Over the weekend I did a tune up on my 07 h3 3.7l with 153k miles. Little background: it’s been going through oil like nobody’s business with no leaks found (600 miles and oil was low enough that it didn’t read on dipstick) and had an antifreeze leak. Over the weekend I replaced thermostat, lower rad hose, cleaned throttle body and MAF sensor, replaced intake manifold gaskets and valve cover gaskets, new pcv hose, and new iridium spark plugs. Drove it approximately 90 miles the day after finishing all that and it ran great. This morning it idled a bit rough and check engine light was flashing but turned off shortly after and then ran fine taking my son to school. I don’t have a code reader on hand to see if it stored a code but I’m assuming it was a misfire. My question is could all of the work we did just be confusing the whole system? I don’t see any oil leaking out of the valve cover so I don’t “think” it didn’t seat properly.

 

Please go to an auto parts store and have them read the code(s) and post here for help.

Nothing you did is going to "confuse the whole system."

If you used ACDelco direct replacement plugs you are fine. If you went with an aftermarket plug, I5s do NOT like those and you will be changing them again in less than 20K miles.

 

They are Bosch double iridium plugs. Heading into town now so I’ll have the codes read. Started up perfect this time around.

 

Are the boxes marked "Made in China"? Btw, Denso manufactures AcDelco plugs.

 

Okay I borrowed a friends code reader so I can hold onto it for a couple days. Plugged it in and no codes were stored 🤔 so I’m pretty much lost on what went on this morning. Flashing CEL is a misfire according to everything I have read, but it didn’t save a code. I have the reader in case it happens again.

 

does temperature affect the issue. fine when cold acts up when hot or vice versa. if so you might have an intake air leak and probably need to go over the intake bolts you removed and check the gaskets to see in they moved out of place during install

 

A code reader can provide an existing code. To read history codes, pending codes, etc., you need a scanner.

 

So far I am unsure as it’s just done it the one time. It was fairly cold this morning when it happened so it’s possible, however when I drove it the second time today everything was fine.

 

Yep, I'll give them about 12.5K miles until they disintegrate and you'll be replacing them. Seen it many times, search it here. Members have posted pic of their "aftermarket spark plugs" with their center and/or side electrode completely eaten away = gone. The I5s use a fairly intense coil on plug charge and the ACDelcos are designed to handle it, others............ not so much.

From a nine year old post of mine addressing a slightly different question regarding aftermarket performance spark plugs.:

"Since you guys insist upon keeping this 2009 thread alive, let me sum it up for you:
1) Spark plug change for all H3s is 100,000 Miles, change them before that and you are just pissin away $$;
2) Use OEM ACDelco plugs; and,
3) Aftermarket super duper special spark plugs (insert brand name x here) are not going to create any performance increase in a high capacity discharge computer controlled distributorless ignition. Spark timing, length and intensity are all computer controlled. The GM systems put out tons of Juice and the ACDelcos are engineered to take it. The plug itself is simply the conduit, today a good one is measured by its ability to reliably withstand long service, it can ONLY do what the computer tells it."

Here is another from hummerz near 6 years ago...
"Save yourself some time and avoid driveability issues, ONLY use ACDelco 41-103 (12625058) iridium spark plugs (Alpha use ACDelco 41-110 (12621258))."

 

Thank you! Looks like I’ll be getting new plugs again. I can’t believe I didn’t see that post prior to this. Now I feel silly 😜 ha. Anyway, it hasn’t had any issues since that one incident so that makes me happy. My air doc will be here tomorrow or Friday. I know I’m late to the party in modifying my h3 but better late than never right?! I appreciate the reply.