Engine Smokes When Started


Old 09-09-08, 05:46 AM
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Join Date: Sep 2008
Location: Philly
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Engine Smokes When Started

My 1994 Isuzu Trooper always had a tapping sound coming from the engine which I beleive was a valve tap. I recently read on the internet to try using thicker oil to stop the tapping noise. About 1 week after trying the thicker oil the engine began smoking when started and after sitting at idle for stop lights etc. The smoke pours out for a short period of time and then burns off and disappears once the vehicle is at cruising speed. Is it possible that the thicker oil is actually causing the smoking by causing the valve to not seat properly or could it be the thick oil gets hung up in the valve cover area for a longer period thus allowing increased time for the oil to seep past the valve seal? Should I try going back to the normal 5W-30 and drain the straight 40 weight oil?
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Old 09-09-08, 06:45 AM
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Is this smoke color primarily blue?, or white?, or blue-white?, or steam color?

Are you using noticeably more oil?

Are you losing any engine coolant?

Have you made sure you are not using any brake fluid? (Someone recently brought that one up, here.)

Have you checked your PCV valve to make sure it works, so you are sucking blowby gases out of the crankcase at high engine vacuum/idle?, using that one test where you hold your finger over the end of it while vehicle idles, and feel it suck in and click loudly, and where when vehicle is off, you can shake the PCV valve and it freely rattles inside?

Any oil being sucked up into where the air cleaner is?

Couple of schools of thought regarding oil viscosity: One is thinner oil would be easier to pump and get in everywhere it is supposed to, including high up in the valvetrain. Also manufacturers set clearances between parts, in the thousandths of an inch, and are designed for the certain viscosity oil, actually.

The other is that on older engines, thicker can better fill worn areas, and perhaps remain longer in pushrod lifters and valve adjusters without leaking back out, and cling to surfaces longer, like all bearings and cylinder walls, etc..

Also petroleum distillate products on the market are made to help clean parts, like up in the valve train, and make sticky parts start operating freely again, in theory.

I have never heard any theory about thick oil holding a valve open though.

Last edited by ecman51; 09-09-08 at 07:35 AM. Reason: added more
Old 09-10-08, 07:47 AM
Thread Starter
Join Date: Sep 2008
Location: Philly
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Smoke when started

The engine is burning oil and no coolant. When started the engine smokes very badly, blue smoke all oil. I always had a tapping sound, like a valve tap. I decided to try to use thicker oil and about 1 week later the smoking began when started or after the car sits at idle such as a stop light for 1 minute. When I pull away from the light it smokes and then burns off after 30 seconds or so. Same in the morning, 30 seconds to 1 minute the smoke burns off. After driving around town I lose a lot of oil, but I do not see smoke as long as i'm cruising with little stopping, it appears to be fine cruising at 30mph or more.

I eventually tried adding the thick honey type additives, as much as 2 quarts were used but did not work out. I have not checked the PCV yet but I will soon. I just wondered if I should try to go back to the thin 5W-30 and see if that works?? I guess I have a bad valve guide seal or something but I don't plan to keep this vehicle and want to drive it from Philly to Nashville this weekend but I don't want to blow the motor. Like I said it seemd to be ok on the highway, I hope I'm not burning a ton of oil while I am driving at 55mph, it does not appear to be smoking at that speed but it's hard to tell at that rate of speed. In the morning though, you can't miss the smoke, it's terrible but goes away after a short period of time.

So, the main question is, can thicker oil actually do something to the valve seal to create more smoke, anyone ever encounter this?
Old 09-10-08, 03:11 PM
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I am envisioning you driving something like the smoking van in "School of Rock". Sounds like you could have ring issues also if you are leaving clouds during acceleration. I can't say your engine is even ready to blow, at all. I'd be thinking about being pulled over by the police, is what would be on MY mind. And that can sort of ruin the experience.

You could do a compression test with and without squirting some oil in the spark plug hole to see if it is the rings.

It sounds like you are in for some overhaul work, unfortunately. Or seeing what you can get for the thing. Don't 'give it away' either, as they are paying pretty good for even junked vehicles now. That should make the used vehicles market prices go up, one would think.
Old 09-10-08, 03:28 PM
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Join Date: Jun 2008
Posts: 92
if it smokes black, it's burning oil, if it smokes light grey, it's burning coolant.
this is the thumb rule.
now, with your vehicle being of japanese dissent, i have diagnosis for you: valve stem seals gone bad.
i think it's japanese philosophy of making them. all 3 mitsubishes we had had them gone bad. many other japanese cars have same achilles heel.
what happens when you switch to heavier oil, you increase oil pressure in the system. now, what was weak before, gets under higher stress - and blows.

tapping sound is oil lifters sticky, unless you have honda type rockers and they can - and need to be adjusted. which is possible, as honda was in kahutz with isuzu at some point in time.

yep, they had isuzu trooper marketed under honda something, forgot the name.
Old 09-10-08, 08:08 PM
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black is over rich on fuel, not oil. most likely the thicker oil just coinsided with the oil use. valve guide seals are not under pressure unless your pcv valve is bad. check to see if your drain back holes in the heads are slightly pluged allowing oil to build up and not drain back to the oil pan, that could cause oil to be drawn down past the valve guide seals or pvc valve sucking oil from the valve cover and causing the problem.

life begins when the kids leave home and the dog dies.

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