i have a mild street port (rx7 store's stage 2) and just installed a t-78( proberly broken in and all that crap) had it tuned and all and the other day after getting on it a few times i noticed what sounded like an exhaust leak when it was at idle and now the vacuum is reading 7-9in/hg. ( it was reading about a steady 10in/hg before i noticed the leak) If it is an exhaust leak would it cause vacuum to be that much higher?

 

properly***

 

i know that a stock port is around 18in so i dont think it should be that far off maybe 14in.

 

7-9in is way low. 10in is still way low. Is your boost guage reading from the MAP sensor?

 

No, an exhaust leak would not cause a significant drop.

Did it always read 10in since you installed the turbo?

 

An exhaust leak will not effect your vacuum unless the ecu is trying to compensate for it by dumping in loads of fuel. 7-9 in of vacuum at idle sounds like you cracked an apex seal. 10in of vacuum on a mild streetport is pretty bad, we get a minumimum of 14 out of large streetports after break-in and initial tuning. I would say do a compression test, if that all checks out OK, then look for vacuum leaks between the TB and LIM.

 

i checked it again and i forgot it reads 2psi higher so 9in/hg vacuum is actaully 11in/hg. since i have had the ported engine ( about 1,100 miles on it) with the t-78 it had always read 10in/hg which is actually 12in/hg since my gauge is off.
Its running pretty good and strong with plenty of boost coming on very strong. If not a cracked header could it be the gasket on the header against the turbo compressor or even the bolts coming loose on the header?

I havent heard of greddy headers with the t-78 kit cracking with so little use.

since its running good i wouldnt think apex seal..or am i wrong?

 

odd thing is that i had put about 150miles or so on the t-78 and some of those miles were getting on it pretty good then just the other day after doing just (2) 60-160 timed runs for the fun of it and after the runs is when i heard what sounded like an exhaust leak when it was ideling. The next day i realized the vacuum reading was a bit higher although its still running strong.

 

Why are you assuming it's an exhaust leak that's causing the low vacuum?

How is the idle? Is it rough? What is the idle speed when fully warmed up?

Usually, if an apex seal goes bad but the engine still runs fine, the idle will be rough and unsteady, but I've never seen one running that low on vacuum that didn't have a leak (and still ran okay). You can do a compression test to make sure.

If you're hearing that much extra noise at idle, and it started suddenly after "getting on it", I'd check the intake tract. Check the hoses and crossover pipe for cracking/splitting first.

 

WHAT IN THE HELL IS GOING ON.....


ok well after checking some hoses everything seemed to be on tight so i just filled it with with 5 gallons of C16 and took it for a spin like 15 minutes ago. By the way ever since the other day when i put 5 gallons of torco 110 just to get me back home at high revs and boost it would stumble bigtime. Well after getting almost all of the torco out and filling it with c16 i took it out let it get warm and got it on mildly...its still stumbling alot above 5k under boost. So i turned around and in 2nd gear gave it some gas then it seemed ok until it stumbled bad again then just completly shut down..all gauges went off , the boost controller and PFC turned off as well so i costed off the road and tried starting it and nothing just keeps trying to turn over. Everything comes on expect the boost controller (AVC-R) and PFC. Still getting 40psi fuel pressure so the pumps are working.

Does anyone have a clue to what could be wrong?

 

oh...yes the idle is slightly rought but its been rough since the streetport..but it hasnt gotten any rougher since the port job.

 

I've never seen or heard of PFC's going bad... but is it possable that the PFC and AVC-R went bad. I know the avc-r plugs into the pfc for readings and power so perhaps maybe the pfc took a crap???????? the damn thing is not even a year old and the avc-r is about 2 yrs old

 

So now when you turn the ignition to "ON", you're saying everything appears to be working except the ECU and boost controller? Do you hear the ABS actuator cycle when you turn it to "ON"? Does lighting work? And it cranks when you turn the key to "START"?

I would have said to check the negative battery cable if nothing else was working. Otherwise, check the fuses in the engine bay.

On the bright side, the vacuum issue doesn't seem to be your highest priority anymore...

 

Check the fuses in the engine bay and make sure the battery terminals are tight.

 

While you are checking fuses, also check the engine fuse in the interior .

 

while your "guessing" what the problem is you need to be getting a comp test. because if your out there still pushing that motor and there is a cracked seal and it decides to break on you.. well..say byebye to t78 turbo when that seal goes flying into it. So stop being in denial about your motor possibly going south. get a comp test and rule it all out.

 

yes everything turns on expect the PFC and avc-r. It does try to crank over

 

hows your suspension?

you can rub thru the chasis harness on the drivers side front fender...short out ignition/map related items. Just a thought.

 

yes i know i need to get an comp test but i was just trying to rule out everything before i get one since the last time i got a comp test it was like $$200 at the dealer. You just cant use a comp tester for pistion engines since it wont read each apex seal while cranking.

But now i need to find out if its a fuse for the PFC and avc-r... i replaced the only fuses( replaced 2) that i thought went to the pfc and still nothing unless there is an inline fuse for the pfc that i cant see. if no more fuses go to the pfc..... im thinking it must have craped out since all other electronics are working and the car wont start but keeps cranking

 

Sure you can. You just have to hold down the pressure release button while someone else cranks it. And watch the needle carefully. Use the trailing plug holes.

Regardless, compression isn't going to keep your PFC from getting power.


What fuses did you check? You might be overlooking something.

 

I checked the fuses in the cabin. i think there are 2- 15 amp fuses that are for gauges and interior lighing they ddint look bad but i replaced them anyway. The rest underthere look good. checked the connections on the PFC and avc-r and they are all connected. i dont see any inline fuses for the pfc and avc-r..are there any? Also what possable fuses under the hood are there for the pfc/ecu?........

also is it possable that the pfc was on its way out since the car would majorly stumble under boost and high rpm until it finally died?

 

huh?

 

........uhhhhh yeah HUH? say what

 

Look in the engine bay. The box that bolts onto the positive battery terminal. Check all of these while you're in there, but specifically the "EGI" fuse. Also check the 15A "ENGINE" fuse in the cabin fuse box.

Of course it's possible the PFC somehow died, but I'd check elsewhere first. I suspect a fuse or a harness got damaged.

 

yeah i checked and replaced that cabin fuse...checked the fuse bank on the batterypost and all looks well.....i'll check again