SR20 - Problems after switching back to stock intake

[akruger34]

To preface this post: 1993 hatch w/ blacktop s13 sr20det type 62 ecu, 255 pump, new 370cc injectors and seals, turbo elbow, hks bov, fmic, new z32 fuel filter.

So I was having issues where the car would idle very rich (mid 11's) and wouldnt seem to get low enough under WOT until further up in the rpms. I performed a boost leak test and could hear hissing around the intake manifold, so I decided it was time to swap from the greddy rep my swap came with back to a stock manifold. I picked up a manifold with the throttle body and IACV installed and installed it. Now I am still having a somewhat rich idle (mid 13's, but dives to 11's sometimes) and fluctuation after setting the tps. (set to .45 V closed) When I turn it on it idles at a normal rpm, but after a couple minutes it jumps up to 1500, then seems to waver between 1k and 1500. Another oddity that is occuring now but not before is when I press the brake and release, the afrs jump 2-3 points all the way up to 16's. I performed the generic tests I found online to test booster diaphragm leaks (holding brake and starting the car, and holding brake and turning off engine) and it seemed to pass. I ordered a new fpr to ensure that I am not over fueling due to a worn out fpr, but that doesnt seem to explain the wandering idle and brake effect. Engine pulls -22 vacuum at idle and is not affected by the brakes. I have tried spraying starter fluid around any joints and fittings with no effect. For reference, the pcv on the passenger side of the valve cover is blocked and the line on the manifold is plugged, on the drivers side there is a line running to the case and a vent to atmosphere. Any directions are appreciated!

[Kingtal0n]

lol the brake 'vacuum' is actually unmetered air entering the maf circuit. so it will always make an engine run lean when you depress the brake because brake booster air comes from after the maf. that is completely normal.

You just need to start with a pressure test. Boost leak test the system from JUST after the maf (PRE turbo) all the way through the intake manifold to find all the leaks. Make sure you hit 15psi or whatever you run +

And make sure you do NOT pressurize the crankcase. Pull the dipstick and disconnect the fresh air tube from the valve cover (I plug it with a marker :D) If you think air is entering the crankcase seal all exits except the dipstick tube and listen carefully in the dipstick tube for air rushing out. That means air is getting into the crankcase somehow still.

[akruger34]

Okay, if I already have the front leg of the T fitting to atmosphere there shouldnt be an issue with pressurizing ?

[Kingtal0n]

Well. That is the question, now isn't it? Air can leak past a piston ring, and into the crankcase from the intake manifold. if an intake valve is open and an exhaust valve is closed. If the exhaust valve is also open overlap will allow flow into the exhaust as well and prevent pressure from building in the piston cylinder. Also air can leak into coolant passages from the head. It can also leak from the cylinder, through a guide, into the valve cover area. Also from the compressor wheel seal to oil drain -> crankcase is always something. Borg Warner engineer warned me not to inject methanol pre-turbo because it will mix with drain oil.

So this is what you are trying to discover. The more sensitive you are to the pressure test the more leaks you will be able to find. because all rings leak, almost every seal leaks something sometimes. The PCV system is an essential oil control system which is supposed to "mop up" and put the entire system at a slight (or more) negative pressure (below atmospheric) to take care of all these leaking gasses. Keep them out of the engine oil and keep them from blowing out oil all over the place also, damaging seals and causing oil leaks.