Lack of power

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.

Thank you so much I wish I tried what you said because I took it into the shop and charged me 340.00 for the sensor replacement and I found the sensor for 45.98.

I have a 2004 Trailblazer and I have always been happy with the performance until a about a month ago. When I start up the vehicle in morning it runs rough, so after it has warmed I notice as I am driving I do not have the pick up and go that it used to. I have changed the fuel filter, air filter. I want to know if I should change spark plugs? I have read a number of posts that say that it may be the Idle air control valve and/or the Cam Actuator Solenoid. Not sure if I should try to replace these as well.

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

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?

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.

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.

My Trailblazer has no power and will not go over 2,000 RPMs. I have replaced the spark plug, gas filter, throttle body acceleration pedal when I'm using A/C it stops, no going car. No any power. What can I do? Please can you help me? Thank you