I have a 2002 Chevy swb trailblazer. It started hesitating every now and again when I would start to go up an incline on the highway. Just for a second though. It would have like a quick miss or hesitation, and then go fine. It has gradually gotten more frequent. If I floor it from a stop it hesitates for about 1 second exactly, and then starts to go normal. It doesn't miss at idle, or cruising speeds. Its always when giving it partial, and more often full throttle. An engine code has popped up twice. I had it scanned. It was cam position sensor out of time, or something to that nature. The guy told me it was probably bad gas. The check engine light went off a couple cycles later. So I just thought maybe It was bad gas, but it has continued to do it. Any ideas what to check?
Hesitation at full throttle, sometimes partial.
- Thread starter deerslayer1985
- Start date
Wooluf1952
Member
First, how many miles, what is the maintenance history, and the actual code will help us.
Have you ever removed and cleaned the throttle body? The t-body gets really gunked-up (< that's a technical term
) and can stick, causing hesitation.
Have you ever removed and cleaned the throttle body? The t-body gets really gunked-up (< that's a technical term
) and can stick, causing hesitation.
Its got 145,000 miles. I did clean the throttle body last summer. Wasn't real dirty, but cleaned it anyway. I changed the fuel filter at the same time. I put a new air filter on. It got new iridium spark plugs, and I replaced 1 coil that went bad. I change my oil every 5,000 miles with full synthetic. I try to keep up with it. Umm the code. I can't remember what number and what exactly it said. The guy at autozone didn't give me the paper. He just said what it showed on the scanner and told me it was probably bad gas. I know he said something about the cam sensor out of time.
I had to go to the store, and was planning on stopping and getting he engine light scanned again to get the code. When I started it the light went off, and never came back on the whole trip. It still has the hesitation, but the light will go off for days at a time, and then come back on for days at a time. There is no rhyme or reason as to when it comes on, or goes off.
smt 59
Member
Get it scanned with or without the light on as codes are stored until deleted.
Mooseman
Moderator
Another option is to buy a >$20 OBD scanner on Amazon and scan it yourself. If you have an Android device, I highly recommend this one:
https://www.amazon.com/gp/product/B00T5G53ZM/?tag=gmtnation-20
If you want just a basic scanner, something like this will work:
https://www.amazon.com/gp/product/B001LHQBMC/?tag=gmtnation-20
Like smt mentioned, codes will remain in memory even if the light is off.
https://www.amazon.com/gp/product/B00T5G53ZM/?tag=gmtnation-20
If you want just a basic scanner, something like this will work:
https://www.amazon.com/gp/product/B001LHQBMC/?tag=gmtnation-20
Like smt mentioned, codes will remain in memory even if the light is off.
Thanks! I just ordered the one that works with an android device. I'll let you guys know the code as soon as I get it.
I went ahead and stopped to get the engine light checked. It came back code P0014 It says cam phasing error. Any ideas?
Its not bad gas 
maybe try pulling the sensor connector and check / clean it. After that you are likely looking at the sensor itself.
maybe try pulling the sensor connector and check / clean it. After that you are likely looking at the sensor itself.
So I've been researching this a little. This is caused by oil clogging the screens on the actuator. So that is behind the power steering pump reservoir right? Can you usually get those to work correctly by cleaning the screens? What do you use to clean the screens? Also does that sound like what would be causing the hesitation? Thanks for any help.
Wooluf1952
Member
Have you checked the actuator plug? They've been known to develop a leak, letting oil come out and causing trouble. If it leaks, there's no way to fix it. It has to be replaced.
I had some advice to put some marvel mystery oil in the oil, and run it for a couple hundred miles, and then change the oil to a 0w-30 with a mobil one oil filter. I did that and cleared the code off. It has been 2 full tanks of gas ran through since the oil change, and the light hasn't came back on, and it hasn't hesitated any. I'm hoping this fixed it. The guy told me the marvel mystery oil would clean the screens on the actuator, and then the 0w-30 would make sure it doesn't get them gummed up again. He said I could go back to 5w-30 at the next oil change and I should be good. Has anyone ever done this? It seems to be working so far......lol
Well I thought the problem had went away, but it started again......So I took the power steering pump off and cleaned the actuator. It wasn't real dirty looking the middle screen had some brownish black stuff on the screen above the holes, but the others looked good. I reassembled everything, and fired it up. It missed way worse for a minute prolly. Then it kinda started running more normal. I think maybe getting oil back in everything up there....? Anyways It only hesitates if I give it full throttle. Just for a second it like stumbles, and then continues to miss until I let off the throttle and re accelerate. If I start out accelerating slowly it never misses, or hesitates. Its only on an initail wide open throttle. I can be accelerating slowly and gradually get up to wide open throttle and it wont miss, but if I go staright to wide open it misses....Any ideas?
Mooseman
Moderator
I'd pull the CPAS and either clean it or replace it (ACDelco or Delphi/OEM), especially if there is oil in the connector.
How To: Clean The Camshaft Position Actuator Solenoid (CPAS) Picture Heavy
How To: Clean The Camshaft Position Actuator Solenoid (CPAS) Picture Heavy
I did pull it off and clean it. It didn't look real bad. It is not leaking, and there was no oil in the connector. Is there a way you can test it?
Mooseman
Moderator
If you're still getting P0014, I'd replace it just to be sure, especially at that mileage.
Thats the thing its not popping any engine code now....Ever since I changed the oil, and cleared the code. It has never popped that code again. It has just started the missing again in the last couple weeks. Still no engine code. I scanned it to be sure....Its kind of weird. I hate replacing parts if I'm unsure if they are bad....lol Looks like I might have to....
Alright I am getting aggravated.....lol I bought a new CPAS put it on, and started it up....It missed worse at first....When it is idling it doesnt miss...It is only when you give it gas it misses, but if you let off the gas and push again it stops missing....Then you start driving and occasionally when you go to give it more gas it will miss, but like before if you let off the gas pedal and then re accelerate it stops missing....The longer you drive the less it does this. What else could it be? It is no longer popping an engine code, and I scanned it anyways, but no codes are showing up.
More diagnostics will be necessary to confirm this notion... but with the advent of the CPAS Swap presenting this new issue... more and more, it is beginning to sound like a combination of Timing Chain Stretch, Worn Chain Guides and a Timing Chain Tensioner that has either reached its maximum plunger distance and locked out... or it is not always keeping the plunger ratchet on the bottom locked in place and might be allowing a sudden relaxation depending upon whether the engine is either under direct, smooth acceleration that would put the chain under the normal tug and drag of the Crankshaft Cog... but changes its referencing slightly upon deceleration when the apparatus relaxes and the chain develops any slack that the Tensioner is supposed to deal with to keep things tight during both modes.
When this situation prevails... it becomes impossible to keep the relationship between the position of the Crankshaft and Both Overhead Camshafts in their proper timing referencing. The discrepancy can make the correct timing of the valve train almost impossible over the entire range of the Engine's RPM... and a Brand New CPAS cannot compensate for these mechanical issues. A failure of the Cam Phaser can have the same effect. If it comes down to cases... both of these repairs are quite complex; topping the scale of difficulty and requiring a very robust skill set as a Mechanic ...with the added burdens of time, money and the aggravation to accomplish the job(s). It is just as difficult to have the average repair shop tackle the work... and the costs at the dealership might be astronomical in the end.
But before things get to that point... Do you think you could shoot a 30-60 second video at idle with the the Oil Filler Cap removed and while directing the camera sound and video pick up to record the sounds of the Timing Chain Set emanating from the top of the engine? The idea would be to have someone pressing the accelerator pedal to carefully duplicate the situation with the vehicle in park and the Emergency Brake applied with wheel Chocks as well for safety's sake and see if the sounds of severe Timing Chain Rattling occurs. This is sometimes difficult to achieve as the wind coming from the EV Fan will drown out the sound being investigated... but its a painless thing to try at this point.
When this situation prevails... it becomes impossible to keep the relationship between the position of the Crankshaft and Both Overhead Camshafts in their proper timing referencing. The discrepancy can make the correct timing of the valve train almost impossible over the entire range of the Engine's RPM... and a Brand New CPAS cannot compensate for these mechanical issues. A failure of the Cam Phaser can have the same effect. If it comes down to cases... both of these repairs are quite complex; topping the scale of difficulty and requiring a very robust skill set as a Mechanic ...with the added burdens of time, money and the aggravation to accomplish the job(s). It is just as difficult to have the average repair shop tackle the work... and the costs at the dealership might be astronomical in the end.
But before things get to that point... Do you think you could shoot a 30-60 second video at idle with the the Oil Filler Cap removed and while directing the camera sound and video pick up to record the sounds of the Timing Chain Set emanating from the top of the engine? The idea would be to have someone pressing the accelerator pedal to carefully duplicate the situation with the vehicle in park and the Emergency Brake applied with wheel Chocks as well for safety's sake and see if the sounds of severe Timing Chain Rattling occurs. This is sometimes difficult to achieve as the wind coming from the EV Fan will drown out the sound being investigated... but its a painless thing to try at this point.
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Now I am a little worried....lol I will try and get a video tomorrow. Like I said tough it is very random....The longer it runs the less it does it. I drove it today and it only did it once. When I first started driving it missed for a second then stopped. Never did it again for 20-30 minutes of driving.
Mooseman
Moderator
I doubt very much it's chain stretch, tensioner failure or the chain shoes. I have heard of just one chain shoe failure. The noise from that would be horrendous. Tensioner failure I know first hand and it would actually run fine. The chain would just rattle at idle.
However, I would suspect the cam phaser but you are not getting any codes now, right?
I've attached the diagnostics procedures for P0014 from GM-SI. It gives a good description of what happens when this code sets but to diagnose using those methods requires a Tech 2.
The other thing to do is check your fuel trims using Torque. Maybe record the graphs and see if they stay between 10 and -10.
However, I would suspect the cam phaser but you are not getting any codes now, right?
I've attached the diagnostics procedures for P0014 from GM-SI. It gives a good description of what happens when this code sets but to diagnose using those methods requires a Tech 2.
The other thing to do is check your fuel trims using Torque. Maybe record the graphs and see if they stay between 10 and -10.
Nope, I am no longer popping any engine codes. It was popping the p0014 code when this all began a few month ago. No codes will pop now though. So far I have put a new actuator the thing with the screens right beside the power steering pump. It is still doing about the same thing it has always done. So I am assuming its doing the same thing as when it popped the p0014 code.
I neglected to mention that when shooting the investigative video… be mindful to first hold something absorbent over the exposed Oil Filler Neck and have your assistant gradually raise the Engine RPM from 600 at a steady Idle ... then suddenly let off the pedal at around 750-1000 RPM. This is done to ensure that no Engine Oil is being centrifugally thrown off of the Cam Phaser Sprocket and Timing Chain, then upwards through the narrow semi-barrier with the cross-hair apparatus just below the Filler Neck and wind up decorating the Digital Camera and engine compartment in Motor Oil.
At a normal Idle of 600 RPM ...the Cam Phaser-Camshaft is only rotating at 300 RPM… and likewise 500 when the engine RPM is raised to 1,000. So hopefully, you can find the sweet spot and perform this experiment below the threshold of ‘slinging oil’ and still get the video and sound imagery posted back here for other Members to help you with the diagnosis.
I took some images of the Old Design for the 2002-2005 Valve Cover to illustrate the ‘idiot proof’ opening design molded into it to prevent anyone from stuffing a funnel down inside and having it get ground down to plastic powder by making contact with the sprocket and timing chain rotating just below. The later versions of the Valve Cover that are made of Aluminum have a cast-in ledge down inside there instead. Please ignore the small, JB-Welded in Glass Windows in the images… this is just an old cover I modified to test a 12V Electric Pump Engine Pre-Oiler and be able to observe it in action while pre-lubricating the camshaft lobes:
At a normal Idle of 600 RPM ...the Cam Phaser-Camshaft is only rotating at 300 RPM… and likewise 500 when the engine RPM is raised to 1,000. So hopefully, you can find the sweet spot and perform this experiment below the threshold of ‘slinging oil’ and still get the video and sound imagery posted back here for other Members to help you with the diagnosis.
I took some images of the Old Design for the 2002-2005 Valve Cover to illustrate the ‘idiot proof’ opening design molded into it to prevent anyone from stuffing a funnel down inside and having it get ground down to plastic powder by making contact with the sprocket and timing chain rotating just below. The later versions of the Valve Cover that are made of Aluminum have a cast-in ledge down inside there instead. Please ignore the small, JB-Welded in Glass Windows in the images… this is just an old cover I modified to test a 12V Electric Pump Engine Pre-Oiler and be able to observe it in action while pre-lubricating the camshaft lobes:
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Here is a link to the video. It is crappy quality.
It didnt miss while I was doing this video also... Go figure...I tried for about 10 minutes to get it to miss, but it wouldnt......It has its bad days and good days...lol
It didnt miss while I was doing this video also... Go figure...I tried for about 10 minutes to get it to miss, but it wouldnt......It has its bad days and good days...lol
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Mooseman
Moderator
It has always had a very faint ticking noise. I've got family that has trailblazers and they have the same sound. Is there any other way to tell possibly what it could be?
shovenose
Member
Yeah, I'd stick with 5w-30 on these vehicles. They seem rather picky. All the 4.2s I've heard aren't the most quiet engines.
Ok, but another question. Is there a way I can remove the cover where you put oil in it to see if the timing chain is stretched for sure? I mean is it pretty simple to just take that off and check? Something tells me thats not what it is, but I'm not opposed to checking everything. What other things would you guys check, or test that might be easier, or something else it could be? I dont understand why it was popping an engine code p0014 and now it doesnt...?
Mooseman
Moderator
Not an easy job. You have to remove the intake manifold to remove the valve cover. I doubt VERY much that it's the chain.
I don't really think its the chain either, but not ruling it out I guess I have the worst luck.......What else could cause code p0014? Even though its not popping a code now it is doing the same thing it was. I have already replaced the actuator thing that you have to move the power steering pump back to get to. So what step do I take next? I really appreciate the help.
There is another recent thread that goes into much greater detail on the possible other causes of the P0014 Code to be found here:
http://gmtnation.com/forums/threads...ine-swap-in-02-trailblazer.16865/#post-533113
But the 'shorthand' answers to your non-trivial questions requires answering these questions first:
(1) Has anyone replaced the (CKP) Crankshaft Sensor located alongside the Rear Knock Sensor at the lower back Driver's Side of the Engine Block? If this was done by your repair man and he failed to mention it... and if he did not perform a CASE Relearn for that event... it is the next thing to determine and can be easily rectified by spending $100.00 at the Dealership... or by anyone skilled with a TECH II Scanner Tool or similar higher end scanner device who might charge much less to perform the task.
(2) Has anyone either loosened, removed and/or re-installed the Harmonic Balancer on this Motor? A Loose TTY Crankshaft Bolt can cause the dreaded P0014 to intermittently appear and presents with a very serious problem for this engine as an ever loosening Harmonic Balancer can ruin the engine if not replaced properly and fastened down with a New GM OEM Crankshaft bolt.
First it gets tightened down to 110 Ft Lbs... and then it requires having another 180 Degrees of rotational Torque Angle force applied to the bolt head to secure the Harmonic Balancer in place. This is one of those jobs that cannot be done casually or be guessed at and requires first fixing the Crankshaft firmly in place at the Flex-Plate. Doing this prevents the Crankshaft from rotating around with the movement of the Bolt on its way into the nose of the Crankshaft and having both slipping loosely around inside of the bore hole of the Harmonic Balancer.
http://gmtnation.com/forums/threads...ine-swap-in-02-trailblazer.16865/#post-533113
But the 'shorthand' answers to your non-trivial questions requires answering these questions first:
(1) Has anyone replaced the (CKP) Crankshaft Sensor located alongside the Rear Knock Sensor at the lower back Driver's Side of the Engine Block? If this was done by your repair man and he failed to mention it... and if he did not perform a CASE Relearn for that event... it is the next thing to determine and can be easily rectified by spending $100.00 at the Dealership... or by anyone skilled with a TECH II Scanner Tool or similar higher end scanner device who might charge much less to perform the task.
(2) Has anyone either loosened, removed and/or re-installed the Harmonic Balancer on this Motor? A Loose TTY Crankshaft Bolt can cause the dreaded P0014 to intermittently appear and presents with a very serious problem for this engine as an ever loosening Harmonic Balancer can ruin the engine if not replaced properly and fastened down with a New GM OEM Crankshaft bolt.
First it gets tightened down to 110 Ft Lbs... and then it requires having another 180 Degrees of rotational Torque Angle force applied to the bolt head to secure the Harmonic Balancer in place. This is one of those jobs that cannot be done casually or be guessed at and requires first fixing the Crankshaft firmly in place at the Flex-Plate. Doing this prevents the Crankshaft from rotating around with the movement of the Bolt on its way into the nose of the Crankshaft and having both slipping loosely around inside of the bore hole of the Harmonic Balancer.
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To answer those questions. Nothing has been done since this started happening by anyone but me. The only thing I have done is clean the original cpas, then after that didnt work I bought a new one, and installed it. I have never had any other work done on the engine, besides what I have done myself. I have never messed with the harmonic balancer, or any other sensor. I replaced a coil pack, a/c clutch bearing, and water pump. That is all I have done. So what now...? I am lost and hate to pay someone to diagnose it if it is something I can figure out. I have a scanner that operates through my phone. Is there anything I can do with that?
Mooseman
Moderator
Its not really got a noise. I mean that slight ticking noise, but every trailblazer I have heard sounded like that. I meanT for the miss. It will start missing when I accelerate sometimes. Thats what it was doing when it originally popped the code p0014. After changing to 0w30 oil with marvel mystery oil in it the check engine light hasnt popped since. It did quit missing for awhile, but it is doing the same thing again as it was, but now it is not throwing the code. If it was anything else causing it to misfire randomly shouldnt it throw a code? I' am just confsed all around.
I think I get what your saying remove the belt and see if that ticking goes away to tell if it could be the timing chain....
Ordinarily... Checking Compression for symptomatic causes for misfires under acceleration can be difficult on V6 and V8 Engines... but it is not such a PITA on the LL8 I-6 Engines. So perhaps pulling the spark plugs and confirming that all six look 'Fried Chicken Brown" and then performing this test as per these GM 4.2L Specific Instructions is yet another avenue worth investigating:
http://troubleshootmyvehicle.com/gm/3.5L/how-to-do-an-engine-compression-test-1
NOTE:
Please obtain a few cans of Compressed Air ordinarily used for cleaning the dust out of keyboards and computers and blow out the debris from down inside the Spark Plug Wells before removing the plugs. Often on older engines... they will display being partially filled with engine oil that has leaked in from the failed gaskets in the perimeters of the spark plug wells, too. So not allowing that crap access to the inside of each cylinder will be important. The "canned air' will make checking and cleaning out those tight spaces much more convenient than setting up a Shop Air Compressor...and do a much better job in snaking down in there with the thin red plastic tube.
http://troubleshootmyvehicle.com/gm/3.5L/how-to-do-an-engine-compression-test-1
NOTE:
Please obtain a few cans of Compressed Air ordinarily used for cleaning the dust out of keyboards and computers and blow out the debris from down inside the Spark Plug Wells before removing the plugs. Often on older engines... they will display being partially filled with engine oil that has leaked in from the failed gaskets in the perimeters of the spark plug wells, too. So not allowing that crap access to the inside of each cylinder will be important. The "canned air' will make checking and cleaning out those tight spaces much more convenient than setting up a Shop Air Compressor...and do a much better job in snaking down in there with the thin red plastic tube.
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Mooseman
Moderator
If you were getting an actual misfire, the PCM would detect that, flash the CEL and set a code. A compression check is a good idea to verify the overall mechanical health of the engine.
If it was previously throwing a P0014 code and now it's not, it is possible that the CPAS or the cam phaser is marginal. Eliminate the cheaper/easier first. If you haven't replaced the CPAS, I'd do that with an OEM/ACDelco/Delphi unit.
If it was previously throwing a P0014 code and now it's not, it is possible that the CPAS or the cam phaser is marginal. Eliminate the cheaper/easier first. If you haven't replaced the CPAS, I'd do that with an OEM/ACDelco/Delphi unit.
I did replace the cpas. The code is not being thrown now, but it hesitates and will like sputter when accelerating sometimes. Usually letting off the gas and re accelerating gets rid of the hesitation stutter, or miss as I call it. Like I said sometimes it runs great for awhile. If it had bad compression wouldnt it do that all the time? I mean it is sporadic. It has new iridium spark plugs in it from last year when I replaced a coil pack. Should I unhook the battery for 15 minutes and see if maybe it just needs to relearn idle or something?