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Spark plug choices and idle stumble missfire

blazed16

Active Member
Messages
26
Location
canada
Hey guys

ac delco iridium at $9 each gap is .44
or
ngk iridium xl at $9 each gap is .43

Question whats a better plug on a 07 hummer h3 with the 3.7 and why are both plugs show for the vehicle but different gaps.?


Next heres a missfire issue

not so perfect idle.Well its fine but if i give it gas then left off the gas the rpms drop and go very low then stumbles then evens out and runs fine but i had shop hook up to computer and there was a couple codes since last time.

P0300
B3152

Also the live data shows cyc 3 missfire and when you press the gas and let go cyc 3 will give 3 or 4 missfires and cyc 2 and 5 show 1 but then dissapears and then all cyclinders show none and then after couple minutes cyc 3 will show again and after 10 minutes of running there was 16 on cyc 3 and 2 on 5.

Could this be cause by dirty throttle body?

I have changed battery terminals and enhuast manifold gasket and welded crack.
spark plugs were changed a couple thousand kms ago due to random missfire. i checked and these are the plugs that were used [h=1]12625058 ACDelco Iridium Spark[/h]
Any ideas?
07 hummer h3 with the 3.7
 
Last edited:

rascole

Well-Known Member
Messages
2,580
Location
Bellflower, CA
Swap coils around and see if the misfires shows up on the new cylinder. If the misfire moves then replace all the coils.
 

blazed16

Active Member
Messages
26
Location
canada
3 2 and 5 all showed but 3 was worst. Im going to order a coil and switch with 3 and so on.

Brand of coil motor products or ad delco ngk does it matter?
 

blazed16

Active Member
Messages
26
Location
canada
COP as replace all 5 coils?

I have the maf and TB cleaner waiting just for some nice weather we still getting snow haha.
3 2 and 5 all showed but 3 was worst. Im going to order a coil and switch with 3 and so on.

Brand of coil motor products or ad delco ngk does it matter?
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Stay OEM and minimize any issues with aftermarket especially when troubleshooting an issue like this. You're not going to see a performance gain with different plugs or coils

Sent from my SM-N950U using Tapatalk
 

blazed16

Active Member
Messages
26
Location
canada
Ok guys so i cleaned the maf and also pulled the throttle body and gave it a good cleaning.
My crappy idle is alot better now.

Hooked up for miss fire data and now cyl 5 had 16 misses and cyl 3 only had 3 in 4 minutes of idle. None on the other cylinders this time either.
This was different from before as before cyl 3 was the one showing a bunch.
 

mjferencak

Well-Known Member
Messages
308
Location
Elbert, CO
How do your plugs look? How many miles are on the engine? And are you burning oil? Your plugs could be building up carbon deposits and fouling out from worn out valve seats dispensing oil into the combustion camber. Thats the problem I'm having with my Charger right now.
 

scoreh3

Well-Known Member
Messages
1,024
Location
SoCal
Stick with the stock plugs and from what I’ve read NEVER USE E3 plugs. All of the Hummer and Colorado forums say they will cause major issues...
 

blazed16

Active Member
Messages
26
Location
canada
Plugs look ok only about 8000km on them now and there the acdelco iridium thats recommended. No burning oil either. and there is 200,000km on the motor so that is high but really maintained.
 

blazed16

Active Member
Messages
26
Location
canada
Ok guys so i cleaned the maf and also pulled the throttle body and gave it a good cleaning.
My crappy idle is alot better now.

Hooked up for miss fire data and now cyl 5 had 16 misses and cyl 3 only had 3 in 4 minutes of idle. None on the other cylinders this time either.
This was different from before as before cyl 3 was the one showing a bunch.

How do your plugs look? How many miles are on the engine? And are you burning oil? Your plugs could be building up carbon deposits and fouling out from worn out valve seats dispensing oil into the combustion camber. Thats the problem I'm having with my Charger right now.

Plugs look ok only about 8000km on them now and there the acdelco iridium thats recommended. No burning oil either. and there is 200,000km on the motor so that is high but really maintained.
 
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