# Inspecting spark plugs in a high mileage car



## Jackofall1 (Dec 5, 2010)

There is an old saying, and it is used all the time --- If it ain't broken don't fix it!

Pulling plugs in an old engine can cause other problems like stripping out the plug threads if the cylinder head is aluminum like most are.

Mark


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## Bigplanz (Apr 10, 2009)

Interestingly enough, the 'if it ain't broke don't fix it' thought occurred to me before I pulled the plug. 

Since this particular engine has cast iron heads, I wasn't too concerned about stripping the threads. The plug wire breaking at the boot is a new one on me, though. After ten+ years, I guess it fused to the plug. I've changed wire sets and plugs before and never had that happen. Should have had a new wire set and plugs on hand before I messed with it. Grrrrrrr.


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## hyunelan2 (Aug 14, 2007)

Jackofall1 said:


> There is an old saying, and it is used all the time --- If it ain't broken don't fix it!


I typically go by the "if it ain't broke, fix it until it is" mantra of automotive tinkering. 

Depending on the type of plugs, and what the car is, I like to do them at 30K or 60K with wires at 60K or 100K. You should see an mpg improvement with some clean firing plugs.


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## ukrkoz (Dec 31, 2010)

big, spark produced at the electrodes tips is like plasma cutter. it is continuously erroding electrode metal. as a result, you either have gap ever slightly widening, or metal buildup on one of the electrodes. hence, for common plugs, it is normal to be replaced at around 30-40 000 miles.
now, they try to extend that, but using ever so harder and more conductive materials, like iridium. warranty goes up to 100 000 miles, allegedly, so does useful time. i still change them at 60 or so K miles.
you can have gapless spark plugs, like HALO plugs. there still will be some crown corrosion.

as of the wires... running same set for 10 years - there's no polite way to call it. not only do you have oxidation build up. conductive properties of the core change, and never the good way. tips become overheated and brittle, as you have noticed.

combined, you have crappy and crappier and crappier running ignition, with ever lower spark quality. in your case, "don't fix it if it ain't brok" is not even applicable. "replace it when it's old" is the word. simply think of how much money you lost in poor engine performance and mpg due to this.


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## 95025 (Nov 14, 2010)

Bigplanz said:


> My mini-van has 179K miles, and I've had it nine years. I've never changed the plugs so today I got curious as to their condition. I checked number 6, since it was easiest to get to. I twisted the wire boot and pulled off the wire. Took out the plug and it was in bad shape. Ok, curiosity satisfied I put it back in, put the plug wire back on and...had a miss on cylinder 6.
> 
> I pulled the wire to reseat it (thinking that was the problem) and discovered the wire connector inside the boot had completely broken off. Note to self: ten year old plug wires are probably going to break if disturbed. Now I'm limping along until Friday when I get paid on a V5.  Don't test something unless you can repair right then!


You are a true man!

That said, don't wait to fix this! Most likely, you can pull apart that wire and get it to work temporarily.


When you replace your plugs and wires, you're going to see/feel a noticeable difference in the way that van runs!


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## Bigplanz (Apr 10, 2009)

I went to pull a part and bought two plug wires for a buck, figuring one would work. One does, so at least I have V6 again. This will get me by until I can order a wire set and new plugs from rock auto.


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## Bigplanz (Apr 10, 2009)

Follow-up: I started replacing the plugs today. My goal was to do the front bank. Got two in, but the third was frozen. I put enough force on it to move but it didn't, so I stopped. I squirted PB blaster in it, put the plug wires on and called it a day. Tomorrow, I'll move the torque strut for better access and try again. Breaking a plug off in the head would be a disaster!!

Even with just two new plugs and three new wires and a new coil wire, the van idles better.


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## concretemasonry (Oct 10, 2006)

After 170,000 miles and no replacement, problems can be expected, especially if there is long term corrosion and no periodic replacement after after the magic 100,000 mile period even if they "look" good. It is commonly referred to as deferred maintence.

I have been guilty of going 120,000 miles, but the complete replacement of plugs and wires made a world of difference in economy, performance and even in radio reception.

Dick


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## Bigplanz (Apr 10, 2009)

I don't know when the plugs were last changed. I got the van in May 2002 and it had 119k on it. It now has 179k on it. The plugs were regular copper ac delcos. The two I got out were in bad shape, as you can imagine. I am being careful with replacement. Cylinder 2 plug is pretty frozen! 4 and 6 came out ok.

The wires all disintigrated when I pulled them off the plugs.


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## Bigplanz (Apr 10, 2009)

Got the frozen plug out today. It took a lot of blaster a breaker bar and a 3 pound sledge. I soaked it in blaster overnight put the breaker bar on it and 'tapped' it with the sledge in each direction twice. Gave it a turn and it broke loose. The threads were fine. The body of the plug was rust welded inside the plug well. What a struggle! And this is the EASY side in the front. No wonder shops charge $150 to change plugs!


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## Thurman (Feb 9, 2009)

I work part-time for a friend who owns his own parts store and see this way too often in the last few years. People are trying to get those "last few miles" out of their vehicles, and I don't blame them. Let's look at it this way: You have had the vehicle for nine years now, 179,000 miles or so. Let's say you invest in a new set of plugs and some new wires= about say $35 or so. Divide that by the nine (9) years and that's pretty cheap insurance to keep the van running better and don't ask me to calculate the money savings on gas mileage. Give up a coke a day, or coffee a day, or something for a few weeks, treat your van to some new plugs, wires, air filter and a good oil change. As stated; you will be surprised at how much better it will operate.


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## Bigplanz (Apr 10, 2009)

I put the back bank of plugs and wires in today. Had to them in totally by feel, since I couldn't see any of them. Cylinder one was the hardest. I could barely reach it with one hand and the plug wire broke off so it took 20 minutes of laying across the engine fishing with a pair of pliers to get the plug connector off the plug. I have long skinny arms so could reach around the engine go under and behind the alternator to get two hands on it. Finally got it out, covered in sweat, and got the new one in. Tip: use the end of an old plug wire and use it to thread the new plug. You can turn it enough to get it started but it won't crossthread. Be patient and have a flex head ratchet and several extension bars and you can do it in a few hours.

Haynes Manuals kill me. Changing plugs and wires take up four steps (1. Remove wires. 2. Remove plugs... Etc.) Not exactly helpful. 

Tip: it's really crowded behind the engine. It's hard to reach the plugs and you can't anything. Get stubby ratchets and a finger ratchet. Be aware lots of sensors lurk back there. Found my O2 sensor and pigtail for instance.


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## Bigplanz (Apr 10, 2009)

I put the back bank of plugs and wires today. Had to put them in totally by feel, since I couldn't see any of them. Cylinder one was the hardest. I could barely reach it with one hand and the plug wire broke off so it took 20 minutes of laying across the engine fishing with a pair of pliers to get the plug connector off the plug. I have long skinny arms so I could reach around the engine and go under and behind the alternator to get two hands on it. Finally got it out, covered in sweat, and got the new one in. Tip: use the end of an old plug wire and use it to thread the new plug. You can turn it enough to get it started but it won't crossthread. Be patient and have a flex head ratchet and several extension bars and you can do it in a few hours.

Haynes Manuals kill me. Changing plugs and wires take up four steps (1. Remove wires. 2. Remove plugs... Etc.) Not exactly helpful. 

Tip: it's really crowded behind the engine. It's hard to reach the plugs and you can't see anything. Get stubby ratchets and a finger ratchet. Be aware lots of sensors lurk back there. Found my O2 sensor and pigtail for instance.


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## Marty1Mc (Mar 19, 2011)

Bigplanz said:


> Haynes Manuals kill me. Changing plugs and wires take up four steps (1. Remove wires. 2. Remove plugs... Etc.) Not exactly helpful.


LOL, gotta love Haynes manuals. I had one for my Celica, but returned it the same day and bought a Factory Service Manual (well worth owning for any car). To remove the transmission, the Haynes said to "First, remove everything that bolts to the top of the transmission." Duh! I shut it, took it back for a refund...


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## kt82 (Jan 28, 2009)

*proper torque*

2003 chevy van 5.3 liter When you replace the plugs how do you torque them?
the auto zone person to put some antisieze on the threads ,but does not that change the torque readings ??
oh yeah the plugs have a metal tube(heat shield ?) around them. does this come off with the boots or do you leave it in place ?


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## Bigplanz (Apr 10, 2009)

I couldn't get a torque wrench on any of the back bank of plugs, so I hand tightened then turned them a quarter turn or until tight. I used a stubby ratchet so it would be hard to over torque them. Since they only require 15 ft pounds, that was close enough. I put anti seize on mine and so far all is operating normally. My back bank all had heat shields. They came out with the wire. You just take them off and slip them on the new wire.

Sidenote: I was a bit surprised that the plugs that came out were heat range 3 while the replacement plugs were heat range 9. Yet both are listed as suitable for my mini-van. Interesting.


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