pincusa

iTrader: (1)

Maybe someone more advanced then I am with these engines can help me out.
I recently bought the car for a good price because the previous owner couldn't handle an engine rebuild. The car has very low vacuum at idle (12-13") which I expected would be an engine rebuild to fix.
Today before I started pulling the engine, I did a compression check, and things looked OK. Front rotor was a solid 90-90-90 and the rear was 85-90-85 psi. Everything I read tells me the compression is OK. So if it's not a bad engine, what's the cause of the low vacuum?
I've gone over the engine a few times looking for a loose vacuum lines and they have been replaced. I assume if there's a leak, it has be to behind the butterfly and not one of the lines driven off the pressure side around the turbos.

Any ideas before I pull the engine out of desperation?

smg944

iTrader: (34)

the compression is low. that is probably the reason your vac is low. some people say 75 psi is the limit berfore rebuild, some say 90 psi. how many miles on your engine and turbos?

Mindphrame

You have low vacuum is all I got out of that. What’s the problem?

Does the engine run rough? Stall? Smoke? Run at all? Does the boost hold? How's the boost pattern? What time did you get doing a 3rd gear 40-70? What mods are done to the car? Do you have a hose job? Have you checked all the connectors?

IE low vacuum could mean a hell of a lot, or mean absolutely nothing. My car runs at about 13"-16" depending on the outside temperature.

I assume that you just have a vacuum leak, or possibility a solenoid that's not totally functioning properly.

pincusa

iTrader: (1)

What's normal compression for the car? Guess I was expecting 70PSI for that little vacuum...
The car gives the typical one good blue puff at startup and when it's really cold will smoke a little blipping the throttle to 2500 to help it warm up. But once it's warm, it doesn't smoke. Oil pan leaking is another issue...
I was told the turbos are a fresh rebuild. The car has 130K miles on it, and I just bought it so I'm not sure when/if the engine was done.

So am I just kidding myself, and pull the engine to see what's happening inside?

pincusa

iTrader: (1)

Forgot, boost pattern 10-8-10. Usually holds at 10 full throttle, but will creap a little on a good hill at WOT.
Car is totally stock. Runs nice for the most part. Idles at 750PRM. Will sometimes fall into a pattern of up to 900 down to 600 up to 900 and continue until you give it gas. Other then that, I've had no reservations about driving the car long distances.

Mindphrame

If you have the time/money/knowhow and really really want to pull the engine, by all means have at it. Change your plugs, do a full hose job and all thoes other little fun things.

Personally, I'd just remove the UIM and get cracking on a hose job. It really doesn't seem to me that this is one of thoes pull the engine kind of things. Or...iirc spraying Carb Choke cleaner around the hoses will make the engine stumble a little if you have a vaccum leak. Gonna have to look that one up, been a long time.

That 2500 AWS is terrible btw. Tap the gas gently to stop it from doing that. Let it warm up at normal idle. The blue smoke is not a terrible thing, 12+ year old cars will tend to do that, not to mention just about every turbo car will do it now and then no matter how old. White smoke = bad. Usually coolent, will have more of a 'sweet' smell. That's rebuild time.

As far as the compression, going to have to search for that. You will get quite a bit of conflicting info though.

RotaryResurrection

iTrader: (8)

With 85 compression I'd go on with the rebuild regardless of whether or not it has to be done right now or not. DO all your other maintenance items at the same time as well. Turbo rotaries have a great way of turning 90psi into zero in an instant. 85psi is the lower limit acceptable for a running engine, but anywhere below 95psi you begin to worry about how much longer a modified turbo engine will hold up with weak compression. 125 is spec for new, and 105 and up is pretty healthy.

Mindphrame

Oh, and if everything is running fine, why so worried about the low vacuum? Could be just the way your car runs, heh.

Boost pattern is correct, so full hose job may not need to be done.

Still I'd start with the simple stuff first. K.I.S.S. Great motto to live by. I'd personally be pissed if I went through the trouble of pulling the engine to find a small vacuum line with a pin hole in it.

Snook

iTrader: (12)

Kevin what makes an engine with lower compression more likely to break a seal than another. Are you assuming the engine is old and the seals are more likely to be brittle and break easier? Why is a low compression engine more fragile than a brand new one? Do the seals float out more and that causes them to break or totally exit easier? What if an engine was just rebuilt but it has low compression because it wasnt oiled right or something. Would you say that is more likely to break than one that has perfect compression? I know eventually that one will break faster but I mean in a certain situation making the same power with the same turbo and boost level etc all same conditions...

pincusa

iTrader: (1)

The low vacuum could be a good sign of something bigger coming. Everything is usually good until the engine blows and leaves you somewhere walking, a tow bill, a lot more expensive engine rebuild, and a cute date who can't walk 5 blocks in her ****-me shoes.... And if she does, there's little chance that I'll get any that night. And lets be honest, isn't that the point of having an FD?
I have all winter now to fix the car and rebuild the engine if it needs it. I'd rather have the car w/o and engine for 3 months in the winter then in the summer when I want to be driving.