I have a friend with a 1991 Legacy sedan, automatic transmission that has more recently began having problems with a severe shudder and power loss when, say, trying to get on the freeway under more aggressive acceleration. That is, this problem comes up during times when heavier on the throttle-- The entire car starts shaking and looses power. Apparently when accelerating very slowly this problem doesn't happen.

 

The car is mostly used as their around town runabout, and now has about 89,000 miles on it (low for a car this age).

 

Has anyone else experienced a problem of this kind and can perhaps provide an idea as to what the cause is? I was thinking maybe a bad motor mount(s), but she didn't mention that this happens at any other time except when accelerating aggresively. If it was a motor mount I'd expect a "thud" type of sound, or similar, when shifting, say, from neutral into Drive. So it seems more likely the problem is something else...

 

Thanks for your help, all-- They need to keep this car and can't afford to replace it, so ideas as to what's wrong are badly needed!

My first guess would be you're losing spark to one of the cylinders under load. Bad plug, plug wire, or coil.

 

**** ******!

I have a friend with a 1991 Legacy sedan, automatic transmission that has more recently began having problems with a severe shudder and power loss when, say, trying to get on the freeway under more aggressive acceleration. That is, this problem comes up during times when heavier on the throttle-- The entire car starts shaking and looses power. Apparently when accelerating very slowly this problem doesn't happen.

 

The car is mostly used as their around town runabout, and now has about 89,000 miles on it (low for a car this age).

 

Has anyone else experienced a problem of this kind and can perhaps provide an idea as to what the cause is? I was thinking maybe a bad motor mount(s), but she didn't mention that this happens at any other time except when accelerating aggresively. If it was a motor mount I'd expect a "thud" type of sound, or similar, when shifting, say, from neutral into Drive. So it seems more likely the problem is something else...

 

Thanks for your help, all-- They need to keep this car and can't afford to replace it, so ideas as to what's wrong are badly needed!

 

First thing i would suggest is a full tune up and go from there. Plugs Wires Air Fuel filters, PVC valve

 

nipper

I agree with everyone about the tune up and making sure all your normal wear items are in good condition.

 

I had a random loss of power issue several years back that turned out to be a bad MAF sensor. It wasn't always under power, and was intermittant.

 

Have you checked the ECU for codes?

 

If not, read over the procedure on my site

 

www.surrealmirage.com/subaru/engine.html

I agree with everyone about the tune up and making sure all your normal wear items are in good condition.

 

I had a random loss of power issue several years back that turned out to be a bad MAF sensor. It wasn't always under power, and was intermittant.

 

Have you checked the ECU for codes?

 

If not, read over the procedure on my site

 

www.surrealmirage.com/subaru/engine.html

 

 

i agree, i have had a similar situation and it was the MAF sensor.

wouldn't be the MAF sensor on mine?

 

Recently on my Liberty EJ22 whenever I am on cruise control on the highway on flat terrian sometimes I can feel a small repeat shudder feels like missfire but the sparkies (well gapped) & leads are brand new (and fully serviced - new filters, oil and air etc), I recently changed back to the old ones and its still doing the same thing? My thought was the coil at fault? But if it was the coil - it'll fail straight away wouldn't it? No ECM codes has been displayed yet.

 

EDIT - Oh... it shows code 24 which shows air control valve?

Cheers

AP

sure sounds like a bad MAF sensor

 

when the MAF goes 'bad' the car will drive fine... under 3500-4krpm

 

if you try to accellerate hard you will be bogging, bucking, misfires....

 

 

 

and yes... then again...

could be the idle air control valve as well

 

pull codes, fix accordingly.

Jamie