Engine rattle or knock? | Ford Explorer Forums - Serious Explorations

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Engine rattle or knock?

knb416

Member
Joined
November 5, 2008
Messages
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City, State
Calhoun, KY
Year, Model & Trim Level
1994 XLT
Hey everyone. I am hoping to find some kind of definite(hopefully) answer on what is going on with my X. When I am in neutral or park and I rev the engine everything sounds fine. When I am on the highway or going uphill and I try to "hammer down on it" to accelerate I hear this rattling sound. It sounds like it is coming from the front passenger side(?) under the hood. It sounds like a sewing machine or someone doing a drum roll with a couple of ball peen hammers. If I get up to speed gradually I don't hear it. If I accelerate to pass I hear it.

I put new Bosch platinum plugs with the factory preset gap and new Bosch plugs wires in.....still hear the rattle. I put Seafoam in the gas tank thinking MAYBE it might help....still hear the rattle. Haven't cleaned the MAF sensor yet and haven't changed the fuel filter because I don't know where to get the tool to loose the demon clips.:D

My X has almost 184,000 miles on it and I think I am the 3rd(?) owner. I know the previous owner took pretty good care of it because I have the paperwork but he never said anything about the transmission giving him trouble. The interior dome lights stay on though so I pulled the bulbs. Anyone know what's the fix to that one?

I think I got a pretty good deal for $500 and really want to keep this X for a long time. Can anyone help me out? Thanks in advance.
 



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The symtoms sound a bit like "carbon knock", and as for your interior lights being on all the time, make sure the headlight dimmer switch isn't turned all the way to the right (clockwise) as this is how the switch works. If that's not it, you could have a bad door switch, also check the rear hatch switch. There are extensive schematics in the link in my signature that may help.
 






If cleaning the MAF doesn't work, try running about half a can of seafoam through the intake. Just suck it in a vacuum line and let it sit for at least a half hour. Then start it up and watch the smoke show.

One other thing...generally Bosch plugs and wires do not agree with the ignition system on explorers. For most cases, the best plug is either an autolite or motorcraft platinum. It's what came on the truck stock, and what it's best with.

Also, when installing new plugs, even when pre-gapped, make sure and check the gap before you install them. It's very easy to change the gap by bumping the electrode a tiny bit, and most of the time I've seen the pre-gapped ones are still off just a touch. Now I'm not saying your current plugs and wires are the problem. But I'm saying this mostly so next time you change them, or if you start having problems with them, that you get the right brand.
 






The most common reasons for engine knock on the 4.0 are:
MAF sensor needs cleaning
Lower intake manifold bolts need to be retorqued
Engine needs to be decarboned. Ford has issued a TSB on this, also the TSB concerning decarboning advises against using premium as this can contribute to carbon buildup and engine knock.
 






The most common reasons for engine knock on the 4.0 are:
MAF sensor needs cleaning
Lower intake manifold bolts need to be retorqued
Engine needs to be decarboned. Ford has issued a TSB on this, also the TSB concerning decarboning advises against using premium as this can contribute to carbon buildup and engine knock.

Does anyone have a pic of where to reach the lower intake manifold bolts? Or can describe how to reach them to tighten? Also...what's the torque spec?

Thanks!
 












and as for your interior lights being on all the time, make sure the headlight dimmer switch isn't turned all the way to the right (clockwise) as this is how the switch works.

Mine works the other way, counterclockwise turns the dome lights on :D Maybe one of ours was built in the southern hemisphere :p
 






The symtoms sound a bit like "carbon knock", and as for your interior lights being on all the time, make sure the headlight dimmer switch isn't turned all the way to the right (clockwise) as this is how the switch works. If that's not it, you could have a bad door switch, also check the rear hatch switch. There are extensive schematics in the link in my signature that may help.

hes right its either door switch or headlight switch.

im a mobile electronics installer and seen a million door switches that were bad
 






Update

Well I fixed the lighting issue....damn you door jamb switches!:D

Autozone only had two in stock so I put them in the front doors....still wasn't working right. I then took an old one and put it in the rear passenger door and ...SHAZAM! It must have been a sight to see a 6'1" 275 lb. man howling like a lunatic in his driveway at midnight, just because his interior lights were working!

I cleaned my MAF sensor too and that seemed to help the rattle just a LITTLE bit. I am close to my next oil change so I think my next step is to seafoam although I am a little leery about it. I don't want to loosen up something that is going to clog my engine cuz that would SUCK!:mad:

Wish me luck....
 






This will not "clog" your engine. Carbon simply builds up on the face of the piston, valves, valve stem, and intake ports. As carbon builds up it can restrict air flow, and cause the incoming air charge to no longer be "smooth". Carbon also soaks up fuel; considering that with the fact that the areas mentioned above are the "quench" areas of the combustion chamber, this can lead to carbon knock, poor fuel mileage, and decreased performance benchmarks. And to clarify carbon knock: Carbon will soak up the incoming fuel; causing the pcm (computer) to become confused about ignition timing. When ignition timing is off it will ping or knock/tap.


Good luck, and remember one can may not cure it. These engines are known for this problem. If you need anymore advice feel free to ask.
 






Could also be the switch to winter blended fuels...If the noise occurs under load it might just be the crappy gas we have to run. I switched to a mid-grade and that solved the poblem.
 






Actually vehicles designed to run on 87 octane fuels will have increased carbon build up when a higher octane fuel is used. Even the TSB Ford issued touched on that subject. The sound may have stopped, but it probably was due to revving the engine at a higher RPM while driving. That's why the TSB states drive the vehicle while RPM's are near 3500; to break the carbon loose from the quench areas of the combustion chamber. Think about the saying "blowing the cob-webs out of it". That's essentially what you are doing while laying the hammer down. Once again, if you need further advice or explaination please feel free to ask.
 






Is there a safer way to "Blow the cobwebs out" ? How fast will the ex go at 3,500 RPMs? How long to you have to maintain 3,500 to see any benefit?
 






I think if you make a habit of driving on the highway not in overdrive for a few days, that would do the job. I would just be careful, keep the oil full and watch the temp while driving.

If you drive normally on the highway 15-20 miles a day you may not want to do this. But, if the vehicle is used in town and not allowed to heat up to full temp, then it might help.

Also if carbon builds up enough, it can glow red and cause run-on or deiseling. This is when the engine continues to run even after the ignition is shut off. This only happens with carburated engines though.
 






Is there a safer way to "Blow the cobwebs out" ? How fast will the ex go at 3,500 RPMs? How long to you have to maintain 3,500 to see any benefit?

If your engine is mechanically sound, and your cooling is ok, it's perfectly safe, as long as you drive on a road that can handle 80 mph. I use a flat straight interstate highway. On a 4.0 with 3:27 gears and 30" tires, you'll run about 80 mph in fourth (aka "D") at 3,200 rpm.

In my experience, 3000-3200 rpm is sufficient to burn off the carbon, just do it for about 10 minutes on the highway and that should do it.

If you still have pinging after TWO Seafoam + 80 mph for 10 minutes treatments, then I'd say chances are you have other issues (FPR, intake leak, etc.) causing the pinging.
 






Run the explorer down the interstate at normal speeds, just make sure you hit the O/D OFF button located on the gear selector. This will bring RPM up by changing gear ratios (eliminating overdrive ratio) in the auto trans to a near 1:1 or Direct Drive. This is sufficient enough. But after two or three treatments, and you still have a ping, I'd suspect a vacuum leak at one of the following: plenumn gaskets, lower intake/fuel rail gaskets, fuel injector o-rings, or an egr pipe o ring. Keep us posted!
 






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