Blue smoke on cold starts.

Hey everyone,

Got a problem with my 2002 4.7 blowing blue smoke on startup. The truck has 178,000 miles and I've had it for about 2 years now. As of this last fall I've noticed it blows blue smoke on cold starts. At first it was just a puff but now it's quite the smoke show. Only burns for about 30 seconds or until I punch it out of the parking lot. Then I don't see any smoke the rest of the day. Nothing, not at idle, not under load or heavy throttle. I change the oil religiously too. Every 3,000 miles with 5w30. Motor runs super smooth and seems to have lots of power. I don't seem to use any oil between changes. I get 19 mpg highway, no CEL. Ive heard about leaking valve stems but it seems to be getting worse, at least as it's been getting colder and colder this winter. I tried changing the PCV yesterday with an OEM one but still got a smoke show this morning. I noticed the old one wasn't so bad but not as rattly as the new one. There was oil in the old one and I saw oil in the PCV hose as well. Any ideas?

 

Might be the power steering air control valve sucking fluid into the intake. When you turn the wheel at idle, do your RPMs jump?

https://www.tundras.com/threads/05-...ie-looking-for-help.61422/page-7#post-2833199

https://www.tundras.com/threads/mechanics-special-05-dc-refresh.133376/page-4#post-3406132

 

I haven't tried testing the PS that way but I did pop the hoses off to look inside and didn't see any fluid in the PS hoses. Nor have I noticed much fluid loss. I can certainly double check with that method though and report back.

 

Other options are leaky injector, head gasket, or similar.

Any codes stored? (Sometimes check engine light burns out in pre-2005 trucks)

Have you ever overheated the truck?

What color coolant are you running, and when was the last time it was changed?

It’s safe to temporarily clamp shut both hoses going to the valve for a few days to test, it should only bog down the truck when turning the wheel while not moving.

if the smoke puffs don’t subside, you may just want to cut to the chase and compression/leakdown test. If it comes back clean, start digging deeper.

 

I'm not sure, the truck doesn't lose any oil between changes. The oil looks very clean, like honey just before I changed it the other day. Same with the coolant. Still nice and red, no milkshake. I've never overheated it either. I don't believe the build for the CEL is out, I see it flash with all the other lights when I start the truck. I do read the computer every now and then to check fuel trims. The smoke goes away after the first 15-30 seconds after startup. It's blue smoke which makes me think oil, not coolant or excess fuel.

 

Could be valve guide seals. Not common though.

 

How's your brake fluid level? Sometimes the master cylinder leaks into the booster, and subsequently is sucked into the manifold.

 

That is my chief culprit but I'm trying to be sure it's not other things first. I'm open to having it fixed so I want to be sure it's not something else first.

I haven't checked that yet actually. I do eyeball the brake fluid every oil change, I had to do a big break repair when I bought this truck so I'm pretty good about keeping an eye on. I'll check the vacuum hose though maybe there's something there.

 

I hadn't thought about @KNABORES' suggestion, but yours was my other thought. It has to be something getting into the cylinders to burn, and if it's not constant, only at startup, and it's only after the truck sits, and there's no obvious fluid contamination or loss, then it'd be something tangential or easily missed, or invisible. Which leaves leaky injector, power steering fluid, brake fluid, etc. in my mind at least.

 

Ahh the most diabolical form of gremlin. Would a fuel treatment address a leaky injector or does it need to be repaired/replaced? Should there be any oil in my PCV? I suppose it could be sucking oil through there. I've heard of the baffles in the valve cover getting plugged up with sludge and preventing excess oil draining away, causing the Pcv to suck up oil? Anyone experience this?

 

My brake booster went bad and was causing a slight vacuum leak. Before I was able to get the booster replaced, the brake master cylinder also went bad and started leaking into the booster, which then got sucked into the engine.

I had similar symptoms to you- oil burning on startup. Definitely check to see if your booster has a vacuum leak. You can do this just by pressing the pedal when the engine is off. It should be easy to press, as it should be holding a vacuum. After one or two brake applications, the pedal should be firm.

 

PCV valve is slated to be changed every 30k miles IIRC, most people never change. Oil buildup around them is common. If they rattle when you shake it, it's probably functioning. If yours is a pop-out, not a screw-in PCV, be careful of the probably-crumbly gasket holding it in.

I'm definitely not saying it's a leaky injector, only similar symptoms have been that. We have a few of these "smoking at startup" threads currently, a lot of the time it's the PS air control valve, it's been other things, leaky injector was one I've seen once or twice. I'd only suspect it was a leaky injector if the cloud puff was larger after the truck sat for a longer period of time (7 days vs. 1 day, for example). If you have a bore cam/snake cam, you could pop the spark plugs out and scope the cylinders before startup to look for fuel buildup in the cylinder also, might tell you which it was *if* that was it. Or for oil, for that matter.

Heed what folks are saying about the brake booster and its vacuum line also. It's sage advice. Its also something easy to check.

 

Yep. Could pull the vacuum line to booster after you drove it for a while to eliminate any chance of brake fluid getting sucked in. Let it cool - start it up and see what the deal is. Quick way to eliminate that.

 

And note that, when capping a vacuum line, or pulling one, the result may take half a dozen cold starts before you see results.

 

This is all good stuff about the brake booster I will definitely investigate the brakes and power steering further. I'll be out of town till Monday and then I'll report my findings. I replaced the PCV Wednesday and the old one rattled, but not nearly as well as the new Toyota one. I replaced the grommet as well. It looked pretty grimey behind that grommet. On the brakes and PS, would it burn the most at startup because of Vacuum? Also, I don't see any smoke on subsequent startups, only the very first start up in the morning.

 

Just a quick update, I just got home from a 3 day trip and my trucks been sitting since. I was expecting a huge smoke cloud but didn't get too much at all, barely noticed. Maybe started showing blue smoke about 5 seconds after the first exhaust showed and continued for another 5-10 seconds. Seems like something is getting burned only within the first 5-10 seconds after a cold starts. I will start some more diagnostics either tomorrow or the following day.

 

Sounds more like the power steering or PCV then.

 

I replaced the PCV last week. I'll check the power steering today or tomorrow

 

Following along, as my truck also blows blue, but I don't want to hijack!

 

I honestly think we should have a process to follow for this "smoke at startup only" situation.

To date, from what I've seen during my ownership and participation here, it seems like the two big sources for fluids are the brake booster and the power steering air control valve with the latter of those two being more prevalent (test process here, and more info on correct vacuum hose routing for earlier vehicles here, but read on!)

Though there was one (or possibly two) folks who had injector-related issues (o-ring or other seal issue, or failed injector) causing a slow leak into one cylinder if left to sit overnight or longer, there are the "big two" which are pretty easy to check, looking for fluid and vacuum hose issues on these.

Obviously others may differ in appearance from what I'm showing here because I'm '05+ year, not '04 and lower, but generally speaking, two things:

1. The PS air control valve will be where the blue circle is, a bunny-eared looking thing, with two vacuum hoses coming off,
2. Vacuum line from the brake booster to the top-end of the engine somewhere, obviously the red circle.

You should be checking both for clear signs of fluid being sucked up into the hoses on all three hoses (two to the PS valve, one for the brake booster) before you really start digging into other stuff, and verify the hoses are routed correctly, and they're not cracked/broken.

NOTE: Vacuum hoses and their routing look slightly different from 00-04 than the 05-06. Showing 05-06 in this picture. For 00-04, see the link above, you have one line from a metal tube on top of the manifold down to one port of the valve, and one from the other port of the valve up to the intake box, passenger side.

And of course, when in doubt, a compression+leakdown test may tell you if you've got a blow-by or head gasket situation, but lack of compression on one or more cylinders DOES NOT indicate your head, it's gasket, or other major stuff is fucked. Stuck valves will cause bad compression numbers, as will bad timing.

​

 

Wow that was some awesome stuff. I haven't started doing my investigation yet but I did pop the hood this morning to check the oil level (right where I last saw it) and remembered to look at the two air hoses that run to the PS and so far I didn't see any fluid in either hose. I did forget about the brake booster hose but I'll check that later today.

Another quick update on the blue smoke level, today there was none that I could see. This would be the third start since I replaced my PCV. As a refresher, I pulled the PCV when I changed my oil last Wednesday. The old one l, which I replaced with an aftermarket one last year or so, still rattled, albeit muffled and gummy compared to the new Toyota one I replaced it with. It also had a lot of oil inside both the PCV and the PCV hose. Since replacing it I had some big smoke the morning after, much reduced smoke the following cold start, ending with today with no smoke that I could see. I will still do my inspection later and keep an eye on the smoke but that's been my observations thus far.

As per shifty's and others recommendations, I still need to check the brake booster line and spark plugs

 

Another thing that I would like to know is, regardless of what the actual cause in my case is, what's so special about a stone cold start that causes some fluid to get burned? I get it's because something broke but we are talking about 5 or 6 different things that can break and cause blue smoke only on cold starts but what's so special about a cold start that these things only show up then?

 

Let me explain it in human terms, hopefully it works.

My buddy Matt recently had a portal vein clot. It's pretty serious, if you know what your portal vein is. He went in for surgery, was in bed. When you're laying down idle, your blood pressure naturally drops (just like oil pressure), and blood tends to settle in various parts your body. This is why they need to turn patients over periodically, and why corpses show lividity post-mortem. Anyway, Matt had to pee abruptly. He stood up, blood pressure still low, after heart surgery to boot, and his body couldn't send enough blood to his brain, and just as fast as he was standing, he was back on the floor.

The reason is simple: your heart, like an engine, is a glorified pump. While your engine is one big air pump (pumping air in and out of exploding cylinders), your heart is a fluid pump, pumping blood. It's great what it's running with adequate pressure to keep lubricated, as long as you can get the volume (pressure) of blood where it needs to go. But when you turn it off, and that heart stops pumping, as you see with corpses and you see with engines, fluids settle/puddle/pool anywhere they can.

In corpses, you'll see dark marks at the lowest point they contact the ground, the only thing holding it in is skin. With engines, you'll find it in whatever containerized space that may be - a droopy part of a vacuum hose, or if it's in the intake passages, it may drain from there down into the cylinders. Next time you start your engine, you've got all that gunk that was up in the intake down in the cylinder,, and it gets burned up with the first few rounds of combustion, until it's all gone. Or if you've got a leaky injector, maybe you've got extra fuel down in the cylinder, and that takes a few rounds to burn out.

Hopefully the human body vs. engine analogy wasn't convoluted or confusing. There are definitely parallels there.

 

Thanks shifty for trying to break this down for me. I've been DIYing it on cars for a little while now and I mean to keep doing that, so I like to try understand the why and the how, not just the what. I find such an understanding helps break down future problems more easily, and since there is at least two other people following along this thread with similar issues, I thought I'd pose the question so it may help them.
So onto what I'm trying to understand, I understand that whatever is being burned, is being burned on the first couple engine cycles until it's all burned up and then the smoke goes away. My confusion is, why don't I see blue smoke all the time? I understand that would be the case with worn piston right rings. I understand you would see burning oil on a cold start if you had worn valve guide seals because of pooled oil seeping past the valve guides and into the engine while it sits, but in the case of say a faulty PS pump breather, a brake booster, or PCV, why do we only see the blue smoke on a cold start? Is there a stronger vacuum in the intake on a cold start? Or at least stronger than normal running or idling that allows these fluids to get sucked up? Maybe I'm getting into the weeds a bit but I thought I'd try and dig a little deeper into the phenomenon that seems to cause such similar symptoms for so many possible causes.

 

Likely you'd only see it at start, because again, what you're burning off is stuff that's had time to settle down and concentrate. During normal operation, you're going to be steadily burning miniscule trace amounts. When you stop the truck, and trace amounts start to collect, then work their way downward into a puddle, larger concentration of burnable = larger puff of smoke.

If you have a jug full of steam, and you sent that thru your engine, you're not going to see the trace amounts of mist out the back end.

Let that jug of steam sit for a while, it'll stick to the sides of the glass, and form a puddle in the bottom of the jug. Send that thru your engine, you're going to see a huge puff of smoke.

Same concept.

 

Thanks Yall. This advice helped me trouble shoot.

I checked the vacuum hoses shifty noted above, as well as additional vacuum lines for any oil or fluid. I also pulled my intake tube and inspected it for fluid/oil and visually inspected my throttle body which are both dry.

What's the etiquette here on consolidating info for further review vs not hijacking the OPs thread? Should I start another now that I have pinpointed my symptoms to certain starts to get the smoke that is a little different than the OP?

 

New update,

Small amount of blue smoke this morning on startup, but not terribly noticeable. I checked the PC hoses and brake booster hoses, no fluid I could see. I checked the PCV line and it was full of gunk but not really wet oil. I replaced the spark plugs which all looked pretty great actually. A tiny bit of soot on the base of each plug but not much that would have queued me to burning oil without knowing about the smokey starts. I'm not noticing much oil loss by the dipstick either. If the PCV was the cause, would take a couple dozen starts to clear any oil still working up the intake?

 

If you resolve the issue, and it's related to latent fluids getting burned on your next startup, after they've had time to settle, I'd expect to see things clear up within a dozen starts, if not half that. Last person I recall replacing their failed PS air control valve on here said there was half to two-thirds less smoke on the first startup and within a couple more, it was gone. But I also didn't ask how many miles they typically drive, which could clearly be a factor.

 

Okay as of now I've had maybe 4 or 5 starts since the PCV change. I'll keep monitoring for blue smoke, but in the mean time, is there anything else I should look at?

 

I mean, the big thing for me, before anything else, is to make sure the check engine light is working. If it is, just putting the key in the ON position (not starting) should make it turn on.

If it clearly is lit/working ... I guess my next course of action would be letting the truck set for a day or two, then pulling the spark plugs for two reasons:

• One - Checking the plugs to see if any show extra buildup or discoloration, clear signs of a problem. Note: When doing this, I like to get a piece of cardboard and write down numbers in a grid of 1-6 (if V6) or 1-8 (if V8) and lay the spark plugs next to their cylinder as I pull them IF I'm taking them all out at the same time, helps me track what was where. If you haven't changed the spark plugs in the last 50k miles or so, now would probably be the time to do it, so you're not doing it twice.
• Two - While each plug is out, I'd probably take my borescope camera and take a peek in each cylinder for any pooling of liquids. If any specific cylinder has puddled liquid, I'd probably get a straw, a cotton swab on a stick, whatever I can SAFELY put down into the cylinder and swab into it so I can smell/taste to see what it is (I'm dead serious). If it's fuel in the cylinder, lucky you, you know you only need to replace one fuel injector, and exactly which to replace. If it's oil in the cylinder, I'd go get a compression/leakdown test done sooner than later.

But you said you already replaced the plugs and didn't see anything. So I guess you maybe want to borescope/camera in the cylinder after it sets, or just go straight to compression/leakdown test. It'd possible someone installed counterfeit plugs in the truck, and lost the end of one of the spark plugs in a cylinder, it scored the cylinder wall, and you're getting some oil leakby, a tiny bit?