When engine is warm there is blue smoke coming from the dual exhaust, also misfire code reading on cylinder number five

Tiny
LISA SIEGMAN
  • MEMBER
  • 1998 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 153,000 MILES
I have blue smoke coming out of my dual exhaust only when it is warm and I am getting a misfire reading on cylinder number five. Oil is good and so is the pressure, oil cap is good and antifreeze level is good. I did a compression test and it passed. What could this be it is driving me insane?
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Friday, December 16th, 2016 AT 3:29 PM

45 Replies

Tiny
HMAC300
  • EXPERT
Misfires are a tough to find even for a mechanic. He has to check sensors with his scanner and injectors. If compression is okay it can be a bad wire/spark plug really anything these are best handled by a professional for your cheapest option.
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Friday, December 16th, 2016 AT 3:35 PM
Tiny
LISA SIEGMAN
  • MEMBER
Plugs are brand new and so is coil pack, plugs and wires. It is just on number five.
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Friday, December 16th, 2016 AT 3:40 PM
Tiny
JOHNNY G.JR
  • MEMBER
Blue smoke, check your PCV valve and engine breathing system.
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Friday, December 16th, 2016 AT 3:47 PM
Tiny
STEVE W.
  • EXPERT
I take it all this was done for the misfire and smoke?

Blue smoke, misfire on 5 in a 5.7, could be a split intake valve stem seal or a collapsed oil control ring. Pull the plug out and see what it looks like. Borrow/rent an inspection camera and take a look inside the cylinder for carbon on the head/piston. Compare it to a couple other cylinders. If it is clean then it probably is not the seal. If it is oily/sooted up then you are getting oil. Compression test would not show either one. Both require visual inspection.
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Friday, December 16th, 2016 AT 4:26 PM
Tiny
HMAC300
  • EXPERT
Normally on this engine the seals for valve stems wear out at the mileage and age that would clear up smoke if all intakes were replaced but misfire is something else. Unless guides were worn out.
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Friday, December 16th, 2016 AT 5:05 PM
Tiny
LISA SIEGMAN
  • MEMBER
It ran fine until I had a fine tune done and after I had it done it started doing this.
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Friday, December 16th, 2016 AT 6:06 PM
Tiny
STEVE W.
  • EXPERT
What did they do for the fine tune? Did that include all the new parts or were those to repair the current problem? It is not unheard of to get a bad part out of the box.
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Friday, December 16th, 2016 AT 6:53 PM
Tiny
LISA SIEGMAN
  • MEMBER
I had to replace my distributor cap and rotor and then I replaced timing chain and gears and my cam and crank was out of wack so I took it into the shop and they said I was out of tune so they hooked it to a scanner and had it timed right and ever since then I blew a coil pack and five plugs. I replaced the coil plugs and wires and now five will not quit fouling.
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Friday, December 16th, 2016 AT 7:17 PM
Tiny
HMAC300
  • EXPERT
If you have the resources put air into cylinder five and see if you can see air leaking into valve cover remove the valve cover if it is fouling like really quick it may be a broken ring. Or if you pull valve cover and a lot of oil comes out from that then clean your drain returns and clean out sludge then see if it continues.
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Saturday, December 17th, 2016 AT 7:37 AM
Tiny
LISA SIEGMAN
  • MEMBER
That is something I will try. What is the best cleaner to use for the sludge? I have been doing this work with a little help.
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Saturday, December 17th, 2016 AT 7:50 AM
Tiny
HMAC300
  • EXPERT
Scrape out as much as you can then once drain holes are clean. I used to use a little mineral spirits, then change oil. That is if you have sludge and check PCV to see if it works.
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Saturday, December 17th, 2016 AT 10:40 AM
Tiny
LISA SIEGMAN
  • MEMBER
Wierd question if u have a blown head will it constantly overheat or no or could I have a blown intake because I have heat don't overheat but I do have a blue tinted smoke coming from the exhaust and it looks like a fog machine
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Saturday, December 17th, 2016 AT 6:50 PM
Tiny
STEVE W.
  • EXPERT
It's possible that an intake gasket has cracked and it's pulling oil in. Not real common for them to fail that way (these usually fail on the ends and leak coolant into the engine). Not that hard to pull the upper off and snake a camera in and check.
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Saturday, December 17th, 2016 AT 11:20 PM
Tiny
HMAC300
  • EXPERT
If it looks like a fog machine then pressure check coolant system for a blown head gasket or intake gasket
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Sunday, December 18th, 2016 AT 8:01 AM
Tiny
LISA SIEGMAN
  • MEMBER
If I do the intake then I might as well do the heads right just to be safe
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Sunday, December 18th, 2016 AT 8:17 AM
Tiny
HMAC300
  • EXPERT
Sure
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Sunday, December 18th, 2016 AT 9:23 AM
Tiny
LISA SIEGMAN
  • MEMBER
What's the easiest way to do a head gasket on my 98 Chevrolet silverado 5.7
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Monday, December 19th, 2016 AT 6:11 AM
Tiny
HMAC300
  • EXPERT
Rent a manual from us you can print instructions right from manual for what ever you need to do on your truck it's best done inside vehicle.
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Monday, December 19th, 2016 AT 6:57 AM
Tiny
LISA SIEGMAN
  • MEMBER
What is a ported vacuum switch for some reason I can not find it anywhere to buy
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Tuesday, December 20th, 2016 AT 5:18 PM
Tiny
STEVE W.
  • EXPERT
That looks like the vacuum port adapter for the power brake booster. Circled part yes?
Think it's a salvage yard or dealer only piece. Never really needed one. I'll look at the parts book and see if it shows up.
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Tuesday, December 20th, 2016 AT 7:25 PM

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