Stevey629

Just yesterday, I noticed that my boost just decided to go way down. I always have a clean 10-8-10 boost pattern, then got off the gas, then got back on and wow. No power, and the 5-3-6 boost pattern. Vacuum is as it always is at idle, and the car doesn't stumble, sputter or anything. Ideas? Im assuming its either the cross over pipe or any of the intercooler hoses and couplers, but I checked them and none seem to be leaking. I've replaced all the couplers, and the pipes seem fine. However, maybe it is time for a replacement of the stock hoses themselves.

Would a leaky BOV or CRV cause this pattern? Perhaps a clogged up primary turbo intake? Im assuming a leaky vacuum line wouldn't cause this much of a boost loss.

Occassionally I get a 5-3-7 pattern, but I have not been pushing it far enough to produce a consistent secondary turbo reading. I feel scared to get on it hard enough to get the second turbo to kick in just in case I might be further damaging something. So I've been holding off on the second turbo.

Speed of light

iTrader: (8)

One possibility is an exhaust leak. I once had a cover come lose on the exh manifold and it produced exactly this type of result. It wasn't obvious and it took some time to find the problem but it was an easy fix. I think I wrote another thread about it a year or so ago.

CantGoStraight

check the hose on the blow off valve where it connects to the y-pipe and see if it's really hard/brittle and may hve split/cracked. Low boost on the primary will delay boost when the secondary kicks in and with the amount your missing I would suspect a couper or poor connection at the coupler (perhaps not noticable) Take them of turn them inside out looking for cracks or splits if you damage a coupler while doing this it needed to be replaced any way.

Stevey629

about the exhaust leak, a cover came off? What was your post titled? If its a fix with basic hand tools, I'm in. Im gonna go look at the Y-pipe right now to see if I can 't figure this out. Thanks for the help, I'd appreciate any new suggestions, as now my boost pattern is 4-3-5. Its getting worse. I have to drive it though, since its my everyday driver. So it needs fixing asap.

quicksilver_rx7

Get the first turbo boosting properly first. Then worry about the second one. Do a search with the keywords Boost Leak or Boost Problem. That should answer a lot of your questions.

Here is one article that I found from searching a long time ago.

Joe

Larz

A check valve or faulty pressure chamber can limit boost. Not sure if it would do exactly that, as I had a "sticky" check valve and was still able to boost to full when it didn't stick. Right now I'm battling the same problem over again. Hope it's the turbo solenoid I just ordered or I'm out of ideas.

Kento

I would check the vacuum hose from the primary turbo housing to the turbo pre-control valve (with the pill in it). Sounds like it's leaking, causing the pre-control door to remain open, which vents off too much boost pressure to the secondary.

Also check the hose to the CRV/CCV. That could also be leaking, causing the same symptom.

An exhaust leak will not affect boost.

The pressure tank only affects secondary turbo actuation.

dgeesaman

iTrader: (7)

But then the secondary should be full boost in that case. I suppose he's not really tested the secondary, but in 4th or 5th it's so very easy to throttle into full boost.

I agree with the OPs first notion - a boost leak. In any case, the simple hand tools/quick solution that you should always check out first is the boost leak. Check the hoses leading to each BOV, check the coupler on each end of the crossover pipe (remember, remove the rubber piece and inspect it thoroughly off of the car), and check the elbow at the bottom of the intercooler, removing the metal shield as required.

Exhaust leaks are pretty far down the list as far as likelihood.

Stevey629

thanks so much for the suggestions. Is there any way to check the CRV besides looking at the thing after removal? I have an aftermarket BOV, but have left the stock CRV in place. And, if someone could point me in the direction of the primary turbo housing vacuum line that leads to the pre control valve with the pill in it, it'd help too. And of course how to fix it, or what to look for. I still have yet to thoroughly inspect all boost pipes and couplers. I will take them off individually and inspect them in the morning. Again, if someone has a simple rundown or checklist and a simple "how to" for each test, I'd sincerely appreciate the effort. Or perhaps a thread you know of that effectively resolves a boost issue like mine. Thanks again.

quicksilver_rx7

Did you read anything in the link I posted? Sounds like you really need to do a lot more reading on the turbo system.

Joe

Kento

That's true, although if the pre-control door was slow to respond and remained open, it would continue to vent off exhaust energy to the primary once he got past the transition point, causing a loss of boost until enough exhaust energy was built up to get full boost on the secondary. It originally sounded like he wasn't running it very far past the transition point, thus not building up enough boost.

But I see the real problem here:

From his first post:
And then from his last post:

quicksilver_rx7

I saw that too, especially after post #9

Joe

Stevey629

ok. Finally got around to taking each individual pipe off, and after thorough inspection, I found that the "S" pipe that goes TO the intercooler had a 3 inch long split right down the middle of it. wasn't apparent by just looking, I actually had to flex the pipe, and have it off the car. Thanks for all the help, sorry to cause such a stir with this post. But it was as most of you guessed, me included, just needed the time to take her apart. Thanks again! I purchased the 3 pc. greddy kit to replace it all, and its boosting like a champ now. Now for the oil leak and stumbly idle....to be continued.