I have a 98 subaru outback legacy 2.5 dohc engine shakes bad at idle i pulled plugs one at a time they all made difference except #3 cyl. checked compresion all good exept #3 in was only 50. goin down the road or accelerating it seems to run fine but mpg dropped big time.

does anybody have any clue that could help me out.

did you squirt a little oil in the cylinder and than recheck compression? (wet compression test)..If compression increases chances are you have bad rings...otherwise from the info youve given I will say maybe you dropped a valve....How many miles are on the car? Have the HG's ever been replaced?

HG have never been replaced that i know of. car has 130,00 miles. one mechanic told since it is the num 3 cyl. it may have some thing to do with the fuel presser reg. that it may be washing the cyl. does that make any sence.

I have heard of this.....for the price of the FPR...its prob worth replacing....because otherwise....my bet is it is something internal...

ok well thanks for your help. But if it was a dropped valve wouldnt i have no compresion at all? cause it did have 50psi

You could have the beginning of a burned exhaust valve, run the wet compression check, you will know more after that.

You could also try a leak down test...but i guess with such low compression it wouldnt really tell you anything...

Edited March 26, 200917 yr by EVOthis