Hunting Idle, No Boost

[rimbimbambo]

I was pulling off the highway this morning and noticed a little jerk when I was breaking. As I put the clutch in, the idle started hunting between 1000 and 2000 rpms.

Thought it was a little weird, but couldn't really stop, so I turned my left turn after the light and my boost completely cut out. I can hear the turbos spooling and I can bring the negative pressure to neutral, but I can't get anything past that. Thought it might be a hose that had come loose or the wastegate got stuck open, but I couldn't see anything obvious when I looked under the hood before I had to go into work... Am I on the right track?

A little bit of history - Failed aircare BADLY (I doubled everything) and I've noticed it's been running rich. Also seems to nearly stall when I put the clutch in to stop. I checked the compression last year, nothing was under 150... Had trouble with leaky injectors and I have a hunch my mafs are on their way out. Also noticed that unplugging the coil packs on #2 and #5 don't effect the idle at all. I took out a loan last week to prepare for getting all this stuff fixed so I have some Yellowjackets in the mail, got the oil changed, new fuel filter, and have been researching getting new injectors (although it looks like 555cc tomei ones are cheaper injector per injector, but I'd have to upgrade the pump and ECU, which is gonna put me almost 3000$ in the hole). Anyways I'm thinking of getting a tomei ECU and a set of used stock injectors since the difference in overall cost is in the thousands and then I don't need the mafs. This was all right before the idle/boost issue on the way to work.

I guess the first thing is getting my boost back - Any ideas? Maybe just a confirmation that it's probably a boost leak/stuck wastegate? Any good tutorials on how to fix this stuff? I have to do all my work in a lit underground parking garage...

[Black BNR32]

sounds like a big leak between the turbos and throttle bodies...at least that's where i'd check first. i assume you're a/f ratios are rich at idle?

you can try pressure testing the intake system

[gtrjon]

sounds to me like you poped a charge pipe. check all your intercooler piping everwhere. check all your couplers and make sure they are tight.

[DarkCaporaL]

+1 on checking intercooler piping. You will have to remove the front bumper, since that's where it pops off 90% of the time and you can't see it by just opening the hood.

[rimbimbambo]

Alllright - Found the leak - was a blown intake gasket - Fixed... The idle is fixed, everything back to normal and sounds like a healthy idle...

Took it out on the road for a test drive - No boost.

Goes from negative boost to atmospheric pressure, but will not go any higher...

Again - Thinking it's a stuck waste gate or BOV... Fearing blown turbos, but I don't think it would even boost out of negative pressure if that was the case... Also I would have assumed something a little more dramatic considering all I did was get off the highway when it started.

[gtrjon]

well if it makes you feel any better i really doubt that its blown turbos. That would be really weird for them both to die completly and have 0 boost. If you want to make sure take off your catylitc converter. if your turbos are blown there will most likely be pieces of the wheels stuck in the cat. (being ceramic wheeled turbos and all. assuming its a r32) did you check all of your ic piping? all the couplers and charge pipes?

[rimbimbambo]

Checked for leaks... It seems to idle perfectly and it doesn't stutter when you're stomping on the gas - Doesn't seem to be running rich (or at least not nearly as rich as it was before). The IC piping was fine, didn't notice any leaks around the BOV's. I brought it to a shop and they said if it was the wastegates, then I'd have to buy new turbos. :-/ Not really stoked on that idea.

[gtrjon]

I don't thiink you would have to buy new turbos..... That doesn't make any sense to me at all. If you want to take it to a shop go to allan in new west. Evolution automotive! My gtr is there right now being built and he personally is rebuilding his gtr. He does a lot of jdm and knows his stuff. Plus he does work for cheap! Pm me if you want his contact info.

[Black BNR32]

you'll need to check for leaks on the exhaust side too, and make sure the lines to your wg and bov are hooked up

[DarkCaporaL]

Finding boost leaks is awesome. Pressure test the system you'll know right away where it's leaking.

[Terrh]

I don't want to be the negative guy here but it really sounds to me like you lost an exhaust wheel.

are you able to see individual maf voltages with anything in your car? if you are and they start to read dramatically different as you increase throttle, it's a bad turbo.

if you go WOT does the car run smoothly all the way up the RPM's?

Does it smoke at all now?


The only other option is a HUGE intake leak, and with that, generally the car will stall as soon as you give it enough throttle to move, because the turbos will flow a lot of metered air into the atmosphere, which will dump gas into the engine that doesn't have the corresponding air to burn it with.

[nelsonmxmarc]

sounds to me like you lost an exhaust wheel.

Yup

Happened to me. Will NEVER see more than 0 (atmos). If your shaft has remained relatively well balanced, it won't make a notable noise, your only obvious symptom will be not reaching boost. A large leak would not likely cause this. Generally you'll see it creep past 0 then flutter/pop as it struggles to compensate for the extra air, but in this case, if you've explained it properly, then it's most certainly a failed turbo, or two.

[gtrjon]

exactly check your cat for pieces of the wheels!!!!

[SkyLizzle]

I had the exact same issue on my 92 gtr, its your exhaust wheel.....check your intake piping for oil.

[mikedkchow]

did you ever figure out the problem currently having the exact same problem with my rb20