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Posted: 1/25/2021 10:43:58 PM EDT
ETA: Gap on the plugs was actually .038. I closed all of them to .035 and the car runs smooth.
I installed these on my car but it ran rough. I checked the gap and it is too wide, .37 instead of .35. With the extra tip, how can I adjust this without damaging it?  This might be a stupid question. |
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Posted: 1/25/2021 10:49:27 PM EDT
[#1]
You push the electrode on the top of the bench but careful not to go to far.
I can tell you the .002 discrepancy isn't causing your rough running. Are they the same plugs as the ones you pulled out? Year/make/model/engine type? |
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Posted: 1/25/2021 10:57:06 PM EDT
[#2]
Quoted: I installed these on my car but it ran rough. I checked the gap and it is too wide, .37 instead of .35. With the extra tip, how can I adjust this without damaging it? https://www.ar15.com/media/mediaFiles/54288/20210125_204014-1796977.jpg This might be a stupid question. You shouldn't adjust the gap on iridium plugs. You'll damage the tip and destroy the plug. |
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Posted: 1/25/2021 11:01:46 PM EDT
[#3]
the difference between .35 and .37 is less then negligible on any vehicle with a modern ignition system. You could gap it to .60 and likely notice no difference.
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Posted: 1/25/2021 11:11:46 PM EDT
[#4]
Quote HistoryQuoted: the difference between .35 and .37 is less then negligible on any vehicle with a modern ignition system. You could gap it to .60 and likely notice no difference. |
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Posted: 1/25/2021 11:16:34 PM EDT
[#5]
I ordered a gap setting tool on amazon. That should make it easy to gap properly.
2011 Volvo XC 60. 120k, OEM plugs. Please do not quote me. I will be deleting this PII as soon as my prob is fixed. |
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Posted: 1/25/2021 11:18:06 PM EDT
[#6]
.037 ?
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Posted: 1/25/2021 11:18:18 PM EDT
[#7]
Quote HistoryQuoted: You can't adjust the gap on iridium plugs. You'll damage the tip and destroy the plug. You can't open the gap in a conventional sense (There are ways) It also doesn't destroy the plug but it does remove the micron thick layer of iridium, which defeats the purpose of using them. You can however close the gap in the way I just mentioned. The iridium is only on the tips of the very fine points between the two electrodes. |
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Posted: 1/25/2021 11:20:09 PM EDT
[#8]
Quote HistoryQuoted: 3/8 inch is a bit wide. Quote HistoryQuoted: Quoted: the difference between .35 and .37 is less then negligible on any vehicle with a modern ignition system. You could gap it to .60 and likely notice no difference. I know but I'd bet that they would still work fine until the gap opened up even more. Modern ignition systems are pretty darn good. No more puny 20k output nowadays in a good system. |
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Posted: 1/25/2021 11:54:24 PM EDT
[#9]
Y’all don’t know how thousandths work. A human hair measures three thousandths so I don’t think two is worth worrying about.
Edit: op meant to say .035” and .037” which is a difference of .002” .370 or .600 would be way too large with the heat and pressure inside the combustion chamber during engine operation. |
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Posted: 1/26/2021 12:52:17 AM EDT
[#10]
Quoted: I installed these on my car but it ran rough. I checked the gap and it is too wide, .37 instead of .35. With the extra tip, how can I adjust this without damaging it? https://www.ar15.com/media/mediaFiles/54288/20210125_204014-1796977.jpg This might be a stupid question. I think you mean .037 and .035. The difference is nothing and is not gonna cause any running issues. If you changed plugs and it caused a running issue, it’s possible you have a bad plug. It does happen. Use a spark plug gapping tool. You absolutely can adjust iridium plug gaps without issue. |
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Posted: 1/26/2021 1:05:28 AM EDT
[#11]
Are the plug wires still in good condition (20 years old?)?
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Posted: 1/26/2021 1:06:23 AM EDT
[#12]
A .002 difference isn't even going to show up on a kv measurement, much less make the engine run rough.
If it was running fine before replacing the plugs, and rough afterwards, you either got one or more bad plugs, or you tore a coil boot, or something of that nature. It's not uncommon to get new plugs that have been damaged during shipping and handling. Usually, the damage is a barely visible or invisible crack in the porcelain. |
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Posted: 1/26/2021 1:09:23 AM EDT
[#13]
Quote HistoryQuoted: You can't adjust the gap on iridium plugs. You'll damage the tip and destroy the plug. Not exactly. I was with a tuner who adjusted gap on such plugs by just letting them bop down using the plug weight against a piece of wood. It would very gently take a thousand or so off each drop / bop or so, and he was able to close down gaps very well without touching the electrode (big No No) But as others have said, a 2/1000 difference in gap would NOT be the cause of bad running if they are fresh plugs. Most likely you have a bad wire or weak coil / coil pack. |
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Posted: 1/26/2021 1:13:25 AM EDT
[#14]
Do you have a ODBII Code Reader?
I had an issue on a 5.0 Ford and the ODBII reader identified the cylinder to check for misfire - bad plug wire. I had an issue on a Volvo straight 6 (2.9 Liter) code reader that misfires to the specific cylinder which meant a bad spark coil. An ODBII reader can find and store Codes that DO NOT TRIP the Check Engine Light. They are inexpensive AND GREAT to have! |
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Posted: 1/26/2021 11:54:51 AM EDT
[#15]
just changed the plugs in my 2010 terrain..gm calls for a gap of .43..the plugs were gapped at .40.
I installed them and it ran and idled just fine. |
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Posted: 1/26/2021 2:23:46 PM EDT
[#16]
.002 not worth adjusting, but you can adjust a plug like that
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Posted: 1/26/2021 3:41:12 PM EDT
[#17]
Anyone here that says you cannot adjust the gap on an iridium plug, you are full of shit, and do not need to be giving out advice.
You cannot PRY AGAINST the electrode to open up the gap like you can on copper plugs as the iridium is extremely brittle, and will snap off. They make a tool that levers the ground strap out to pull the tip away if you need to open the gap, which is usually pretty rare. More often, you need to close the gap to keep from getting spark blowout on forced induction setups. I simply use a vice and a feeler gage, and on NGK Iridium plugs, the ground straps have about .005 spring back and my go-to initial gap is about .025 gap. With the plug in the vise lengthwise, I close up the gap until a .020 feeler gage just starts dragging between the ground strap and the electrode and it give me a damn consistent .025-.026 gap. The ideal gap is the largest possible without compression and boost blowing the spark out. |
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Posted: 1/26/2021 7:19:10 PM EDT
[#18]
Quote HistoryQuoted: Anyone here that says you cannot adjust the gap on an iridium plug, you are full of shit, and do not need to be giving out advice. You cannot PRY AGAINST the electrode to open up the gap like you can on copper plugs as the iridium is extremely brittle, and will snap off. They make a tool that levers the ground strap out to pull the tip away if you need to open the gap, which is usually pretty rare. More often, you need to close the gap to keep from getting spark blowout on forced induction setups. I simply use a vice and a feeler gage, and on NGK Iridium plugs, the ground straps have about .005 spring back and my go-to initial gap is about .025 gap. With the plug in the vise lengthwise, I close up the gap until a .020 feeler gage just starts dragging between the ground strap and the electrode and it give me a damn consistent .025-.026 gap. The ideal gap is the largest possible without compression and boost blowing the spark out. This. To add to this, you really shouldn't be prying on the center electrode to adjust the gap on ANY spark plugs. I know it's done but it's not smart to pry on the center electrode. |
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Posted: 1/28/2021 8:56:38 PM EDT
[#19]
These are OEM plugs you installed, OP? If so, and you have rough idle before and after, you have an issue elsewhere.
The posts above that say you can adjust modern iridium style plugs are correct, as long as you are adjusting at the base of the ground electrode. But you should not have to do that, unless they were all dropped on their tips. Please don't tell us you put Walmart Autolite plugs in your engine. |
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Posted: 1/28/2021 10:50:51 PM EDT
[#20]
Quote HistoryQuoted: Anyone here that says you cannot adjust the gap on an iridium plug, you are full of shit, and do not need to be giving out advice. You cannot PRY AGAINST the electrode to open up the gap like you can on copper plugs as the iridium is extremely brittle, and will snap off. They make a tool that levers the ground strap out to pull the tip away if you need to open the gap, which is usually pretty rare. More often, you need to close the gap to keep from getting spark blowout on forced induction setups. I simply use a vice and a feeler gage, and on NGK Iridium plugs, the ground straps have about .005 spring back and my go-to initial gap is about .025 gap. With the plug in the vise lengthwise, I close up the gap until a .020 feeler gage just starts dragging between the ground strap and the electrode and it give me a damn consistent .025-.026 gap. The ideal gap is the largest possible without compression and boost blowing the spark out. I corrected my post and changed "can't" to "shouldn't". Someone with the proper tools and training can do it but the average layman has neither and will just end up with a car running like shit. |
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Posted: 1/29/2021 10:31:04 AM EDT
[#21]
Quote HistoryQuoted: I corrected my post and changed "can't" to "shouldn't". Someone with the proper tools and training can do it but the average layman has neither and will just end up with a car running like shit. I don’t think you need specialty training to adjust a spark plug electrode. It’s really not hard or complicated. |
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Posted: 1/29/2021 12:07:29 PM EDT
[#22]
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Posted: 1/29/2021 12:42:05 PM EDT
[#23]
Something I’d caution you about. The various feeler guages/spark plug guages I’ve checked with my calipers are often WAY off thickness. Especially before ya start sweating about .002”.
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Posted: 1/30/2021 10:28:37 AM EDT
[#24]
Quote HistoryQuoted: These are OEM plugs you installed, OP? If so, and you have rough idle before and after, you have an issue elsewhere. The posts above that say you can adjust modern iridium style plugs are correct, as long as you are adjusting at the base of the ground electrode. But you should not have to do that, unless they were all dropped on their tips. Please don't tell us you put Walmart Autolite plugs in your engine. @turtlemaster F walmart. The plugs came from FCP Euro OE Denso plugs Car ran fine but the OEM plugs were old so I changed them out. Car did not run fine with new plugs in. I put the OEM plugs back in and the car ran fine again. I checked the gap on the plug, instead of .035, it was 0.37 if I recall correctly. I sat on the plugs for months. |
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Posted: 1/30/2021 10:31:41 AM EDT
[#25]
This is my plan:
I think I may have a pad plug... 1) Verify correct gap on all plugs 2) Install 1 plug and test drive, if its ok, 3) Install another plug... 4) etc until either all work or I can ID a bad spark plug. ETA: All of plugs had a .038 gap. I closed it to .035 and everything runs smooth. |
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Posted: 1/30/2021 11:01:43 AM EDT
[#26]
Take a pic of new/old plugs with close up of electrode and post, many here can tell a lot based on look
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Posted: 1/30/2021 11:22:22 AM EDT
[#27]
Buy this, download the app, scan your car and see what is going on. Yes, it sounds like you have a bad plug out of the box, or multiple. 0.002 of excess gap is not the end of the world, and will not effect how your car runs at this point in a way you can feel. |
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Posted: 1/30/2021 12:03:44 PM EDT
[#28]
Quote HistoryQuoted: This is my plan: I think I may have a pad plug... 1) Verify correct gap on all plugs 2) Install 1 plug and test drive, if its ok, 3) Install another plug... 4) etc until either all work or I can ID a bad spark plug. Another way to do it is start the car and let it run. Unplug each spark plug one at a time and see what happens. It should run worse each time until you get to the bad one and then there should be little to no change. Plug each one back in after unplugging it. |
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Posted: 1/30/2021 12:15:21 PM EDT
[#29]
Quote HistoryQuoted: You shouldn't adjust the gap on iridium plugs. You'll damage the tip and destroy the plug. Quote HistoryQuoted: Quoted: I installed these on my car but it ran rough. I checked the gap and it is too wide, .37 instead of .35. With the extra tip, how can I adjust this without damaging it? https://www.ar15.com/media/mediaFiles/54288/20210125_204014-1796977.jpg This might be a stupid question. You shouldn't adjust the gap on iridium plugs. You'll damage the tip and destroy the plug. Incorrect. IF you DO need to gap them, you simply use a different method than the old 'insert gap spacer. Hammer electrode. Remove spacer'. The smaller tips on Iridum plugs will dig into the spacer and the tips will snap off when you pull the spacer. To properly gap Iridium plugs (again, that's IF you actually need to do that), you use a spark plug electrode tool (basically looks like a screwdriver handle with a gap in the side of the tip, that's big enough to slide onto the electrode/strap). You carefully use this to bend the electrode/strap WITHOUT a spacer inserted, THEN measure the gap, and fine tune as needed. So, yes, you CAN adjust the gap on iridium plugs. All that said, the much smaller tips on Iridium plugs, generally means they're FAR less finicky about electrode gaps than regular plugs. If the engine is running rough, check elsewhere (IF you're sure that you have the correct heat range plugs. THAT still makes a difference, Iridium plugs or not). |
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Posted: 1/30/2021 12:37:26 PM EDT
[#30]
Quote HistoryQuoted: @turtlemaster F walmart. The plugs came from FCP Euro OE Denso plugs Car ran fine but the OEM plugs were old so I changed them out. Car did not run fine with new plugs in. I put the OEM plugs back in and the car ran fine again. I checked the gap on the plug, instead of .035, it was 0.37 if I recall correctly. I sat on the plugs for months. Quote HistoryQuoted: Quoted: These are OEM plugs you installed, OP? If so, and you have rough idle before and after, you have an issue elsewhere. The posts above that say you can adjust modern iridium style plugs are correct, as long as you are adjusting at the base of the ground electrode. But you should not have to do that, unless they were all dropped on their tips. Please don't tell us you put Walmart Autolite plugs in your engine. @turtlemaster F walmart. The plugs came from FCP Euro OE Denso plugs Car ran fine but the OEM plugs were old so I changed them out. Car did not run fine with new plugs in. I put the OEM plugs back in and the car ran fine again. I checked the gap on the plug, instead of .035, it was 0.37 if I recall correctly. I sat on the plugs for months. I'm going to say a bad plug, or counterfeit plugs. LOTS of counterfeit plugs out there. I won't buy Bosch plugs because I've had so many issues with new ones being shit right out of the box. Not a fan of Champions any more either. NGK if at all possible for me nowadays. |
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Posted: 1/30/2021 1:19:37 PM EDT
[#31]
Quote HistoryThe tool on the left (or something very similar) is what I use. But then again, I side gap my plugs 
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Posted: 1/30/2021 1:29:25 PM EDT
[#32]
Put a .036 shim between the electrodes and push down on a bench until the electrodes contact the shim. Remove shim and check with feeler gages. Just for example a piece of binder paper is .003. .002 is not going to be the cause for rough idle. Check other stuff like your wires and connections. Double check everything including if these are the correct plugs and if the gap you are trying to set is correct.
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Posted: 1/30/2021 1:50:11 PM EDT
[#33]
Quote HistoryQuoted: Put a .036 shim between the electrodes and push down on a bench until the electrodes contact the shim. Remove shim and check with feeler gages. Just for example a piece of binder paper is .003. .002 is not going to be the cause for rough idle. Check other stuff like your wires and connections. Double check everything including if these are the correct plugs and if the gap you are trying to set is correct. As detailed above; DO NOT USE THIS METHOD WITH IRIDIUM PLUGS. |
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Posted: 1/30/2021 2:04:23 PM EDT
[#34]
Quote HistoryQuoted: Are the plug wires still in good condition (20 years old?)? Nick |
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Posted: 1/30/2021 4:22:18 PM EDT
[#35]
Quote HistoryQuoted: The tool on the left (or something very similar) is what I use. But then again, I side gap my plugs Ya, I hate those short ground straps that come in from the side  very hard to adjust
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Posted: 1/30/2021 6:39:19 PM EDT
[#36]
Well.
Attempt #2 was a success. "Pre gaped" my ass. All of the plugs were off by 0.003. Sure, not much, but enough to cause rough idle. I used this tool to adjust the gap. It took a while to figure out how much force was need to close the gap.  I used this tool to verify the gap.  I put in one plug at a time. Car ran smooth after each one. After the 3rd one was in, I put the rest it. I will take a longer test drive later today. I measured the old plug. Geez. I have not idea how it idled so well with such gaps. C1 .052 C2 .039 C3 .046 C4 .049 C5 .036 C6 .047 |
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Posted: 1/30/2021 6:59:25 PM EDT
[#37]
Good job OP, some modern engines are very sensitive to small changes. It was probably running fine on the old plugs because the ECM was used to them.
Modern adaptive learning in ECMs can cause weird issues when parts are changed. The idle could have very possibly smoothed out after a 15 or so minute drive, even if you did not re-gap the new plugs. |
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