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Can you hear an engine misfire through the air filter?

This is a discussion on Can you hear an engine misfire through the air filter? within the General Help forums, part of the LSx Technical Help Section category; I decided to take the vacuum hose off the EGR and capped of try to eliminate the EGR to test ...

  1. #61
    Senior Member JayTA98's Avatar
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    I decided to take the vacuum hose off the EGR and capped of try to eliminate the EGR to test while driving. So far it has help with the hesitation under light acceleration or cruising but the idle is not shaky or erratic. It seems to idle with a/c on at 750RPM give or take. which is better than 600 rpm.
    Of course this is setting off the SES but i'm wondering if I have a separate issue affecting the idle.

    Going to try to fabricate the block off plate today to test. I have also read people that have similar issues have found out it was a faulty O2 sensor after the dealer ran a diagnostics. my scanner have some live data features and i can read the o2 voltages. I just have to figure out the normal parameters. I will do some more digging but i'm close to take it to ford just to see if it is not major.
    Last edited by JayTA98; 10-26-2014 at 08:15 AM.

  2. #62
    Senior Member JayTA98's Avatar
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    ok so I fabricated a small shim to block the egr hole. It looked like it drove a little better but the hesitation is still there. I'm done with this crap. I'm going to let ford find out what's wrong. I'm about to put this sucker for sale and just buy me a brand new trundra...

  3. #63
    Senior Member JayTA98's Avatar
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    I forgot to mentioned that I hooked the vacuum gauge back. I have 20in steady at idle. If I rev it up it and hold it the vacuum goes to almost 50in and then quickly levels back to 20in. Is that normal? I follow a test I found online to check the upstream o2 sensors. I connected my scanner and warmed the truck up. I was reading 0.1v to 0.8v at idle. I then sprayed carb cleaner in a vacuum line (to create a rich mix). The volts went up to .750v and stayed there while is continue to spray carb cleaner. When I stopped spraying carb cleaner the senosr continued to read.750v for about 6-8 secs before it went back 0.1v -0.9v. Does this sounds like the o2 are good?

    Just trying these last couple of things but I calling tomorrow to schedule visit to ford. I just don't want to do it lol. I never taken a car to the dealership...

  4. #64
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    A properly working O2 sender will rapidly cycle up and down. If it is holding steady, or its response is sluggish to throttle input, then it most likely needs replaced.

  5. #65
    Senior Member JayTA98's Avatar
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    Quote Originally Posted by pajeff02 View Post
    A properly working O2 sender will rapidly cycle up and down. If it is holding steady, or its response is sluggish to throttle input, then it most likely needs replaced.
    ok thanks jeff. most people keep telling me i have a bad coil. there is no way. all the coils are brand new 3 weeks old and the problem was not solved once i installed them.

    So you are saying that if im spraying the carb cleaner in the vac hose while i rev up a little to keep the truck from dying and the o2 sensor is reading a steady voltage; as soon as i stop spraying the carb cleaner the o2 should reset to cycling up and down? Is this supposed to happen instantly?
    1998 TA 130k A4, LS6 intake, TunedByFrost, Airlid, AIR and EGR delete, Borla exhaust, front Eibach lowering springs, LS6 valley cover, UMI TQ arm, UMI LCA's, UMI panhard bar, Poly engine mounts, BMR relocation brackets, Blistein HD shocks and struts, Oil catch can, Autotrix window fix.

    Now I have an 2001 F150 5.4L

  6. #66
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    If you hook up a scanner and watch the live sensor data it will rapidly bounce up and down. The narrowband O2 senders (which is what the factory installs -- widebands are for aftermarket gauges and tuning) will cycle from approximately 150 mV to 800 mv with 450 mV being stoichiometric, or an A/F of around 14.7:1. The vehicle's PCM... I think Ford calls it EEC or something like that, is trying to hit stoich but it is essentially a moving target. It'll enrich the mixture, then lean it, then enrichen it, then lean it, all the while coming out to an average that is around stoich. Hope this makes sense.

  7. #67
    Senior Member JayTA98's Avatar
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    Quote Originally Posted by pajeff02 View Post
    If you hook up a scanner and watch the live sensor data it will rapidly bounce up and down. The narrowband O2 senders (which is what the factory installs -- widebands are for aftermarket gauges and tuning) will cycle from approximately 150 mV to 800 mv with 450 mV being stoichiometric, or an A/F of around 14.7:1. The vehicle's PCM... I think Ford calls it EEC or something like that, is trying to hit stoich but it is essentially a moving target. It'll enrich the mixture, then lean it, then enrichen it, then lean it, all the while coming out to an average that is around stoich. Hope this makes sense.
    a little lol. I believe they are working fine.

  8. #68
    Senior Member JayTA98's Avatar
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    I can see they cycling fast with my obd2 scanner. So I guess they are good then.

  9. #69
    Senior Member JayTA98's Avatar
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    well appointment with ford made for tuesday. Will see what happens. During these days the hesitation seems to be getting worse.

  10. #70
    Senior Member JayTA98's Avatar
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    Well took it to ford and they ran some tests. They can't find nothing wrong. The tech drove it while watching live data and nothing is coming out of the ordinary. They showed me the graphs and it all seems fine. They didn't charge me and told me to bring it back when the issue is happening for them to look at it immediately. When I left about two lights down the road I feel the idle lightly shaking but I'm sure they must have felt it. It might now be as bad. So I have to see what i'm going to do. I put an add to see if I can sell it but nothing yet. I'm also looking to see how much will a new truck will cost me.

  11. #71
    Member RONS98TA's Avatar
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    Damn that sucks, but also doesn't surprise me at all. It seems like every time I took a car into a shop to have an intermediate problem looked at, it wouldnt happen to anyone else but me. I have also been on the other side of THAT fence to though, where I was the tech at the dealer and I couldn't find the issue the customer complained about. I found that if you have the tech go with you for a ride, then maybe when the issue occurs you can then say, "there it is!!" It may be a very subtle stumble that the tech doesn't notice, but you do. He may have not even noticed it.

  12. #72
    Senior Member JayTA98's Avatar
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    Quote Originally Posted by RONS98TA View Post
    Damn that sucks, but also doesn't surprise me at all. It seems like every time I took a car into a shop to have an intermediate problem looked at, it wouldnt happen to anyone else but me. I have also been on the other side of THAT fence to though, where I was the tech at the dealer and I couldn't find the issue the customer complained about. I found that if you have the tech go with you for a ride, then maybe when the issue occurs you can then say, "there it is!!" It may be a very subtle stumble that the tech doesn't notice, but you do. He may have not even noticed it.
    yes it is very possible.

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