealer(shudder) or mechanic/service tec.. My Legacy idles smoother than my Nissan. I always recommend,for myself anyway, starting with the least expensive and the things I am capable of doing myself. It usually works and always gets me off alot cheaper.

01-23-2005, 10:47 AM
I just had the same problem starting when cold. I changed the Coolant Temp Sensor($24) and it started like a champ. The computer uses it to control radiator fans and to adjust the fuel delivery when starting cold. Question for you. Do the fans run when you put the ignition key to start(when cold). That may be another indication. The ignition coil might be another way to go. It is a bit more expensive($130 or so) but with 113K it may not be a bad idea. Cables and plugs may also be in order. PCV($6.00) valve is a cheap change and it might do it to. Go to AutoZone and they will hook your car up to the comp and give you a diag for free. Let me know if this helps. Good luck!!

01-23-2005, 09:46 PM
A friend and I just recently converted a Subaru Legacy 1995 GTB into a single (aftermarket) turbo machine, specced mostly with Sti components such as intercooler blah blah blah. Before we converted it, it was smooth as - no vibrations above the norm. But since conversion, at idle we now notice a slight vibration cold or warmed up. So we checked mounting brackets and everything else figuring that in our maniac fever of converting something into something FASTER ( YeeAAARRR!!) that we must have left something a lil' loose. oopsies.

However, we still cant find anything and it still vibrates, and continues to vibrate through the rev range pretty much.

Open up your bonnet, and just have a listen and try n figure out what kinda vibration/shaking it is. For example, does it sound rattly/tinny? Or is it more of a buzz? Does it seems to come from the engine block, or side of the car? Or does the entire car just vibrate in general? Also, can you only feel the vibration - or can you actually hear it as well? One other thing - When you open up the bonnet can you still hear/feel it vibrating over and above normal engine movement, compared to hearing/feeling it from just sitting in the driver's seat? The reason I ask so much is because it could just be something simple and easy to fix such as exhaust mounting.

Let's hope its not something inside the engine block... like cylinder heads... :O <---- You would know because your performance would be up #$$!@#$ Creek pronto. ;)

01-24-2005, 12:51 PM
Question for you. Do the fans run when you put the ignition key to start(when cold).

No they do stay off for a while, and seem to function properly with temperature. The vehicle MIL(check engine) isn't on, but I will scan the ECM tomorrow with my palm unit and check out the sensors. All the vehicle fluids look okay, levels, color, etc. I think a set of plugs and wires and general service(synthetic oil, air filter, etc) may be in order. The existing engine oil seems too thick, it's been under -10 to -20F here the last few nights, and that isn't helping with the cold starting problems.
Thanks for your reply. I'll try to post results when I have them.

02-22-2005, 04:54 PM
I bought a '99 Outback october of 2004 with 28,000 miles- very low for the year. From the very beginning I also noticed a vibration when driving my vehicle, especially around 1700-2300rpms. (Not always, but sometimes) The engine doesn't produce this vibration at anyother time. I should mention that it is not a hard starter in the cold, and believe me, being from MN it gets damn cold. Currently, it has 63,000 miles on it and I have had no problems with it. Not a one. I have been to Subaru and asked them what they thought it was- they figured it was piston slap- but I don't think it is. The engine has no noises coming from it, rather it just vibrates. They have put their computer on it and nothing pops up. I figure I am not going to worry about something no one can diagnose and just drive.........isn't that what they are for?

02-22-2005, 05:18 PM
Could just be crappy ground or plug wire connection.

03-01-2005, 08:09 AM
My '98 Legacy L wagon with EJ22, 4EAT with 142k on the clock use to idle rough all the time. I got a can of Seafoam upper engine cleaner warmed up the car. Pulled teh vacuum hose off the top of TB on the engine. Stuck the hose in a dish with 1/3 of the can of Seafoam in it. Started it up and reved it till all the fluid was gone from the dish. Then shut the car off let it sit for 5 min. then started it up and took it for a drive where I red lined every shift. I did not run this good when it was NEW!!! then I treated the TB latter with the spray Seafoam called Deep Creep!

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