spark plugs

I am always one for over maintaining my cars. With that said my park has 55,000 miles on it should I change the plugs at $6.00 a piece or wait another 15,000 miles? Yes I know gm says 100,000 miles...thinking if I swap them out maybe I can squeak out a mile or two per gallon.

I would never wait 'til 100K miles no matter what they say. $6 a peice, is that for the recommended stock plug?

I agree with the accelerated maintenance intervals, to a certian extent; However, unless you are experiencing random misfire, why waste 30 bucks. Even if you pick up a mile or two a gallon, it would take several years to get a ROI for the plug replacement. If you have Iridium plugs, run them until you approach 80-100K, or if you experience misfire, then do a complete wire and plug change. I run regular NGK Part # 3951 {V-Power #TR55} @ $1.79 ea in both of my Ultra's and change them every year. The ones I remove look new, so I may be wasting money, however, I do have the enjoyment & satisfaction of changing the plugs and knowing that they are in good shape!


BTW, you can change your plugs three times @ (33K X 3 = 99K) using NGK TR55's for less than the cost of one set of Iridium plugs! The engine is quite happy with either one (as long as they are in good condition) and it will deliver the same performance. Believe me, I have tried both types of new plugs on the dyno and there was not any significant difference in HP or TQ throughout the full rpm range!

55K miles?...:lol:....:rolleyes:

As the old saying goes if it ain't broke don't fix it. :wink:

I agree with Bo unless you are experiencing misfires or other abnormal engine conditions the original AC Delco Double Platinums or Iridiums are good for at least 100K miles or more. We've had people on the forum with 150K miles on the original spark plugs with normal fuel economy. The AC Delco plugs will typically out last the ignition wires.

If you get a 1 to 2 mpg increase with just replacement spark plugs (any brand) then show me. Wishful thinking.

55K miles?...:lol:....:rolleyes:

As the old saying goes if it ain't broke don't fix it. :wink:



Yeah like the other old saying "what you don't know can't hurt you" right?

I'd rather be pulling my plugs for the simple fact of:

A-I refused to touch eninges that had plugs in them for more than 50K miles, I've never had plug break on me before, and I am not about to learn how to helicoil one out no matter what a manufacturer says.

B-Plug reading tells you alot about what is going on inside your engine. Hence the term it used to be under, preventive maintenance. . :grinno:

Thanks for the replies. I think I am going to pull them, put never seize on them and let it ride. I fiquired 55,000 was a bit early, but I do not want any problems at a later date when I try to pull them. Thanks.

Yeah like the other old saying "what you don't know can't hurt you" right?

I'd rather be pulling my plugs for the simple fact of:

A-I refused to touch eninges that had plugs in them for more than 50K miles, I've never had plug break on me before, and I am not about to learn how to helicoil one out no matter what a manufacturer says.

B-Plug reading tells you alot about what is going on inside your engine. Hence the term it used to be under, preventive maintenance. . :grinno:

You can do what you want to include the OP. It is his car. I own three GM cars with either the L36 or L67 the Series II 3800 engine and never had a plug break or seize on me. The problem will be getting the heat shields and plug boots off the spark plugs especially the rear bank. Also, proper spark removal tools help along with patience. The recommended GM maintenance intervals are right on based on my experiences.

:rolleyes:

Plug read is absolutely unnecessary for the typical modern car owner and most couldn't read a plug properly to determine what is going on inside the engine or the fuel injection and/or emissions system. The PCM module does a good job letting you know of problems along with proper diagnostics equipment like a good odb-ii scanner. :grinyes:

I don't believe in irrelevant sayings like "what you don't know can't hurt you" right? :wink:

Plug read is absolutely unnecessary for the typical modern car owner and most couldn't read a plug properly to determine what is going on inside the engine or the fuel injection and/or emissions system. The PCM module does a good job letting you know of problems along with proper diagnostics equipment like a good odb-ii scanner. :grinyes:

And there in lies all the problem of todays vehicle owners spending $85-100/HR on diagnotstic testing that 3 of 4 times, "the problem could not be duplicated"/ :disappoin

And when finally successful, you may get a good 'ol P030X misfire code, amd the first thing to do in most shops is strt with the most expenxive, injectors.

100% agreed, your car is your car, do with it as you please, but to me, occasionally pulling the plugs so I know what is going on and not relying on the PCM is no different than pulling the dipstick every other fuel-up to check oil level and quality, who does that anymore?...probably the same as plugs, not too many, they just wait fo rthe oil light to come on and by that time, the damage has begun. :2cents:

Pull the plugs, inspect them, adjust gaps as necessary, anti-seize them, and install them. Visually inspect and continuity test the plug wires and inspect the coil pack tower terminals. Use silicone dielectric grease on both ends of the plug wires.

I've had plugs seize. It's not a fun day. Ford modulars are really bad for that, and the 3-4 head threads which Dearborn deemed "adequate" come out with the plug. I've also had plugs rot away:

http://72.19.213.157/files/ACSparkPlug3.jpg

I'm was running original plugs in a '96 Lumina 191 CID up to 140K and have original plugs in a '96 GMC Sonoma 134-incher at 137K. I've pulled and cleaned/gapped them more than once. They remain in good condition but the gaps DO grow, especially on wasted spark systems.

What is this? Show and tell day. Ford? Lumina? GMC? I thought this was Buick forum. :lol:

On the other side of the discussion here is a pic of the original AC Delco Double Platinums 41-921 out of a 2000 PA with normally aspirated SII 3800 engine. Removed at 95K miles for routine maintenance as suggested by the so called brilliant GM engineers. :rolleyes:

Quite obvious there was no seizure, .060" gap was right on, and the plug read looked excellent. Amazing how the PCM keeps that air/fuel mixture ratio at 14.7:1. :wink: This engine had no misfires before the plugs were removed but misfires on two rear bank plugs (2 & 6) DTC P0302 and P0306 afterwards because the owner failed to replace the ignition wires at the same time. The OEM AC Delco Silicone 7mm wires are the best around but get flaky around 100K miles. The newer AC Delco Premium Silicone 7mm ignition wires were used which already had dielectric silicone grease applied to both ends. That was any easy $50 bucks. :grinyes:

Also, not a good idea to regap the AC Delco Double Platinum or Iridium spark plugs. Check and verify only. Good way to damage or break off the tit at the negative electrode. If gap is off which I highly doubt at 55K miles replace the spark plug which will be pregapped to .060".

Finally, best way to prevent plug seizure in addition to anti-seize compound is not to use "BFFI" when installing the spark plugs. Although difficult at times they should be torqued to around 20 lb-ft with a torque wrench. Also, doesn't hurt to use a little PB Blaster and let sit a short period of time before wrenching at removal.

http://i5.photobucket.com/albums/y186/lizzywiz/ac41921_3.jpg

http://72.19.213.157/files/ACSparkPlug3.jpg

What the hell did you pull that out of Jeff? Last time I saw a plug like that was out of my '79 Camaro Z28, of course not in that condition. Now that I have some time lets get this clarified. That wouldn't by chance be an AC Delco conventional spark plug like a R43TS6? That is a old fashioned standard copper core which GM/AC Delco had a 12K mile/1 Year recommendation on. Actually, they had a 12-month/12,000-mile limited warranty. I seriously doubt that happened in one year at which time the plug should have been replaced anyways. :eek:

Now getting back on track, does anyone have any modern AC Delco Double Platinum (41-921), Iridiums (41-101) or alternate NGK PTR4B-15 Double Platinums from a Buick or any GM car with a L36 or L67 Series II 3800 engine with around 100K miles or less in that condition I'd like to see a pic.

:useless:

Interesting info on the AC Delco Iridium:


ACDelco iridium spark plugs are the latest evolution in high performance plugs. The natural properties of iridium, with a melting point of approximately 700 degrees Celsius higher than platinum, help enable the plug to burn fuel more efficiently and to deliver better performance. As a result, the iridium plugs have a minimum service life of 100,000 miles (service life varies with individual driving conditions.) Since iridium is one of the densest materials found on earth, the iridium-tipped center electrode is 50 percent the size of a platinum electrode, and 20 percent the size of a conventional nickel electrode. The secondary micro-discharge of the center electrode burns off carbon deposits as they form, for superior anti-fouling performance that, along with the tapered cut-ground electrode, offers enhanced flame spread during combustion. The specially designed electrodes increase the electric field strength at the gap, reducing the voltage required for sparking to begin, for improved cold starting and quicker acceleration. The application coverage of ACDelco iridium spark plugs continues to grow, with the plugs being backed by a 100,000-mile limited warranty.

http://www.acdelco.com/parts/sparkplugs/iridium.jsp


AC Delco Platinum:

http://www.acdelco.com/parts/sparkplugs/professional-platinum.jsp

To answer the original thread starter, I think you're wasting both your time and money changing your plugs at 55k unless there is a problem. Other than to check gap erosion as you near service interval or if the car is using coolant/burning oil, there really is no reason to inspect the plugs on a modern car.

IMO, that plug Blue shows came out of something exposed to lots of water (Marine engine, mud bogger, etc...). Look at both the ground and center electrodes, virtually no wear. It rusted from the outside, not anything to do with mileage according to what I see. As bnaylor said, comparing an old R43TS6 copper core plug to the iridium/platinum of today is apples to oranges.