As you may have seen, my Zed failed its MOT due to excessive blue smoke at idle and under heavy acceleration.

 

I have done a compression test today and the results range from 165 – 171 (done dry if that is important). From other threads this is good isn’t it?

 

Does this mean that it is likely to be the PCV assembly for the idle (only happens once warmed up and left to idle for a few minutes) and the turbo’s for the heavy acceleration?

 

I have the option to buy some replacement turbo’s today, so advice would be greatly appreciated.

 

Thanks Mark

According to data I have read, your compression results are very good!

http://www.twinturbo.net/nissan/300zx/forums/technical/view/868155/Compression-Test-How-To.html

 

The blue smoke could be due to bad PCV's so considering the price (

Bear in mind once changed, there will still be some residue that needs burning off - may take 300miles or so.

However, should it continue to smoke this could indicate worn turbo seals, but since its so costly to change these, try the PCVs first.

Just a pointer, make sure you use UK spec PCVs+hoses and not US spec PCVs+hoses cos the restrictors are a different size on the US spec cars and this can actually cause smoke problems on Jap/UK spec cars!! And if you don't//can't change all 5 hoses then at least change the ones that connect directly to the PCVs....try MJP's to get them.

:)

Would the PCV's also cause the smoke on heavy acceleration as well ?

Don't know TBH. Sorry. Would have thought that if a PCV got stuck open then yes it would.

Try a few searches on here to get more answers.

Still for the price, worth a try.

Tubbs usually smoke worse on overrun ie after you lift off, back pressure tries to suck the oil into the rear housing causing smoke.

 

as a temp measure you could remove the inlet breathers and then blank off the pcv valves and run it with non to rule them out before deciding a course of action, if you could be bothered to get to the inlet side of the tubs you could check he shaft for play.

 

It could be either at the moment or both

Well I have PCV Valves ordered and two turbo's arrived today. :cool3:

 

Will try the PCV asssembly and if that doesn't work think about doing the turbo's. Will have to decide whether to take engine out or not...:confused1:

 

Aim is to take it easy and get it on the road for JEA.

Well I spent the day on the car. Replaced the PCV assemblies and 3 of the pipes (I couldn't see where the other 2 went) then fires her up.

 

Let her warm up and no smoke :sweatdrop:

 

Reved her up and some smoke but after idling for 15 minutes or so it got less and less.

 

Now when I rev it there is only smoke when it goes into redline and it is black smoke.

 

Anyone know what revs they take it to on an MOT ?

 

While I was waiting for a lift home, decided to strip the rear light assemblies to fix reverse and fog lights. Found the earth lead disconnected on the fog light, so that fixed as well :thumbup1:

 

Overall a good days work !

Well I spent the day on the car. Replaced the PCV assemblies and 3 of the pipes (I couldn't see where the other 2 went) then fires her up.

 

Let her warm up and no smoke :sweatdrop:

 

Reved her up and some smoke but after idling for 15 minutes or so it got less and less.

 

Now when I rev it there is only smoke when it goes into redline and it is black smoke.

 

Anyone know what revs they take it to on an MOT ?

 

While I was waiting for a lift home, decided to strip the rear light assemblies to fix reverse and fog lights. Found the earth lead disconnected on the fog light, so that fixed as well :thumbup1:

 

Overall a good days work !

 

That's good news mate!!

 

Richard:sorcerer:

Well I spent the day on the car. Replaced the PCV assemblies and 3 of the pipes (I couldn't see where the other 2 went) then fires her up.

 

Let her warm up and no smoke :sweatdrop:

 

Reved her up and some smoke but after idling for 15 minutes or so it got less and less.

 

Now when I rev it there is only smoke when it goes into redline and it is black smoke.

 

Anyone know what revs they take it to on an MOT ?

 

While I was waiting for a lift home, decided to strip the rear light assemblies to fix reverse and fog lights. Found the earth lead disconnected on the fog light, so that fixed as well :thumbup1:

Overall a good days work !

 

In theory then you should now pass an MOT.

When they tested mine, last week, they didn't take it any where near red line.

Maybe reached around 3k revs.

Should be fine mate.

Tester should never rev the car hard, he only needs to raise the revs not put the pedal through the floor, emissions are tested at 2.5-3k, sounds to me like you have a bit of a w@nker of a tester to be honest, some testers will fail your car just for the simple fact they can and are never helpfull, another thing some testers havn't got a clue about is that if your car is an import the emissions aren't tested as normal imports have to be tested as pre-cat, I.e. Before cats were fitted to cars, the year of the car doesn't matter

As this thread is quite relavent to what i am now asking on the back end of my thread "in at the deep end" i was hoping to get some clarification here as a backup plan :) Firstly i thank all the guys who have helped me out over the last couple of weeks to get my car running.

I have managed to get it air leak tested and it had many leaks which are now fixed,it did smoke for a few minutes the first time it was started but that cleared and it does not smoke when idleing at all ,but once going down the road when i slightly boost the car it blows quite a lot of blue smoke out of the passenger exhaust,this was the side which has had the new piston and i know the car had been run prior to me purchasing the car so i was wondering if there could have been lots of oil in the exhaust which could cause this problem as it had a broken piston.

The blue smoke clears within a few seconds once the car is idleing again and it will rev up lots without any sign of smoke,then the blue smoke re apears once its pushing any boost at all,someone mentioned to me that it could be the EGR valve or PCV ?,the turbos are not the ones fitted to the car from new as i am led to believe they were replaced with after market ones. I also checked the pcv valves when the plenum was off and they are both free moving and the pipes are clear and free from any signs of gunk.

just a thought as i have similar problem having only blue smoke from one exhaust when car is driving and giving boost,so could you clarify that you now have no blue smoke on acceleration.

thanks.

Anthony.

:cool3:

According to data I have read, your compression results are very good!

http://www.twinturbo.net/nissan/300zx/forums/technical/view/868155/Compression-Test-How-To.html

 

The blue smoke could be due to bad PCV's so considering the price (

Bear in mind once changed, there will still be some residue that needs burning off - may take 300miles or so.

However, should it continue to smoke this could indicate worn turbo seals, but since its so costly to change these, try the PCVs first.

Just a pointer, make sure you use UK spec PCVs+hoses and not US spec PCVs+hoses cos the restrictors are a different size on the US spec cars and this can actually cause smoke problems on Jap/UK spec cars!! And if you don't//can't change all 5 hoses then at least change the ones that connect directly to the PCVs....try MJP's to get them.

:)

 

i didnt know that!

 

dan.