Puff of smoke... doesn't smell like oil, not sure what it is. (Page 1/2)
82-T/A [At Work] JAN 02, 07:27 PM
Hey guys,

Still working my daughter's car through it's paces after the engine rebuild and re-install. Car has about 25 miles on it since rebuild... engine drives fantastic, and we've been driving it mostly calm, but allowing it to climb in the RPM (up to 4,250-300 rpms)... now that I have a working tachometer (thanks Gunsett)!

Car doesn't smoke at all while we're driving it, or even when it's idling.


But if we let the car idle for a few minutes... like, maybe 2-3 minutes, and then I stab the throttle in idle (to like 2,250 rpms for a quick second), I get this huge cloud of greyish smoke. It doesn't smell sweet, so I know it's not coolant, but it's also not blue, and doesn't really smell like burnt oil. It's more acrid smelling.

Really, I have no idea what's causing it. Since the engine only has 25 miles on it, does it take time for the rings to properly seat?


I almost wonder if it's a combination of oil and too much gas. The TBI unit was completely rebuilt, new fuel pump, new lines, etc.

The only thing back there that's old is the EGR valve... but it seemed good so we just painted it and re-installed it.


Thoughts?


It doesn't happen every time I stab the gas... and in those other times, there's no smoke coming out of the exhaust at all... driving around, or even bliping the gas while it's stopped... no smoke at all. It's only when I've allowed it to sit idling for a few minutes (idling at like 800 rpms) and then I stab the gas... I get a big puff of smoke.

I'm wondering... is it possible that fuel is pooling in the intake?
Thanks!
Vintage-Nut JAN 02, 08:20 PM

quote
Since the engine only has 25 miles on it, does it take time for the rings to properly seat?



Two Methods to Seat New Piston Rings
*Baby It - low RPS for XXX miles and step-up to midrange, finally higher RPS but to me - the piston rings will never seat properly.
*Fast then Cool - accelerate rapid and vary the speed continuously under load to higher and higher RPS {until at redline} BUT at a very short time and then fully cool

This forces the rings against the cylinder wall during break-in.

To me, I use the latter than the former, the rings seat fast and better for the long haul; it makes for a tightly sealed combustion chamber, and less oil consumption too.

EDIT - second conventional oil change?

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

[This message has been edited by Vintage-Nut (edited 01-02-2025).]

sleek fiero JAN 02, 08:35 PM
Hi Todd You put on a new cat didn't you. I am wondering if when it cools idling and then you hit the throttle that maybe it's clearing it's throat so to speak and burning off any buildup from idling. Just a thought. also it probably will take 500 miles to fully seat the rings and i think you said you used hastings rings which sometimes take a little longer than other brands I found when I used them in our shop. sleek
82-T/A [At Work] JAN 02, 09:19 PM

quote
Originally posted by Vintage-Nut:
Two Methods to Seat New Piston Rings
*Baby It - low RPS for XXX miles and step-up to midrange, finally higher RPS but to me - the piston rings will never seat properly.
*Fast then Cool - accelerate and vary the speed continuously under load to higher and higher RPS {until at redline} BUT at a very short time and then fully cool

This forces the rings against the cylinder wall during break-in.

To me, I use the latter than the former, the rings seat fast and better for the long haul; it makes for a tightly sealed combustion chamber, and less oil consumption too.

EDIT - second conventional oil change?




Thank you! I appreciate this response. I'll probably do the first since I'm going to have my daughter start to drive herself to school (and then we change seats) every day when we drop her off... and it'll be mostly slower / low-speed driving. I'll just calm down my upper rpms (which was rare anyway).

I have not yet changed the oil. I still have the original break-in oil that I purchased, along with all the mixed "other stuff" that's in with it... including the dry moly spray, and the assembly lube. The oil is still super-clear, so that's the only reason why I haven't changed it yet... but of course the filter is working well.

Should I have her change it now? Or should I wait a little longer? It's got about 25-26 miles since the very first startup.



quote
Originally posted by sleek fiero:

Hi Todd You put on a new cat didn't you. I am wondering if when it cools idling and then you hit the throttle that maybe it's clearing it's throat so to speak and burning off any buildup from idling. Just a thought. also it probably will take 500 miles to fully seat the rings and i think you said you used hastings rings which sometimes take a little longer than other brands I found when I used them in our shop. sleek



Hi, I totally did. It's a newer high-performance 2" Ocelot Catalytic converter which normally would be with the V6. I ordered the 2" piping because it fit over the original 1-7/8ths piping perfectly so I could weld it without any seams.

I also wonder if it has a lot to do with the fact that the car has barely been warmed up either... and the catalytic converter never reaching operating temperature? I drove it again today for a few miles, and it's been like in the low 60s outside. We turned on the heater, and we couldn't get much more than 75-80 degrees tops coming out of the heater core. It has a massive 6-core radiator, plus the radiator fan is running with key-on full blast. So I finally re-installed the 195 degree thermostat tonight. It's probably running so cold that it's just dumping fuel into it like crazy.


Thanks for the response!!! 500 miles shouldn't be too hard to get to. The car is a blast to drive, and we just submitted all the paperwork for a custom plate, so we should be getting that in the mail in the next couple of weeks (with a temporary by Tuesday). It definitely doesn't have the power of my V6 Fiero (or what it'll have with the 3.4), but the power is very smooth, and I can so easily toss it in the corners and it just takes it. Even with the totally shot front end (we haven't even touched the front end yet), it tracks really straight!
Frenchrafe JAN 03, 03:00 AM
I'm not an expert with the Iron Duke motor, but in all my experience of rebuilt engines, the first several hundred km of run in will always send out some smoke.
The acrid smell (eye watering!) seems to be a normal result.
You did follow a good break in procedure?
I informed my neighbours that I would be running an engine at 2500/3000rpm for 15 minutes to get up to operating temperature before driving out of the garage!
After which it was several hundred km with constantly changing "mild" engine regime: no hard accelerations (just some throttle "blips") and no slow long idling/cruising neither.
I changed the oil well before the 500km mark, but's that just me being over cautious.


------------------
"Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero
https://youtu.be/hUzOAeyWLfM

Dukesterpro JAN 03, 08:44 AM
Grey smoke is indicative of a rich mixture, typically.


The fact that you didnt have a thermostat in on 60 degree days, likely meant your car wasn't or was barely getting out of closed loop when driving. That would mess with you fuel tables and would cause what you are describing. . .
82-T/A [At Work] JAN 03, 09:26 PM

quote
Originally posted by Frenchrafe:

I'm not an expert with the Iron Duke motor, but in all my experience of rebuilt engines, the first several hundred km of run in will always send out some smoke.
The acrid smell (eye watering!) seems to be a normal result.
You did follow a good break in procedure?
I informed my neighbours that I would be running an engine at 2500/3000rpm for 15 minutes to get up to operating temperature before driving out of the garage!
After which it was several hundred km with constantly changing "mild" engine regime: no hard accelerations (just some throttle "blips") and no slow long idling/cruising neither.
I changed the oil well before the 500km mark, but's that just me being over cautious.




Thanks Rafe, I really appreciate it... that definitely makes me feel a bit better about all of it. We drove it again today, and there was still "less" smoke than before. Only one belch of smoke after it had been idling for a bit.

As for break-in procedures... this engine has roller lifters, so I wasn't too concerned about a "proper" break-in. I know with flat-tappet that I need to do some crazy stuff with the engine (like you said, 2,500 rpms for 15 minutes), but in this case, I've just been driving it around and trying not to really abuse it.

I'll try to get to 100 miles, and then we'll change the oil. The oil is crystal clear so I've just been reluctant to do so... but I have fresh 5W30 that I'll swap in as soon as we do it. I'll eventually have my daughter go to synthetic, but probably won't do that until 5,000 miles.



quote
Originally posted by Dukesterpro:

Grey smoke is indicative of a rich mixture, typically.

The fact that you didnt have a thermostat in on 60 degree days, likely meant your car wasn't or was barely getting out of closed loop when driving. That would mess with you fuel tables and would cause what you are describing. . .



For sure, and the gas gauge went down fast too... I think it's definitely some of what Sleek said too with the catalytic converter. I put in the 180, just until I have a working temperature gauge, but I plan to run a 195 in it when everything is together. Especially because it's now got a 6-core radiator, which is wildly over-kill for this motor.


Thanks!!!
82-T/A [At Work] JAN 04, 01:18 PM
Figured I'd post this here. I had my daughter make a quick video (despite my daughter's protests) and posted a video of the engine running so everyone could see the puff of smoke, and / or hear the motor idling.

More information in the description, which I'll post below the video:





It idles and sounds a lot better than the video is giving it credit... there's no rattles or squeaks or anything bad...


- - -


I wanted to post a quick video that I felt might be helpful to others, and also low-key to show that I've actually been working on the car and made progress. I'll still continue to the show the progress in order, but wanted to post this for anyone who's curious what a properly stock / well-running Fiero should sound like on cold start-up and idle.

The engine has 25 miles on it since the engine rebuild, still has break-in oil in it with the assembly lube. There's a slight bit of smoke on start-up, which is normal for an engine rebuild, and usually results in a little bit of start-up smoke for the first 500 miles or so.

The engine has all the factory emissions systems installed, including:
- Fully-functional ThermAC w/ manifold heat stove & ducting
- Reconditioned fuel evaporative canister & new filter.
- Ocelot (aftermarket) Catalytic Converter (replaces the pellet style)
- Functional E.G.R. System


Content Timestamps:
0:00 Intro / Description
0:10 Engine Start-Up
0:23 ThermAC Adjusts Air Temperature
0:35 ECM Enters "Open Loop" Mode
1:20 Idle drops to ~1,200 RPMs
2:30 Idle drops to 850 RPMs
cliffw JAN 04, 01:28 PM
Not all piston rings are created equal.

Not all the materials are the same.

[This message has been edited by cliffw (edited 01-04-2025).]

Riney JAN 07, 05:24 PM
I saw the video just a few hours after it was posted on you tube and yes i did notice the puff of "smoke". I just figured it still needs broken in. With the rebuild your daughter did I would drop the oil around 500 miles then continue what ever break in process you prefer. I think the puff will clear up after everything gets seated. I am doing my break following by the baby it method. However my break in period is stalled out waiting on me to drop the cradle, find that oil seep near the rear main, fix, and reinstall.

We were at about the same stages on our rebuilds it is just you are getting yours done quicker than I am. My suspension rebuild is completed (still need to go to alignment shop). Paint will be next on my agenda, debating about changing the color from white to candy apple red on the base model I have. I would leave it white but I picked up an Indy a few years ago that is complete, in decent shape, does not run, and not been driven since 1997. No sense of having two white ones is there?

Good job on the videos and congratulations on keeping the 2.5.