Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 20 of 30 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
I have a 2006 Chevy Trailblazer with the 5.3 V8. The engine light is on for a cylinder 1 misfire and the engine light flashes while driving along with smoke that comes out the exhaust. Im mechanically inclined for the most part but i am no mechanic so i dont know everything. Any suggestions would be greatly appreciated. I also had it checked over and there is spark and fuel to that cylinder but little to no compression. I bought it about a month ago and it has been doing it since i bought it.
 

·
Registered
Joined
·
21 Posts
Sounds like a bad coil.
Pull it and the plug and see what the plug looks like.
You can swap coils from one cylinder to the other and see if #1 works.
If it does then #1 coil is bad.
Good luck,
Peter C.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
I have done the trick with swapping the coils nothing changes. I have also checked the sparkplug and its new. Plug wires are also new. I forgot to add that I'm sorry
 

·
Registered
Joined
·
2,103 Posts
No matter what --- the flashing light is telling you that you are killing your cat.

I've always said that just a flashing light without a small hammer that comes out of the headrest to really get the attention of the driver, is a waste of a good light bulb.
 

·
Registered
Joined
·
2,103 Posts
Does the smoke linger or disappear quic6? (*quick)

Smell it ... is it sweet or sharp enough to water your eyes or smells like hot coolant?
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #8 ·
Its not bad enough that it waters your eyes but its a strongish smell it smokes mostly when you are driving and when idling its more of a slight smoke
 

·
Registered
2003 chevy trailblazer_ltz
Joined
·
237 Posts
The engine light is on for a cylinder 1 misfire and the engine light flashes
Fix this NOW. MAYBE you can still save the catalyst. Maybe. (Probably not, given the amount of time the misfire has been going on. Might as well budget for catalyst replacement, and then hope for the best.)

I also had it checked over and there is spark and fuel to that cylinder but little to no compression.
That sounds expensive.

Next step is to do a cylinder leakdown test. Find out where the compression is going. If you hear air escaping out the throttle body, the intake valve doesn't seal. If you hear air escaping out the tailpipe, the exhaust valve isn't sealing. Either way, you're likely pulling the cylinder heads for a "valve job".

If you see air bubbles in the coolant, you've got a cracked casting, or perhaps a failed head gasket. Again, the head(s) are coming off.

You're going to hear air escaping at the oil fill (remove the cap), the question is "how much", which is why you need the leakdown tester--so you can use the pressure gauge(s) to determine acceptable leakage from excessive leakage.

When it was my money, I bought a leakdown tester intended for Continental/Teledyne aircraft-engine use. The important parts are the orifice size (.040, for engines with a bore size of 5" or less, tapered inlet) and the Master Orifice which allows you to "test the tester". Without the Master Orifice, you need to use the tester on several "Known-Good" cylinders having the same bore size as the engine you're trying to diagnose. At minimum, you'd need to test the other seven cylinders that aren't giving you trouble, and compare the results to the reading from the Problem Child.

 
  • Like
Reactions: Ravalli Surfer

·
Registered
Joined
·
112 Posts
Guys he said little to no compression. Is it possible that the exhaust valve is stuck open?
 

·
Registered
2003 chevy trailblazer_ltz
Joined
·
237 Posts
Guys he said little to no compression. Is it possible that the exhaust valve is stuck open?
Sure. How much damage did it do when the piston hit it? Valve seized in the guide? Bent valve?

Any way you look at it, that head is coming off for repairs if there's no compression.
 

·
Registered
Joined
·
2,103 Posts
Fix this NOW. MAYBE you can still save the catalyst. Maybe. (Probably not, given the amount of time the misfire has been going on. Might as well budget for catalyst replacement, and then hope for the best.)


That sounds expensive.

Next step is to do a cylinder leakdown test. Find out where the compression is going. If you hear air escaping out the throttle body, the intake valve doesn't seal. If you hear air escaping out the tailpipe, the exhaust valve isn't sealing. Either way, you're likely pulling the cylinder heads for a "valve job".

If you see air bubbles in the coolant, you've got a cracked casting, or perhaps a failed head gasket. Again, the head(s) are coming off.

You're going to hear air escaping at the oil fill (remove the cap), the question is "how much", which is why you need the leakdown tester--so you can use the pressure gauge(s) to determine acceptable leakage from excessive leakage.

When it was my money, I bought a leakdown tester intended for Continental/Teledyne aircraft-engine use. The important parts are the orifice size (.040, for engines with a bore size of 5" or less, tapered inlet) and the Master Orifice which allows you to "test the tester". Without the Master Orifice, you need to use the tester on several "Known-Good" cylinders having the same bore size as the engine you're trying to diagnose. At minimum, you'd need to test the other seven cylinders that aren't giving you trouble, and compare the results to the reading from the Problem Child.

I think it's really "swept volume" of the cylinders that are the testing criteria, since one engine with a 5" bore and a 3/4" stroke is gonna be miles different from an engine with a 5" bore and a 10" stroke.
 

·
Registered
Joined
·
2,103 Posts
I have by now seen not just a few 4.2s with followers that have jumped off the camshaft and cease to motivate their intended valve ... hence: loss of compression.

Oops! You've got a 5.3 --- nevermind
 

·
Registered
2003 chevy trailblazer_ltz
Joined
·
237 Posts
I think it's really "swept volume" of the cylinders that are the testing criteria, since one engine with a 5" bore and a 3/4" stroke is gonna be miles different from an engine with a 5" bore and a 10" stroke.
Nope.

The leakage is past the rings. Bore diameter has a major impact on ring circumference, and ring end-gap, both of which have an effect on leakage. Big bore = tendency towards more leakage. Smaller bore = tendency for less leakage.

The cylinder length/stroke length is of no importance for leakdown testing, since the piston is held at TDC or very close. Which works out well, as "most" cylinders have the most wear at the top, so not only are you testing ring leakage, but you're testing it in the part of the bore that's most-likely to be worn, and within a few crankshaft degrees of maximum cylinder pressure when the engine runs. Some folks do the leakdown testing at about 7--10 degrees past TDC, but I don't bother.

So--for engines with a bore diameter of less than 5", a .040 orifice in the leakdown tester is correct.
 

·
Registered
Joined
·
2,103 Posts
Nope.

The leakage is past the rings. Bore diameter has a major impact on ring circumference, and ring end-gap, both of which have an effect on leakage. Big bore = tendency towards more leakage. Smaller bore = tendency for less leakage.

The cylinder length/stroke length is of no importance for leakdown testing, since the piston is held at TDC or very close. Which works out well, as "most" cylinders have the most wear at the top, so not only are you testing ring leakage, but you're testing it in the part of the bore that's most-likely to be worn, and within a few crankshaft degrees of maximum cylinder pressure when the engine runs. Some folks do the leakdown testing at about 7--10 degrees past TDC, but I don't bother.

So--for engines with a bore diameter of less than 5", a .040 orifice in the leakdown tester is correct.
You're doing a static blowdown? That's so 1960-ish.

The Snap-on dynamic version can use cranking or running blowdown tests that are pressure wave readings through the sparkplug hole to plot air bypassing the rings in an either high or low value, plotted by a piezoelectric sensor.

Mucho more accurate because it is dynamic, mimicking actual operation conditions and not in just one place (tdc).

Rings that are worn can show a false disadvantage at tdc where the bore, coupled with ring land wear might show high losses, but at lower than tdc position, the rings become moved closer into the piston land bottoms --- and out of the land bellmouth --- and they will be more than adequate in holding compression pretty much in any place out of tdc anyway.

Low pressure static testing doesn't mimic any actual operating condition in an internal combustion engine and I've had rings with less than 1000 miles on them test as bad ... so I quit using the test you recommend as grossly inaccurate and drawing to absurd convictions when it was used by me.

Power contribution values should all be within 10% of each other per cylinder for a good running engine that is nearing its prime-of-life downcurve.



.
 

·
Registered
2003 chevy trailblazer_ltz
Joined
·
237 Posts
In a cylinder already known to have "no" compression, a static test is a wonderful way to verify intake vs. exhaust valve seal, and (low-pressure) leaks into the cooling system. Used with care, it's good for spotting leakage into the crankcase via worn/broken rings or holes in the piston. I've been doing "1960-ish" low pressure leakdown testing since the late 1980s; I've found it to be extremely useful.

A dynamic test like you describe can plot cylinder pressure vs. degrees of crank rotation; but doesn't tell you where the compression is going. The transducer in the plug hole isn't measuring leakage past rings, past either valve, or into the coolant. Right? And you'd never hear the leakage at the throttle body or tailpipe with the crank turning.

PS: What equipment are you using from Snap-On that does this--Modis/Vantage + pressure transducer?
 

·
Registered
Joined
·
2,103 Posts
Really when it comes down to what component is leaking, it becomes moot in a production shop because if its rings, a hole in a piston, a bent or bad valve or a blown head gasket... it's surgery time anyway.

Over diagnosing an engine against a slam-dunk loss of compression is great in academic theaters, but of little practical value in the field.

I've had scrolling compression testers, aneroid and mercury column styles, but unless I'm trying to sell a job, they're time consuming and damnably expensive up front.

The Snap-on dynamic tester is in my shop ... somewhere .... it was for me when I owned 1/2 interest in a Citabria and considered getting an A&P ... and I used it a few dozen times automotive-ly, but not once more in over 40 years now.

But I just use a blower nozzle in the spark plug hole and I know it's going to come out somewhere ... exhaust, intake or oil filler and possibly the dipstick. If I can catch the cylinder at TDC ... I can usually get some blowby at very low air pressure on most any engines because of the cylinder taper or ring gap ... this I tend to ignore because ... again ... it ain't dynamic.

If the leak is very subtle ... I've always got my Steelman Electric Ears/Stethoscope. If it's MY engine ... I'll play with it for a while ... but low or loss of compression will always start with excision of the valve cover .... and from there it's progressive revelation.

Dig we must!


.
 

·
Registered
buick rainier
Joined
·
26 Posts
My bet is that your DOD (Displacement on Demand) has gone bad. How the DOD works is there are oil passages that collapse the #1,4,6 & 7 Cylinder lifters, what happens is the lifters wear and they get jammed and will not release. I am not sure how or why, but that is what happened to me. Before this happens, usually you have a problem with one of those 4 cylinders (1,4,6,7) will keep fowling out the spark plug with oil.
The bad news is 99% of the Mechanics will tell you that your engine will need to have the intake, heads removed and replace the lifters. which is true, if you do it as per the book. However there is an easier way to fix it.
I did this and it worked perfect.
1) I was having #1 fouling issues, every 6 months I would have to change the #1 spark plug,
2) When replacing the spark plug no longer worked
3) I did a compression test, compression seemed fine, #1 was a little lower, something like 130PSI, The others were around 150PSI
4) Removed the (drivers side) valve colver, and discovered that the intake lifter was collapsed, I could wiggle the rocker.
5) Removed the intake, and then used this guy's tool worked like a champ, I broke my intake just as he showed,
6) I was not going to drive it so I sent my ECM to LT1 Swap and for $under $100 I sent him my ECM, he disabled DOD, and sent it back to me.
All in all I think I was around $400 in parts for everything, the tool, the ECM DOD delete, the intake gaskets, and the special tools I did not have to into the engine.

If you have a mechanic fix it, expect to pay $2500-$3000 as they will want to remove the entire top of the engine, replace everything, which is not a bad thing, but it seems much for a vehicle that is probably worth $3000.
 
1 - 20 of 30 Posts
Top