Timing Chain Noise?

[arco777]

One of my 94 Explorers has never felt as powerful as the other, despite the same miles on each (190k) and all maintenance up to date.

Today I noticed a brief CEL during highway cruising that went away quickly. It was code 176, system lean. Ran a KOEO and KOER, passing both besides for the 176 in memory, then a cylinder balance test. Test indicated cylinder 4 weak, but not bad. Swapped some plug wires around, checked the spark plug on 4 (was fine, same as others). Re-tested. Test indicated cylinders 1, 5, and 6 weak. Drives as normal without a CEL though.

Also, I have noticed a new noise - sounds like a chain slapping, varies with RPM, and sounds like it's coming from the timing chain area though I am not 100%. It is not the AC compressor and I don't think it is a pulley. I know the OHV is not known for timing chain wear, but could this all be timing chain related?

Thanks in advance!

 

[Anime]

A lean system CEL can be from a few minor things, like a dirty MAF, air intake leak, either the filter, airbox/adapter, intake tube cracks/holes, or leaky gaskets. You can also just have worn out ignition wires or it could even just be an old or clogged fuel filter that isn't letting the right amount of fuel through or an old fuel pump that can't keep up anymore, or a combination of these.

The timing chains do stretch, some who have replaced the timing chain, gears, and tensioner on the OHV with a quality aftermarket set report smoother, quieter operation and better performance. The OHV is famous for wearing down the rocker arms due to soft metal being used on the stock units, so noise like valve clatter tends to be from that. Replacement of the timing assembly and the rocker arms and pushrods with quality parts is generally a sure-fire way to restore much of the stock HP/torque on a high-mileage 4.0L OHV.

 

[arco777]

Thanks Anime!

I may have to just do the timing chain and check the valvetrain. Have fixed or tested everything else you've mentioned.

My valvetrain makes a little noise but this noise isn't coming from there, sounds like it's coming from behind the water pump. Sounds exactly like a chain to me, or a tambourine (ha).

As an aside, I've had pretty bad luck with Borg Warner Select (BWD) plug wires lately... have had several go bad in under 3 months and they come apart way too easily. My engine was weak before installing these and they didn't help a bit, only gave headaches as they failed one after another. Going back to Motorcraft.

 

[Anime]

Could always just be dirty clogged/injectors, when I used cheap gas in mine it went from mild ping/clatter under load to eventually sounding like someone was hitting the passenger side of the block with a sledge hammer. Fuel injector cleaner and using top tier gas (Chevron/Shell) cleared it up after a few months.

It may sound like a chain, but as the rocker arms wear, they can make very interesting noises. It could be the timing chain in that particular motor is worn, or the tensioner is worn out.

BWD is just cheap China stuff. Motorcraft is of course ok, but they don't last that long either. I replaced the Motorcraft wires when mine developed a hesitation, went to Magnecor wires, they have lasted the past 125,000+ miles and will probably never wear out. They are an expensive initial purchase, but are cheap in the long run compared to buying new wires over and over and over.