Intermittent rough engine and misfires both in idle and while driving, codes p0305 and p0300

I have some ideas on what this could be but we need to address the fuel pressure first. At key on with 55 PSI is just about perfect. However, when you start the vehicle and it jumps 100 PSI does not sound possible. This pump is a low pressure pump so we have to be missing something.

Are you testing this with a gauge or looking at a scan tool? Here is a guide on how we need to do this with a gauge:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If you are using a gauge can we get a video of the gauge when this happens? Next we may need to try another gauge because it may be the issue.

I am so sorry, that was a typo. It is jumping between 55-65.

I think I got the video to upload this time.

Okay. that makes more sense. As for the fluttering, that is not uncommon to flutter a little bit but that seems pretty large.

Let's try monitoring the fuel pressure and rev the engine and see if the gauge stops bouncing when you rev the engine. If it does the fuel pump is failing.

The other possible cause is a leaking injector which would make more sense with the misfire that you are getting.

Lastly, we should monitor live PCM data when the engine is running to see if it is rich. If it is running rich then we can feel better about going after an injector or other fuel issue. This would require a scan tool capable of doing this. Any chance you have one?

I do have one. Been trying to keep and eye on it without crashing, lol. I took a peak at it when it was doing some sputtering at idle the other day. I’ll post the picture.

It doesn’t always stay that way, noticed that it will come back around normal range while driving but still goes up and down. Mostly in the positive side as the pic suggests.

Also the vehicle was driven pretty heavy today. Started off running almost perfect (didn’t run A/C) The more start and stopping I did it would have little sputters when restating big would go away pretty quick. Ended up having to hook up a trailer to it to pick up and drop off a dryer and had the A/C running as well (hot day) The sputtering and hesitations kept getting worse the longer we drove. When restarting and heading back it got rough enough for the CEL to start blinking for a couple seconds and then stopped. Turned off the A/C and drove it back. Had some hesitations and stutters but made it. When parking it stalled on me. Let it cool down for a couple hours and when heading back home (no ac and no trailer) barley had any issues. A Few stutters at the beginning and slower on acceleration but got better as I went. Checked the codes and had p0305, p0300 and now also p0304. Checked the misfire counts on the scanner and had misfires in all the cylinders, at least half were in the teens.
Sorry for the long post but trying to be as specific as possible. Going to go ahead and order the fuel pump while I wait for your reply. Thank you so much for the help.

We may have an o2 sensor issue as well. You short and long term on bank one are pretty positive. That would indicate to the PCM that there is too much oxygen so it adds more fuel. However, it seems like there is too much fuel already. That means the o2 sensor could be reading it wrong. You can try swapping from side to side and see if the numbers change. If not, then we may have a fuel injector issue on that bank.

Well, I ordered a fuel pump. What should I be looking for as far as the sensors or injectors go while waiting for it to come in? I can see the sensors oscillating on my scanner while running.

Drove the vehicle today. I’ll post a pic of the fuel trims at startup. While driving I noticed they would go up and down both short term and long term. The long terms would briefly get to mid to upper terms positive then come back down pretty quickly. Seemed to go higher when coming off the gas or braking and also seemed like they were higher when feeling some sputtering.

That sounds pretty normal. The short term fuel trims should be bouncing up and down around 0 and long term should be more consistent and not bounce as much.

I think the sputtering is related to the pressure bouncing so erratically. Let us know what happens after the pump is replaced. Thanks

Okay, so first Happy 4th!

Got the fuel pump swapped last night. It was running pretty rough before the change and after it started up and idled smooth. Felt good driving, no hiccups and acceleration seemed better. Didn’t run the AC at first but did when got closer to home. Didn’t seem to have any issues though it was in the mid 70's out.

Got home, stopped and restarted. I let it idle for at least 20 minutes. It did good at first then would start getting smaller sputters but not as bad as before and not as frequent. I’ll see how it does when it’s hotter out.

I plugged my scanner in to look at fuel trims at idle. I’ll post the pics but my long terms were +13.3 and +9.4 and stayed at those numbers pretty much the whole time. I would give it gas and they would move a little and immediately go back to those numbers.

I also went in the test part of the scanner to see misfire counts and went in the O2 heater monitor test. This is after it was idling for a bit. B1S1 was at 77 F which was outside temp. B1S2 was 95F. B2S1 was 113F and B2S2 was 59F. Not sure if that’s even important but found it strange the temps would be so different. The live data always shows both my Cat converters at the same temperature.

I also noticed that my thermometer in the car was reading 76F but my ambient temperature sensor on the scanner was reading 115F. Are these supposed the same?

Happy 4th as well.

The sensor could be an issue but let's do as you suggested first. Let's let it run for a little bit and see how it does because those long term fuel trims should begin to change. What were the short term trims? On a properly running engine they will go negative and positive. Kind of bounce around 0 as the engine runs.

Also, does your scan tool have the ability to reset the adaptive numerator? This will reset the long term fuel trim so the PCM will run the engine based off of current numbers vs old numbers. That may be why you are getting the stumble because it is still running off the lean exhaust numbers so it is dumping more fuel causing the stumble when it doesn't really need the fuel now because the pump is supplying the proper amount of fuel now.

Let me know and we can go from there. Thanks

The short term at that time were -7.0 on B1 and -5.5 on B2. They would fluctuate as I gave gas in idle and the long term numbers would drop as well but immediately go back to the same numbers as before when letting off the gas. I do not believe my scanner has the ability to reset adaptive numerator. Not sure what it is honestly. How can that be done?

The adaptive numerator is the long and short fuel trims. It is how it is calculated and resetting it, will basically wipe its memory. This adaptive so it will adjust the fuel trims over time but it is not immediate.

I believe you have what is called a GPEC controller on that vehicle which means this process may work to reset it.

Disconnect the battery positive terminal and touch the positive terminal to the negative battery post. This is called a capacitive discharge. Basically that means it depletes the keep alive memory the PCM so that it forgets all its learned data like the adaptives.

If this doesn't work then it is okay. Just drive the vehicle and it will bring those numbers closer to 0.

As for short term fuel trims, that makes sense that they are slightly negative and that is because the long term are positive. It is basically trying to bring those down.

Long story short, I think you fixed it and it will run better as those numbers are relearned.

I’ll keep you posted. Thank you for your help.

Sounds great. Thanks. We will wait to hear back.

Okay, so drove it around today. Really hot day so running A/C. At first no issues at all start and stopped about 3 times. Soon as I got it on the highway you can feel a few stumbles. After about 10 miles and getting back into stop and go and then parking and keeping it running I am getting the sputtering again. Not as bad as before and seems to kind of go away when I turn off the A/C. Ran the scanner and have pending p0305 and p0300 again. Not sure where to go next.

Just got back, had quite a few big stumbles and had my scanner running, the short term trims on both banks would jump up to +20’s and +30’s while it’s happening. They are also jumping up almost as high while it’s sputtering in idle. I did notice the long term was moving up and down like a short term trims while giving it gas or driving. Thought the long terms are supposed to be slow moving. CEL is back on for p0300.

Okay. We need to run through this complete testing for number 5 misfire. We need to suspect an issue with the base engine. Number 9 of this testing is where we need to make sure we cross all these off the list. I suspect a vacuum issue so if you have a vacuum gauge, we need to make sure the needle stays steady. Due to the fuel gauge jumping, we may have a valve spring issue which will show up on a vacuum gauge as well if it is the intake valve.

Take a look at this testing and let me know what you find. However, we are looking for something causing that cylinder to go lean so that is increased oxygen or decreased fuel. Valve spring not sealing would make sense.

We may just want to run a compression check on number 5 and compare it with a couple other cylinders.

https://www.2carpros.com/articles/how-to-test-engine-compression

Compression test has been done. Right around 150 psi all around.

Also today I drove it. Cleared the codes, it rode good first trip not much issue I noticed. Did have a pending 305 Afterwards though. When I drove it back it was pretty much perfect, no issues. Was keeping an eye on the o2 sensors the whole time. After I got back home (25 miles or so) I let it idle as I kept looking at the data and the o2 graphs. It started sputtering finally and it actually stalled once as well. It fired right back up no issue. I will post some pictures of the sensor graphs as well.
Also I did a fuel pressure test with the new pump. At key on it was actually at 52-53 and at idle the needle was jumping upper 50’ and 60. I did notice the fuel pressure would start dropping as soon as I turned it off. Even from key on to off it would start to drop almost immediately. Not too fast but noticeable.

These are what the sensors looked like when it started sputtering after getting back.

This is what one looked like after first trip earlier in the day (idling).

Here’s what they looked like right after starting in the evening. Cold start.

And these are some while driving on the highway.

I don’t know if it’s just a coincidence or a reaction to what’s happening but I see the sensors oscillating a lot more rapid at a cold start then after it gets hot.
Trying to get you as much information as possible.

These are graphs of both upstream o2 sensors while holding 2,000 rpm's.

Do you have a vacuum gauge? That is good that we have good compression but we need to make sure we don't have a valve sticking while running. The gauge will tell us if the intake is hanging open or sticking. The way to check the exhaust is to actually take a dollar bill and hold it over the exhaust pipe. If it feels like it is being pulled into the pipe then the exhaust valve is sticking on cylinder 5.

Your o2 sensors are reacting to the misfire on 5 so I figure we have a mechanical issue on that cylinder. So we need to eliminate valves and go from there.

I do not have a vacuum gauge. Never used one before. I’ll do the dollar over the exhaust. Would it always happen if it were to get sucked in or just while the misfires are occurring?
It’s been mostly p0300 coming up lately. Also had p0304 come on recently as well but hasn’t come back

Correct. It would only be sucked in while misfiring. It is worth a try. However, with that info, I doubt this is the issue. Let's try it and rule it out then move on.

Will do.
Is a sticky valve something that happens only after getting hot and intermittent or would it be constant?

Okay, so gave it a shot and honestly not sure what it did. A few times while it was sputtering it felt like maybe it was getting sucked back a little but I was holding it tight to the tailpipe. Then if I looked at it closer while it was sputtering it looked like it actually pushed it out. I’ll have to do it again.
Also just to keep you updated first 20 miles I drove it today no issues I noticed. Towards the end of my trip it started up. Had some real bad stumbles at one point where it felt like it was trying to stall and jump back to normal. The stft did jump up real high while that occurred. After a few seconds it stopped and when I got pulled in I had the sputters on and off and started the test.
While idling I snapped the throttle a few times. I noticed the first couple of times I had some smoke or vapor come out the exhaust briefly. Wasn’t heavy and it dissipated quick. It happened a couple of times but then no more smoke when snapping the throttle. I kept it running and noticed the sputtering had pretty much stopped. I drove it up and down the street and didn’t really feel anything. Stopped and got gas and didn’t have any issues after restating and driving back. Kind of weed cause other times the sputtering would get worse and worse. Even would get some stalls. I did notice a strong smell of maybe burnt fuel if that makes sense from the exhaust and it was really hot back there.

PS, not sure if this is important or not but noticing when I get a check engine light whether it a 300 or 305 the freeze frame data shows that it went into open loop.

Okay. That is good info. Just to clarify, when you started and it was not having an issue, it was running in open loop. Then it went to closed loop and the issue started, then it switched back to open loop?

Let's swap the o2 sensors from side to side. So swap the upstream with each other and the down stream with each other. Then clear the codes let is sit to get cold to ensure when you start it is in open loop then see if the codes come back to the same cylinder.

After this, we are going to need to start monitoring the PCM input sensors to ensure they are telling the PCM accurate info.

No sir, when I started it was pretty much in closed loop immediately. For example I took picture of the freeze frame data (I’ll post them) while key on engine off today. Cleared the codes then started the engine. I went right into live data and it was already in closed loop. I saw where the 300 code that I deleted was in open loop on the freeze frame and the pending 305 is as well.

These pictures are all the freeze frame data from the stored 300 code I deleted earlier.

And these are the freeze frames for the pending 305 code. It has not set the light on yet in about 40-50 miles with of driving.

And this is what the fuel trims looked like as soon as I got back home after 25 miles or so. Didn’t have much issue, a couple of stumbles here and there on the highway but nothing crazy and no rough idle when I stopped.
I hope I’m not over doing it with the pics and info. Thank you so much for your help! I hope we can get this fixed and the info can help someone else having this type of issue.

Hello,

I just read this thread my feeling is the injectors are dirty. I would put a bottle of Seafoam treatment into a tank of gas and burn it through and see if you get a change.
Tom

Hey Tom, thanks for the response. I’ve actually done multiple bottles of Seafoam treatment through the tank and have also done the spray treatment in the intake. Thinking about doing the spray again.

Interesting, did it make any change at all? Maybe bench test one of them and make sure you have a good spray pattern.