CHECK YOUR PLUGS!

[Ion]

I have had a series of issues relating to my '94 Eldorado (see my topic list). I had addressed all successfully except the "surging" or "bucking" issue. After a myriad of replaced parts it occured to me that upon doing a tuneup with Delco parts, I recall maybe torquing one of the plugs a bit too much, but didn't think it would be an issue. Well...it WAS! That very plug had a stress crack running vertically through the insulator, causing the PCM to think that on occasion, that cylinder was dead, causing it to compensate for it, which caused the surging. I replaced the fractured plug and all is finally well! KNOCK ON WOOD!

Cheers!

[jking220]

Congrats!

[BodybyFisher]

I have had a series of issues relating to my '94 Eldorado (see my topic list). I had addressed all successfully except the "surging" or "bucking" issue. After a myriad of replaced parts it occured to me that upon doing a tuneup with Delco parts, I recall maybe torquing one of the plugs a bit too much, but didn't think it would be an issue. Well...it WAS! That very plug had a stress crack running vertically through the insulator, causing the PCM to think that on occasion, that cylinder was dead, causing it to compensate for it, which caused the surging. I replaced the fractured plug and all is finally well! KNOCK ON WOOD!

Cheers!

A cracked plug would cause a mis. In the OBD 2 cars it would cause a P0300 code, in your car, no code would be set. You had a miss, and the PCM does not compensate for that. If you don't do so, it is important to use a torque wrench to install plugs in these engines to avoid damaging the threads in the block, the torque is only about 12 ft lbs or so, which is NOT a tight feeling if you didn't use a torque wrench. A cracked plug is a cracked plug thats all. I doubt that you cracked it by over torquing it (and I REALLY hope not), but just the same USE A TORQUE WRENCH. If you accidently torqued them to 25 ft lbs now, you may have a hard time getting them out and wipe the threads in the process, I would loosen them now and re-torque to SPEC if I didn't use a torque wrench. Look up your exact torque spec.

[jackc]

I've never been a plug-breaker, until I became a Northstar owner. Now I've broken at least 3 plugs and I really don't know how. I think there's something about the standard AC northstar plug that make it especially prone to cracking.

[Cadillac Jim]

Knock on Zebrano, that is.

I used three torque wrenches and two thread lockers to change the plugs on my Quad 4 HO that preceded my Northstar. I know where they all are. I'll need at least one of the torque wrenches, for the plugs. I cracked a plug on my 1971 Honda 750cc motorcycle in 1972, and bought the torque wrench for spark plugs at that time. I would never change plugs on anything, even a flathead lawn mower, without a plug wrench anymore.

When I was young, I discovered that putting in a spark plug too loose or too tight would cause the copper gasket either to not seal or be flattened and lose its ability to seal in a few weeks. I developed a feel then, knowing when the plug bottomed the gasket, then just how far to turn it to compress the gasket half-way. But, there's no substitute for a torque wrench.

[Bruce Nunnally]

Good job catching this. On the other hand, if you have NO ISSUES / symptoms, please leave your sparkplugs alone and let them do their job. Problems can be induced by people pulling the plugs out just to examine them, one of the reasons that Cadillac went to 100k plugs.

[BodybyFisher]

Bruce is correct, my advice above is wrong, do not loosen and re-torgue the plugs. They are coated with zinc plating on the threads to keep them from corroding / binding in the head, if you remove them the zinc plating is depleted/disturbed, and THEN they will be difficult to remove. The next time you replace your plugs however use a torque wrench and make sure your spark plug socket has a rubber insert to protect the plug. I think a lot of these cracks we are seeing are caused in shipping.

[Ed Hall]

Good job catching this. On the other hand, if you have NO ISSUES / symptoms, please leave your sparkplugs alone and let them do their job. Problems can be induced by people pulling the plugs out just to examine them, one of the reasons that Cadillac went to 100k plugs.

When did Cadillac change over to 100k plugs?

[KHE]

Good job catching this. On the other hand, if you have NO ISSUES / symptoms, please leave your sparkplugs alone and let them do their job. Problems can be induced by people pulling the plugs out just to examine them, one of the reasons that Cadillac went to 100k plugs.

When did Cadillac change over to 100k plugs?

In the early '90s. My '93 Fleetwood Brougham has 100K plugs.

[fivepointohman]

Good job catching this. On the other hand, if you have NO ISSUES / symptoms, please leave your sparkplugs alone and let them do their job. Problems can be induced by people pulling the plugs out just to examine them, one of the reasons that Cadillac went to 100k plugs.

When did Cadillac change over to 100k plugs?

The 100K plug maintence really is a myth... At 100K the plugs are beyond out of spec gap wise and shot. Back in the day plugs were replaced every 7k if not even before... I mean way back in the day... Now I would do 20K or yearly, especially when a car sits. I took my plugs out of my 06 cobalt at 23k out and they were 10 thousandths out of spec and the car ran ok, but mileage went down, put new ones in, power and mileage restored, and that was on a new car. The additives today in fuel and the way they blend the fuel is garbage and the plugs really dont last as long as they should. Thats my method, if it runs good leave it alone, just do what you feel your car needs. Plugs are relativly cheep, even at 7 bucks a plug for delco platniums for the northstars its not a big deal to pop for new ones every year knowing that I will have a clean running car and full performance and mileage.

[KHE]

Good job catching this. On the other hand, if you have NO ISSUES / symptoms, please leave your sparkplugs alone and let them do their job. Problems can be induced by people pulling the plugs out just to examine them, one of the reasons that Cadillac went to 100k plugs.

When did Cadillac change over to 100k plugs?

The 100K plug maintence really is a myth... At 100K the plugs are beyond out of spec gap wise and shot. Back in the day plugs were replaced every 7k if not even before... I mean way back in the day... Now I would do 20K or yearly, especially when a car sits. I took my plugs out of my 06 cobalt at 23k out and they were 10 thousandths out of spec and the car ran ok, but mileage went down, put new ones in, power and mileage restored, and that was on a new car. The additives today in fuel and the way they blend the fuel is garbage and the plugs really dont last as long as they should. Thats my method, if it runs good leave it alone, just do what you feel your car needs. Plugs are relativly cheep, even at 7 bucks a plug for delco platniums for the northstars its not a big deal to pop for new ones every year knowing that I will have a clean running car and full performance and mileage.

I replaced the OEM plugs in my '96 Seville at 95,000 miles and only because the engine began to stumble. It acted like there was water in the gas. I removed the plugs and found that half of them were missing the platinum pad on the ground electrode. I regapped the four plugs that were missing the ground electrode so the engine would run without misfiring and then replaced all the plugs with the same type.

A 20,000 mile plug replacement is an overkill with today's engines. A complete waste of time and parts. Comparing today's engines with those of 40 years ago with breaker point ignitions, distributors, and leaded gas is also not valid. Leaded gas was a primary reason spark plugs did not last much beyond 10,000 miles.

[Ed Hall]

Plugs are relativly cheep, even at 7 bucks a plug for delco platniums for the northstars its not a big deal to pop for new ones every year knowing that I will have a clean running car and full performance and mileage.

Where do I buy these plugs for this price ($7.00)? I just bought a set from from Rockauto but apparently, someone really wanted them when it sat at the front door after delivered. Urhh!!! If I can buy these plugs locally for that price, I'll do that.

[BodybyFisher]

Good job catching this. On the other hand, if you have NO ISSUES / symptoms, please leave your sparkplugs alone and let them do their job. Problems can be induced by people pulling the plugs out just to examine them, one of the reasons that Cadillac went to 100k plugs.

When did Cadillac change over to 100k plugs?

The 100K plug maintence really is a myth... At 100K the plugs are beyond out of spec gap wise and shot. Back in the day plugs were replaced every 7k if not even before... I mean way back in the day... Now I would do 20K or yearly, especially when a car sits. I took my plugs out of my 06 cobalt at 23k out and they were 10 thousandths out of spec and the car ran ok, but mileage went down, put new ones in, power and mileage restored, and that was on a new car. The additives today in fuel and the way they blend the fuel is garbage and the plugs really dont last as long as they should. Thats my method, if it runs good leave it alone, just do what you feel your car needs. Plugs are relativly cheep, even at 7 bucks a plug for delco platniums for the northstars its not a big deal to pop for new ones every year knowing that I will have a clean running car and full performance and mileage.

Only if they lose their platinum pads THEN, that gap opens up wide and fast.

[Cadillac Jim]

My experience with plugs on my Nortstar is that the are good for in excess of 60,000 miles. I do believe the 95,000 mile performance that KHE cites.

One thing for certain: if you pull them out, throw them away and put new ones back.

[Texas Jim]

The 100K plug maintence really is a myth... At 100K the plugs are beyond out of spec gap wise and shot. Back in the day plugs were replaced every 7k if not even before... I mean way back in the day.../quote]

I have to respectfully disagree about the frequency of plug changes. At least as far as my own experience goes.

When my 1999 Chevy van burned in my garage fire last year... it had almost 175,000 miles on it.

Still had original plugs, wires, hoses, belts, etc etc etc.

The one I sold about two years ago, had 190,000. Still all original. Never changed plugs or wires on either one.

My 2002 Taurus, now has 90,000. All original. Plugs have never been touched. In fact, the wires have never been off of the plugs.

My 2006 DTS has over 30,000 on it now and is a year and a half old. It runs like a champ and gets the same mileage it got when brand new.

My 2006 Chevy van has over 36,000 on it. It is also a year and a half old.

I am sensitive to the way my cars run, and if I EVER feel a problem, a set of plugs is the first thing I would do to it. But as of now.... having no problems.

[Cadillac Jim]

That's why you can't get those old spark plugs anymore. Way back when the President was bald, I used to change plugs every 15,000 miles, too. But, if you try to get one of those old AC 44 or Champion J8C spark plugs you will get a selection that includes iridium and platinum versions, and the "standard" R43 spark plug isn't the same as the old 44 or J8C.