Perfect 10-8-10 during both my morning commute and lunch run today.

On the way home, (98-F outside) and the engine temp already at 180-F, I went WOT in 3rd, and just got 10-8-5 all the way to 7500 RPM.

I let off to see if I needed to build some vaccuum, but still 10-8-5 all the way to 7500 RPM.

I let her cool, and checked for loose or broken vaccuum lines, connectors, or pipes. NOTHING.

I pulled the UIM, and looked around for anything loose, chaffed, pinched, etc. and found nothing, and all the check-valves test good. I tested all the chambers. GOOD.

Will a bad Turbo Control solenoid on the ACV under the UIM, produce this symptom ? And would it happen all of sudden ? I've heard it can be killed by heat. I measured the resistance and it was 33.4 ohms, and when under hot water, it changed to 34.2 ohms after 5-minutes.

Thanks,
:-) neil

PS: ALL solenoids, vaccuum lines, check valves changed out less than 5K miles ago, all though I do track days (already have done three of them since January).

 

I replaced the Turbo Control Solenoid, and did the CRV test (disconnect from airbox, and listen for rushing AIR above 4500RPM--to-redline, which is bad). CRV did not produce any rushing air above 4500RPM-to-redline.

Now I get 10-8-0.

What could cause a flat zero boost on the secondary turbo ?

Note, I didn't find any loose/broken vaccuum hoses, bad check valves, or bad solenoids.

Thanks,
:-) neil

 

Check the UKL near the HUN alonside the RTJ. If it reads GHE try doing a SHX.

For the non Americans that prefer English..........

Normal soleniod resistance is around the 40 Ohm area. To be getting 32-34 Ohms is quite normal & not an issue. If the reading started to creep more than 20% above the other soleniods, then you may want to try some preventative maintainence & swap it over before it goes open-circuit.

If your boost drops to zero after the change-over then chances are the 1st turbo is dumping into the 2nd turbo & not into the engine. This may be due to the 2nd turbo actuator failing to open the gate yet the charge control gate opening on the intake side allowing the alll boost to be sucked away.

Check the pressure storage tank after driving or better still, T-piece into the tank with a boost gauge & ensure its storing boost when the 2nd turbo change over occurs. If you are not storing boost, go looking why. 1-way valves or cracked hoses on the hot actuator underneath are common places to start from.

As the 2nd turbo actuator uses pressure + vacum to open, do the same with the vacum storage circuit. T-piece into the vacum storage tank & watch the gauge. It should maintain vacum when you are on boost. If not, then go looking places like 1-way valves.

REgards

 

You can continue inspecting, or run the KOKO test. http://www.fd3s.net/boost_test.html

You did check the CRV, which is one of the only leak paths. You might as well do the same for the ABV, just to be thorough.

I'm pretty sure that if your CCV is misbehaving (not opening), you'd still get primary boost all the way to redline, which would be a few psi above 4500. If one of the TCA lines was misbehaving, you'd still have primary boost and it would at least be powered by the vacuum or pressure side, since both don't usually fail. (But it's possible, especially if it develops a big internal leak).

I'm willing to bet the KOKO and ABV tests will turn up something.

Dave

 

I forgot to plug-in the electrical connector to the turbo-control solenoid valve (adjacent to the ACV).

Now my boost pattern is 10-8-5, and then immediately falls down to zero boost in less than 1-second.

Is there another name for the "2nd turbo actuator" ? Where is it located ? Is it also known as "turbo control actuator" ?

TIA,
:-) neil

 

On the KOKO test, am I reading it correctly that I watch the charge control actuator and the turbo control actuator work each time (6 KOKO), WITH the vacuum hose REMOVED from the charge relief actuator/valve ?

:-) neil

 

When running the KOKO test everything should be connected like normal. The actuators will move in when the key is on, and out when the key is off (or vice-versa, I forget). If you have a little trouble getting boost in neutral, just take the car for a short drive and boost once - that will charge the pressure tank also.

Dave

 

Dave, I did the KOKO test, and I also did a vacuum test on the turbo control actuator.

Low and behold, the E-clip was missing AND the linkage was not engaged.

Before I put everything back, is it OK to use a USED E-clip, or should I wait and get a NEW one ?

More importantly, is one of the symptoms of an immediate loss of secondary boost due to a missing E-clip and the door NOT being hooked up ?

I'm heading to the track (Roebling Road) Friday, and just want to make sure . . .

TIA,
:-) neil

 

That all makes sense. I thought about that possibility, but I wasn't sure what that would do to a boost pattern.

Anyway, whatever e-clip you can find is fine. I've used ones from the hardware store.

Dave

 

Any issue with wrapping safety wire around the groove and then the rod ?

:-) neil

https://www.rx7club.com/attachment.p...hmentid=119277

 

That'll work in a pinch. BTW, Ray at Malloy should have those E-clips in stock, and they're MAYBE a buck each. I got like 10 of them or something when I found out how cheap they were .

As I like to say, "if that's not the problem, that sure isn't helpin' anything".

Dale