1997 Ford Crown Victoria - 4.6 V8 (2v SOHC) - auto - 101K miles

For quite some time (years, really) this car has made a tapping sound under load, primarily when ascending hills at highway speeds. If it does it around town, I don't notice. It's most noticeable when the car goes from traveling on flat ground to ascending a hill, presumably while overdrive is engaged. Usually it will kick down a gear eventually, but until it does so, the sound is very clear.

Garden-variety detonation/pinging? Shouldn't be, as it specifies 87 octane, plus it doesn't seem to have done any damage over time (I've only had the car since January but my parents owned it from '03 until then so I "know" it well). If not, what then? I'm trying to take care of any impending issues before they might become a problem--I want this car to last until our newer car is paid off (probably January '16 depending on what we do with the loan). 100K miles should be nothing for a 4.6 but the car is now 17+ years old.

10/4/2013 3:38:57 PM

Probably just worn bearings starting to speak to you.

My 5.4 f-150 does what yours is doing I think, gets a little quieter as the truck gets warm.

10/4/2013 3:49:27 PM

sounds like detonation to me. fill up with 93 and see if it goes away. also try ethanol-free gas. my '90 cherokee runs like new when i fill up with gas without ethanol.

10/4/2013 4:33:38 PM

I would also first rule out detonation (or more likely, pre-ignition). Try 93 oct and see if it eliminates/lessens the problem.

Even with low compression ratios and conservative ignition mapping, etc, an engine that would otherwise run fine on regular gas may, over time, begin detonating, usually due to carbon deposits, etc (these retain heat and become "hot spots", and can cause pre-ignition.) Also make sure your spark plugs are the correct heat range.

10/4/2013 5:37:13 PM

^ & ^^ I agree with these two. Run 93 long enough for the computer to sense the change and adjust the timing. If that works you can try 89 to see how it reacts. I bet it will go away with high test gas. After that it's up to you to decide how much maintenance/tuning you want to do to try to get it to run right on 87 again.

10/4/2013 5:46:12 PM

I vote for exhaust leak

$100 lafta bucks

10/5/2013 12:26:43 PM

Might be an exhaust leak on the Passenger side

10/5/2013 4:35:40 PM

I'll try a couple of tanks of 93. I'll also consider the exhaust leak possibility; if on the passenger side, are you talking about the exhaust manifold on that side? It's not dual exhaust (no CVPI or trailer towing package, though those aren't true duals anyway).

[Edited on October 5, 2013 at 8:09 PM. Reason : .]

10/5/2013 8:09:27 PM

i thought this thread was about banging fat chicks.

10/5/2013 11:35:43 PM

Used to have the same problem once in a while with a 95 town car. I'm putting it back on the road as a beater after not driving it for 3 or 4 years. I'd run a tank of 93 through it, and it would quiet off for a few thousand miles. I've seen plenty of those engines with over 250k and running good.

10/6/2013 8:47:25 PM

It has been a bunch of years since I worked on one of these, but IIRC they were known for EGR problems due to carbon buildup- same type of buildup that can cause detonation.

10/7/2013 11:36:05 AM

every modular ford v6 ive ever driven / rode around in has rattling valves. higher octane gas is a temporary fix (these motors are made for regular).

im going to vote egr system problem...

...or do the standard ford forum: "Seafoam will cure it, other things like changing spark plugs, wires coil pack, and pcv valve will also help. You can clean your maf sensor, iac, and throtle body as well."

10/7/2013 12:09:04 PM

I've thought of seafoam.
Plugs, wires, egr, cleaning maf, etc. are things that I am capable of doing but would need to have a place to work on it (street parking sucks btw). So if any of those are required it'd probably be at Thanksgiving.

10/8/2013 10:13:55 AM