Spark Plugs

[Petra]

My old Mercury was supposed to have new spark plugs installed at the 180,000 mile point. However, I didn't notice this until recently, so I've already put about 300 more miles on the car. My concern is: How long can I go before the spark plugs will need to be replaced? I'd like to wait until my next oil change @ 291,000-some kilometers (roughly 180,820 miles), because I need my money for other things right now, like paying back my parents for buying the car in the first place. Any advice?

[rkmdogs]

My old Mercury was supposed to have new spark plugs installed at the 180,000 mile point. However, I didn't notice this until recently, so I've already put about 300 more miles on the car. My concern is: How long can I go before the spark plugs will need to be replaced? I'd like to wait until my next oil change @ 291,000-some kilometers (roughly 180,820 miles), because I need my money for other things right now, like paying back my parents for buying the car in the first place. Any advice?

[post="957"]<{POST_SNAPBACK}>[/post]

Petra, you did not state what year and model of Merc you had. That could be a factor. More important, how is the car running? Does it start easy? Do you keep track of your mileage, from tank to tank?

Depending on the vintage, older vehicles usually suggested a spark plug change every 40,000- 50,000 miles. Newer cars with platinum plugs have a suggested
interval of 100,000 miles.
You nedd to have a mechanic that you trust pull a plug and examine it for its'
condition. That will tell you if it is time to change spark plugs!

[Petra]

It's a 1993, LS, with the 4.6L. engine. It starts fine, but the engine seems to shake and shudder and just generally idle rougher than it used to. Also, every once in a while if I listen closely, I can hear a faint popping noise coming from the exhaust (though that could just be the exhaust system, because it needs to be replaced, too). There's also a bit of squealing from a belt underhood; I figure that probably has to do with the A/C not working, but who knows? Like with the popping noise, you can't really hear it unless you pay attention... yet.

[rkmdogs]

[quote name='Petra' date='Aug 22 2005, 01:02 PM']
"It's a 1993, LS, with the 4.6L. engine. It starts fine, but the engine seems to shake and shudder and just generally idle rougher than it used to. Also, every once in a while if I listen closely, I can hear a faint popping noise coming from the exhaust.... There's also a bit of squealing from a belt underhood; I figure that probably has to do with the A/C not working, but who knows? Like with the popping noise, you can't really hear it unless you pay attention... "

From your description, two things apparent. You do have an electrical problem.
It may not just be the spark plugs, as the "popping noise" could indicate a sticking valve, hanging open on the ignition cycle, or your distributor could need attention.
I am not that familiar with Ford products, but they have, thru the years been noted for having ignition electrical problems.

Second, check out that squealing belt noise. It could be serious. It may not just be belt slippage, but an indication that something being driven by the belt may be trying to "freeze" or lock up. If this occurs, you can kiss the belt goodbye, and with it your drive to the water pump, which means, SHUT DOWN NOW!!!---- that is,
unless you are sitting in your driveway, or you want to do a complete engine
replacement due to overheating & warpage!

In a lot of these cases with a serpentine belt drive, it is the tensioner pulley
that stops self-adjusting, with either the pulley seizing or the pivot point not
staying movable. Either case, the tensioner needs replacement, 'cause there is no way to re-lube them.
The last one that I had let go was because the alternator bearings went, and the
alternator seized, throwing the belt, which chewed it up.
If the belt squeal is just caused by old-age stretch, then you need to replace it,
because everything being driven by that belt is not running at its' correct speed
when under load. That can cause a lot of other failures.

You seem to be a young person with not a lot of mechanical background. Let me just advise you that preventative maintenence is a lot cheaper that fix it 'cause it broke maintenence! Lotsa luck!!

[Sixty8panther]

If the car is driving fine, the MPG and performance are not affected then take your time. MOst used cars I get I replace the spark plugs and by the time that they need to be replaced the car is long sold.

[Petra]

Thanks for the info, guys. You guessed correctly, rkmdogs... I'm not exactly mechanically inclined, but my brother is. Interestingly enough, I'm now more worried about the belt than the spark plugs! The question still persists, though: I've got about 3,000 kilometers (1,864 miles) until my next oil change... Should I bring it in now, or wait?

[rkmdogs]

Oil Changes are not scheduled like on an alarm clock! Since you need to check out some other things, kill two birds with one stone & do the oil change too. Don't forget to do the filter, and lube the chassis fittings.

[Petra]

Oil Changes are not scheduled like on an alarm clock!

[post="2500"]<{POST_SNAPBACK}>[/post]

I don't follow you. How are they not scheduled? I mean, sure, a car that gets driven 30,000 miles a year will need to have its oil changed more frequently than a car that gets driven 20,000 miles a year. That's why they put both a date and a 3,000 mile interval on the window sticker... whichever comes first.

But, yeah, I think I will wait it out. From what I've read here and elsewhere, the car should be fine, it just won't deliever peak performance. I can deal with that.

[rkmdogs]

Frequency of servicing is based on how the vehicle is used, and most people do not understand that fast driving, highway use is actually "light" duty! Stop & go city driving, short distances, without complete warm-ups and temperature stabilization is actually "severe" use! It is the operating conditions, and the quality of filtration that determines when fluids need to be changed due to property exhaustion or contamination. Short hauldriving, where the engine does not get up to operating temperature for a sustained period produces the most contaminates, mainly water in the oil. Cold oil when mixed with water causes sludge to form in your engine and in your oil filter. This sludge prevents proper lubrication of the moving parts in an engine, which causes premature wear! 3000 mile intervals are just a rule of thumb. If you drive only short distances infrequently, you could need an oil change as often as every 1000 miles! On the other hand, if when you turn on the engine you then drive 50 or 100 miles without turning off the engine, and not doing stop & go driving, but steady highway use, you could go 4000-6000 miles between changes. It all depends on how you use the car.

[Petra]

Well, I do have some stop & go driving when I do my Pizza delieveries, but I live in a rural area, so I have a lot of highway driving, too. I'd say that I probably drive 10-15 miles on the open road for every 5 miles I drive in town.