Smoke at idle but not while driving

[CBatstone]

Hello Everyone, I’ve gone through the forums and tried all the major first steps for diagnosing this problem, and am looking for your help to further narrow it down.

Symptoms: Smokes at Idle (blue), but does not appear to while driving

UPDATE: Now smoking on deceleration, seems to smoke now and then when throttle plate is closed (coasting in gear)

Short Drive Scenario 1: Start car, idle 3 minutes, drive around the block no faster than 20mph, stop and get out of the car. For 5 seconds after stopping the exhaust is clear and healthy. Then it will begin smoking. When it first began it would start and seem to clear up, but now it starts and will not stop until you drive again.



It appears that when there is a load on the engine it will not blow smoke.

The car will smoke at nearly every stop, so bad now (and getting worse) that I have stopped driving it because it is affecting others on the road around me.

Details:
Car/Engine

1700 Miles on freshly rebuilt lower end
Remanufactured Head from CylendarHeads.com in Rockwood, PA
Rebuilt Turbo from a private turbo rebuilding service. Used a shaft from old CT26 and a fresh rebuild kit and had the kit installed by Ron’s Turbo Service, Utah.

What I have tested

Intake Piping appears to be very clean.
Compression Test.

#1 140
#2 153
#3 155
#4 160
#5 160
#6 155

Disconnected PCV system and vented into the air and blocked off 2 ports with tape.
Cleaned K&N Air filter.
Replaced Valve Cover Gaskets.

Thank you

 

[Poodles]

Compression numbers are supposed to be closer to each other, especially if it's that fresh.

Rings might not have fully seated, get the PCV system hooked back up properly, and try and get them broken in properly.

Turbo would do it right after boosting, like when you come up to a light in most cases...

 

[CBatstone]

Well it does do it after you come up to a light, used to be a now and then thing, but now it is doing it habitually when you are in neutral, idling. It also used to clear up after it idled a bit and now it is blowing smoke for a long period of time at idle.

The car did not blow any smoke until the last few hundred miles. We broke it in by driving it hard and doing the proper loading to seat the rings. (hard accel and decel)

 

[Poodles]

the low #1 cylinder is bad...

Looks like it may have been another case of overtightening the timing belt tensioner pully bolt...

 

[simpsons7s]

Did they change your valve stem seals?

 

[Whasian]

Sounds like valve stem seals to me...but why the low compression on one?

Whasian

 

[CBatstone]

the low #1 cylinder is bad...

Looks like it may have been another case of over tightening the timing belt tensioner pully bolt...

Poodles, can you please elaborate more on the over-tightening of the timing belt tensioner pulley bolt?

Cyl 1 does seem a bit low, how could this have affected it?

 

[7MGTEsup]

Poodles, can you please elaborate more on the over-tightening of the timing belt tensioner pulley bolt?

Cyl 1 does seem a bit low, how could this have affected it?

If you torque the timing belt tensioner to more than 36lbs/ft you get a fair bit of deflection in the wall of cylinder #1 enough to give you blowby.

 

[CBatstone]

If you torque the timing belt tensioner to more than 36lbs/ft you get a fair bit of deflection in the wall of cylinder #1 enough to give you blowby.

Do you think this can be resolved by re torquing the bolt? What are the chances it would do any permanent damage to the wall.

There are soooo many things you need to know about rebuilding a 7M, I felt like I honestly put due diligence in. A reputable machine shop, learned and applied as much as I could. I tried not to take any shortcuts, and now after years of careful engine build and body work, not to mention countless dollars spent, I feel my dream of owning a 7M powered supra slipping into obscurity. Does it really have to be trying to own these cars?​

 

[Poodles]

It MIGHT, but usually not...

Never torque anything to "good enough," pretty much every fastener is given a torque setting in the TSRM, it's in your best intrest to use them.

Not trying to be a prick, but just giving you a heads up that while engines are fairly simple, if you don't follow specs exactly it will bite you in the ass somewhere.

 

[Syris]

Disconnected PCV system and vented into the air and blocked off 2 ports with tape.


This is the area you need to go back through and fix. I bet the problem will disappear

 

[CBatstone]

Disconnected PCV system and vented into the air and blocked off 2 ports with tape.


This is the area you need to go back through and fix. I bet the problem will disappear

The PCV route was a temporary thing that I tried as to eliminate the PCV system as a culprit.


We did follow all of the TSRM torque specs, and I would be surprised to learn that this tensioner was not torqued correctly. I will get into it tomorrow after work and find out what it was set to.

 

[arizzle]

i had the same symtoms after my headgasket fix and mine was pvc problem so i installed a catch can, and also my timing was to advanced, it was advanced almost 30deg. it ran fine and didnt seem to be any power lose. i adjusted it and just adv it 10deg and theres no more smoke at red lights and at idle.

 

[CBatstone]

UPDATE: Now smoking on deceleration, seems to smoke when throttle plate is closed (coasting in gear)


At Cold Start after not running for 48 hours: Idles clear for 2-3 minutes then begins smoking.


Advice from Forum:
I checked my timing belt tensioner, it was torqued correctly.

Will double check my timing, not sure how this could affect it. We triple checked it when we initially set it and believed it to be correct, however it could have moved. I am not sure how this could cause smoking though (oil) maybe gasoline?

 

[arizzle]

UPDATE: Now smoking on deceleration, seems to smoke when throttle plate is closed (coasting in gear)


At Cold Start after not running for 48 hours: Idles clear for 2-3 minutes then begins smoking.


Advice from Forum:
I checked my timing belt tensioner, it was torqued correctly.

Will double check my timing, not sure how this could affect it. We triple checked it when we initially set it and believed it to be correct, however it could have moved. I am not sure how this could cause smoking though (oil) maybe gasoline?

well my timing was advanced and running my car really rich and was smoking in decel and idle it was smoking blue and black. but i dont know what yours could be.

 

[Pantaloon007]

If its a fresh engine and smoking constantly you might want to go back through it. Either that or break-in broke out.

 

[CBatstone]

The solution to this turned out to be a bad turbo, specifically the exhaust side journal bearing of the CT26 was bad, where the compressor side was tight, made it hard to tell when pulling off the air filter to check for play.