280Zx Blowing Blue Smoke On Acceleration

[Captain Slow]

Hello everybody,

 

A short introduction,

 

My name is Ben and I own a Z32 300zx twin turbo. I also am into many other cars unfortunately for my wallet and garage space, including VW's, Citroens and Peugeots, Jaguars, Pontiacs, and an eclectic assortment of other makes.

 

Anyway, I was hoping to get some thoughts on a problem with a friends 280zx.

 

I'll try to keep it brief. He hadn't drove it in at least 6 months when he took it out and after a few klms it started blowing quite alot of smoke. No a complete smoke screen but definitely more than enough to get you noticed every where you go. After a few test drives myself it mainly does it under hard acceleration and gets thicker the harder you push it. It's very minor or non existant at idle, with no puff on startup. 

 

He dropped it off to me to and here's what i've done so far. Some work is just for maintenance.

 

Replaced valve seals

Compression test - All ok around 150 160 psi

New timing chain and guides and tensioner.

New water pump

Checked PCV valve, also tried disconnecting and plugging valve temporarily

Checked it's not sucking trans fluid from the auto

Checked same from brake booster

Checked for blown head gasket with coolant test. Test fluid is blue and is supposed to turn yellow if HG is bad, but mine very slowly turned greenish so not sure what to make of that.

 

It seems most likely i'm just left with rings. Although compression is good could it just have a stuck or broken oil ring?

Anything I can do to test/fix?

 

I think i've seen some products that claim to loosen frozen rings and lifters etc, worth a shot perhaps?

 

Any thought's or other information would be very much appreciated

 

Thanks guys

Ben

 

 

 

[Linton]

your diagnosis and testing sounds great to me, still could be a head gasket leak at the oil gallery, were the plugs oiled up or clean and dry? how much oil is in the motor is it overfull?  if they are ok it is time to pull the motor down check the rings and replace the head gasket, start by removing the head if that doesn't show any thing pull the engine. keeping on driving it and hoping it will fix itself just aint gunna work. good luck, also I doubt that an oil additive will fix the problem.

Edited March 4, 2017 by Linton

[zeds4ever]

What colour is the smoke , if its grey'ish it's oil , if its black'ish then its petrol possible choke not operating properly in conjunction with primer fuel injector. Check the exhaust for fluid emission , if significant possible head gasket also check oil filler cap for milky colour along with radiator cap for oil traces . Lastly pull spark plugs out & check for fouling as sometimes if they foul up they will not burn all fuel in chamber & naturally this then finishes up in the exhaust. Other than that best of luck .

 

                                        Regards : Alan.

[PB260Z]

Hi

 

Looks like you have covered most things.

Is it running rich ? ie does the exhaust have a string petrol smell.

Could be a fault in the cold start circuit. Try disconnecting the 7th injector and see if that makes a difference.

How the fuel pressure regulator ?

 

Does the cooling system hold pressure in a leak down test ?

 

Just a few thoughts

 

************************

Edit - Just realised you are getting blue smoke. Not going to be fuel related.

************************

Edited March 4, 2017 by PB260Z

[dat2kman]

Sounds like a new set of rings, and some Up-Down work with a decent hand drill and a Flex-Hone, might be needed.

 

There are various additive type things to reduce oil smoke, you could try one or three, see if it works, first!

[Captain Slow]

Thanks guys,

 

I still need to do a coolant pressure test thanks for reminding me.

 

Yeah smoke is more blue than black, no petrol smell, and no glycol smell really either.

 

I remember when doing the compression test that the rear spark plug looked a bit oily where as the rest looked mostly dry if I recall correctly.

Worth cleaning/replacing them all, going for a drive the re-inspecting them I guess. That might tell me something.

 

Ben

[Captain Slow]

PS, can anyone tell me if there is an oil gallery near the rear cylinder? Ie. Could a faulty head gasket be allowing oil into the rear combustion chamber.

 

Ta.

[260DET]

Sounds like some spark plug reading is in order.

[road rider]

What colour is the smoke , if its grey'ish it's oil , if its black'ish then its petrol possible choke not operating properly in conjunction with primer fuel injector. Check the exhaust for fluid emission , if significant possible head gasket also check oil filler cap for milky colour along with radiator cap for oil traces . Lastly pull spark plugs out & check for fouling as sometimes if they foul up they will not burn all fuel in chamber & naturally this then finishes up in the exhaust. Other than that best of luck .

 

                                        Regards : Alan.

 

 

Hi

 

Looks like you have covered most things.

Is it running rich ? ie does the exhaust have a string petrol smell.

Could be a fault in the cold start circuit. Try disconnecting the 7th injector and see if that makes a difference.

How the fuel pressure regulator ?

 

Does the cooling system hold pressure in a leak down test ?

 

Just a few thoughts

 

************************

Edit - Just realised you are getting blue smoke. Not going to be fuel related.

************************

 

I was thinking that it could have been something in the cold start circuit as well.

Look at the cold start solenoid(think that's what it's called) They can get stuck in the closed position and make the engine run rich.

 

Would do this at least, look at the cold start circuit, before you go doing a reco of the block. At least rule it out.

 

Good luck either way.

[dat2kman]

Not so much an oil gallery at rear of motor, but, a large oil drain hole through head, block, into sump.

your comp readings dont indicate that this would be a oil source.

I'm still at worn/broken rings and scored bores.

Out she comes!

[Captain Slow]

Hey Folks,

 

Just a bit of an addendum to this thread.

 

I was feeling a little annoyed that all my efforts hadn't seemed to provide a positive result (not a new feeling haha)

So I was thinking, this problem was seemingly a sudden onset thing, and consitering all alternatives have been addressed I must be left with a stuck ring.

 

So what do you do when a car has been sitting for a while and is being cantankerous? A good old Italian tune up!

I gave the car some good enthusiastic drives several times over a week period and the smoke appears to have cleared up i'm happy to say.

It's been a few weeks and the car has been out several times and it's still good so result!

 

Thank you everyone who contributed thoughts and advice, I very much appreciate it.

 

Kind regards

Ben