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Engine sputters sometimes when accelerating but acts normal when restart

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  • zedjr10
    replied
    Was a fuel injector or injectors. My junkyard refurbished ones didn't work right and i ordered some rebuilt ones. I learned a bunch of lessons on this little venture. Never clean ur own fuel injectors and just get professionally remanned ones.

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  • zedjr10
    replied
    Originally posted by Raf99 View Post
    "Maybe i should just swap out my FPR to see just in case something weird is going" , ya, i mean you just keep ignoring steps suggested here and doing what you want with no testing. If you have an air leak in the manifold then it will affect FPR, so a vacuum test is required.
    So ya. do whatever you want. This went from only happens when hot, to happens when cold. & no-one would notice the issue to ..... no acceleration for 15 seconds. & if you have an engine code, then start there.

    https://www.yourmechanic.com/service...ing-inspection
    https://www.motor.com/magazine-summa...-vacuum-gauge/

    It definitely took some time for symptoms to be noticed and confirmed. I only spend a little time here and there working thru it. Part of it is i don't want to just swap parts out and some of these testing steps i have never done before. I still do think it could be an injector and i have 4 replacement injectors and all the seals. But then i am never going to know really why or what injector it is. I do suspect an injector but not definitive. As i also think it could be resistor box but i am not totally sure how that box works or even how to test it while car is running. Or even if that matters. I will test some later tonight.

    The fpr is very unlikely giving the fuel pressure is good and moves as it should. If it wasn't working then fuel pressure would build up much higher than what it is or much lower. It only regulates fuel pressure by releasing what is too high over a pressure release valve. The injectors only need a certain pressure for given certain spray rates. So the reason it rises to 34.5 while misfiring keeping throttle at 2500 rpms. The map is about close to what it would be if it was idling. SO 34.5 is where the valve will open an release fuel back to tank. So that does point imo to a fuel injector but am guessing a bit and can't wait to find out if i am right or wrong. I honesty could be wrong but good to know if I am.

    The o2 code is cause of prolonged 2500rpm's while engine was misfiring. It isn't the cause of this as it is a new sensor anyways. Too bad it isn't obd2 so i could read the trim ratios and other things and i would know more specifically what it is.

    BTW u don't got to help. IT almost sounds like u want me to do things ur way honestly. I mostly am writing this down for my own documentation later so i can look back years later and go hmm.

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  • Raf99
    replied
    "Maybe i should just swap out my FPR to see just in case something weird is going" , ya, i mean you just keep ignoring steps suggested here and doing what you want with no testing. If you have an air leak in the manifold then it will affect FPR, so a vacuum test is required.
    So ya. do whatever you want. This went from only happens when hot, to happens when cold. & no-one would notice the issue to ..... no acceleration for 15 seconds. & if you have an engine code, then start there.

    https://www.yourmechanic.com/service...ing-inspection
    https://www.motor.com/magazine-summa...-vacuum-gauge/


    Leave a comment:


  • zedjr10
    replied
    Injector and injector resistance box checked. Both are within specs. Injector resistance was at edge of specs with all being 24-25 ohms. Injector resistance box fine also. I got cel code 43(02 sensor) while trying to induce symptoms by keeping it revved at 2500 rpms. The o2 sensor was replaced after these symptoms started so how can it be that. How else can I test injectors? What other ways are there to test injectors as those two tests won't tell me for sure they are good to go. They could still be bad right? I have 4 spare injectors i just might swap out and see. I have a few more things to try tomorrow like injector voltage test while it is running. Am at the end of the road almost. Maybe ill repost this with all my new updated symptoms and tests. I have been writing this stuff down.

    What are the possible ways if any air is being restricted in intake and plenum. Isn't there a butterfly plate that opens at certain rpms and throttle position?

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  • zedjr10
    replied
    Originally posted by Raf99 View Post
    Implies the engine is consuming more fuel, ie: failing injector or malfunctioning FPR. Have you tested the resistance of your injectors with a multimeter?
    We need to keep in mind the important role the FPR has on the fuel delivery too. There's the hose that goes from the FPR to the intake manifold for proper vacuum at different rpms/vacuum. Check this hose for cracks, or take it off and look at it.
    Maybe i should just swap out my FPR to see just in case something weird is going. Is measuring the ohms going to tell me if it is a sticky Injector?

    i do forget to mention that this happens when driving cold. I keep forgetting this as I have been testing lately only when sitting still. It is more of a hesitation than misfire that is overcome by WOT. I know that sounds just like a tps but it isn't. I guess this rules out all air & temp sensors. Definitely clogged cat also. It really does sound like an injector issue but i still can't rule out some air possibility.
    I guess i am getting a good education in troubleshooting engine issues.

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  • Raf99
    replied
    Best of luck.

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  • zedjr10
    replied
    Originally posted by Raf99 View Post
    Implies the engine is consuming more fuel, ie: failing injector or malfunctioning FPR. Have you tested the resistance of your injectors with a multimeter?
    We need to keep in mind the important role the FPR has on the fuel delivery too. There's the hose that goes from the FPR to the intake manifold for proper vacuum at different rpms/vacuum. Check this hose for cracks, or take it off and look at it.
    Too much fuel or not enough air. There is a slight gas smell from exhaust once misfiring starts happening.

    FPR has been tested and works within specs. Is on the very load low side of specs but still within specs. 31psi on idle and 41 on wot. Injectors I have only tested with a stethoscope and seem to be working fine also. Only a sticky injector would cause these symptoms and not sure how to even test for sticky injector. I will have to look up how to test with meter. I wish I had an Air fuel ratio gauge now as this would tell me alot more. On my list to install.

    Sticky injector still don't make any sense that it makes the fuel pressure rise once missing starts. Is air being cut off somehow into the plenum and that is what is causing the slight rise in fuel pressure maybe? I don't see how air is being cut off though. Restricted air equals more manifold pressure and hence why is sits 2.5 psi above what it did. But why don't the fuel pressure fluctuate if that is case. Fuel pressure only goes down when I left off gas and then it returns to normal operation. I know this is trying to tell me something i jsut don't know system well enough yet to tell for sure. Would restricted air cause more manifold pressure which in turns causes miss and fuel pressure to rise slightly. Which would mean possibly it has to be a air flap past the throttle body and very close to fpr. Who knows i guess. Will find out soon enough. Still could be a sensor that is causing too much fuel to be dumped in.

    Could it be the air somehow that only manifests itself between 1200 rpms to 3k and got to be warmed up.
    Last edited by zedjr10; 09-01-2021, 01:13 PM.

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  • Raf99
    replied
    Implies the engine is consuming more fuel, ie: failing injector or malfunctioning FPR. Have you tested the resistance of your injectors with a multimeter?
    We need to keep in mind the important role the FPR has on the fuel delivery too. There's the hose that goes from the FPR to the intake manifold for proper vacuum at different rpms/vacuum. Check this hose for cracks, or take it off and look at it.

    Leave a comment:


  • zedjr10
    replied
    Originally posted by Raf99 View Post
    The point of the pics of ALL 4 spark plugs was to compare them, see if one looks different, hotter, less gap, etc. A cylinder with a fuel issue is going to look different than the rest if this is happening over long period of time.
    And no point in worrying about open-loop / closed-loop, you can't adjust that anyways. Closed loop conditions are several (temp, load on engine, speed etc.). And injectors have different spray percentages based on the engine requirements. So ya, technically at a certain rpm the injector is failing. But at this point we need to see a video. Need to see the hesitation on the rpm gauge, maybe others had the issue and just need to see some videos.
    they look exactly the same as the one i showed. All of them. Exactly. To understand closed and open is to understand what is going on better. I got to get a stethoscope to see if and what injector is failing. Why is fuel pressure rising while misfiring going on. Answer that. Or is it possible for the evap port on TB to suck more than gas vapors over from the evap canister.

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  • Raf99
    replied
    The point of the pics of ALL 4 spark plugs was to compare them, see if one looks different, hotter, less gap, etc. A cylinder with a fuel issue is going to look different than the rest if this is happening over long period of time.
    And no point in worrying about open-loop / closed-loop, you can't adjust that anyways. Closed loop conditions are several (temp, load on engine, speed etc.). And injectors have different spray percentages based on the engine requirements. So ya, technically at a certain rpm the injector is failing. But at this point we need to see a video. Need to see the hesitation on the rpm gauge, maybe others had the issue and just need to see some videos.

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  • zedjr10
    replied
    after studying a bit how this EVAP system works i just can't see how it could cause a misfire and stumbling.
    I am totally out of ideals and things to check.
    THe only thing left that hasn't been confirmed is sticky injector and dumping too much fuel in and why when more air is introduced it goes away. But why not do this below 1300 rpms also.
    Last edited by zedjr10; 08-31-2021, 01:04 AM.

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  • zedjr10
    replied
    Not spark or egr. I disconnect EGR vacuum so it will remain closed and same symptoms come about. This isn't right way to test it I know but if I just make it closed all the time and symptoms come about then it can't be it is my thinking. I am down to only a couple possibilities now. AM going to check the EVAP system next. I don't even know how ot check. I am guessing removing pressure by removing gas cap will do but i have no ideal actually.

    1. ECM
    2. Some sensor. IAT - I don't think so as can accelerate fine and don't affect idle or anything else at all. ECT- don't think so as warms up and idles fine.
    3. EVAP system - something in evap system just mostly thru process of elimination and this thing changes behavior based on engine temp. Can a malfunctioning evap even cause misfires?
    4. Dizzy- It seems all good. The spark was fine too all plugs and regular when misfiring. So spark is good but couldn't test spark strength. AM assuming some of those sensors inside dizzy send signal to ecm and then changes are made.
    5. Fuel Injector- Possible- will one cylinder cause such a misfire where it won't accelerate. In neutral at times it does seem like just one cylinder missing. Which could only be a sticky injector causing these symptoms at low rpm. Why does it not stick at lower and cause it to bog down. Would this explain the rise in fuel pressure by 2.5 psi when misfiring starts happening.
    Last edited by zedjr10; 08-31-2021, 12:52 AM.

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  • zedjr10
    replied
    Originally posted by Raf99 View Post
    Waiting for a video and pics of plugs
    Click image for larger version  Name:	IMG_58441.jpg Views:	0 Size:	15.2 KB ID:	4980363
    Plugs are perfectly fine. Good lord. Why does the fuel pressure shoot up 2.5 psi a half second after sputtering(misfire) happens. Answer that if you can. Video i will try maybe later to take and upload. It isn't going to be a eureka moment or anything.

    I really need to answer if the misfire is coming from injector side or spark. So am going to do that somehow. The misfire is at certain conditions so not sure how i am going to test injector side but testing spark side is easy enough.

    Would also be helpful in knowing the cycles the ecm goes thru when engine is cold and hot.
    Last edited by zedjr10; 08-30-2021, 06:28 PM.

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  • Raf99
    replied
    Waiting for a video and pics of plugs

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  • zedjr10
    replied
    I really need to find out if this misfire is coming from injector side or dizzy side. I honestly don't know how to do this. Going to have to look this up. If it was coming from dizzy side then why don't my gas smell like eggs and why does fuel pressure shoot up almost 3 psi.

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