Engine smokes only while idling (intermittently)

[botachi]

Hey guys, I'm new here and was hoping you guys could help me out with my engine smoke problem.

 

Below is the situation I'm having with my car. I love the Supra, it's just that this problem is really getting annoying and embarassing to other road users!

 

My 1995 USDM OBD1 Supra has a surplus Aristo twin turbo engine. As far as I know I installed all the right and proper Supra 2JZ engine parts for it to mate into my engine bay. It runs the USDM OBDI ('95 model) ECU and BNEW USDM harness and everything seems to be working properly on the electronics side.

 

The problem is the engine's exhaust emits white smoke every so often while idling. A typical scenario is when I've been runing it through bumper-to-bumper traffic for 30-60 minutes, crawling at a snail's pace, the engine emits white smoke. Sometimes there's very little, sometimes there's a lot of smoke.

 

When I pump the throttle pedal with the transmission in neutral and the car standing still, the smoke goes away though. On the run, when the car is moving there's absolutely no smoke at all. The smoke comes out particularly if I drive it a bit jerkily in traffic, or when I ground the exhaust onto something. It really does seem weird this way.

 

We've checked the engine compression and it's ok, the values are within the shop manual and all 6 cylinders are close to each other. We've checked the spark plugs and there's no hint of moisture from oil on the plugs. The radiator is always full and the oil level never changes whenever I examine the dipstick.

 

It's gotten better now compared to before. Originally you think there was a bonefire going on when the car emits the smoke while standing still. Now it's more manageable but of course I want to completely get rid of it. Maybe you can help me check by telling me where to look, given the situation?

 

Other than that the engine idels perfectly, and we will be tuning it this weekend and see where the smoking problem leads to anyway afterwards.

 

Thanks guys, hope you can help me out here!

[ManwithSupra]

Is the smoke definatly white? or does it have a blue look?

 

If its just white and you are having no other issues such as missfire, loosing coolant, oil level dropping etc then its more than likely normal exhaust steam.

 

You see when an exhaust starts to cool (i.e you sat in traffic) the gases that have been converted from the cat may start condense (Some of the gases are converted are from the oxidation of unburnt hydrocarbons which create carbon dioxide and water) on a cooler day you will then see steam coming from your exhaust tip as the gas hits the cold air condenses to form steam.

 

Sometimes it can seem quite severe (depending on weather conditions usualy - colder the more steam you will see) there are a few threads on here about owners that are worried about this and all its turned out to be the above.

 

If its blue and you have checked eveything like you have in your post then it indicates worn valve stem seals, or potential piston ring failuire.

[botachi]

hey thanks for the reply!

 

You are the second guy that told me that, I just find it weird. The other guy from TRIAL in Japan said the same thing. Somehow though, I'm not convinced yet that that is the problem. Our climate is very very hot and humid here, in the middle of summer with temperatures reaching close to 40 degrees celsius. I'm not sure how that affects / influences condensation hehehe

 

I've changed the valve stem seals when we put in the new engine as a precaution in the past. I've also recently changed the one-way PCV valve from the intake side of the engine and there was improvement on the smoking issue.

 

I originally thought my problem was a vacuum problem, that there wasn't enough vacuum sucking out blow-by exhaust gasses from the cylinder head. Until we got hold of a WSM, there were some vacuum lines missing or disconnected. Now that we've attached them all and I plumbed in additional vacuum lines from the head and into the intake tract leading to the twin turbos, the problem has been much lessened. I was also thinking of tapping another vacuum line into the intake plenum but seems to be such a big hassle to do.

 

Now when the engine starts smoking, I just pump the gas and the smoke goes away. Before, it used to take forever.

 

I just realized now that my car, since it was originally built for drag racing (though never actually raced) had twin Walbro pumps with 6AN lines and 1000cc injectors. I took these out but left one Walbro pump and one 6AN fuel line. The injectors currently installed are only JDM-spec 440cc injectors. We used a GReddy E-Manage to interface between the injectors and ECU and compensate for the smaller sized injectors but without taking into account the high-flow / high-pressure pump and bigger lines. It seems to be running really really rich at idle (I can really smell the unburnt gas while idling) but leans out past 50% throttle at 5000rpm and above (I can hear a few pings past that).

 

Since the car is running rich at idle, could this be somehow related in causing the engine to smoke? Specifically, is the vacuum from the intake plenum weak because the idle AFR is rich? That's what I'd like to know.

 

Anyways, I really hope you can help me out here guys!

[Guest mtol]

did you find out what caused the smoke?

[kitch79]

Mine does exactly the same! Embarrassing in busy traffic to say the least.

[Mk4Gaz]

Holy thread revival batman!

 

Sounds like turbo seals to me

[kitch79]

Haha, damnnnn - didn't notice the year!