Needing some help from you guys. I have an 04 trailblazer. 4.2 engine with 192,000 miles on it. I had a rough idle two weeks ago. I was getting various codes. They were P0016, P0171, P0301, P0300, P0136, and P0014. The oil change was overdue. Had it changed and still ran rough. thought the injectors were plugged so I put seafoam in the tank and crankcase. Seem to make it worse. I replaced the camshaft sensor. No change. Swapped the #1 & 2 plugs. No change. Did the #1 & 2 coils. No change. Bought ac delco iridium plugs 41-103. Checked the gap before I installed them. No change. Changed the vvt sensor. Ran a little better. The only code I get now is P0300 multiple random misfires. I haven’t checked the coils yet. I didn’t buy the better ones. Thinking I should have. I really don’t want to be buying things it doesn’t need. Wondering if it’s the coils. Any ideas what it could be? Thanks in advance!!!!
NEED HELP😩
- Thread starter Wawuce
- Start date
Was it hot outside? My truck runs rough when it is hot out and sometimes dies when I pull from a stop. I have the same P0300 code, but my throttle body is also jacked and giving a code for that too. I think it has to do with the ignition coil design and the stupid springs in them. I've heard there is a fix that replaces the spring with a thick piece of metal and helps the idle.
If the oil change was overdue, more than likely the CPAS is plugged or it's just defective (related to P0016, P0014). Replace your O2 sensor (P0136 and possibly P0171). for your misfires, do you have a scan tool that can show live data? Look at the misfire data to see which ones are misfiring. It usually throws P0300 at first when it's determining which one is misfiring but if it's staying on, it may have more than one.
P0301 Misfire Cylinder #1 (Loose Intake Manifold Fasteners)
P0300 Random Misfire (Loose Intake Manifold Fasteners)
P0136 O2 Sensor
P0171 ( Possibly a Stuck SAIS Pump Solenoid )
P0016 Faulty Camshaft Position Sensor (CPS NOT THE CPAS)
This particular "cluster of codes" can point towards an Intake Manifold Vacuum Leak that is allowing Un-Metered Air into the F/A Stream ...leaning out the Fuel Mixture enough to cause Random Misfires and/or prompt the upstream O2 Sensor to pick up those extra O2 Molecules. Those "Captured Fasteners" require only 87 INCH Pounds of Torque to be snugged back down.
This is because it is NOT excessive pressure between the Plastic Flange Lines and the smooth face of the Intake ports that secures such leaks... but rather having the need for some nice, New Plump "O" Ring Style Gaskets that can lose their ability to seal over time on very high mileage engines. The counterweight actions of having the heavy Throttle Body on one side of the IM and the PCM bolted on the outside of the IM can allow the IM to wobble back and forth from excessive Engine Vibrations (Bad Motor Mounts) over the long hall... and flatten out those 'Round' gaskets over time.
There are two of those IM fasteners that will give you some trouble with gaining access to them. The first is hidden under a small Rubber Hose Elbow that joins the lower, center Plastic IM Flange to the Upper Intake plenum short tube...roughly centered along the length of the IM and is necessary to pipe Blow By Gas Over Pressure into the inducted air stream and burn off any excess Gas/Oil Vapors in each Cylinder. The second problematic fastener is the last one closest to the Firewall, and getting the right combination and length of wobble socket, extensions and small ratchet back there can vex even the best of us in those tight quarters.
The P0171 Code can sometimes be traced back to a failed SAIS Pump Solenoid (Secondary Air Injection System) which is one of the easiest R&R Repairs to perform. The Solenoid is roughly located in the Center of the Passenger Side upper outer Engine Head and simply has the need for unplugging the Harness Connector and loosening two fasteners, and replacing the Solenoid and the Gasket beneath it and plugging back in the Harness Connector. The SAIS Solenoid sometimes fails by "sticking open" and likewise, allows excessive amounts of air to pass into the exhaust stream and confuse the O2 Sensors.
@MAY03LT shows How to Replace the Upstream O2 Sensor:
Also, on occasion, a Failing Fuel Pressure Regulator (Check the condition of the Vacuum Hose, First) can diminish Fuel Delivery enough to starve each Cylinder and cause Lean Conditions that will throw P0300 Random Misfires. This is also fairly easy repair if necessary as most go with these SUVS and this video shows how to R&R The Fuel Pressure Regulator on your aging 2004 Trailblazer:
The P0016 Code is caused by a Faulty Camshaft Position Sensor. This Video covers all of the aspects of this fairly simple R&R.
While it never hurts to Pull the CPAS shown in this Video and "clean the screens" and then perform a Fresh Oil and Oil Filter Change... it is NOT necessary nor indicated right now with your SUV vehicle unless you start getting a P0014 Code:
P0300 Random Misfire (Loose Intake Manifold Fasteners)
P0136 O2 Sensor
P0171 ( Possibly a Stuck SAIS Pump Solenoid )
P0016 Faulty Camshaft Position Sensor (CPS NOT THE CPAS)
This particular "cluster of codes" can point towards an Intake Manifold Vacuum Leak that is allowing Un-Metered Air into the F/A Stream ...leaning out the Fuel Mixture enough to cause Random Misfires and/or prompt the upstream O2 Sensor to pick up those extra O2 Molecules. Those "Captured Fasteners" require only 87 INCH Pounds of Torque to be snugged back down.
This is because it is NOT excessive pressure between the Plastic Flange Lines and the smooth face of the Intake ports that secures such leaks... but rather having the need for some nice, New Plump "O" Ring Style Gaskets that can lose their ability to seal over time on very high mileage engines. The counterweight actions of having the heavy Throttle Body on one side of the IM and the PCM bolted on the outside of the IM can allow the IM to wobble back and forth from excessive Engine Vibrations (Bad Motor Mounts) over the long hall... and flatten out those 'Round' gaskets over time.
There are two of those IM fasteners that will give you some trouble with gaining access to them. The first is hidden under a small Rubber Hose Elbow that joins the lower, center Plastic IM Flange to the Upper Intake plenum short tube...roughly centered along the length of the IM and is necessary to pipe Blow By Gas Over Pressure into the inducted air stream and burn off any excess Gas/Oil Vapors in each Cylinder. The second problematic fastener is the last one closest to the Firewall, and getting the right combination and length of wobble socket, extensions and small ratchet back there can vex even the best of us in those tight quarters.
The P0171 Code can sometimes be traced back to a failed SAIS Pump Solenoid (Secondary Air Injection System) which is one of the easiest R&R Repairs to perform. The Solenoid is roughly located in the Center of the Passenger Side upper outer Engine Head and simply has the need for unplugging the Harness Connector and loosening two fasteners, and replacing the Solenoid and the Gasket beneath it and plugging back in the Harness Connector. The SAIS Solenoid sometimes fails by "sticking open" and likewise, allows excessive amounts of air to pass into the exhaust stream and confuse the O2 Sensors.
@MAY03LT shows How to Replace the Upstream O2 Sensor:
Also, on occasion, a Failing Fuel Pressure Regulator (Check the condition of the Vacuum Hose, First) can diminish Fuel Delivery enough to starve each Cylinder and cause Lean Conditions that will throw P0300 Random Misfires. This is also fairly easy repair if necessary as most go with these SUVS and this video shows how to R&R The Fuel Pressure Regulator on your aging 2004 Trailblazer:
The P0016 Code is caused by a Faulty Camshaft Position Sensor. This Video covers all of the aspects of this fairly simple R&R.
While it never hurts to Pull the CPAS shown in this Video and "clean the screens" and then perform a Fresh Oil and Oil Filter Change... it is NOT necessary nor indicated right now with your SUV vehicle unless you start getting a P0014 Code:
Last edited:
C-ya
Member
- Joined
- Aug 24, 2012
- Posts
- 1,098
Torque (Android app, $5 for the full version) and an OBD Bluetooth adapter ($15-$20 on ebay or Amazon) will show live data. When I go through a car wash, the underbody wash sets my truck to misfiring (V8) so I go through it quickly. While waiting for the wash, I'll check Torque and see which cylinder(s) is/are chugging.
Thank you for the info. On my way home it finally threw p0301. That means it’s the number 1 cylinder. I’m going to swap coils 1 & 2. Then I’ll swap plugs from those cylinders. Coil 1 with plug 2 and coil 2 with plug 1. If cylinder 2 is good that means I definitely have an issue with cylinder 1. So then where do I go from there? I also get the p0016 camshaft position correlation code. For some reason I’m thinking that it’s an internal issue. I’m hoping not because I’m not really looking to tearing it down to fix it. It has 192,xxx miles. If it’s expensive to fix I might just run it till it dies. Can’t see putting a lot of $$ in it since it’s an 04.
P0016 could be as simple as a camshaft sensor, then a crank sensor. Could also be the CPAS Or it just needs a CASE relearn. The cam phaser could also be defective. In the extreme, it could be an issue with the timing chain.
I replaced the camshaft sensor and the crank sensor. Didn’t seem to really make a difference. I was checking the coils to see if one was bad by taking one off a time and see if it made a difference. I got a cylinder 1 misfire. So then I swapped coils from 1 & 3. With it running I unplugged coil 1 and it slowed down. Plugged it back in and went to 3. Didn’t make a difference. Ordered a new ac delco coil. Hope that works.
christo829
Member
You might also consider swapping coils/plugs 1 and 4 (or just anything further away than 2). My #2 coil went bad, and I replaced it. Maybe 8 months later, the engine started misfiring badly again, and the code was first a P0300, then P0301. When I looked at the logs, misfires were between #1 and #2. Since I had replaced #2 not that long ago, I assumed it was #1 and proceeded to replace it and the plug. That didn't solve the problem. I swapped 1 and 2, still no change. Turned out that #2 had failed again (and it was marked as AC Delco), but the misfire sensor hadn't been able to pinpoint that it was #2 that had failed again. Had I tested with a coil/plug further away, I might have been able to narrow down the failure faster.
Good Luck!
Chris
EDIT: Never mind, I see that you did go for #3, but I'll leave the post in there just for anyone's information.
Good Luck!
Chris
EDIT: Never mind, I see that you did go for #3, but I'll leave the post in there just for anyone's information.
Take care of the misfire first. Then attack the P0016. Since you replaced the sensors, next would be the CPAS. If you pull the plug and there's oil in it, replace it. If it seems fine and you pull it and there's crud on the screens, you could try cleaning it out but for the trouble of getting it out, might as well just replace it. The screens often get swallowed up inside it or is just old.
You will need a CASE relearn because you did replace the crank sensor.
You will need a CASE relearn because you did replace the crank sensor.
Depends if you can find an independent shop with a high end scanner that can do it or a dealer. Literally takes just 5 minutes but you would probably be charged their minimum rate.