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2005 gmc envoy_slt_xl
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Discussion Starter · #1 ·
This is a long story so I'll leave out the "why i did it" and give the facts. Bought the 4.2l evnoy used with 85k miles. It ran ok but used oil. Found out #2 cylinder was using the oil. Finally I burned a #2 exhaust valve. I changed the valve. About 5000 miles later, I burned the adjacent exhaust valve. I just change the entire head with a rebuilt one. I have it all back together and running. But its not running right, using my obd tool, the water temp is about 175, the timing jumps around between 8 and 20 degrees then jumps to 25 once the throttle is pushed, it idles fine but when i hold a rpm above idle, say 2000, the rpms will oscillate from 1800 to 2000, and the exhaust is no longer blue but faint white and it has a bad smell, but I can't tell if its rich or lean. No codes, but I only drove it around the corner. Power seems to be better than before. I also have the following concerns:
I would like to know if a bad injector, bad coil pack or bad exhaust cam actuator cause a burnt valve?
The manual said to install the exhaust cam actuator full advanced, it came off the cam in one piece and I put it on the same way. There is a spring in the middle and i tried to turn it but it wouldn't budge. Should I have been able to rotate the parts?
Also, I can spin the Exhaust Cam Actuator Solenoid housing. I found out by accident when I was trying to remove it. Is that bad?
Since it was burning oil, should i change the O2 sensors? How about the Cat? meow
 

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2005 gmc envoy_slt_xl
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Discussion Starter · #2 ·
New info

I went out and drove around, i checked for codes at all my stops and accumulated these codes 128 x2 and 526. Code 041 (I think) showed up once but then went away. 128 is for the thermostat, 526 is for the fan speed sensor and 041 (if i remember right) is for cam timing. On occasion, the engine did seem to surge under acceleration.
 

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2005 gmc envoy_slt_xl
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Discussion Starter · #3 ·
No one?

I'm suprise nobody has anything to say. Is this issue to complex for this forum? I just like doing things myself no matter how complex. Anyway, i've included some pictures of the plugs and compression numbers. Compression on all six are between 200 and 195, the bad plug is #2, the same cylinder I burnt the valve in. Is it the injector? Could an injector cause a burnt valve. The engine still seems to be burning oil.
 

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2002 gmc envoy_slt
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I think the problem is that not too many of the currently active members have either pulled their heads or actually swapped the actuator assembly in the head. Most service of the cam phasing is via the solenoid, which can fail....located sort of behind the power steering unit. First thought that comes to mind is are you sure there's nothing else leaking into the combustion camber? - White smoke usually indicates a water/coolant leak, which begs that question, has the coolant level changed at all since you swapped the head.

I would expect the O2 sensor to generate a specific codes and other than plug #2, they don't look too bad. My thoughts go towards either the cam phase isn't right or the engine is out of mechanical time from the swap. Did you take extreme care to both prevent the crank from turning and light up the both cam sprockets in the exact same position as the they were prior to pulling the head? - It sort of sounds like the mechanical timing (crank to cam positioning) may be a little off or there's too much slack in the timing chain. I haven't done this sort of work on my I6, but I have done heads and timing belts/chains before on other motors and being just 1 or 2 sprockets off can make for a really bad running motor. (If this is the problem, you risk burning valves and/or damaging a valve.....the 4.2 is an interference motor, if memory serves correctly). The real PITA part is that to check/set mechanical timing, I think it may be necessary to pull the oil pan to align the crank sprocket. (It's going to be easier to re-check the cam phaser first).

Unfortunately (or is that thankfully for me?), I haven't needed to pull the cam phaser assembly off, so I can't with any certainty tell you how it re-assembles. If you disconnect the phase solenoid, does it steady out the timing? You'll get a code for the cam timing, but that should prevent the engine from attempting to adjust exhaust timing. If it does, it might help narrow down the issue to the phaser assembly not being right, as opposed to mis-alignment of the crank to cam sprockets (mechanical timing).
 

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2005 gmc envoy_slt_xl
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Discussion Starter · #5 · (Edited)
I appreciate the input. I did take extreme care to make sure the timing was good. Early in the story I changed the valve so I had the original head off once. That was when I learned about the ONE friggin bolt that holds the front cover on that is located in the oil pan. The other lesson was TTY bolts. So this time I took extreme care. I peeked through the plug hole and the top of the piston looks wet. If its oil, I guess its coming from the block. What if the injector is bad? Maybe too much gas? Would that give me symptom of wet piston top, carbon on the plug, white/gray smoke? I've gone away from the timing diagnosis due to one cylinder running incorrectly. I let the truck sit overnight and I checked the oil this morning. I'm going to drive it some and then let it sit overnight again to see if the level changes. The coolant level hasn't changed. I have another post on carjunky.com called #2 cylinder fouling, no serious replies there yet.
 

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Discussion Starter · #6 ·
So i haven't driven it yet like i said I was going to, i decided to ohm the injectors first. All were between 13.9-14.2 ohms. From what I read in other posts, that should be good. So I swapped injectors between #2 and #1 to see if the fouled plug moves with it. Both plugs in #1 and #2 are clean and I moved the #2 coil pack to #4 and the dirty plug is now in #3. Before I drive it I"m going to clean the throttle body.

While I had the intake off I inspected it and ensured no holes were plugged. I don't see any cracks or evidence of leaking around the gasket but the inside did seem overly oily and the #2 runner in the head had carbon around the lip.

Is the oil getting into the intake some how? If so, how would it only effect #2 cylinder? There isn't a leak from the valve cover.:suicide:
 

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Discussion Starter · #7 · (Edited)
A note to add about the timing. When I got the timing chain/gears all set, I rotated the engine by hand a couple of times and then set the #1 at TDC. the flats of the cams were nearly straight up. It wasn't off much and I chocked it up to the wear on the gears and chain after 112K.

PS I feel like I'm talking to myself.
 

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2002 chevy trailblazer_ls
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post 4 sums it up pretty well... some knowledgeable people left here and a ton of stuff in the old threads, but some highly technical stuff may take time for someone with knowledge to answer here if you can't find something on the old threads in search that is similar.
 

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2002 chevy trailblazer_ls
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see the 4th message... but add a 't' looks like he missed a letter
g m t n a t i o n. c o m
this site doesn't like they made a new site due to the owners adding ads that don't relate to our trucks, and that they would make not improvements to the site and basically only support they provide is to kick people off for telling the truth or continually asking for simple upgrades to the site. and they don't like links to the other site. the new site is composed of people who started this site originally, and many are engineers. Dollars over good service. Owners of this site own many others and only care about ad money :coffee
 
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