Weirdness after spark plugs change

[wjburken]

Iridium plugs are supposed to come with the gap preset properly for the application. You're not supposed to change it since most standard gap tools can damage the Iridium tip. Yes, you can adjust it, you have to grab the ground electrode with smooth pliers and exercise LOTS of hand control. The AC Delco 41-110 Iridium plugs should be pre-gapped to .040".

You should also check the gap with a wire style gap tool, not a flat style.

 

[RizwanWali]

Iridium plugs are supposed to come with the gap preset properly for the application. You're not supposed to change it since most standard gap tools can damage the Iridium tip. Yes, you can adjust it, you have to grab the ground electrode with smooth pliers and exercise LOTS of hand control. The AC Delco 41-110 Iridium plugs should be pre-gapped to .040". Even if they were a little tighter, it wouldn't affect it much at all, nothing like what you're experiencing. SES light on? Checked the intake tube for improper reinstallation/leak?

I recently had my battery disconnected for about a month straight, if not more for an engine refresh. Intake manifold was removed and sprayed out with a garden hose, brake cleaner, high-pressure air, etc. TB blade, TB throat and MAF was all cleaned. It fired right up on the first pop and didn't have to relearn idle or anything. It just loped and idled goofy because of the cam and still on the stock tune.


Have you checked the wires to ensure they're all fully snapped into place?

thanks for the suggestions but yes the intake has been fitted properly and no lights on dash... more than the rough idle I am more anxious about the jerky gear shift! That did not happen before I changed the plugs.
I don’t see how they are connected.

 

[Doubeleive]

thanks for the suggestions but yes the intake has been fitted properly and no lights on dash... more than the rough idle I am more anxious about the jerky gear shift! That did not happen before I changed the plugs.
I don’t see how they are connected.

MAF Can cause that be sure it is plugged in and clean

 

[iamdub]

thanks for the suggestions but yes the intake has been fitted properly and no lights on dash... more than the rough idle I am more anxious about the jerky gear shift! That did not happen before I changed the plugs.
I don’t see how they are connected.

MAF affects trans shift characteristics and misfires can, too. Is there any chance you may have knocked a vacuum hose loose? Did you lean on the intake manifold while trying to reach the rearmost plugs? A vacuum leak would cause a high and/or rough idle and affect the trans due to the unmetered air. Chances are, you'd have an SES light with it. Unless it's very small.

Kinda grasping at straws here.

 

[RizwanWali]

MAF affects trans shift characteristics and misfires can, too. Is there any chance you may have knocked a vacuum hose loose? Did you lean on the intake manifold while trying to reach the rearmost plugs? A vacuum leak would cause a high and/or rough idle and affect the trans due to the unmetered air. Chances are, you'd have an SES light with it. Unless it's very small.

Kinda grasping at straws here.

when I was trying to remove the TB for cleaning, in attempts to unhook the maf harness I did break the little plastic stud (see picture) However, when I was done I had secured it tightly with electrical and it wasn’t loose. I will check this again as per your suspicion and will post some actual pictures of what I’m explaining when I get home. Thank you!

 

[RizwanWali]

MAF Can cause that be sure it is plugged in and clean

Thanks. I did break a connection “stud” in the maf sensor but had taped it tight when I was done. I will check to see if it’s still tightly secured when I get home

 

[Jwc15]

Have you ever replaced your carbon filter, blown out evap lines, changed fuel pump, cleaned fuel tank, replaced evap solenoids, purge valve on block, etc? All that fuel management can cause a rough idle. Mine seems to be idling smoother and responding better than ever after all that. 08 Tahoe with about 71k. Yeah his also fixed my slow fillup at the pump problem.

So I have a ‘08 Yukon XL Denali (only 74k miles) which had a slight pulsing shakiness in idle like a misfire.

This is what I have done to try to smoothen the idle:

1. Ran a bottle of fuel system cleaner STP brand in the gas tank - no difference.
2. I thoroughly cleaned the intake and throttle body - no difference
3. Changed all spark plugs. Old ones were AC DELCO 41-993 and the new ones I installed were AC DELCO professional iridium 41-110.

I had the battery disconnected for 30 minutes and now idle has become more shaky than before. Also noticed a more pronounced jerk shifting from first into second. I drove it on the highway and did a few pulls but no difference.

Anyone have any idea what could be the problem here? What does the transmission have to do with the plugs? Did I use the wrong plugs?

 

[ReedR]

So I have a ‘08 Yukon XL Denali (only 74k miles) which had a slight pulsing shakiness in idle like a misfire.

This is what I have done to try to smoothen the idle:

1. Ran a bottle of fuel system cleaner STP brand in the gas tank - no difference.
2. I thoroughly cleaned the intake and throttle body - no difference
3. Changed all spark plugs. Old ones were AC DELCO 41-993 and the new ones I installed were AC DELCO professional iridium 41-110.

I had the battery disconnected for 30 minutes and now idle has become more shaky than before. Also noticed a more pronounced jerk shifting from first into second. I drove it on the highway and did a few pulls but no difference.

Anyone have any idea what could be the problem here? What does the transmission have to do with the plugs? Did I use the wrong plugs?

One thing you need to rule out is the tb. Speaking from experience and as it was mentioned before you may have nocked the tb out of wack when you cleaned it. It will definitely mess with shifting from 1st to 2nd and not as much from 2nd on. To make sure it's OK just rev it up above 2000 rpm in park, if it stays rev'd and doesn't idle back down as soon as you release the gas then it needs to be relearned.

 

[Abuilyas]

Can I throw a suggestion? Check the engine mount, I had mine split and never had noticeable shake, I just replaced it couple of weeks ago with cheap after market one (driver side) and now I can feel little vibration on the ground and pedals, on the passenger side I didn’t change anything and now if you set on the passenger side you feel the vibration on the seat, now am not an expert in any mean but the cheap engine mount’s rubber felt very bad thats why I didn’t even bother to change the other side even thought I have bought the part.
For the gear shifting issue, I would disconnect the battery again and drove for more than 10 miles in the city (avoid highway) as if am not mistaken it need to relearn the shifting based on your driving habits, that helped me a lot when I bought mine and make huge difference on the fuel consumption.

for the spark plugs AC DELCO has quality parts and low quality parts I always go with the factory requirements if you want smoothness rather than performance. For example in GCC countries the AC DELCO battery made in Saudi Arabia and it would not last more than 12 months whatever you do.

 

[avalonandl]

make sure your plug wires are ALL seated correctly.


It sounds like you have a loose connection....