1990 GMC C1500 4.3L smoke out of tailpipe?

White smoke usually means water/coolant getting burned. The white smoke in the morning is usually just condensation in the exhaust pipes getting burned off. Bad valve seals (or rings for that matter) should be bluish smoke.

I would strongly recommend that you put the proper coolant ln as soon as possible. Not so much for the anti freezing properties but to protect the block and the rest of the cooling system from corrosion

See I thought me deleting my smog pump could have a little to do with it but everyone I’ve asked couldn’t be sure. When I took out the pump and lines (I capped off the holes in the motor. I did it all correctly) a bunch of black crud came out of them. Like…a lot. And when I shook it I could hear tons of pieces shaking around. Plus the pump was SHOT. Ate a hose and everything. Seems to get better mpg without it. My question is how sure are you this is contributing??

Consider the fact of what its purpose is:
Allows the exhaust system (Cat ) to heat up quickly after startup and during normal engine operation.
I would imagine that having the CAT run at lower temps will have an affect.

[i]OK I’m glad I tested it again. At first? Its a cloud of white smoke at startup. Then once that goes away, the reving seems to be a vapor that evaporates somewhat quickly. Not instantly though. Its also not overheating. During my first test drive POST work that was something I was testing (since water pump and whatnot got replaced) so I forced it to stay in traffic a bit but I did take it on the freeway a little. It was rush hour and the truck isn’t at my house so I’m limited on when I can mess with it. It drove beautifully. Best its ever done since I’ve owned it.
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That sounds about right considering the mileage on the motor.
Initial smoke @ start up would indicate possible worn valve stem seals.

[i]Yeah I thought those numbers were low too. It WAS during the coldest part of the season here and after it had been sitting for 2 months. Its the 3rd compression test I’ve done to it since I’ve owned it. In October (when the weather was still stupid hot here…) it scored more like 145-150 constant throughout all cylinders PLUS it was being driven 1,000-1,500+ miles per week (most times loaded down)
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Seems that normal is between 160 psi and 190 psi.
The engine should NOT be at normal operating temperature and yet, it should be not be completely cold. So, if you have just turned off the engine, after an extended run time, let it cool down about 30 minutes. If the engine is cold, start it up and let it run a few minutes.

How expensive is that scope you mentioned? I don’t have one nor have anyone who would I can think of.
You can get them for under $75.00
http://www.amazon.com/Best-Sellers-Industrial-Scientific-Borescopes/zgbs/industrial/401578011

Are there way around needing one?
You could try looking down the spark plug hole…
But lets face it, you’ll have a very limited view.

How would I check the PCV valve? What am I looking for? There’s no CEL for it.
Remove it and shake it.. it should rattle freely.
Also look for excessive oil indicating higher blow by pressure in the crank case.

[i]What are the most effective ways to remove carbon? You said with a spray bottle? I’ve always known people to use treatments??
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Cheapest and effective is to inject water into the combustion camber, it will turn to steam and literally steam clean the combustion camber.
Reason I mention using a spray bottle…..
Too much water will cause hydro-lock and could possibly damage the engine.
Using a spray bottle you have a bit more control as to how much water you put in the intake.

What I meant by that was… Would carbon build up remain even after a couple test drives and start ups? Its gone through maybe a 1/5 tank of gas. At 24mpg.
Carbon deposits do not clear out that easily.
Do a search on youtube to see testing results.
https://www.youtube.com/results?search_query=gas+treatment+testing

Ive wanted to use sea foam on this. I figured it could benefit greatly from it. Using the due, intake and oil treatments. Although I’ve seen it used and heard great things about it… I have a friend who swears he used it and didn’t know he had a blown head gasket and it blew his motor. So I worry about not knowing about a bad seal or something and using sea foam and then blowing my motor before I can buy the new one I’ll eventually be swapping into it.

Not trying to be a smart a$$ here.
But if your friend didn’t realize he had a major issue with his engine (blown head gasket ) his motor blowing up is due to his lack of mechanical knowledge.
Not because he used SeaFoam.

Damn.. I’m using tap water. I didn’t know it was a big deal. I mean… I know batteries require distilled but didn’t know that about radiators. Always seen family members just throwing the garden hose in and filling it up after a head gaasket replacement or whatever have you. Always thought as long as it isn’t cold enough to freeze I was all good. Guess I gotta make that knock sensor and freeze plugs a higher priority so it doesn’t blow through coolant anymore!

Chemicals and minerals in tap water can react with metal engine components.

[i]Sorry I’m on a phone that doesn’t allow me to compose a message as nice as that lol
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Life’s a beach ain’t it :S

So the extra, hotter exhaust hitting the, as you say, cooler CAT causes more smoke??

Can’t say for sure..never owned a car with a air injection pump system.
But it was there by design for a reason.
You opting to remove it changes the way the system was designed to operate.

Ok that’s what I’ve thought. How bad is it to drive on those?

I assume you mean the valve stem seals..
Listen, the motor has 334K on it.. you have to ask yourself …”do I really want to invest in a motor that old or would I benefit more by putting those funds towards a replacement motor”

And could I replace them without speeding up the process of something internal motor breaking?

You could, but reread my last statement / question

What about the vapor what does that indicate? It IS in a garage (with multiple open doors…lol) when I’m usually running it. So I can see exhaust well. However, I’m color blind.

Most likely a mix of burning oil (blueish color) and water vapor (white color)
I can see where it would be tough for you to tell the difference being color blind.

Interesting. I was told something different online. I thought 150 was real good for it?? I’m gonna probably run another test then. Try and get a better reading especially since its warmed back up here.

You can search out the compression specs yourself.
Remember the conditions required in order to get a proper reading

Damn $75 is a little out of my price range for a tool right now :/ I recently lost my job. My spark plugs are also completely horizontal.

Sorry to hear that.
But assume for the present there are carbon deposits ( no big surprise there)
As I said earlier, you can watch what products were tested and their results.

[i]Ok for sure. What would excessive oil on PCV mean? Bad valve seals right??

Ummmm no, not really.
PCV vents crank case gases and sends them back into the intake manifold to be burned.
If you get oil in the PCV system, that may indicate a higher crank case pressure due to blow by.
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Interesting. Just straight water? I’m guessing preferable distilled??

Correct

I don’t need to mix it with a solvent or anything?

Nope

What exactly is the process (assuming I already have the spray bottle and know how to spray it into my intake)

Quite simple really.
Choose your point intake vacuum ..IE throttle body, brake booster vac hose
Bring the motor up to operating temp.
Set a high RPM 1500 – 2000
Start spraying water, but listen for the motor stumbling, don’t over do to the point of stalling the motor ( which is why using a spray bottle help limit the amount of water you can put into the intake)

[i]Touché lol he was still learning cars at that point. I just worry. I’ll be fixing all of this on a budget for a while. Can’t afford to screw things up worse. That’s why I’m being so cautious. I’d rather the more experienced guide me towards the proper way the first time.
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No one was born with the knowledge, but you have to start some where.

Ah, makes sense. Once I replace those plugs and sensor it’ll be back to coolant. I know I already have rust in my coolant. Not sure how to remove it. Radiator flush didn’t seem to do a whole lot. Water is still as discolored and gross. But by the looks of my freeze plugs? They aren’t going to be nice when I go to remove them.

Major flushing to try to remove the rust.
Might try this

Never had a rusting issue with my vehicles so I can not say how well this may work for you.
Freeze out plugs are a press fit.
Suggest you clean the area of gunk and rust as best as you can, then apply some Penetrating Catalyst (PB Blaster or some such)

[i]Yes it is lol but eh… Could be worse lol

Ah. Makes sense. It sucks because all the research I found all said their vehicles run better post air pump delete but no one ever stated whether or not it made their car smoke or not.

I definitely want to invest in a new motor OR rebuilding this one. Even if I pay my friends shop to do it for $1200. I was just curious if driving it on these bad valve seals can cause further extreme damage or just sort of maintain its crap condition for a while? Lol the valve seals are like $16 for the set + the $22 total in valve cover gaskets. I also considered just buying a long block but strip pump/pulleys off of it except the crank (since mine are all new with lifetime warranties) from pick a part on a 1/2 off day out of one with between 100k-200k. Figured even those should be in better shape than mine. Know any of the drills for testing the engine I find before pulling it??[/i]

[color=#ff8800]1 Give it a good look over. (oil leaks, cracks etc, take some time going over it)
2 Better if it has all the spark plugs, distributor, etc that way you know (sorta) that water and debris for the most part did not get inside of it.
3 Check the condition of the oil (if it has any in it)
4 Try to at least hand crank the motor to see if it is not seized.[/color]

[i]Touche haha

Yeah, sorry lol it all looks white to me. I’ll be honest. And from the sound of it? I think i prefer it to be white smoke lol

OK for sure. Running a new compression test couldn’t hurt. Doesn’t cost me anything but a little time.

I heard from someone else on here hat zmaxx is good and safe. What’s your opinion? From what I’ve read it sounds like a safe bet. Especially for vehicles as badly carbonated as this is sure to be.[/i]

[color=#ff8800]In your situation, I’d still use the water method.
Any chemical treatment will only partial remove deposits ( some more than others ) so why spend the money if you can get the same results by using water.[/color]

Ok for sure. Would the blow by be my rings then??

Yes

[i]I just found Eric’s video for it. It looks stupid simple. Can’t believe I’ve never heard of that before.

Thanks for taking the time to help me out man. I’m sort of teaching myself almost everything. And though I do a clean job (because I take extra time to figure out what NOT to do before performing the task) there’s still a ton I have to learn.[/i]

There is always a ton of stuff to learn, no matter how long you go at it.

Ooo that looks like some heat duty stuff there lol exactly what this jalopy needs haha I’ve stuck my fingers in the coolant res. And its just like a reddish brown water haha it did get slightly better after I flushed EVERYTHING and replaced the water pump and thermo though.

[color=#ff8800]Like I said, I’ve never had rust in a cooling system.
But if it were me in that situation… I’d give it a try myself.[/color]

Hmm… Didn’t even think about using my PB blaster and all before attempting to remove them. Speaking of which… How would you suggest removing them assuming they’re corroded and rusty??

[color=#ff8800]That all depends on their location and how difficult they are to get at.
I’ve see people use a slide hammer with a self tapping screw to yank them out.
Others have drilled a hole in the middle of them and used a big screw driver and pried the out.
Still others have used a hammer and screw driver and beat one side of the plug in to push the other side up.
All depends on location and working space.[/color]

[color=#ff8800]Also know that they make both metal and rubber replacements
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When using the metal replacements ..suggest you use a sealant prior to installing

I’ve been looking it over. Do far the only leak I can find is at my knock sensor and both of my freeze plugs. Along the valve covers and heads? No leaks that I can see. Everything looks real clean.

Odd that a knock sensor would leak oil..
Are you sure it isn’t a oil sending unit or oil pressure switch?

Could you explain #2 again? I checked my spark plugs during the compression test. They seemed work but good still.

This was a basic outline when looking for a replacement motor..
1 Give it a good look over. (oil leaks, cracks etc, take some time going over it)
2 Better if it has all the spark plugs, distributor, etc that way you know (sorta) that water and debris for the most part did not get inside of it.
3 Check the condition of the oil (if it has any in it)
4 Try to at least hand crank the motor to see if it is not seized.

The oil looks…fine?? Lol what exactly am I looking for other than dubris??

Old dirty oil

[i]Oh it’ll start by key and everything, I’ve been driving it around the last 2 days. Besides a sorta poor battery condition and a whining while in gear (I’m suspecting to be either my trans pump, filter or torque converter… Only whines while in gear and goes away 100% in “P” or “N”) its running great other than that damn smoke! Its reduced considerably after I took it on the Fwy for a bit over an hour holding 80 the whole time haha
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Might check the level and condition of your tranny fluid

Yeah I’m gonna at very LEAST start with the water method. It costs virtually nothing and its the most gentle procedure I’ve seen for carbon build up. I’ll suffer some mpg to keep this engine running a little longer until I buy the one I’m rebuilding/replacing it with. You know those engine treatments? The ones meant to help reseal rings and all to help your engine last a tad bit longer? Any you’d suggest considering the mileage of this thing? I’d like it to b effective without COMPLETELY destroying my mpg altogether. It gets 22-24 right now.

Never a big fan of oil additives, but might try RESTORE

[i]I was thinking about running another compression test now that she’s been driven a little bit??
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If it makes you feel better

Right? I want to learn bikes next. Particularly Honda.

CLR won’t be too rough to use in a car cooling system??

Shouldn’t be….

Ok for sure. The rubber replacements are a bit more expensive but… They seem more effective?? Plus I like that you crank down on them rather than hammering them a bunch. Seems easier to replace too.

It’s a toss up, granted you do not need to hammer them in but rubber does have a shorter life than the metal which are a bit more work to install