Still have no boost but been working on trying to get to the bottom of the issue before taking it to PowerZed or LA Autos.

 

Car has had a full service and "supposedly" a boost test that came up negative. However I have been speaking to various people and hooked the car to Datascan and noticed some anomalies..

 

 

The Duty Cycle is blank and the A/F Ration stays permanently on lean even when I take it out for a drive. I thought it was supposed to oscillate on lea and rich?

 

Checked the TPS and the connection had green crud on it, cleaned it as much as I can but not difference. There is also no difference if I disconnect while engine is running.

 

No error codes being reported.

 

Still no smoke either, which after 18 months of this, if it was a seized turbo, I would have thought would have happened by now.

 

Any ideas before I save up to take it to an expert?

How do you know it has no boost? Have you hooked up a gauge to it?

Who did the boost leak tests and what does 'negative' equate to? No system pressure at all? Partial pressure?

 

Gas test is the best way to check for leaks in the system.

 

You'd still get some boost if you had a seized turbo, it would just be a lot less. Are you getting any boost at all?

Edited August 28, 20178 yr by Funkysi

Take it to lee mate the issue it's most probably something small

So as is often the case with the 300zx looking too technical too soon is throwing you off track, so lets assume you are getting NO boost, nothings past the 0 on the gauge, or maybe a very, very slight bit, if you had a boost leak that big the engine would run very poorly, there is nothing on any of those read outs that can effect the boost to that amount ( no boost ) although the duty cycle been off is odd.

 

So your should be looking for a basic mechanical issue and that will be a seized turbo, and a seized turbo almost never leaks oil so no smoke ! because the oil feed is compromised which is why is seized in the first place.

 

Simple check, disconnect the afm, slacken both large boost pipes into the throttles but do not remove, now start engine, remove one pipe completely. pull a latex glove over the pipe coming from the turbo / inter cooler, ( not the throttle ) now raise the revs and if the turbo is working the glove will inflate, if not its not boosting, do both sides and at a guess you will have the most common failed passenger turbo, the boost the other turbo is creating is simply lost straight past the seized one and down the exhaust.

 

 

Jeff

Were your O2 sensors fluctuating when increasing RPM above say, 2,000.RPM.?

Both should be switching between, say.. 15 and 90 approximately.

This may seem silly but when I bought my car I reported no boost in the gauge. Recently I checked all the vacuum hoses everywhere and found that the small vacuum pipe to the clock boost gauge was completely disconnected. So the boost was showing ambient always.

Were your O2 sensors fluctuating when increasing RPM above say, 2,000.RPM.?

Both should be switching between, say.. 15 and 90 approximately.

 

Either way not going to effect the lack of boost, noticed the egr is showing as active too which is odd, think there maybe be some communication issues.

 

This may seem silly but when I bought my car I reported no boost in the gauge. Recently I checked all the vacuum hoses everywhere and found that the small vacuum pipe to the clock boost gauge was completely disconnected. So the boost was showing ambient always.

 

Yes that can happen but the lack of boost is very noticeable, assuming of course there is no actual boost, sure the OP knows the difference though.

 

Jeff

Edited August 28, 20178 yr by JeffTT

Either way not going to effect the lack of boost, noticed the egr is showing as active too which is odd, thing there maybe be some communication issues.

 

Jeff

 

Agreed Jeff, I just thought it might be relevant to the OP's reference to the continuous lean reading.

Agreed Jeff, I just thought it might be relevant to the OP's reference to the continuous lean reading.

 

Yeh good point.

 

 

Jeff

Who did the boost leak tests and what does 'negative' equate to? No system pressure at all? Partial pressure?

 

Gas test is the best way to check for leaks in the system.

 

You'd still get some boost if you had a seized turbo, it would just be a lot less. Are you getting any boost at all?

 

Sorry Si, the mechanic said that when he did the test it held pressure. When I drive and put my foot down, the gauge goes to 0 and then stops. You can also feel some resistance as though it wants to accelerate but there's nothing there.

How do you know it has no boost? Have you hooked up a gauge to it?

 

Only going off the stock boost gauge but there is no power there...

Were your O2 sensors fluctuating when increasing RPM above say, 2,000.RPM.?

Both should be switching between, say.. 15 and 90 approximately.

 

They fluctuate but not by much. From what Jeff told me on my last Zed, I think I need to change them but want to get the boost sorted first (unless this may be causing it)

This may seem silly but when I bought my car I reported no boost in the gauge. Recently I checked all the vacuum hoses everywhere and found that the small vacuum pipe to the clock boost gauge was completely disconnected. So the boost was showing ambient always.

 

Is this the little black box by the Brake Master cylinder, attached to the inner wing? If so the pipe had split where it connects, I have replaced the pipe.

So as is often the case with the 300zx looking too technical too soon is throwing you off track, so lets assume you are getting NO boost, nothings past the 0 on the gauge, or maybe a very, very slight bit, if you had a boost leak that big the engine would run very poorly, there is nothing on any of those read outs that can effect the boost to that amount ( no boost ) although the duty cycle been off is odd.

 

So your should be looking for a basic mechanical issue and that will be a seized turbo, and a seized turbo almost never leaks oil so no smoke ! because the oil feed is compromised which is why is seized in the first place.

 

Simple check, disconnect the afm, slacken both large boost pipes into the throttles but do not remove, now start engine, remove one pipe completely. pull a latex glove over the pipe coming from the turbo / inter cooler, ( not the throttle ) now raise the revs and if the turbo is working the glove will inflate, if not its not boosting, do both sides and at a guess you will have the most common failed passenger turbo, the boost the other turbo is creating is simply lost straight past the seized one and down the exhaust.

 

 

Jeff

 

Thanks Jeff, I will try this tonight and see what happens...

Well I ran the test Jeff suggested and got nothing from the drivers side, passenger side was blowing.

 

Just my luck.... looks like I will be saving some pennies to get a turbo swap...

Well I ran the test Jeff suggested and got nothing from the drivers side, passenger side was blowing.

 

Just my luck.... looks like I will be saving some pennies to get a turbo swap...

 

Whoever you get to do the work matey don't just fit another turbo without first finding out why it seized..blocked oil feed ect:wink: