I went to an independent shop with my 2008 GS350 AWD, and they changed my spark plugs and said they used iridium ones. That night I noticed my car jerking after I turned it on, I would see the RPMs jump slightly down for a split second and the car would shake. It would happen like every 10-20 seconds and stopped once I started driving. Would this be caused by improperly installed plugs?

For my 60k service I also got an oil change, new engine air filter, cabin air filter, balance and rotate tires, and they checked everything else on the list. They checked my brake fluid and said it was still clean and did not need to be drained and replaced. Is this something that needs to be done to keep your Certified Warranty?

Also, at my last oil change Lexus told me I needed a new drive belt since mine was cracked. This shop said they did not see anything wrong with it. They said it did not look dry and cracked at all. Is this something I should just have them do anyway or can it wait? I didn't use Lexus since they wanted over $900 for the service and the drive belt. It seemed like 90 percent of the maintenance was just checking stuff which this shop did for free.

Thank you!

 

hey man I had the same problem with my Lexus Gs and the spark plugs. But my problem was that I got the spark plugs from auto zone instead of going to the Lexus Dealer or a special foreign auto parts store. And when I put those auto zone spark plugs in my car was jerking as well. But I would say maybe in your case someone didnt gap the plugs correctly when installing them. Those plugs have to be gapped correctly.

 

I was going to say gapped wrong as well.

 

Surprisingly enough the gap will cause this. I am sure the proper gap is listed on here somewhere...either that or Google it.

 

Yep sounds like the gap wasn't set to correct Lexus spec. Although maybe it's only the Toyota parts but they already come gaped could be crappy spark plugs what brand did they use.

 

It has been awhile, but just an FYI, one of the plugs was not properly installed. They fixed it and everything is fine. Thank you everyone for the help!

 

Just out of curiousity, how does one improperly install a spark plug? Incorrect torque? Crossthreaded?
Thanks.

 

I don't remember, I think they said one was loose, but I don't do any car maintenance myself, so he could have told me anything and I probably would have believed it.

 

As far as I know, iridium plugs come pre gapped. I once carefully tried to mess with the gap on one for my Acura and it broke.

As for autozone, that's where I bought my OEM iridium Denso plugs.

 

That is correct. You don't gap iridiums, I just put some own ngk iridiums purchased at oreillys auto parts in my brothers gs400. No issues.

 

probably just didnt install it all the way. sounds pretty simple and basic but i never put anything past people anymore

i still double check them anyway. even if they say that the plugs are pre-gapped, it only takes about a minute to check all of them. just a peace of mind thing.

 

best practice is to recheck the gap before inserting, never know who dropped one or two from production, shipping, transport to installation.
Theres a tool that does this very well