The engine was rebuilt, stock ports, stock 2mm seals. Less than 50 miles on the engine and it only pulls between 9 - 11 inHg when it idles at about 850 rpm. Is this normal? Even a new engine with 0 miles is supposed to pull 15 inHg correct? Input appreciated.

 

not broke in most likely i was only getting 11 or 12 on my new 0 mile but its slowly getting better.

 

Mine was low when I purchased my car in 06. the motor was a "new" rebuild and when I sold it I think it was getting weak. I dont know if this helps but it was an indicator to me of a sub-par build possibly. Get it checked!

 

That is definitely wrong, who did the re-build on the engine? I'm surprised you don't have any starting and idling problems. Do check for vacuum leaks first.

 

Vacuum leaks would raise the idle and give him better (lower) vacuum readings

Sounds like high mileage rotor housings. Who did the build? I'd put more miles on it and check the compression.

Every rebuild that Ihor and I do at the shop pulls better vacuum than that, and we have turned out some pretty large SP'ed motors which tends to lead to worse (higher) vacuum.

 

Check the line going to your boost gauge, if it has a leak then the reading will be way off. Could also be the gauge itself, I have a car in the shop right now that when it is not running it shows 2psi of boost, so when idling the vacuum reading is wrong.

An overly rich idle can also cause a low vacuum reading.

 

I did a compression test on each housing and found that the front housing pulled 93 psi and the rear 87 psi. There were 4 bumps of the needle instead of the standard 3. What I mean by this is that it would build pressure as follows : 25 - 50 - 75 - 87/93.

The idle itself is rough but I thought most of it was due to the light weight flywheel.

 

when I try to pull it out the driveway I notice I get some back firing. This is a recent development.

 

Those compression numbers are bad. You need three even pulses, or close to even. Looks like a rebuild with new housings is in your future. Good luck.

 

could a bad or loose gasket cause my problem? I spoke to the shop that rebuilt my engine and they make it out to be a minor issue. I still need them to look at it though since its under warranty.

 

That wouldn't change actual motor compression numbers if you test it at the spark plug.

thewird

 

I'd recommend getting it compression tested with a rotary tester that gives three readings per rotor. Those numbers aren't great. I take it you're purposely keeping the shop name quiet for now?

 

90 psi on a used housing rebuild isnt horrible if it only has a few miles on it. 90psi engine would pull more than 10 inhg if everything else is fine. Sounds to me like it is an issue with a fuel injector, sounds as if it is running extremely rich.

 

afr shows to be about 12.6 idling at 850 - 900 rpm. Still the same issues after examining all the vacuum lines, removing the turbos and LIM and inspecting the gaskets, all of which are in good shape.

Any more ideas?

Thanks

 

well checked all the injectors, had them tested and new o rings put on, new spark plugs (7s and 9s), checked all the coils for spark, check all the turbo gaskets, the LIM gasket, got a power fc and it still runs like crap.

idles at 1000 rpm 10 - 12 in Hg vacuum, very thin oil due to fuel mixing in it. Rechecked compression and was found to be the same with the rear housing showing even worse compression after about 40 miles of driving. Front housing showing a strong 100 - 105 psi with 3 distinct jumps of the needle where as the rear shows about 85 psi with 4 distinct bounces of the needle.

Any more input? Im losing hope.

Thanks.

 

i hate to say it but it but i can guess where this thread is going and it aint lookin good. Im not saying its toast or anything im just seeing a trend here and hope its not what everyones thinking. heres hoping it will be ok!

 

What he said.

I'm surprised you did all that work w/o getting a real compression test.

 

A few random thoughts:

could be loose/sloppily clearanced side seals.
could be a failing/bad OMP leading to premature wear.

 

Where can I get a hold of a rotary compression tester?


Also I noticed that when I pull the rear 2 plugs, there is quite a bit of oil on the head of the plugs. The front housing doesn't show the same. Any indications of anything?

 

were in torrance are you>? i live in gardena, i can help ya check out the car if you need any help,

 

I'd say the shop where you got the rebuild from should have a rotary compression tester...

If not...