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85zxt

No power according to the smog shop operator

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Just returned from the smog shop. The operator said he had to abort the test - because the Z had no power - I assume this was under load. Hmmm?  - The owner is also a friend of mine. His is a test only shop.  To my knowledge he is not a mechanic but just a smog test guy. I say this because he had very little explanation as to what may be my issue. Having just driven about 5 miles to his shop I can attest that the car seems to have plenty of power. The car is an 85T 5 spd GLL.  The engine is an 88W Turbo. I installed the engine a number of years ago and due to  Z31 gremlins that I seemed to have sorted out is now running pretty well.  Apparently not as well as I thought. A few years back I pulled a the driver side head and replaced some lifters so I can say for sure it is a turbo engine having seen the piston tops. My compression is not astounding - 144 - 148. I blow no smoke or water vapor. I have a cm 3" turbo back - which has had very few miles on it. At one point I was blowing a lot of black smoke - It has a Magnaflow Hi Flow Cat - California spec. I just wonder if the cat could have gotten clogged. I can see through the large holes but I know nothing about a plugged cat. I assume a muffler shop would be able to tell.  If that is not the issue -  Could I have misaligned the timing belt a notch?  Would this be enough to  cause a lack of power under load. It is timed to 15degrees and it is steady at that mark.  I guess I will drive over to the muffler shop. Any suggestions would be appreciated. The engine is stock with the exception of having the turbo remanned to T3/T4 spec. Injectors are top feed original to the car and seem to be working fine and most everything sensors etc. TPS IAA and  many other items have been replaced. It also has a manual boost controller which is set to minimum. 

Edited by 85zxt

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It's probably a code that his machine shows related to something like throttle opening, or RPM.  Try to find a smog test reference.

 

Did a Google and found this - http://smogcheck.ca.gov/pdf/Smog_Check_Manual_ENG_2013.pdf

 

with the page shown.   Could be that his equipment actually lost power, not the car.  Worth a follow-up.  He should have been able to tell you what the code meant but many people today are just trained to a minimum level.  Just do what the computer says.

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Since he can't plug his odb probe into the Z, he probably tried to use the hall sensor on your spark plug wires (or some other stupid place) and didn't get a proper rpm signal...

 

I'm guessing this was a stationary test without using the dyno?

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He ran it on the dyno GE - I just took it for a little test ride and it is pretty slow getting out of the gate from a stop. Makes it a bit difficult to get out of someone's way who is coming up on u  a bit fast. Once it gets rolling it is just fine. The turbo shouldn't be causing this I'm sure. Wonder if I have enough of a small vac leak to cause this but not be obvious at idle etc.  I am having a bit of trouble getting the idle down to 7.  It idles  at 8-9  and coming to a stop  is staying up  at 12 a  bit and then drops down to idle about 8. 

Edited by 85zxt

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Yes - I have sprayed starting fluid in around the intake and turbo and no idle change - no smoke test.  Done this quite a few times and just the other day again.  I'm just wondering about the cat but exhaust out the muffler seems free flowing at idle. But I assume when pressure builds up - oh hell what do I know - just guessing at shit anymore.  Being in California it is difficult to just go for a drive and fool with an unlicensed car in broad daylight. I have a "moving" permit that I keep with me just in case.  Of course it is like a one time only thing to take the car to the shop or whatever and not really for joy riding or testing purposes - so I have to be pretty careful - PITA.  I am going to remove the cat and see what happens maybe today or go over to the muffler shop- wonder if they can just look at the cat and tell me anything ?  

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Here is a test you should all do. Go out to your running engine and spray some starter fluid into the air cleaner and see if your RPM rises. I've always wondered why adding starter fluid to the intake air will cause a rise in RPM. Increasing throttle opening is about the only thing that has a first order effect on RPM. Or an engine is stumbling at idle due to a lean condition might "Smooth out" by artifical richening with spray.

 

In my experience nothing happens. At least with carburated engines. Maybe MAF's or O2 sensors or something get a changing signal that gets the ECU reacting by increasing RPM on "modern" engines, but I have never found a vacuum leak with starter fluid spray...

 

Just a warning to not be dependent on "common" diagnostic techniques....

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Here is a test you should all do. Go out to your running engine and spray some starter fluid into the air cleaner and see if your RPM rises. I've always wondered why adding starter fluid to the intake air will cause a rise in RPM. Increasing throttle opening is about the only thing that has a first order effect on RPM. Or an engine is stumbling at idle due to a lean condition might "Smooth out" by artifical richening with spray.

 

In my experience nothing happens. At least with carburated engines. Maybe MAF's or O2 sensors or something get a changing signal that gets the ECU reacting by increasing RPM on "modern" engines, but I have never found a vacuum leak with starter fluid spray...

 

Just a warning to not be dependent on "common" diagnostic techniques....

I have done that in the past as well - sprayed some into the K & N and it made it stumble.  Mostly checking for vacuum leaks around the upper lower intake manifold. Got a rise in rpm once retorqued everything - went away. Just came back from another broad daylight "stealth" mission - She has been running like a raped ape all morning - I think I have blow out the carbon a little - tach and speedo back on line - think I hit the rev limiter a couple times this am or blew out the cat a bit -  didn't have a problem - boost is kicking in at 3k and she's ripping. really well now. Bad thing about not being able to "legally" get it out on the road and opening her up. Feels good to have her running pretty good. So maybe we might have a little better luck at the smog shop. Gonna try another friends shop that is allowed to work on cars as well as test. Here's hoping! 

Edited by 85zxt

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As an update : I finally got her to smog using a Calif.  88Turbo ecu and Fed spec mafs. In California of all place. It ran pretty rich and just barely passed the Hydrocarbons but it passed!  Thank God, Now I'm tweaking and tuning her but she is still a bit sluggish off the line - but once moving she gets with it quite well. I'm thinking my T3/T4 turbo upgrade might be a bit much for a pretty stock engine (88W turbo)  I have a 3" turbo back CM exhaust, KnN filter and a Walbro 155 fpump for mods.. Anyway, she is good for 2 years and I'm happy to have her back running around a bit. I'm not runnng the 88T ecu any longer and working with the stock ecu's I have about 4 84 and 85T ecu's. The stupid part is the 85Turbo spec remanned ecu i bought from Rock Auto - I think - quite some time back - $400 - doesn't work as well as the originals. Oh well, I'm sure there are some wiring gremlins to sort out still but she's back. I'll figure it out eventually now that I can legally test drive it.  Thanks for the replies all. 

Edited by 85zxt

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