Smokes on decel and only when warm

[97GsXfreak]

Alright I got a brand new block .020 over, je pistons, eagle rods, new crank bearings everything. I took my head to a local shop to look it over and they said everything is good just throw it on your new block. So i put everything together and now I have 250 miles on the motor and I have already replaced the oil and been breaking it in (10w/30 not synthetic and varying rpms and letting car decel on its own). However when I am in gear and let off the gas and let the motor decel the car smokes like crazy, but it doesnt do this untill the car is driven around for a while after it is warmed up. If i just let my car warm up to operating temp and drive around it won't smoke for like 5 min. When sit at a light after decel it continues to smoke a lot but when I start to drive again it goes away.

People say that valve seals smoke more when they are cold so that probably isnt my problem.

I will do a compression test tomorrow but I just want some ideas because this is bothering me.

 

[Bmxr152]

Do a leakdown test too. That sounds like valve seals to me. What color smoke is it?

 

[hopwoodp]

I agree. smoke on decel is most likely bad valve seals. Who built your motor?

 

[bighroder]

also sometimes if your motor is burning to rich, the car will have black smoke come out the exhaust

 

[97GsXfreak]

Alright compression test... 150-150-110-150

The valve seals would mess up the compression numbers right? So are just the seals in the third cylinder shot?

Wouldn't the seals leak more when the car is cold??

And it is blueish smoke

 

[hopwoodp]

Blue smoke means you are burning a seal or oil. I would change all your valve seals. But, do a leak down test.

 

[bighroder]

200 psi in every cylinder is perfect 150 isnt bad but you would half to be the judge on whether you want to take all the seals out

 

[99gst_racer]

200 psi in every cylinder is perfect

That would depend what compression ratio his engine is. Without knowing that, it would be impossible to determine what perfect compression test results should be.

 

[97GsXfreak]

8.3:1 compression but if the seals are bad in the third cylinder it would cause the compression test to show 110 right?? I am just trying to make sure nothing is wrong with my brand new block...

 

[95GSXBLUR]

How new is your turbo?

I have a similar issue with my turbo seals going out. Smokes after hard boost/hot motor/decel ONLY. no smoke when it's cold, cruise, Partial throttle nothing. Only after I do a pull and decel.

 

[tsi20gawd]

usually smoking on decel after warming up is worn valve guides. The low cylinder is rather odd though. Have you tried a little oil in the low cylinder and retesting it?

Bryan

 

[bighroder]

sorry i think 200 is for 9:1 compression. yes it would hopefully fix the loss of compression but you also could have a bent valve, crack or a number of other things causing it besides the seal.

 

[99gst_racer]

8.3:1 compression but if the seals are bad in the third cylinder it would cause the compression test to show 110 right?? I am just trying to make sure nothing is wrong with my brand new block...

For an 8.3:1 4g63, 150's are good numbers, but you do still have one low cylinder. It could be valves, head gasket, or piston rings. Your stem seals could be the cause of a smokey decel, but they aren't causing the low compression cylinder.

If I had to guess, I would guess rings. But it could be any of the three that I listed. You need to do a leakdown test to determine what the problem is.

 

[pitbull419]

General diagnosis for smoke.

blue smoke= burning oil/poor oil control
White smoke=coolant/water
black smoke= running rich/carbon

I would say valve seals in your case.If thats not it I would check your oil control ring gap and clearance.

 

[99gst_racer]

I would say valve seals in your case.

Then explain how a valve stem seal causes a cylinder to read low....

Bad piston rings, on the other hand, can cause both- smoke on decel and low compression test results.

 

[hopwoodp]

Then explain how a valve stem seal causes a cylinder to read low....

Bad piston rings, on the other hand, can cause both- smoke on decel and low compression test results.

That is why you got to do a leak down test after reading low compression numbers.

 

[pitbull419]

Sorry,I missed that.Your not ganna beat me up are you

So then yes I would look into your oil control ring gap and clearance.
I would take it to who ever built it and make them check.

 

[toybreaker]

How are you venting the crankcase?

A fully functional p.c.v. system *may* help with decel smoking.
By applying some engine vacum to the crankcase thru the p.c.v. system, the pressure above the valve seal is lowered. This will help on decel because there will be less of a positive difference in pressure above the guide driving the air/oil down the guide to the low pressure in the ports around the valves.

As was stated previously, a faulty valve stem oil seal won't have any direct affect on your compression numbers. The oil coming down the guide can lead to carbon build up on the valves which can cause them to seat poorly. (When the carbon gets trapped between the seat and the valve...it won't allow the valve to seat properly.) This generally happens over time, and at 250 miles. I wouldn't think that would be a problem.

I have seen something similiar to this problem, and it was an assembly problem. Whoever did the headwork didn't get the valve stem seals firmly seated on top of the valve guides, and the seals were floating up and down on the valve stems.

Another possible assembly problem would be a damaged/overlapped oil control expander ring spacer supplying insufficient tension to the oil control rings themselves. They are quite thin and require the expander to keep them aligned, and tensioned against the cylinder wall in order to do their job of scraping the oil off the walls.

One other question, what killed the last motor, and is this a fresh turbo?

I like the leak-down test recomendation , try and do it with the engine warm.