Boost Problem Pt. 2 -- It *won't* boost more than 2psi after I shift. (please help)
 

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/i-have-odd-intermittent-boost-problem-mhmm-335315/ -- That was the 1st part. I turned the intermittent boost problem into one that I can replicate each and everytime.

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-If I *start* to boost before 4500RPM (I can boost ~10psi all the way to redline, but can't get more than 2psi in the next gear if I do)

-If I boost at low rpms (~2000rpm) to any rpm before 4,500 rpm, and shift, the
next gear is able to boost fine.

-If I rev the motor to past 4,500rpm, and then start to boost, I will get no more than 2psi.
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I have checked all the one-way check valves (not with a handheld vaccum pump, though), and I replaced one of the clogged ones with one from Kragen Autoparts. This did nothing. This problem is driving me nuts -- I have read through the various guides, but I have yet to figure out which solenoid/actuator is the sole cause for such a problem. Should I recheck the check valves with a handheld pump or should I start tearing down into the rats nest to test me solenoids? If it is the solenoids, which one(s) would cause such a problem? Thanks in advance.

Sounds like a hose job is in your immediate future! It'll give you the chance to check all of the solenoids, check valves, the vacuum tank, and the pressure tank. Here are the links to my hose job writeup:

http://www.rotormafia.com/96koverhaul/index.html
http://www.rotormafia.com/96koverhaul/index2.html
http://www.rotormafia.com/96koverhaul/index3.html

Sonny

I finally checked everything with a MityVac, and everything turned out okay.

I have a suspicion that it might be one of the actuators on the turbo assembly -- does anyone know how I can diagnose the actual actuators (I think there are two, pre-control and wastegate) to see if they are actually functioning correctly?

you can apply vaccum and pressure to them to see if they move all the way in and out. its pretty weird that you would only get 2psi boost though unless you have a major leak in your piping or your bov is leaking. on a side note, i was able to get 8 psi boost on my turbos when there was a 1/2 inch hold in my bov hose... do you hear anything weird when you cant get boost?

My car is rather loud with the DP and the PFS exhaust, so I really can't tell. I'm pretty sure there isn't a leak, as I get good boost in one gear. If it was a boost leak, I think boost would be similar for all gears.

Anyone?:(

When you get off the gas when there is no boost, do you hear a mooing sound from the left side of the car?

Well, I took out the turbo pre-control solenoid and the wastegate control solenoid to test it. It passed all of the tests as listed on the manual. Does anyone have any ideas?

Yes -- it's the air pump moo at ~3000rpm.

Well I am actually having the same problem. I've checked all check valves, pressure and vacuum tank, and all solenoids that still exist. Changed all hoses with new ones. The CRV and blowoff valve appear to be within specs. I am leaning towards one of the actuators as having a problem but I am not sure how to test those since I need to apply pressure to do it. All of the rods are attached also.

You need a hand pump or an air compressor. LMK if you find out your problem.

PROBLEM SOLVED!

It turned out to be the dumbest thing ever. Buried behind the air pump was a hose that had a small slit on it, which was also a bit dry. You could not tell when inspecting it while on the rats nest. The hose was the one that goes to the vaccum side of the turbo control actuator. Well, my car boosts fine now!

After checking all of the rats nest for loose hoses, all of the solenoids with an air pump and a 12v power supply, checking the actuators with a mityvac, pressure chamber, vaccum chamber, one-way check valves, hose clamps, couplers, and much more that I probably forgot, it turned out to be a measley hose.

dang that has to suck checking all that to find a lose hose! oh well at least you know everything is ok, glad to hear you fixed it.

Yeah, that was a real bummer. On the brighter note, I did learn a LOT about the seq-TT system.

Good work, man! :bigthumb: If I ever have a sequential problem, I'll be calling you! :p:

Sonny

Haha, of course! I might as well put to use the information that I gathered.=P

doyou happen to have any pics of this hose? im confused on which one it is.

http://www.scuderiaciriani.com/rx7/v...e_diagram2.jpg

is it the blue solid line or the one which has red dots in that pic?

Hey Sonny. Great write up I found it very useful. My car will some day need this work done. I found the part numbers especially useful. time to order parts

No, I don't have any pics of the hose, but the blue solid line with red dots is the one that connects to the TCA (Turbo Control Actuator) is the one that provides the boost. The lavendar one is for the vaccum. The TCA needs both vaccum and boost to operate, and operate quickly.

i currently have a problem w/ my boost pattern as it seems that i can only get 3lbs after shifting up a gear. 1st gear pulls good but as soon as i shift and get into the next gear, as son as i reach 4500+rpms i only get 3lbs. Sounds like ive got the same problem so im going to check that hose. hopefully its as easy as that and i wont have to be checking all the damn solenoids.

justin

anyone have any idea as to what the home position of the tca is on idle..
rod extended (closed) or rod retracted (open).....

Well I still have this problem, one little difference is that my transition always jumps a few times before I get full boost. I'd love some recommendations. I am leaning to either something acting flaky only when hot or a sticking actuator of some sort. I am completely unsure. Below is everything I have tried to date.

I've check all solenoids using the shop manual. They check out ok.

I have checked all actuators and they all check out according to shop manual. Also performed the KOKOKO test. (TCA was bad on the pressure side but has since been replaced with a new one.)

I also checked all of the actuators from the hose that connects to the relevant solenoids and none of them leak through their path. All new hoses last summer(applied vacuum or pressure to specs and held it there. None leaked)

I have checked both vacuum and pressure tanks.

I have checked to ensure that there are no vacuum leaks if I use the mityvac in place of the vacuum tank, so all solenoids/check valves are working. I did the same thing with the pressure tank by plugging into one of the nipples on the tank and applying pressure. It held so then I tried the other nipple and it works fine too. I also get the rush of air (in or out depending on which hose of course) if I run the car and then take off a hose after its been sitting for an hour. System does not appear to be leaking.

Both the blow off valve and charge relief valve are within specs. I've swapped them just to try it and no difference.

I've replaced all 1 inch hoses with new ones and they are very tight with new clamps.

So I sure hope someone might be able to point me in a direction that I might have missed. The only thing that seems different is that when I transition during my initial run I always get a jumpy transition before it hits full boost. Then of course once I shift its down to 2-3psi at the highest. Oh and boost is around 13psi for both primary and secondary if anyone is wondering. Don't want anyone to think I have my wastegate/pre-control switched. :)

Wish I had seen this sooner. I would have had the answer for you in a second! I had the same problem. Took me a month to find it.

Can someone sticky this one as that particular set of vac hoses are rarely mentioned in any of the troubleshooting threads/pages and it really is a simple fix.

Mine held a vaccum/pressure even when the car was off for hours. The solenoids close off at certain directions when it does not get a 12V signal, thus you are able to retain a vaccum/pressure at certain hoses. Your best bet would be to check *EVERY* hose that relates to the turbo control system. Since you get full (though not a perfect pattern) boost in one gear, I would most likely think that it is not the wastegate actuator/solenoid (but that doesn't mean that it absolutely can't be the problem).

I would check that the pressure and vaccum lines going to your TCA are on the correct nipple. Since you did check the solenoids and actuators, your problem lies in your vaccum lines. Take each hose off and see which ones are worn and need to be replaced. Also use a GOOD diagram to check all of your vaccum connections. I would reccomend printing it out. I really hope you can figure out your problem.:)

http://web.newsguy.com/geesaman/vac_...iagram_dlg.jpg

Hi, im having just the exact prob, u couldnt put a pic of where this hose is could ya? Im a bit of a noob and not quite sure where the air pump is. Cheers. I've had to live with this prob for ages now! Please post a pic up. Thnks

Yeah. I've tested from both turbo control solenoids to the TCA and couldn't get a leak in that direction either. Plus all those hoses are new. I'll probably check all those again anyway.

Walien, did you have a problem with your transition fluttering?