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Can't Get Rid of Engine Ping/Knock

Discussion in 'Stock 1991 - 1994 Explorers' started by luvmonterey, August 11, 2017.


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    1. luvmonterey

      luvmonterey Member

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      Hi all. Hope someone can help me. I have a '94 XLT with 225k miles. Engine has been knocking terribly and I haven't been able to get it to stop. I have done the following:

      Replaced plugs, wires, coil pack.
      Run Seafoam through the intake twice, let it sit, and then ran the engine about 15 miles at 3k rpm. Check engine light went on when I did this last, but then went off. I ran the engine pretty hard. Then changed the oil.

      I'm running 91 octane premium because anything less knocks worse. I have been running Arco gas recently. It's the least expensive around generally, and am wondering if that may be part of the problem?

      Also wondering if a blown head gasket could cause knock. I am loosing some coolant, but I think it could be a slow leak from around the neck of the thermostat cover, as there is some buildup around the hose there. I can also smell coolant under the hood. How can I diagnose or rule out a bad head gasket? Any help would be appreciated! Thanks!
       
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    3. 2stroke

      2stroke Elite Explorer

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      This sounds like it could be a bad lower intake manifold gasket. Both air intake, and coolant ports go through the intake manifold, and a vacuum leak is a common cause of pinging.
       
    4. luvmonterey

      luvmonterey Member

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      Well that would be easier to deal with than a head gasket I would imagine. Is there any way to diagnose, short of just doing the tear down and replacement?
       
    5. Rick

      Rick Pumpkin Pilot Staff Member Admin Elite Explorer

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      I have to clean my MAF regularly in my '93 or my engine knocks. Here is a thread on cleaning the MAF on a 2nd gen. http://www.explorerforum.com/forums...af-sensor-and-the-iac-valve-2002-2003.339793/ The procedure is the same, but the 1st gen MAF only has one wire to clean.

      In the thread he shows MAF cleaner, you can also use electronic contact cleaner with the same results, just don't use brake cleaner, or anything, but cleaners made for electronics.
       
    6. Rhett

      Rhett Let Them Eat Cake Elite Explorer

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      I thought the worst (lim gasket leak) but on my truck, I had cracks in my intake tube (the tube from the air filter to the throttle body) and once I repaired the tube, pinging disappeared. And I can tell you -- I had pretty bad, persistent partial throttle /full throttle pinging, even on 93 octane gas. Unmetered air is really bad on our trucks it seems.

      You can also check for vac leaks on the vac lines, and on the vac octopus on the upper intake manifold. Not all of those ports are used, and they are supposed to have a cap on them. Every now and then a cap blows off, or wears out and falls off.
       
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    7. luvmonterey

      luvmonterey Member

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      I completely forgot about the MAF. It has been a while since I cleaned it, so I picked up a can of contact cleaner when I was out and cleaned the MAF in the parking lot. I drove about 18 miles back home and it seems to be better, but it could just be my imagination also. I have about a quarter tank left, and will also try some better gas this time around. Thanks for the suggestion regarding the MAF!
       
    8. luvmonterey

      luvmonterey Member

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      Thanks for the suggestions. I will check for leaks on the intake tube. I know that the rubber seal at the end that connects to the throttle body on my '94 is falling apart. I have been meaning to go to a yard to see if I can find a replacement, as I'm sure Ford no longer makes them. My vacuume hoses seem to be ok. On the octopus, if I do remove a cap, the engine immediately runs really rough, and I have had hoses blow off before. This seems to be a different issue. The pinging seems to be worse between 1500-2000 rpm in the higher gears, at highway speeds or near them on flat roads.
       
    9. Rhett

      Rhett Let Them Eat Cake Elite Explorer

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      I repaired mine using Permatex Black. It dries to a rubber-like material and it sealed my tube (the end was getting ragged just like yours). Pinging was as you described -- worse on partial throttle, and actually at full throttle or near-WOT it was ok, no pinging then. I figure the unmetered air was really leaning the air/fuel mix.

      The other option is either junkyard or e-bay...I used to see intake tubes on e-bay but they were like $180, so I said, "I'll try the Permatex Black first...". If my pipe had been cracked everywhere, then yes, I would have bought a replacement. I may still...
       
    10. luvmonterey

      luvmonterey Member

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      I will check out my intake tube more carefully for cracks. Was yours cracked in the flexible ribbed areas or in other spots? I was just thinking about trying to repair the rubber seal on the end with black Gorilla duct tape. It's just the bottom portion that is really worn out. Thanks for the suggestions!
       
    11. Rhett

      Rhett Let Them Eat Cake Elite Explorer

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      It was mainly the end by the throttle body that was chewed up. Permatex Black is messy. I didn't want to use tape because I thought tape might wear out from heat cycles. If Gorilla tape is anything like Gorilla glue then maybe it is good stuff and will hold for a long time.
       
    12. luvmonterey

      luvmonterey Member

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      I will try it and let you know how it goes. It's very strong and sticky tape. Much thicker and heavier duty than traditional duct tape. It really sticks, plus it's black.
       
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    13. RangerX

      RangerX Elite Ranger Staff Member Moderator Elite Explorer

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      Well this is very interesting. I've have pinging/ marbling for a while now, and have recently noticed my intake tube has not just cracks but actual holes. Never made the connection until now! Thanks.
       
    14. RangerX

      RangerX Elite Ranger Staff Member Moderator Elite Explorer

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    15. shucker1

      shucker1 Elite Explorer

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      What about that "Flex Seal" stuff they sell on TV late night infomercials?

      If he can cut a boat in half then fix it and ride around like noting happened..

      Who knows.

      Just kidding.

      There has got to be a way to fab up a new inlet hose.
       
    16. luvmonterey

      luvmonterey Member

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    17. Rick

      Rick Pumpkin Pilot Staff Member Admin Elite Explorer

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    18. Highflow50

      Highflow50 New Member

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      At 225k I would look at the timing chain. It could be stretched out a bit.
       
    19. natenkiki2004

      natenkiki2004 Blue Bomb!

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      Just throwing this out there... I've never gotten rid of my ping, just tamed it. Upper and lower intake gaskets, throttle body gasket, intake tube swap (and inspection), valve cover gaskets, timing gasket, timing set, new silicone vacuum hoses with minimal loops... Nothing's fixed it. I run premium gas and it doesn't ping 98% of the time. If I put regular in, it will ping on cold nights at highway speed on flat ground. I think some of us just have to deal with it, whether it's inherent to older computers, caused by carbon build up or a worn engine.
       
    20. luvmonterey

      luvmonterey Member

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      It looks like it would probably work as well as anything else available. Too bad it's not 1.5" or 2", but maybe those widths are available. I think the biggest issue with using any tape product is going to be how well the adhesive withstands heat. At least with the silicone tape, it's not going to melt, which is a definite advantage.
       
    21. luvmonterey

      luvmonterey Member

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      Yes, I have thought about that also. Not something I am looking forward to replacing. I am hoping that since the pinging is somewhat intermittent, in that it gets really bad, subsides some, goes away, comes back, that it's not the chain, which I would think, if was a cause, would cause the issue to be more consistent. I could be wrong though. Most people on this site know more than I do. That's why I'm here!
       
    22. luvmonterey

      luvmonterey Member

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      Yes, I am resigned to the fact that the pinging may be caused by different issues combined, or individually at different times, depending upon conditions. The computer is old, software is old, engine is old, seals are old, everything is just old...lol! Still, I'm hoping that maybe I will find something that when fixed or changed, will make it much less of an issue. I would love to be 98% ping free. That would be amazing. Thanks for the info!
       
    23. overripeturnip

      overripeturnip New Member

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      Could somebody clarify what you guys mean by pinging? Am I right in saying this is the same as knocking/detonation? What exactly are you guys heading to indicate this is occurring? I'd just like to know the telltale signs. Thanks in advance.
       
    24. luvmonterey

      luvmonterey Member

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    25. luvmonterey

      luvmonterey Member

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      I think I have fixed the problem, thanks to Rhett's suggestions and info! I will do my best to explain, as I haven't figured out how to upload photos to this site yet.

      I removed the intake tube and the rubber seal on the throttle body side. The rubber seal was all chewed up on the bottom, and a large chunk of the plastic intake tube was missing from the end in the same spot the rubber seal was damaged. I believe this allowed unmetered air to enter the intake and leaned out the fuel/air mixture, which can cause ping/knock.

      I removed the seal and cleaned up the end of the tube, removing grease, dirt, and oil from the outside and inside. I abandoned the rubber seal. I cut a 3.5" x 11.5" piece of foil covered bitchithane roofing membrane from a spare roll I had (you can get it from Home Depot). I peeled the protective cover from the bitchethane and used a heat gun to warm it up, along with the end of the intake tube. I then wrapped the bitchethane around the end of the tube once, about 1.75" from the end of the tube, with about a 1/2" overlap. I then pressed it down tight around the outside of the tube. I heated up the exposed inside of the bitchethane and intake tube again, and then folded the bitchethane down around the inside of the tube as far as it would go (about 1.75"). This replaced the rubber seal. I put some silicone lubricant around the inside and fitted the tube back in place and clamped it down with the original clamp ring. Perfect seal! I did a 10 mile test drive on the highway and through town; up and down hills and flats, through all gears. Zero ping/knock! I'm not sure how well the bitchethane will hold up over time, but it's fairly strong and sticky stuff when applied warm, to a clean surface. I will add photos if I can figure out how upload them. Thanks Rhett!
       
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    26. gmbroy

      gmbroy Elite Explorer

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      Glad you got it fixed , that's what this forum is for . this is the best forum i have ever seen .
       
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