chem_man

Sorry that I couldn't just say look at this part or that part. Anymore, so many different sensors involved and other variables, it's just unsafe to guess.

One thing I would advise you to do is to run a can of Berryman B-12 in your gas tank to clean your fuel system if you don't normally buy Top Tier gas or run something like Techron Complete Fuel System Cleaner periodically. If you typically don't run a fuel system cleaner every 3000 - 5000 miles, then I would advise to start using Techron Complete Fuel System Cleaner every 3000 - 5000 miles to keep your injectors clean.

Jacob11531

I am still struggling to track down this problem and guess getting my own scanner to watch live parameters is my only help at this point. I bought the BAFX scanner but the one for IOS so I will wait for that to show up Friday and buy OBD Fusion also. I will go from there. Not sure what live perimeters to watch when the truck is misfiring but I will be on the lookout.

chem_man

Since I am not familiar with OBD Fusion, I'll have to guess based on my experiences with Torque Pro and BlueDriver. Once you get your setup to read basic data such as engine coolant temperature, engine RPMs, etc., start looking around the program for more in depth engine parameters like misfire counter. I imagine that you'll be able to select misfire counter for each cylinder (at least I can in Torque Pro) and then monitor those as you drive in a manner that you described in your initial post. Also, monitor MAF function, short term and long term fuel trim values, manifold pressure or vacuum, etc.

Also set your system up to collect the live data you are monitoring and then have it e-mailed to you in a file type you can open. In my case, I get all the information sent to me in a .CSV file which I open using Excel. Now comes the fun part - looking at and interpreting the collected data. You might be surprised with all that you'll be able to monitor with your OBDII setup. Just remember not to overwhelm yourself with all the information it can provide you.

Good luck!

Jacob11531

Ok so here is where I am at right now. To start the fuel pressure should be between 55 and 62 psi correct?

Waiting for the scanner to show up in the mail tomorrow.to watch live perimeters while driving/codes.

Today a mechanic told me that a possibility to my problem could be the fuel pressure regulator after telling him my symptoms. I did a quick test to see if fuel was in the vacuum line on the fpr when the misfires were happening after getting on the highway and no, the line was dry. Today was one of the worst days this has happened also, the engine light stuck solid this time. I got the codes checked and obviously the bank 1 and bank 2 lean, multiple misfires, also codes for low voltage bank 2 sensor 1 02 sensor and high voltage for bank 2 sensor 2 02 sensor. I also rented a fuel pressure tester from the parts store and I did some testing.

Results: I wanted the truck to be stone cold but I gave it 2 hours to cool down. Temp was around 160 when I did the testing. With the truck off and the key on I got a reading of 50psi, obviously drops slowly since pump doesn't constantly run. While running the truck at idle, I get a shaky reading between 46 and 50 psi. I pulled the vacuum hose off the fpr while running and got 55 psi. To my knowledge, this is low pressure and I dont know if I should look into the pump, fpr, or a vacuum leak. Like I said i have sprayed the **** put of the gaskets and around the injectors so many times and I have gotten no symptoms of leaks. Is the pressure regulator possibly my problem? This probably explains a lot of things though. Still not sure how a bad pump or fpr can cause my misfire problems to only be when the truck heats up from being cold when only taken on the highway but it explains the hesitation and backfires on decel when the truck runs bad. Definitely been told the truck has hesitation from passengers at all times so thats always an ongoing problem.

I'm not sure how else to utilize this pressure tester as I got some decent diagnosing done. I am going to return it tonight but if i need to do more recommended by you guys I will pick it up again. What do you guys think now? Could this just be the fpr? Its $60. OBD2 scanner comes tomorrow. Any help is greatly appreciated as always. Finally feel like I am getting somewhere with this problem.

EDIT: I came across this: "Key on, engine off fuel pressure specification is 55-62 psi. With engine running, the fuel pressure should be slightly less (around 5-7 psi less). The fact that you get 58 psi with vacuum hose disconnected to the regulator puts the fuel pressure right into the proper range and shows that the regulator is working. I don't feel that fuel pressure is the cause of your sluggishness. When you open the throttle. vacuum signal to the regulator will drop and the fuel pressure will increase to 58 psi and this is right in the middle of the specified range of 55-62 psi. I would suspect that you may have a restricted catalytic converter as the cause of the sluggishness, not fuel pressure problems."
Maybe the cats could be clogged. This problem has been ongoing for a year+. The truck has been driven easily 25k miles with the misfire issue in that time frame as it happened daily. That could very well be an issue? Clogged/restricted cats?

Irish_alley

with my 02 i would have a lean code and it couldnt pass anything unless it was standing still. also had an issue when cold and would stall 2 or 3 times before it would stay running. tested fuel pressure and it was between 20-23. so it could run and idle ok with fuel pressure that low and wouldnt hold pressure with the key off. so i changed the pump and it was a different truck, it idled/stared better and would pass anything i wanted. i dont think i checked the pressure with the key off but with it on it was around 58 with it running. from what i understand theres a check valve in the pump thats supposed to stop the pressure from bleeding off when you turn the truck off and if it does bleed off you should replace the pump.

Jacob11531

Got the BAFX scanner.
Got used to using it and got all the gauges that I would deem helpful on my list. However there is no way to find misfires or even misfires per cylinder for that matter. I am watching short term/long term fuel trims, maf, coolent temp, rpm, manifold pressure, 02 sensor data but thats about all the app really has.
I'm getting really ticked off on this problem tho. Its something that's been going on for so long and just one big mystery to everyone and I dont know why this thing has to be such a p.i.t.a, I just want it gone. I cant see it being a vacuum leak, a sensor problem, a fuel problem. Last thing I can do is check if the plugs are normal or black to see if the truck is always rich but thats it.
Only when the truck is "cold" (less than operating temp) and taken on the highway will it just love to misfire and have a horrible decel, all other conditions the thing is just perfect as can be, leaving it hard for others to diagnose. I just don't understand. If it was a fuel pump i would at least have starting problems or constant problems but I don't which makes it hard for me to believe the pump or pressure regulator is bad. As well for any other sensor, (if one is bad) why do they all work fine and the truck has to run perfect in all other conditions except this one? I can always leave my house in town cold or hot and its completely fine, no problems/misfires,etc whatsoever. I'm at such a loss why this only happens when the truck warms up fast on the highway.
I screen recorded my phone with the OBD Fusion app watching the gauges I have set while the truck was at operating temps, running normal as usual just for a quick drive. Any tips before I watch the perimeters on the highway tm when the problem will occour again? I would love to get somewhere with this thing by the end of the weekend. Any help is appreciated

Sorry if I seem angry, this is just such a massive weight on my shoulders that has been ongoing forever and something I cant even diagnose for the life of me. I can get nowhere with this lol.

chem_man

Thanks for the video. I hope others chime in on this too.

The short and long term fuel trim values look really good for the first 16 seconds of the video. Then at 17 seconds your Sensor 2 fuel trim values (yes I realize they are short term) for both banks being high positive indicating that the engine is running lean and are a classic symptom of a vacuum leak.

You might want to consider have a smoke test performed to see where the leak is is you are unable to visually track the leak or leaks down. Have you pulled the manifold cover off and inspected the various vacuum lines going to the EVAP purge solenoid at the front of the engine? I agree with you that something is not right.

Do you know if the intake manifold gaskets have ever been changed?

Hang in there and think about this logically and in a step by step manner.

Again, Good luck!

Jacob11531

Ive always wanted to do a smoke test but no parts store I call rents them out and noone even sells them for that matter (they all act like they have never heared of one). I have no idea where to get a smoke tester which is why I was left to the brake cleaner method. Is there any way I can do the smoke test without the tester since noone sells them? The vacuum lines all look in check visually and i have hose clamps on some also. I will have to search what the EVAP purge solonoid is and look since I have no idea what that is. The manifold gaskets were the first thing told to be changed recommended by a mechanic which I have done myself roughly a year ago. I spray them with brake cleaner a lot to be sure there is no signs of a leak before which is why I never leaned on them being bad again. Is there a chance leaky injectors can cause the vacuum leak? (Truck always starts fine, drives perfect besides the symptom I listed)
I will get another vid loaded when the misfires are going on but It looks like the smoke test will be next, I agree a vacuum leak sounds like a good diagnosis I just cant wrap my head around the fact it only happening in a certain situation.
I will need recommendations of where I can get the smoke tester as I have said noone around me has them. Or is there a homemade way to do it? Thankyou again!

EDIT: I think my best bet is going to have to make my own for $20 based off what i learned online. After work I will get the things needed to make it and i will plug the tube where the brake booster hose goes. Question: do i have to plus the end of the throttle body when doing this test? Thanks

chem_man

There are a lot of you tube videos on how to use a smoke machine to find leaks in the EVAP system. Also, lots of plans online on building your own. Main thing to keep in mind is that it only takes about 1 psi of pressure to pressurize the EVAP system in order to find a leak. DO NOT RUN MORE THAN ABOUT 1 - 2 PSI OR YOU'LL CAUSE MORE PROBLEMS! Also, there should be a green cap that is screwed onto the EVAP test port. That is where you hook up the smoke generator. You do not need to plug anything near the throttle body or anywhere else.

I have to do some work on my Silverado tomorrow, so I'll take a picture of where my EVAP test port is and, if the web gods allow, I will do my best to post a picture for you tomorrow evening.

The EVAP system purge valve is located behind the throttle body under the intake manifold cover. It is about 4 inches long, and looks like a cylinder with an electrical plug and a rigid vacuum line going to it.

Another way to look for a vacuum leak is using carb cleaner or an unlit propane torch and while spraying the carb cleaner/propane around, watch the short term fuel trim values on your android device. When the extra "fuel" gets sucked into the engine, the short term fuel trims will go from a normal value to a high negative value really quick. Remove the carb cleaner/propane and the short term fuel trims go back to normal.

Until tomorrow my friend!

Jacob11531

Made a homemade smoke tester and pumped some vapors in the intake.

2 issues.

1. I have a very bad leak from the oil filler neck which I think is just a swelled up oring. I will pop the fill neck off tomorrow and replace the oring if there is one, not sure what else it could be. I cant see this being my issue/ being a vacuum leak since its off the valve cover and its different from lets say intake gaskets leaking right?. Maybe this could be the issue all along? Im not sure but maybe you guys will know.
2. On cyl 1 side, I think i see a very small (very small) amount of vapor seeping through the injector seal. I think its the injector, not certain tho. Maybe the orings got mesed up when I reinstalled the manifold a year ago but all the rest of the injectors were fine. As far as fixing this, what is the solution? Pull rails with injectors to replace orings?

EDIT: Wow lol 1 min off each other on the thread response. I didn't think to test from the evap test port so what i did was put a glove around the throttle body, cut the finger off and ziptied the hose with the vapor to it. I dont think there would be any difference doing it from the test port or throttle body right. For future reference, if the filler cap and the injector gaskets (if they have to be replaced) just somehow were the problem this entire time, would it be a good idea to clean things like plugs, 02 sensors and of course a can of seafoam or b12, since they have seen so much of a rich mixture and just because? I have plenty of time after fixing the current problems to do this tomorrow. I figure spraying the plugs with brake cleaner and soaking the 02 sensors in gas for a while should clean them nicely. Just a thought. (Just trying to toss all my questiones out there)

At least now i am certain the manifold gaskets are tight and not leaking
All help is appreciated as always!