Lost the boost

I just recently bought a modified 93 vr-4 and had the battery die. Replaced the battery and now boost pressure only gets up to 7 and 8 psi. When pressure starts getting near a positive it feels like the engine gets less efficient and looses power. At any cruising speed 30+ (more drastic 60+) it sometimes gets so bad (usually when EGT gets warm) it starts to choke and can't maintain speed on uphill or 5th 80+ on flats. A/F show's it's not running lean but had to tell if it's to rich.

I originally thought it was my EVC IV that needed to be re-programmed but no matter were I turned that thing up and down to it didn't change boost pressures. From what I've read usually over boosting is a problem when these go bad or don’t work.

Also searched for leaks from vacuum hoses and turbo --> intake man without any luck. Have vacuum on all the hoses I checked and filters looked clean.

Convinced it was a fuel map or some problem with the ECU or O2 sensor I scheduled an appointment with extreme motor sports for a diag and dyno tune. And hoping they'll show me how to tune up the SAFC so I can do it from time to time.

I've heard you can reset the ECU and wanted to know if that had to be reprogrammed... The battery was disconnected for at least 10 minutes since that was the moment that seemed to be the turning point of this mess.

Any idea's of other possible problems causing a lack in boost and poor performace would be very much appreciated


17g TTs
FMIC
Larger injectors
Oversized fuel pump
K&N air filter
MAF
SAFC
EVC IV

For some of the mods that might have an impact with this problem.

http://i51.photobucket.com/albums/f390/CaptCrunchy/3000GT/GTenginecompartmentlowres.jpg

Slightly off topic but needed to ask :1zhelp:

Thuump Thuump Thuump...

Coming from back or under the car in full boost from 1st and 2nd.
When she was running right :(

I thought it may have been the tires slipping on the rims since they had just been installed and don't know if they were glued on.
Or maybe the rear letting loose, then the front catching, then rear grabbing on again ect...
I've never drivin an AWD car before other than trucks so I really dont know what it is and no one else could come up with anything. But I dont have any 3000GT friends with AWD other than WRX's

Last dyno had her in 390's at the wheels / 580's at crank @4200 if that helps at all

wish i could help but im fwd NA and dont know alot of the AWD im sure stealthee or igovert will be able to help you out..they always do.


btw..those hp numbers are very impressive seeing that you bought it with the mods

Not real sure about the boost issue. The thumpiong is probably the driveshaft carrier bearings though.

Not real sure about the boost issue.


ohh no man.... sorry to tell you, but you're fucked :p.

I'm not too sure about that boost issue either, maybe if you take it to a dealership they can run a test on the computer and maybe it'll show up. Good luck dude

The thumpiong is probably the driveshaft carrier bearings though.Is there any real way to check to see if those bearings are going bad or is that just something that is going to happen with a lot of torque?






I tried playing with the SAFC yesterday's morning and set my low throttle end maxed lean (3k-5k) and it brought the A/F from being pegged pig rich under a load to a readable rich measure... and it's no longer choking on the 3k-5k RPM ranges that I leaned up on, had to max the SAFC out lean on 3k-5k to get it down, so I'm guessing the intake sensors are reading more air than is coming in. Is there a pressure sensor (other than barmoetric pressure) for A/F ratios? Might be reading higher than is. Didn’t touch the high throttle settings but it looks to be running pegged pig rich OWT too. Just don’t want to tune that end with the narrow band A/F gauge, and will wait for the dyno.

I've been leaving the boost controller on it's lowest settings so I think they are some what stock PSI levels, and didn’t try turning it back up after it was leaned out. If the EVC IV boost controller still isn't increasing the boost, should I try using a manual boost controller to rule out the EVC IV? And if I do need to replace it what’s a good boost controller to use other than the EVC IV (I hate that POS) that can run .5 - 1.5

Well swapping in a manual boost controller would help eliminate the evc as an option, and you can get a cheap manual one for $20, but before wasting money. I'd do the free stuff

1) It sounds like you are running waste gate pressure. Try inspecting your wastegates and make sure everything is in good working order/attached/and staying shut until it should

2) Pressure test. You said you inspected the manifold and vacuum lines. Visual inspections are pretty much worthless. Yes they will usually be good enough to find a hole the size of a golfball, or a blown off intercooler pipe, but you really need to pressure test to find the leaks.


And yeah, the thump thump does sound like carrier bearings.

Thanks for the help as the problem was resolved with your solution.

Checked the pressures and even while idling we found differant vacums on the up piping, we tore out all the up pipes to find a small rip on the FMIC intake bushings. It's a black ruber POS and had to squeeze it just to see the rip. Gessing that's why I never saw it in the first place.

Replaced the POS chevey rubber hosing with a fiber composit piece, dyno'ed and A/F tuned.

Thanks again :thumbsup: