I installed the ngk 3787's Friday morning and put about 50 miles on them. Tonight i was out cruising around and under light acceleration in 4th/ just cruising at 40mph the car started to miss and cut out. It was fully warmed up. I was only about 4 miles from home so i drove it home very easily no boost etc. When i pulled into drive and parked i let it idle and it held idle smooth like before. Im puzzled because no CEL came on or flashed at all during the missing/cutting out. I did rinse my engine bay down with water today but that was 6 hours before and the missing started well after fully warmed up. Im gonna put stock plugs back in tom when the engine is cold. Any ideas whats happening? Every time it would miss/cutout it would whistle like when letting off the gas but i didn't let off the gas, maybe its another problem not plugs? Any help is much appreciated.

 

Stock plugs seem to be the only plgs that dont have to much trouble, Check the gaps and if that doesnt work, go to stock plugs. The only way I would use colder plugs if I was running meth or had an aggresive tune.

 

Water evaporated when the engine got hot & moisture got into some wiring or the coil packs maybe? I doubt it's the plugs though. See how it runs after it sits all night and dries out.

When I wash the engine bay, I blow all the water out with compressed air & let it dry overnight in the garage with the hood up. I've been running the 3787's around 2k miles now but I boost a bit.

 

Alright, how long must you let the engine cool down before a plug swap, if id drive it tom morning to see and it still does it how long till you know its cool enough to pull the plugs? I do have stage1 but no tune on top. Shouldn't a CEL came on w/e it was? And it happened after about 30 min of driving around, Highway/around town and i rinsed the engine bay around 1 and this occurred around 7.

 

Just change the plugs then if you don't have time to mess with it. I'd wait until the engine is cooled all the way myself.

 

On a side not regarding the 3787, I noticed my LTFT got worse after I changed to these plugs. I know it doesnt help much, just saying...

 

LTFT? what does that mean? And how did you find out it was causing problems.

 

Long Term Fuel Trims. The amount the ECU changes the average amount of fuel the engine gets.

STFT's are Short Term and are constantly adjusting the mixture.

 

Makes no sense to me about the NGK plugs. I been running DensoTT for about 100 miles so far and haven't experience any problems. I made sure the gap was the recommendation at .40 before I put all 4 in and so far they have run smooth. No CEL or anything. I think it could be the gaps on your spark plugs that may have caused the issue in the first place or they aren't really cut out to run in the motor.

 

Stock plugs are gapped about .31 and thats what the ngk 3787's come as, i checked them before i put them in and no i didn't ruin them by opening the gap up etc, becuase i didn't need to open any of the gaps. The plugs you have gapped at .40 seems quite big

 

if you see a double tip spark plug, you wonder why I never once gapped it. I made sure it was at .40 with my gap meter before I threw them in the motor. the only thing that got my attention was the huge spark it created and the benefits I would get out of it.

here is the site to check out http://densott.com/

 

I've had no problems out of the 3787's since I installed them about 2 months ago. I used the .031-.032 gap setting they came with, the only other thing I did was put some die electric grease in each boot.

 

I have the 3787s too for about 2 months now and haven't had any issues. These are 1 step colder plugs and from what I have always been told, unless your car is 70-100hp over stock you shouldnt be using any step colder plug.

for every 70-100hp added over stock = go one step colder on plugs

a stage 1 fom gm only adds 20hp over stock.

 

Actually it's more like 30HP and 60TQ and with a few supporting mods it could be a lot more than that.

 

Well switching the plugs back did not fix the problem. It Started doing it again today after about 30-45 min of driving. No cel at all just missing and hesitation under light accleration and cruising. Any ideas what it might be??? I called the dealer and they sadi to call back when service people are in tom. I don't understand why theres no cel light. Im afraid the dealer will say it didn't duplicate the problem etc.

 

Sounds like a coil pack flakin' out after it gets hot to me. Warranty time.

 

yea i was thinking something like that, Maybe when they installed stage 1 a crimp wasn't done good. How long do you think it will take for a cel to come on?