Safety boost issue, among other things...

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DCaff300ZX
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OK, so three days ago my TT goes into safety boost before I left work for home, and it has never returned to normal boost. One other time months ago it failed to boost for about a mile or two, then everything was back to normal until recently.
Unfortunately I have been chasing some idle issues which has consumed what little time I have to research and try to repair the issue, and since I am a total boost newbie as far as diagnosis and repairs in the turbo area all I can think to do at this moment is ask away at my NICO pals for any insight or assistance.
I will be able to look at this problem this weekend and my first step will be to get codes read, and visually inspect things such as the boost vacuum hoses and anything else I can think of or look at.
Any suggestions or thoughts on where to get started, and/or common or known issues that cause the ECU to go into safety boost?
Ask away for any further details... :yesnod


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Ziggy1621
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Pulling codes is definitely the first place to start. Also, get your hands on a boost leak tester, but I'm going to guess that pulling the ecu codes is going to give you your answer

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DCaff300ZX
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Thanks Ziggy, but a code check yesterday gave up a 55, repeatedly. I do have a "lazy" DS o2 sensor I need to replace as soon as I can, but so far it only is a problem at 30 mph/3rd gear, light pedal pressure and unless those circumstances happen it does not send a 33 code. Since I have the switched injector voltage mod done, the ECU cannot save past codes and can only read current ones from that drive which was as I said 55.

As I mentioned I am currently trying to fix a idle issue, which I may have fixed yesterday although only time will tell. I found a loose idle circuit hose (vacuum) from my PCV repairs and a broken DS boost hose clamp, plus the FICD connector was green with corrosion which were all repaired and the car idled pretty well, and ran smoother with no odd 2000 rpm surges when driving. I am thinking of resetting the idle soon to see if that helps it bottom out at 800rpm+/- more quickly, but although the repairs helped the idle issue they did not allow the car to leave safety boost.
I will be researching this boost issue today and tomorrow, any further info or ideas are definitely appreciated!

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DCaff300ZX
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UPDATE- Unfortunately, my idle is still acting up a bit with suddenly very low idle that was "bouncing" a little, and creeping up slowly until I took it around the block and "all was well" again. FPOS...
So, today (Friday) I began researching safety boost and there seem to be few possibilities- CTS and detonation sensor/circuit issues, and the possibility of no codes thrown as is the case with me. I decided to go ahead and test the CTS side of things, which after a thorough cleaning produced no changes- no codes still, and safety boost.
I will check the detonation sensor and connections tomorrow, and re-check all vacuum hoses.
Question- my understanding is that due to safety boost being an ECU-induced situation, that solving the problem should bring back normal boost immediately? No "reset" procedures or otherwise to do?

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Z-owned
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I was going to say to check the det. as that is usually what I hear causing people to go into safety boost with most then doing a the relocation till they pull the engine.

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DCaff300ZX
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Another question- I've seen two differing drawings showing the det sensor at the rear of the engine under-ish the EGR valve, and another showing it on top of the block...which is the true location?

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Ziggy1621
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It is on top of the block, in the valley between 5 & 6. You have to pull the lower plenum to get to it.

Before you do that, get your hands on a consult cable and run something like ECUtalk to test voltages, timing and ratios

RubyRed300ZX
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Image

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DCaff300ZX
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Thanks a bunch for the pics and info guys, my hope due to the way things have gone is it's the ECU side of the CTS sending a cold signal, but if not then I have some clues where to look for the det sensor.
Odd that the FSM shows the det sensor on the rear of the block under the EGR, and other threads here I have read say theirs are in different places such as the top valley as shown above, and in front by the throttle shaft housing...makes me wonder how often they have been relocated and that the owners aren't aware of it being done by a PO or their mechanic.

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Ziggy1621
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As far as I know, the above pic is the stock location

RubyRed300ZX
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I didn't post a comment with the pic above. Maybe should have mentioned that the picture above is of my Z, which I purchased new in 1992. Nobody has been into the engine that deep other than myself. So, at least for years 1990 through 1992, and 1993 convertibles, that is the stock location.

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DCaff300ZX
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UPDATE-
OK, so now everything has changed after replacing the air control unit on the idle control and cleaning the connector, and replaced the ECU CTS unit and connector.
Car idled 1000-1100, went down to about 950 maybe and went for a drive- still in safety boost. Got a CEL and assumed it was my 33 code from 30 mph/3rd gear, pulled the code and no- it's a 53, EGR! Went out again, came back checked codes again (no CEL this time) and I get a 55. Out again, make sure to try and boost and also cruise light-footed- tosses a CEL and it's 53 again. Same low throttle/low load scenario is when the EGR operates, so it is now suddenly an issue to check? And now no o2 problem??? Since the idle never went low enough I went to reset the idle- removed AAC connector and dialed the screw completely closed, car still ran so looks like I need to hunt for a vacuum leak as well. Set the idle screw to 700-ish, re-attached clip and idle is about 750-ish. Car runs well but a little sluggish, and safety boost still....GRRRRRRRRRRRRR.

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DCaff300ZX
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UPDATE-
OK, Mr. Dumbass mixed up his codes writing them down and so EGR is out (35 code), PS o2 is in (53 code). So I have gone from a 33 to 53 code, seems to indicate the sensors are OK and the connectors not so much...next time under the hood I will find and check them.
Next up is I definitely have a vacuum leak, since I can screw the idle screw shut and the car runs, and pinching the blowby hose off the air valve drops the idle a little. I checked and rechecked anything I could under the hood, no help although the car idles pretty well now and with none of the earlier problems- the idle just drops at times to around 650 RPM during the drive but usually is 700-750.
Still in safety boost, or what I assume is safety boost. My reading on the subject seems to indicate that some people get 7-ish PSI boost or some amount of boost variably, while mine is ALWAYS boosting only to just below the zero on the gauge and not really enough to affect the way the engine runs. Shutting the key off and restarting changes nothing ever, and the car is slow as hell but runs smoothly, never different since this occurred.
I'm stumped and giving up for now, and may just have to admit defeat and take it to my Z guy...or find a way to get all of the deletes done to find the vacuum leak. :confused: :facepalm: :cry:

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DCaff300ZX
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Ziggy1621 wrote: Also, get your hands on a boost leak tester
After reading up all week on all manner of boost scenarios, I am now feeling that you hit it with this comment Ziggy- it really can only be a boost leak that doesn't allow the system to pressurize, because everything else is A-1 right now except no boost and a small vacuum stumble at idle only...which fits a boost leak scenario.
So making a boost leak tester for my compressor is on deck for Friday or Saturday...wish me luck! :gapteeth:

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Awesome, keep up posted!

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DCaff300ZX
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UPDATE- So unfortunately I put things off until today, and had only about 6 hours to "play".
My home made boost leak tester worked perfectly mounted in the old intake "T" hose (I've just installed a dual intake) and at about 5 PSI I immediately found a leak in the PS middle boost tube at the joint to the turbo, tightened it as it surprisingly was accessible and went around to do the driver's side and did the same thing and pulled the bumper to check all the IC connections...about all the time I had, I could not access the accordion tubes without further dis-assembly.
Car runs better but still no boost, obviously I have more loose clamps on the other hot end of the accordion tubes as I can and did access the rest of the boost hoses to the IC's...and so I have a date again next weekend for a DEEP probe into the bowels of the beast to the turbos, and while in the car. :facepalm:
Anyone with any tricks or advise for getting the accordion tubes bared for inspection and tightening feel free to chime in! :bigthumb:

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DCaff300ZX
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NEXT UPDATE- Well, after one of the most frustrating and demanding mechanical ventures I've undertaken the engine bay piping is 100% tight. Still no boost although the engine is running better, though. Today I will boost test and inspect the front end piping/IC/recircs, and the IACV mess since these seem to be the next most logical spots.
I am beginning to think my problem, beyond the obvious need for tightening hoses and repair vacuum issues, is something more like a stuck wastegate or bad wastegate actuation as I DO get turbo action at least what's shown by the boost gauge, it just never goes into positive pressure by the gauge and performance verifies the lack of boost.
Once I can say the piping is 100% tight/inspected front to back I can't go that direction, however, so I must continue to work the boost repair list slowly, apparently. But this whole thing is driving me nuts, not to mention eating up ALL of my available extra time... :whip

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DCaff300ZX
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SUNDAY UPDATE- OK, so the slavish sado-masochist that I am was not able to let the beaten dog lie, and now the entire intake tract is righty-tighty, no-loosee.
ALL clamps are tight and hoses inspected/tested or replaced (vacuum), and yeah they needed it- ALL were at least 5-6 complete turns loose if not more, and two clamps were broken and replaced- both were new ones BTW from Z1 with my new intake boost hoses, replaced by the stockers that are still in good shape which somehow is better than brand new ones.
LOVE crappy fasteners! Unfortunately I have yet to find a vendor who doesn't send crappy fasteners, this includes ALL vendors I've ever used without exception- just CRAP.
Car runs great...for an NA.
No boost past 0 on the dash boost gauge, the gauge is active up to that point at ALL times, but the engine does not boost-accelerate even a little.

So I've been following the Thumper's boost leak guide with all of the excellent info which has led me to many things I've found that needed to be fixed, but no solution (so far) to my problem.
I have from the beginning felt that my problem is not the normal in that it seems like boost is going into the engine cavity somehow and not the intake tract, bolstered by the beginning of this all where my DS PCV vent tube on the valve cover was being pushed out by pressure from inside the engine- I assumed this was a faulty PCV valve and replaced all of them and the hoses. Then today when I ran my final boost test where I can find NO leaks worthy of mention on the engine, or anywhere else on the car, I can hear the compressor air tank filling what sounds like a tire rather than "PSSSSSSSSSsssss-ing" into atmosphere of a typical boost leak- think of a hose air nozzle you can press the lever and hear the hiss, then when you put it on the tire and fill it makes a different, "auditorium" sound as it fills the enclosed tire. Instead of 20-25 seconds to fill the boost hoses/intake to 5 PSI, it takes about 40 seconds for the compressor tank at 5 PSI to "fill" the engine with 5 PSI and stop filling- with NO external boost leaks other than a few small/slow bubbles here and there that another quick tightening made go away. Not enough leak anywhere to cause ANY problem.
SO...WTF???
The next suspects are the Turbos themselves (I assume the wastegates since my soapy water on both turbo exteriors showed no boost leaks), the IACV mess I worked on fixing the erratic idle, and the recirc valves. Since the boost test and soapy water dousing the turbos revealed zero bubbles and the auditorium filling sound was coming from the recirc area, but the recircs hold suction testing at the vacuum hoses and revealed no bubbles on the outside boost test, my brother and I are stuck on what the problem could be.
If the recircs are responsible it seems that if boost is made (active dash boost gauge) it just never makes it to the intake, constantly recirculated...or if it's stuck wastegates, then any boost made is then wasted but into (I assume?) the exhaust. But, how does either make/explain the auditorium/crankcase filling sound we are hearing?
Does any of this even make any sense? :crazy:
I've had enough of this for now...hopefully some of you guys who know a lot more than me and have played with your turbos for a long time can help me out moving forward...God, I hope! :ohno:

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I just had an idea reading that. Are you sure the stock boost gauge isn't shot? or the sending unit? You may have boost and it not reading it?

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DCaff300ZX
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The boost gauge is active at all times which seems to indicate that there is boost created somewhere, but my research reading suggests that one turbo could be seized while the other can boost which could boost the system slightly. As I got the intake tract tightened the car runs better obviously without the vacuum leaks, and seems to actually accelerate better at times as if a small amount of boost happens but normally the car is like a NA.
So I am forced to now physically test each component to ensure they are functioning.
I have had a suspicion about the DS wastegate maybe being stuck which could perhaps explain the filling sound (back into the exhaust?) when boost testing, but without testing them I am just guessing.
I found some tests for the turbos themselves and wastegates/recircs, just gotta find the time for more deep digging/testing.

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DCaff300ZX
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Quick question as I think about diving back in, thinking about concentrating on the wastegates first since I have always had them on my mind, if for no particular reason.

Can I use the long hose from the air tube to actuate the wategates, or do I have to go down low to the short piece off the "t"?
Also, I've seen hints that the actuators on the wastegates can be moved manually, true? I tried moving the DS one lightly as I will never force anything, should I try harder?

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DCaff300ZX
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SMALL UPDATE- Spent some time checking the spark plugs and finalizing some things from the idle repairs, and found time to test the wastegates.
Both open and close consistently with about 6psi of air input/release, so now I guess I'm down to seized turbo or (and no test I can find) a stuck recirc.
So it's looking more and more likely I'm at that dreaded turbo replacement time, with no warning smokeshow and without having had the chance to save up for them...

Nicko500
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Couldn't be stuck Wastegate solenoid ?

If solenoid don't open, pressure comes into Wastegate and make it open @ 7psi

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DCaff300ZX
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Thanks for your response.

In between the last post from me and yours now, I have had my engine totally gone over and all repairs made to everything of issue including new turbos and a host of other things- check my build thread for those details.

The problem actually was a seized turbo (ds), and the other turbo would push boost to 0 before the system dumps boost for balance reasons- I knew this previously, but there aren't many ways to test the turbo for operation and so that was never fully realized until disassembly.

Currently the car runs quite nicely with the 530bb turbos and upgrades!


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