imprezabob

Hi, i have a 96sti which was unfortunately running with 440cc injectors and a standard ecu for 10 weeks.. no noticable running issues. Developed a misfire and a tapping/clicking coming from n/s of the engine.. there was a noticeable smell of petrol.. stopped using immediately

Changed injectors back, changed plugs which were fouled, drained oil.. left all open etc overnight to let any excess petrol evaporate. Worth noting the oil appeared ok with no debris but did smell of petrol a bit..

Filled back up with oil, disconnected crank sensor etc.. reconnected and started up and the tapping/clicking was still there..

got someone to come round yesterday and do a compression test and the results are as follows:

cylinder 1 - 190psi
cylinder 2 - 195psi
cylinder 3 - 190psi
cylinder 4 - 160psi

i let him hear the engine running afterwards and he commented that it didnt sound as bad as most with bottom end issues.. he suggested tying some hydraulic lifter treatment as there could still be oil with petrol in them and could result in this noise..

I plan to follow david @ api's instructions posted on here somewhere with regards to liftertreatment later on today if anyone else can suggest anything (other than rebuild quite yet) please do as i am soooooo annoyed i cant drive my car at the min!

I have heard that normally it is cylinder 3 that goes.. can anyone tell me whether those compression results are acceptable and what it could rule out?? Also maybe this has no real relevance but the noise is definately coming from the o/s of the engine and as far as i am aware cylinder 4 is n/s right?

also doesnt sound like manifold gasket and i suspect not the standard injectors put back in cos the noise was there before i removed the 440's

imprezabob

:update.. just had car mot'd as had run out a while ago, handy tip dont use STS tyre pro their mot practise was appalling.. i adv i had suspected internal problems and they took it out on a "road test" apparantly as part of the procedure when they new it had already failed and without my permission!!..

anyways car failed on a few things but the noise has magically disappeared!! i still plan to do the lifter treatment

1. should i still do the lifter treatment?
2. should i be worried about the results of the compression test given cylinder 4?

i am just after opinions please as i really havent got much of a clue i think i have explained the background to this well enough.. come on guys give me your thoughts!!?

Shaun

From what I know, the kind of % difference yours is showing (circa 18%) is not good. Cylinder 4 seems to have a problem. Valve or ring issues perhaps. Does it smoke?

Best to take it to a Subaru Specialist for diagnoses imo.

imprezabob

Thanks Shaun., how could this be diagnosed without enginebeing taken apart?

imprezabob

Oh and no smoke no tapping and currently sounding fine.

ZEN Performance

Camera inspection and possible a leakdown test would help diagnose a little further than a regular compression test. I would be tempted to repeat the compression test in the first instance too.

The low result for one cylinder is odd, but I would expect them all to be at 160 and not 190psi.

The offside (drivers side) is cylinders 1 and 3 and is the RIGHT hand side of the car and engine. Cylinders 2 and 4 are on the LEFT which is the nearside (passenger side).

imprezabob

thanks paul.. i was just pointing out that the sound that was there was coming from the opposite side to the cylinder in question. This sound has now disappeared.. given this is it likely to have been internal cylinders/seals?

Could you post or pm me the likely costs involved for a camera inspection and leakdown test?

Also can you elaborate a little more on your views on the cylinder results.. is 190psi unusually high and given your comments is 160psi a problem? or does that arise from the differences in pressures between them?

Also would you advise the hydraulic lifter treatment now the noise has gone?

Ultimately i dont want to skimp on the costs but i am a bit low on funds for a rebuild at present and do need to use the car.. if i can get away with a 3 - 6 more months driving before it goes bang i should be able to afford a forged redbuild and new turbo if necessary.

imprezabob

from what i have been reading something definately seems wrong with those compression readings.. i have not seen anyone with a result over 165-170 psi on an sti.. i guess i could get it tested again but can anyone else please comment as to whether the high readings are odd??

ZEN Performance

I would expect 160psi all round. Additional oil in the cylinder can help create an artificially higher result and the results are speed dependant so a poor battery can skew results as you go through the testing!

imprezabob

thanks paul.. the car hadnt been started for about 10 days, the first cylinder he tested was 4 and i remember it turning over slower than normal.

Sorry if this is a stupid question but why may i have additional oil in the cylinder.. is that the mechanical result of the seals/rings going?

i think another compression test is in order

Jolly Green Monster

iTrader: (4)

96sti shouldnt have hydraulic tappets

imprezabob

Simon.. my thoughts were based on a post i read from david @ API :


Mine is pre 97 has 4 coil packs and therefore i presumed hydraulic lifters.. if i am wrong please let me know

Jolly Green Monster

iTrader: (4)

Sti2 was hand built with solid lifters.
Although it is possible they have been swapped out.

merlin24

iTrader: (1)

IIRC the STi V2 RA had solid lifters (top hat inner shims) but the STi V2 had lightweight hydraulic lifters (approx 10g lighter each - when stripped,cleaned and a touch of assembly oil compared to the WRX hydraulic lifters).

As above with the Compression Test results - never seen them that high unless they have N/A pistons fitted. As Paul said, have the comp test done again followed by a Cylinder Leakage Test - will narrow it down a bit.
Early STi Dog Bone pistons with the 'slot type' drain back on the oil control ring land,suffered from breakage in that area but you would normally see that as oil burning/consumption.

Mick

ALi-B

iTrader: (1)

Its quite possible the gauge could be reading high. Even so you'd expect all cylinders to be within 10psi of each other on a healthy engine regardless of the actual number recorded. Unless there was notable battery drain, uneven cylinder temps, etc.

You "may" have a slightly bent valve that's not seating correctly, but that is just a blind guess TBH.

imprezabob

Merlin, Ali-b cheers guys.. Am still gonna do the lifter treatment as per David @ Apis post but first am gonna do a compression test myself tonight.. Kit arrived today in post.

As I wrote above the car had been standing for about 2 weeks prior to the last test so I am hoping that the batt not being 100% did affect the results. Will be running the car for a while and let it get upto temp before testing

Also car has def not been burning oil or had any leaks