blue smoke after lettin off throttle?

35

Asked by Jan 19, 2009 at 03:46 PM about the 1988 Chevrolet C/K 1500

Question type: Maintenance & Repair

the exhaust on my 88 chev silverado smokes blue when i left off the throttle ...i put a new exhaust system on like 4 days ago it only smokes after i rev it up  and its only a short puff of blue ...i wasnt sure what would cause this and didnt know if it was just the newness of the exhaust wearing off since the exhaust would be hotter when its reved up  or what it was .. it doesnt smoke at idle or going down the road or anything ...any pointers would be helpful

21 Answers

8,595

blue smoke is almost invariably engine oil. with a 20+ year old car it can be a leaking seal, gasket, or ring. Or a combination, I wouldn't bother with it, just run the truck into the ground and replace it when it finally dies. But that's just my opinion.

2 of 2 people found this helpful.
45

here's a general rule (not always right but 90% of the time it is). Smoke colour: Blue=burning oil. Black=too much fuel. White= too little fuel

1 of 1 people found this helpful.
10,605

Adam is 100% correct for the most part, although I will lean towards the o-ring(s) leaking causing oil blow by at higher revs.... Chevrolets are known for this issue.... And so long as you keep the oil topped off you can drive it for quite a while before having to overhaul the engine....

1 of 1 people found this helpful.
285

Blue smoke is caused by engine oil entering the cylinder area and being burned along with the fuel air mixture. As with the white smoke, just a small drop of oil leaking into the cylinder can produce blue smoke out the tailpipe. Blue smoke is more likely in older or higher mileage vehicles than newer cars with fewer miles. How did the engine oil get inside the cylinder in the first place? The car has many seals, gaskets, and O-rings that are designed to keep the engine oil from entering the cylinder, and one of them has failed. If too much oil leaks into the cylinder and fouls the spark plug, it will cause a misfire (engine miss) in that cylinder, and the spark plug will have to be replaced or cleaned of the oil. Using thicker weight engine oil or an oil additive designed to reduce oil leaks might help reduce the amount of oil leaking into the cylinder.

2 of 2 people found this helpful.
35

thanks for the help after putting this question up yesterday i topped off the oil remembering its been awhile since i checked it and it was done a fair bit so i add some to bring it up to the top line and i reved it up today and it didnt smoke one bit

1 of 1 people found this helpful.
35,255

white is antifreeze generally a leaking head gasket

2 of 2 people found this helpful.

sounds like the oil in the new exhaust pipes, they're always coated in oil to keep from rusting , give it a few days it'll go away. if not then you probably need valve seals.

I got a question?? I have a 88 chevy Cheyenne k1500,350 engine and 4 spd manual. i got this truck with no exhaust only headers.. well we rigged up the exhaust to get me by until i can afford new exhaust. well we noticed white/grey smoke coming from the exhaust.the heat is hot,the oil isn't milky,and its not burning antifreeze and the guy i got it from said the head gasket were supposedly new.well i seen that the o2 sensor wasn't hooked up.i had a mechanic look at it and said that its dumping way too much fuel.well i had a bung welded and a o2 sensor installed although the o2 sensor wouldn't reach so i spliced into the truck wire,added some 14 gauge wire and tapped it up,then connected the o2 sensor.well after that i started the truck and it didn't want to catch and fire until i held the pedal to the floor and it fired up. still smoke??? i need help!!!! the guy said that the computer system may be messed up but idk help please

35,255

Holding your foot to the floor puts the ECM in clear flood mode which prevents the injectors from opening while cranking. Check fuel pressure, could be a leading injector or leaking fuel pressure regulator diaphragm. Fuel pressure leak down test will help steer us in the right direction.

1 of 1 people found this helpful.
35,255

Intake air temp sensor and engine coolant temp sensor could also both be a culprit

3,335

wait a minute boys ...... It's the valve stem seals , you can change them if your very careful . you need an air compressor ,air hold fitting with the 5/8 20tpi spark plug threads and a tapered seat , and a valve spring compressor that works with the heads still on the car ... this sounds bad but it's easy , just remove the rockers on one cylinder at a time ,air up the cylinder and keep air on it 'tll your done with that cylinder then move on ... don't try this if you ain't ever had a valve cover off before ..

3 of 3 people found this helpful.
3,335

use 90 psi and hope your rings ain't too bad ...PBN

1 of 1 people found this helpful.
35,255

Could be oil but valve seals tend to clear up after initial startup and won't cause the engine to flood.

3,335

who said anything about flooding ? he's got blu smoke when it's at max vacuum it's rings or valve seals ... aint it ? didn't say it missed like if you had a sucked intake gasket it just smoked ... could have been the new pipes ...

3,335

I guess I should finish when you have both valves closed and the 90 psi on the cylinder ,listen for a hissing sound and detect whether it's crankcase ,exhaust or intake in origin then you will know where your weakness is .... rings , exhaust valve or intake valve ...

35,255

well after that i started the truck and it didn't want to catch and fire until i held the pedal to the floor and it fired up. still smoke???  It started when he held the pedal to the floor because the engine was flooded out......

35,255

Nobody reads anything fully on here, they just read the first line and spit an answer.

3,335

nuff said ... I fell into that one .... but hear me .. I won't get fooled again !!

1 of 1 people found this helpful.
35,255

majority of smoking old chevys are from different oil being used every oil change. the different additives kill the valve guide seals mine smokes on startup and thats it the valve guide seals are gone. 2 ways of changing em and they are not pretty.

6 of 6 people found this helpful.

ok i need help you guys i have a 1991 chevy c1500 and my trannys front pump is going out so i have to hit damn near max rpms for it to shift and i was at 6200 rpm, its a stock block but have a chip and it now smokes like a train after like every 10 miles but when it does i shit you not it burns like a half a quart every time it does it and it smokes when i start it , so i have literally gone throught like 15 quarts of oil it the past 3 days i really need some help!!!

oh and its a small block 350

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