CEL P0300-CEL flashed 3 times and engine noise

[movietvet]

My girl was on her way to Wa. this morning and got about 30 minutes away and experienced the CEL flashed 3 times and then stayed out and could hear a very dull pop top noise in engine compartment. She called and headed home. Off she goes in her 1990 K2500 ext cab pickup with 130k miles.

The TB has 75k miles on it. I checked for code(s) and got P0300. I drove it and experienced no problems. Plugs only about 3k miles old and I removed them and they looked like new and so did the OE ignition coils and boots-that were done when I did the plugs. Before that I tapped in at the fuel filter and found good fuel pressure at 54 psi running and throttling. When I had done the plugs, I had replaced the fuel filter and did replace the fuel pressure regulator when I noticed a leak.

Ok, I know I have a problem that is effecting more than one cylinder. I did some research and found that a known weak spot is the VVT solenoid. My shop owner friend allows me to buy parts on his account at a local wholesale warehouse. I wanted a Genuine GM solenoid, 12615873, but was not available. I bought a Standard Motor Parts VVT102 for just under $38 and over the years I have had decent results with Standard. Unbolted the P/S pump and flopped out of the way and changed the solenoid. Reassembled all components and it fired right up. I had already cleared the P0300 code. I went to live info on my scanner and all looked good and drove it slow in neighborhood, 35-40 on major side streets and at 60-65 on the highway and romped on it hard a couple times and am still impressed with that 4.2 engine power. No code(s) came back and will be driving it more while my girl is gone for a couple days.

Almost forgot. I am planning on cleaning the MAF sensor tomorrow and inspecting the MAP sensor.

So, knowing all this and what I did, what are thoughts of the members here? Thanks in advance for input.

 

[Mooseman]

Looks like she got an intermittent or a single instance of misfires. Usually it will throw P0300 until it can determine which cylinder is misfiring but seems yours didn't do it long enough to do that. Who knows what caused it. It could have been a bit of water in the fuel that passed, a failing coil or fuel injector, intermittent bad wiring, etc. All I can suggest is to keep driving it until it happens again and keep driving it until it changes that p0300 to an actual cylinder code, if it does.

 

[movietvet]

I did forget to share this info. The day before, she heard the same noise while backing up in to her parking place at home. I asked if there was a CEL and she said no. I have her trained to always look for a CEL if she hears or feels something strange.

 

[Mooseman]

There is a threshold on the amount of misfires before it will trigger the CEL. I once had a very occasional misfire only at idle and would only trigger the steady CEL and a hard code after a certain number of misfires accumulated for the particular cylinder. Since she was backing up, she was probably going dead slow and may not have had enough misfires.

 

[budwich]

You need to look at the history and current counts for each cylinder. If the threshold is set (TIME AND NUMBER), the code and / or flashing check light get set.... its the same process for "random" and for "hard misfiring".

 

[TollKeeper]

With him replacing the cam sensor, does he need to do a cam/crank correlation relearn?

 

[movietvet]

With him replacing the cam sensor, does he need to do a cam/crank correlation relearn?

I had done the cam and crank sensor months ago and there was no relearn needed. Up to this point, there had been no problems. I did replace the VVT solenoid this time and again, no relearn needed and drove out fine. The MAP and MAF are original. I am going to clean the MAF today and replace the Intake Air Temp sensor because I believe it is original and is cheap. I may go ahead and just change the MAP because of age and I can get a Delphi component today for cheap and she is on the road at times and I do not want to have to worry. Because the problem is intermittent, I want to do any and all that I can to make it reliable for her. Over all, this TB has been great and she really likes the vehicle.

 

[movietvet]

As it turns out, there is no MAF sensor on this TB. Yesterday, when the CEL was out and even after I replaced the VVT solenoid, I did look at live counts and history. All looked good. There were random counts of misfire in history but as far as I could see, no thresholds were reached. I did have the throttle body off yesterday and it was very clean and should have been clean. I cleaned it about 6 months ago and she can go long periods without driving it.

 

[movietvet]

I did get the GM IAT sensor and the Delphi MAP sensor installed. The first thing I noticed was a bit smoother idle. The idle was not bad before but is noticeably smoother now. The rest of the road test was the same as before.

 

[mrrsm]

Post # 17 from @Mooseman in this On Topic Thread covers the need to Change the Fuel Filter (located along the Driver's Side Frame Rail)

Fuel Filter?

As part of a general maintenance service, I was looking to replace the fuel filter. RockAuto shows 3 choices. When I check for local availability through Advance or O’Reilly’s they show n/a. Anyone else have difficulty sourcing a fuel filter locally?

gmtnation.com

...and also well covered by @MAY03LT in THIS Video linked in Post #3 here:

New Fuel Filter....Yes or No.

Owned my 2002 Envoy for 13 years. Bought it with 150 k miles. Now it has 200k miles I've never changed the fuel filter. While it looks easy enough to do, my Envoy is running so great I almost don't want to mess with anything! 😆 I'm not sure if the previous owner ever swapped it out either...

gmtnation.com

There might be another explanation for mysterious transient P0300 being caused by LOOSE Intake Manifold 10mm Fasteners needing a snug of no more than 89 Inch Pounds of Torque.

The Intake Manifold tends to rock to and fro (left to right and right to left and so forth during steering turns) ...counterbalanced between the weight of the Intake Throttle Body and the weight of the mounted PCM. Having BAD MOTOR MOUNTS always accentuates this vibration at idle on the GM 4.2L Motors and can wear out the IM Gaskets sooner than later as a result.

Over time...The Three Figure "8" Intake Port Gaskets will tend to FLATTEN OUT and lose their *Plump* nature. So occasionally, with the resulting looseness of the 10 asymmetric IM Fasteners... The Atmosphere will Randomly Sneak On By.

Thus, TOO Much un-regulated Air can get inside the various Cylinders and FUBAR the Stoichiometric Balance by getting past the control of the PCM and throw P0300 "Lean Mixture" Codes as a result.. Remember that NO PART of the IM should ever touch the Engine Head when New, Plump IM Gaskets have been installed and a mere 89 Inch Pounds of *TIGHTNESS* gets uniformly applied. Those Special Trapped M6 X 1.0 X 12mm Long Fasteners will BOTTOM OUT and Snap OFF if Over-Tightened!

Finally ... working in combination...it could STILL be caused by having a Clogged Fuel Filter in combination with a Very Bad Load of Gasoline. Not using Mid-Octane (89) can also be a problem, too. During the last few weeks.... The Gasoline Supply Industry has been on a Mad Scramble to supply the southern states in the USA with more fuel after the Two Hurricanes (Helene & Milton) did their "Thing".

This tends to stir up an awful lot of *Junk* in ALL of the Tanker Trucks making such deliveries. If your Daughter happened to be fueling up while one of the Tankers was Off Loading at the same time... that might answer The Question of Cause...too.

 

[movietvet]

The fuel filter on this TB is less than 5k miles old and I always and she always uses 89 octane Chevron fuel.

I was NOT AWARE of the intake manifold fasteners loosening. I will check them asap.

 

[movietvet]

I guess I better take a step back here, on the intake manifold fasteners, "check the tension". I watched a video, on you tube, about replacing the manifold and the amount of components to remove or reposition is a bunch, to say the least. If I went that far, to gain access to the fasteners, I would not just retension the fasteners. I would in the very least replace the seals or at least replace the manifold and seals.

Is there something I am missing as far as access the fasteners?

 

[mrrsm]

I just edited my last Post to include the additional data about the Fasteners. Replacing the Gasket Kit for the IM along with the Valve Cover Gasket Kit is a LOT of PITA Work...but likely better done all at once.

 

[movietvet]

I just edited my last Post to include the additional data about the Fasteners. Replacing the Gasket Kit for the IM along with the Valve Cover Gasket Kit is a LOT of PITA Work...but likely better done all at once.

Luckily, when I removed the plugs yesterday, the plug holes were all dry and there is no external oil leaks from the valve cover.

I did not look for the valve cover steps. Is the IM removal required for the valve cover gasket/seal replacement.

 

[mrrsm]

There are several, very "telling" Intake Manifold R&R Threads and just a few good videos that will regale us with just how truly difficult this process can be... mostly because of that Dreaded Black Metal Rack and Harnessing getting in the way and the need to remove the Left Wheel in order to gain enough access to the last few difficult to approach IM Fasteners through the Wheel Well with the SUV safely held up on Jack Stands ...right adjacent the Firewall.

 

[Mooseman]

With him replacing the cam sensor, does he need to do a cam/crank correlation relearn?

No, just with the crank sensor.

I did not look for the valve cover steps. Is the IM removal required for the valve cover gasket/seal replacement.

Yes.

Unless you have an oil leak, it shouldn't need a valve cover gasket replacement.

But for the intake manifold gasket, just try to retorque the bolts. It is a silicone type gasket and usually doesn't deform. Just tightening the bolts usually fixes any leaks there. You can also test for leakage there with the usual methods like propane or carb cleaner.

 

[movietvet]

No, just with the crank sensor.


Yes.

Unless you have an oil leak, it shouldn't need a valve cover gasket replacement.

But for the intake manifold gasket, just try to retorque the bolts. It is a silicone type gasket and usually doesn't deform. Just tightening the bolts usually fixes any leaks there. You can also test for leakage there with the usual methods like propane or carb cleaner.

I get what you are saying about the IM fasteners and tightening them. What I see as a deterrent to doing that is access to those IM fasteners. Looks like that all the components and steps just to gain access are daunting at best and if you go that far, go a little further and replace the IM or at least the seals themselves. Plus, if you remove all that to gain access to the IM fasteners, then do the valve cover gasket/seals while in there.

 

[TollKeeper]

No, just with the crank sensor.

But he replaced the cam and crank, and did not do a relearn. Sorry, as you know, my knowledge of the 4.2 is semi-limited.

 

[movietvet]

The cam and crank sensor replacement was done a while back and I did no relearn and has been fine. The research I did is that, IIRC, if you used a Genuine GM part, a relearn was not needed. I could be completely wrong though. I do know I did not do a relearn and until this current problem and CEL code P0300, the TB was running great.

I am only guessing but, could the fact that this TB does not have a MAF, make the relearn unneeded.

 

[TJBaker57]

N

research I did is that, IIRC, if you used a Genuine GM part, a relearn was not needed. I could be completely wrong though.

Not true. The GM service literature is clear about this Even if there is no code for it they state a learn is required.

That said, I think the only real effect of not having done a learn for a changed CKP is the 'very fine' adjustements to 'tune in' the new CKP are not there and the lack of these compensation factors makes it difficult if not impossible for the PCM to accurately detect a specific cylinder misfire.

I suspect that in the case of an actual misfire condition without the proper learn the PCM will either go no further than setting the P0300 code,,, or if it DOES set a misfire code for a specific cylinder it may be the wrong cylinder?

I have wondered if this lack of fine adjustments/compensation factors also affect the timing of spark and fuel injectors?

My own guess is there are hundreds if not thousands of vehicles out there without the 'proper' learn done after CKP replacement.

 

[TJBaker57]

P1336 — 2002 Chevy Truck TrailBlazer 4WD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2002 Chevy Truck TrailBlazer 4WD L6-4.2L VIN S.

charm.li

 

[movietvet]

Not true. The GM service literature is clear about this Even if there is no code for it they state a learn is required.

That said, I think the only real effect of not having done a learn for a changed CKP is the 'very fine' adjustements to 'tune in' the new CKP are not there and the lack of these compensation factors makes it difficult if not impossible for the PCM to accurately detect a specific cylinder misfire.

I suspect that in the case of an actual misfire condition without the proper learn the PCM will either go no further than setting the P0300 code,,, or if it DOES set a misfire code for a specific cylinder it may be the wrong cylinder?

I have wondered if this lack of fine adjustments/compensation factors also affect the timing of spark and fuel injectors?

My own guess is there are hundreds if not thousands of vehicles out there without the 'proper' learn done after CKP replacement.

BUT, there has been months go by since I replaced the crank sensor.....months.

There has been at least 3 12 hour round trips to northern Wa. since I did the crank sensor.

 

[movietvet]

I made a mistake, I think. I found a receipt from AZ for the Cam Sensor but not the Crank Sensor. I may have only replaced the cam sensor and I remember the reason for it was for leaking oil past it. I do not think I did a crank sensor. The cam sensor I used was a GM 213-1557.

The crank sensor would have been GM 213-970. I am now sure that I only did the cam sensor because of the oil leak and not for running problems.