Problem/Description:
Most of the time I have a great 11-8-11 boost pattern with no creep.

However, sometimes (I'd say 1 out of 6) my boost pattern is 11-8-(random number). The boost gauge needle will actually jump around during secondary boost..... it's not a steady boost level. I can feel the engine struggle and by the sound of the exhaust, it seems like its not getting enough air.

It does this in all gears while going through the transition (1st through 4th, haven't tested 5th), but seems to happen more often in 1st and 2nd gear.

Mods/Info:
* 18.5k on rebuild
* New turbos at rebuild time
* M2 Stage 3 ECU
* Downpipe
* High-Flow Cat
* Greddy Ti Exhaust
* Removed Airpump with pulley kit
* AST Delete
* Halman MBC
* Large SMIC.
* Custom hardpipes
* Double-Throttle Removal

Things I've Checked/Done:
* Checked all vacuum lines. They are silicone and attached with zip-ties.
* Checked all IC piping and other parts of the intake system. No leaks.
* I can build 4+ psi in neutral @ WOT.
* TPS is adjusted perfect.
* Vacuum Chamber holds vacuum
* Pressure Chamber holds pressure.

Troubleshooting plans:
Go through this doc : http://www.fd3s.net/boost_problems.html

My friend has EVERY single sequential component off a 94 RX-7 when it had less than 17k miles. It might be easier to just replace the suspected component than go through all the troubleshooting if one of you has a a good idea of what component could be faulty. What do some of you pros suggest I check/replace?

 

I know some one with the same problem. I'll be interested to see what other people say.

 

^ Woohoo, someone with the same problem!

I am probably going to replace these components anyways, since they are so easy:
I. Wastegate Control
J. Turbo Precontrol

If you are going to suggest a component to replace, please specify its LETTER and NAME.

 

Check this thread:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/turbo-problem-first-second-gear-only-tho-677318/

It has a similar problem and lists some troubleshooting ideas. I would start with checking the things listed in that thread first.

 

I'll check my Turbo Control Actuator and Turbo Control Solenoid in a day or two.

Perhaps swap some solenoids around as a test.

Thanks Mahjik!

 

OK, after some investigating this evening... I believe my Turbo Control Solenoid is bad! Looks like I am going to be pulling the UIM this weekend.

Results:
I CAN freely suck or blow into the red pressure line where the black arrow is. After running the car to WOT in neutral and turning the car off... when I disconnect the pressure line, no pressure was released.

I CANNOT suck or blow into the blue vacuum line going out of the chamber. After running the car to WOT in neutral and turning the car off... when I disconnect the vacuum line, there was a vacuum in the chamber and I could hear it sucking in air.

According to this troubleshooting guide. Nothing should flow through A without voltage applied.

 

Okay, it turns out it was just one bad hose. I replaced the bad hose and other hose that looked like it could go out soon on the solenoids.

The secondary turbo is now really reliable and strong....however.... my idle is now too high. It settles down @ ~1200 rpms and rarely goes lower.

I checked all the vacuum lines to the UIM with it still on and couldn't find anything... so I removed it again.... then put it back on after double checking all the vacuum lines. I checked the IAC and AWS solenoids and the resistance is within specs. Unplugging either of them with the car running doesn't appear to do anything. The butterfly valves are fully closed as well.




Any ideas?!

 

All fixed! Turns out my primary butterfly valve was open some.

I removed the throttle body and adjusted all the little settings per the shop manual. My car idles better than ever now!