2004 Trailblazer loss of power and rough idle after new head gasket

Tiny
JACKCRAYNE
  • MEMBER
  • 2004 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
I have a 2004 trailblazer that had a blown head gasket. I purchase the Camshaft Holding Tool, I already had the angle meter and I purchased the tension-er holding tool to complete the job. Everything went well during the rebuild and I took my time. All the timing marks lined up, etc. I followed detailed instructions during the whole process and took my time. When I fired it up it did ok but I notice a rough idle but did not notice a loss of power. This rough idle go worse and now I get the P0016 code and some loss of power. I can clear the P0016 it and it comes back. I have a scan tool that gives me some data. Camshaft phase solenoid DC 0%, Cam Phase angle desired 0, Cam Phase angle Actual 0, cam phase angle variance 0, CMP and CKP active counters are showing changing data. I have replaced the actuator on the side of the engine and the exhaust cam sensor. When I pulled the old actuator I notice that the screen had some aluminum dust on the screen from where the head was milled down. I had tried to clean this from the head prior to installation but I guess I missed some. I went ahead and put in the new actuator. I have since pull the new actuator and the dust is gone. I have also changed the oil since. I have pinned out the wires from the actuator the PCM and they are good. I need some help and ideas. The question I have is concerning the operation and setting of the actuator sprocket. When following the instructions I was not sure how the advance the actuator on the exhaust sprocket when bolting it up to the cam. I tried to turn the front of the sprocket clockwise and it would not move. I didn’t want to force because I have read you can damage it. I need to know the details on how to advance the actuator on the sprocket so I can confirm if I’m doing it correctly or maybe mine is bad. I can say it would not rotate forward or backward. Also, the timing marks lined up on both sprockets correctly at TDC. Can the crank be off even with the two at the top dead on? The chain seem to be tensioned evenly.
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Tuesday, September 6th, 2016 AT 5:22 AM

14 Replies

Tiny
HMAC300
  • EXPERT
A mechanic has to fix the P0016 code he can do it with his scanner the cam and crank sensor are out of sync.
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Tuesday, September 6th, 2016 AT 5:29 AM
Tiny
JACKCRAYNE
  • MEMBER
Thank you for your quick response. Do you have any comments on how to fully advance the actuator on the exhaust sprocket? I cant find any good information and I would really like to see a video on this to know I have done it correctly. I am planning to find a shop with the scan tool to do the resync as suggested.
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Tuesday, September 6th, 2016 AT 7:52 AM
Tiny
HMAC300
  • EXPERT
The actuator has to be rotated clockwise prior to tightening the bolt that holds it on.
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Tuesday, September 6th, 2016 AT 9:18 AM
Tiny
JACKCRAYNE
  • MEMBER
Just so I understand, once you place it on the cam, then it should rotate clockwise? What actually rotates? Is the the round end that rotates or the whole gear?
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Tuesday, September 6th, 2016 AT 9:27 AM
Tiny
HMAC300
  • EXPERT
The round end see pics
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Tuesday, September 6th, 2016 AT 11:59 AM
Tiny
JACKCRAYNE
  • MEMBER
Again, thank you for your help. I will let you know if the CASE relearn works. We should have this completed in a day or so.
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Wednesday, September 7th, 2016 AT 4:09 AM
Tiny
KEN
  • ADMIN
Please let us know what you find so it will help others.

Best, Ken

PS nice answer Hmac300
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Wednesday, September 14th, 2016 AT 6:17 PM
Tiny
JACKCRAYNE
  • MEMBER
I had the relearn done on Monday and it did not take. Now there is also a code for one of the O2 sensors in addition to the P0016. Before I sent it for the relearn I checked the compression on each cylinder. From one to six 145,142,120,132,119,122. The vehicle has 180,000 miles on it but I think this is very low compared to other posts on compression tests. At this point I am thinking the either the Actuator on the exhaust sprocket has rotated too far past the stop and is stuck/broken or the chain moved a tooth on the crank. My plans are to remove the valve cover to inspect the timing mark alignments. I have also purchase a 5mm endoscope to look at the chain on the crank gear without removing the chain cover. If I can fish the scope down to the crank gear I want to confirm the timing marks are correct on the crank gear as well as the cam sprockets. I will verify the "Delphi" alignment also. From what I understand if the timing marks are correct and the "Delphi" alignment is not parallel to the head, the Actuator is probably bad. I have videos from the whole installation that I have to go back through also to see what it looked like again when going back together.

Any suggestions or comments are welcome
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Thursday, September 15th, 2016 AT 4:51 AM
Tiny
KEN
  • ADMIN
Yes the compression is low, can you do a leak down test to see if the valves are holding you might need a valve job, the reason I say this is because one have two cylinders that are okay.

Please run some tests and get back to us so we can continue helping you.

Best, Ken
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Thursday, September 15th, 2016 AT 10:40 AM
Tiny
JACKCRAYNE
  • MEMBER
I have not gotten around to the leak down test yet.

I did however decide to take the valve cover back off to check the timing marks at TDC. All of my original disassembly marks are still there including the marks I made on the crank pulley. I used a fluorescent pen to mark the position of the crank and both cam sprockets. I could easily verify that the intake and exhaust sprockets are aligned with the timing marks to the cam. However with the DELPHI" and cam flats parallel to the head, my original crank marks that I made during the disassembly were not lining up. When I rotated the crank so that the #1 piston is at top dead center and my original crank marks lined up, the flats on the end of the cam shafts and the "DELPHI" was not parallel to the head (rotated to right). It was obvious the chain was off one tooth on the crank.

I did not want to remove the front cover to correct this. What I did was move the chain back over on the crank sprocket one tooth to make the alignment good again. To do this I removed the exhaust sprocket completely and let the chain be loose. By using a coat hanger and allowing some slack on the intake side I was able to get the chain to just back into place. To get the amount of slack you need, you have to let the chain loose to go down below the crank sprocket. This allows the tensioner to go all the way out. I made sure my crank marks were aligned and the cam flats were parallel to the head. I also made sure there was not any extra slack in the chain between the crank sprocket and the intake sprocket after getting the chain back in the place on the crank sprocket.

Here is my details on the tensioner reset for the readers. To get the tensioner back in, you can fish a coat hanger do the front side of the timing chain compartment between the front wall and the chain guide and pull the lever and push the tensioner back in enough to get the exhaust sprocket back on. It s tight and you have to be in the perfect position to see the lever but it is doable. I recommend looking at some pictures of the tensioner online to see the locking lever mechanism on the side of the tensioner. There is a hole on one end; the left end of the lever when looking from the top. Bend the coat hanger so there is a 2mm wire hook sticking out at a right angle at the end. Don t make the hook too long as it will get stuck in the whole. Push the lever up and down a few times to make sure the tensioner is all the way out. Then pull it up (it should move pretty easily) and then pull on the chain tightly on the exhaust cam side to get the tensioner plunger to go back in. I also used the timing chain tool in the normal recommended holding position to help push the tensioner back in. With the tensioner back in and keeping the chain tight you can put the sprocket on with the timing marks aligned. Take the clothes hanger and try to get the tensioner to go back out. I think this is where I made one of my mistakes on the original reassembly. I didn t do this and remember the chain being a little loose between the crank sprocket and the exhaust sprocket.

I placed the old bolt back in the exhaust sprocket to rotate the engine two of three time to top dead center. Everything is now lining up. The cam flat and DELPHI are parallel to the head. At TDC my crank marks are lined up.
Today I will install the new exhaust cam bolt to specifications and reassemble everything. I also plan to check the compression again along the wat to see if it is any better. I will post the results as soon as possible.

As a side note I did check the rotation of the phaser on the end of the exhaust sprocket. I can only get it to move maybe 1/8 inch back and forth by hand. Is this correct?
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Monday, September 19th, 2016 AT 6:16 AM
Tiny
HMAC300
  • EXPERT
The phaser doesn't move that far and since we can't see it running it is probably ok.
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Monday, September 19th, 2016 AT 10:49 AM
Tiny
JACKCRAYNE
  • MEMBER
Yesterday I was able to put everything back together. I did the compression check again and has similar results as the last. I started the engine and had a rough idle but the P0016 is gone. Before it would show up immediately. Now I get the P0300 with the check engine light flashing. I checked the misfire data with my Autel MD802 scanner (this one scanner has worked great on my BMW, Volvo, ford and Chevy). It showed misfires consistently on the #1 and #6 cylinders. I decided to move the coils from #1 and #6 to #2 and #3. The misfire moved to these cylinders. Today I will pull the two bad coils and check the condition of the spring inside the coil. I want to make sure the spring is making contact with the end of the spark plug. I plan to replace the 2 coils today if I cant get them to work.

I believe the 2 coils have been bad since the head gasket blew and the vehicle ran hot. The rough idle I have been getting was in a large part due to the bad coils. I did not check the misfire data since the code was not showing up. I think that due to the cam and crank sensor sync issue (P0016) the P0300 cannot be detected. From what I read the cam sensor detects the misfire in some way. I guess it expects to see a torque value change when the piston fires. If the P0016 is present maybe the PCM just stops there with the codes.

I will report back with the results of the coil analysis and hopefully a road test.
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Wednesday, September 21st, 2016 AT 5:40 AM
Tiny
JACKCRAYNE
  • MEMBER
Yesterday I was able to install two new coils to replace the failed ones in position 2 and 3. This resolved the misfire problem. I checked for misfires on the scan tool and there are none. The P0016 code has not showed up again. I too the trailblazer out for test drive and it seemed to perform much better than before the head gasket failed. There are no unusual noises or ticking. I was able to see the desired angle, the actual angle and the % of voltage for the actuator. This data was changing normally and the actuator and phaser seemed to be working properly now. I had read that the actuator is disabled when there is a P0016 code as I had previously before I corrected the timing issue. It was nice to see this data changing and these working together now.
If I had to do anything that involved removing the exhaust or intake sprocket again I would definitely use wire to hold tension on the chain so that it would not be dropped back into the timing chain cavity. The instructions say to use the holding tool and let the chain go into the cavity. I found it difficult to keep the tool from moving and the tension-er will move out. If the chain falls off the crank gear the timing chain will likely move a and you could skip a tooth. Also the timing mark I made on the harmonic balancer when taking the head off initially helped to realign the crank and reset the timing chain after I found the chain was off a tooth. I think you can still get the crank in position again buy making sure the #1 piston is at Top Dead Center even if you did not make that alignment marks during disassembly. The chain has to be tight from the intake sprocket to the crank gear. That is the important point to ensure the chain is on the correct crank gear tooth.
I think I have another project ahead of me on the trailblazer. I saw that the harmonic balancer bolt has a slight wobble to it when the engine in running. I think I will have to pull the balance and at least replace the bolt.
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Thursday, September 22nd, 2016 AT 6:05 AM
Tiny
HMAC300
  • EXPERT
Glad we could get it fixed please use 2CarPros. Com anytime we are here to help
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Thursday, September 22nd, 2016 AT 6:36 AM

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