I recently bought a turbo II that had been sitting for about 3 years in the back of an auto shop for penny's on the dollar. He couldn't get it to run, turns out that the injectors were leaking.

The car pulls hard, doesn't smoke except on start up for a second or two, and will start when warm but it pulls a vacuum of around 13-14 on a good day.

I figured if the compression was that bad it would barely run. Is it ported? Is there any way to tell besides pulling the motor apart? What could cause such a low vacuum and allow the car to still run so well? Furthermore if the afr's run leaner that a 12.2 at idle it starts misfiring. It prefers to idle rich (11-11.9) if that's an indication of anything. Any help would be great.

 

Are there any obvious mods to the car? Richer idle seems to be the way of these cars mines happy in the 11.x range. And is the boost gauge working correctly and plumbed right?

 

My freshly built mazdatrix streetported 6port turbo idles at 1000 rpm and has the same vac at idle . But as soon as you tap the throttle it jumps up out of boost .

 

The stock boost gauge doesn't seem to work but all the other gauges do. It's definitely a rebuilt motor seeing as it's painted blue and silver, but other than that it seems to be stock. It's got an aftermarket clutch and apexi exhaust but the stock s4 turbo. I figured if it was ported they wouldn't keep the puny stock turbo.

 

I would do a compression test or even just take the spark plugs out and disable fuel pump/injectors and spin the engine with the starter and a fresh charged battery.

If they are all relatively even pulses it is fine. If there are one or more dead spots, its not fine.

PSH, PSH, PSH, PSH, PSH, PSH, PSH without change or rest is fine.

PSH, PSH, PSH, PSH, PSH, -___ , PSH, PSH, PSH, PSH, PSH, ___ Would be 1 stuck side seal

Probably the low vacuum is just because it was a budget rebuild with used housings and then to top it off it was getting flooded out with fuel instead of breaking in.

Compression should improve over the next 2,000miles.

 

Should I drive it with a stuck side seal or are there major repercussions to driving it like that?

 

I bet you could put-put it around for a loooong time with a broken side seal without any major problems.

If you drive it hard it probably won't last long with a stuck side seal. You have a bunch of blow-by into the sump on that rotor face so now you are filling the intake with oil from the sump if you don't have PCV disabled and a separate oil/air separator.

Then you have the wear put on the engine from uneven combustion forces. Its hard on bearings, stat gear, etc.

Example- I once drove for a while time not knowing a leading plug had lost its ground strap. The uneven combustion forces eventually wobbled the stat gear dowel out of the front iron.

I have 1 stuck side seal in my FD from over-revving it and I don't drive it. Its just sitting there waiting for a rebuild even though it drives fine, just has a tad rougher idle and a tad bit less power under 2,000rpm.

 

Side seals almost never stick though, and only break if clearance too tight during the build.

If the car has been sitting, there could be ANYTHING wrong with it. Check compression. I fit basically seems correct, then suspect clogged/sticking/bad fuel injectors.

 

Side seals sticking is mostly when you over-rev the motor and the rotor flank contacts the side housing smearing rotor material across the sides seal groove trapping them in their compressed state.

This is more of a 9,000rpm + problem and not so much a 8,000rpm problem, so it is rare since most people keep the stock rev-limit and stay out of trouble.
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Another cause of side seal sticking is when people don't properly clearance the side seals.
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The last cause of side seal sticking is when an engine sits and moisture gets inside and rusts the side seals to the rotor.