franckybosnie

hi everybody

I have a 1989 lx 5.0 stock exept few little things (H - pipe , cold air .... stuff like that)
In the last summer I saw that my oil consumption went up . At the end , I had to add 1 and a half qt per 700 miles (around 1000 km) . By the way , excuse my poor english , I speak french , I live in quebec with the beautiful winter . By the way , yesterday I took out my mustang out from the storage .

My friends told me that in the highway , when I downshift hardly ( at 70 mph I can downshift in 3rd) , They see a big puff of black smoke comming out of my exhausts for 1 seconds .

What I saw in the others topics was that , if it would be the oil rings , I would have a bad compression . So I check this morning the compression level of my cylinders , They were all equals (119 or 120 psi each ) . I saw on my Haynes manual that the minimum psi is 101 (At this point I think you need to rebuild your engine ) .
Is 120 is still good or just borderline? Could it be possible that I could get a good compression and bad oils rings? Or could it be the valve seals? If so , I know that the valves seals are inexpensives , but is it a big job?

Thanks

Franck

Jeff 86 GT

black smokeusually meanstoo much fuel

franckybosnie

ok , so there is too much fuel , where goes my oil? I checked and I have no dripping oil under the car , and my gas mileage goes pretty good ....

dman302

leak?

93 LX FiveO

rev it in the driveway and have someone get behind the car

blueish smoke = oil (even if it doesnt smoke alot it should smell)

black smoke = too much fuel (should really smell...)

white smoke = blown headgasket (puffy clouds, smells sweet)

my77stang

sounds to me like hes just romping on it and blowing the soot outta the exhaust, gotta keep them pipes clean

Jfsram

Blue and black smoke look similar to the untrained eye.

Use other hints to verify. If it's smoking during downshifting, decelleration. Most likely the valve seals and or guides are worn.

Rings are usually showing their weakness at full throttle.

Twisted

To answer your question further, it is possible to have good compression (which you don't) and oil consumption past the rings. It's also possible to have no oil consumption and terrible compression...but that's besides the point.Did you hold the throttle open while you performed the compression test? If not, all cylinders would probably read lower that they should. If I had to guess, I'd say that new rings would lessen your oil consumption by a lot, and new valve seals would lessen ita littlemore. If your cranking compression is low across all cylinders, it's a good bet that the motor needs a good freshening.

Also, on the black smoke issue. I've always believed that black was fuel, and blue was oil...and that was that. However, for some reason, I kept owning motorcycles that burned oil and belched out black smoke at high rpms, even though the A/F mixtures were dead on across the band. Then, I'd hone the cylinders and install new rings, and the bikes would never blow black smoke again. I also have some footage of me running my mustang (which uses a quart of oil every 1k miles like clockwork) up a desolate local road, with small puffs of black smoke curling out of the pipes at about 5500 rpms...yet my spark plugs show signs of running lean, if anything. I don't know why I've repeated observed this link between bad piston rings and black smoke, when everyone knows that oil smoke is blue. Weird.

Twisted

After further though, I think that, as mentioned earlier in the thread,the perceived black smoke may just be soot blowing out, from years of burnt oil carboning up your chambers. I say this because I don't think my car blows black at high rpms anymore...because I run the **** out of itoften enough.

franckybosnie

thanks for the replys!
So you say that 120 psi is bad ?