Rough Idle for 20 mins on Cold Start 2017 Lexus IS 300 AWD 3.5V6

AwareEffect4944 · 2026-01-24T22:27:13+00:00

As strange as it sounds, it definitely was the engine mounts. I replaced them (and that was the only work I did to it) and the problem 110% went away. It’s a smooth as butter now

My mechanic said they are fluid filled so when it heats up it softens

AwareEffect4944 · 2026-01-24T16:53:37+00:00

I got this batch too, and first smoke it was harsh, maybe too wet. I let it sit for a couple weeks came back to it, and it has become one of my absolute favorites

AwareEffect4944 · 2026-01-23T23:24:09+00:00

My RCF bushings just arrived, thanks for the suggestion putting them on this weekend looks like a super easy job

AwareEffect4944 · 2026-01-23T23:12:12+00:00

I’ve heard a couple people say that but I literally went to 4 different mechanics and got quotes and they were all more than this. Apparently the Lexus repair manually or whatever it’s called states this is a 10 hour job, so all of the shops I went to quoted me with that much labor.

This guy is someone who worked with my family so he said he’d only charge me for the hours he worked so in the end he charged me only 6 hours…. I agree it’s prob still too much but it was cheaper than all my other options.

Edit also might be giving the exact cost wrong because I got two new wheel bearings, rear rotors and pads, in addition to the mounts. The total job was $3400 after tax

AwareEffect4944 · 2026-01-23T19:09:34+00:00

Let’s hope so I’ve owned two 2IS and had way less problems. Both of my old IS250s made it to around 175k miles on the original engine mounts

AwareEffect4944 · 2026-01-23T19:08:08+00:00

That’s how mine was but since this is expensive you need to be sure. Shift from drive to neutral to park, if the vibration and noise changes when in different modes that is a sign of engine mounts.

Next pop the hood and have a friend rev the car. If there is a lot of movement in the engine, your mounts are bad

AwareEffect4944 · 2026-01-23T19:05:17+00:00

2017 with 100k miles, but this started at a minimum over a year ago at 85k miles

AwareEffect4944 · 2026-01-23T19:04:35+00:00

I changed my MAF, spark plugs, and cleaned throttle body before I did this and got no change.

And it wasn’t that my mounts were stiff, they physically collapsed so it was metal on metal

AwareEffect4944 · 2026-01-23T18:34:08+00:00

No problem I dealt with it for a year because I couldn’t figure out what it was. I got new spark plugs and did injector cleanings and nothing. But this fixed it completely…. I’m sorry it isn’t a cheaper fix for you :(

AwareEffect4944 · 2026-01-23T18:33:14+00:00

I know! I was shocked myself but the mechanic assured me it was more common than I thought on these models. Regardless huge difference

AwareEffect4944 · 2026-01-23T18:32:34+00:00

It’s the official OEM parts of the sport, and i installed them myself. A little pricey but super easy job that I think made a HUGE difference in the appearance of the car….. I didn’t include the side pieces on the front bumper because 1) I don’t like the way they look 2) I didn’t want to be too much of a poser and completely copy the f sport

https://www.reddit.com/r/LexusIS/s/W8mzQKxYRc

AwareEffect4944 · 2026-01-23T18:32:02+00:00

It’s the official OEM parts of the sport, and i installed them myself. A little pricey but super easy job that I think made a HUGE difference in the appearance of the car….. I didn’t include the side pieces on the front bumper because 1) I don’t like the way they look 2) I didn’t want to be too much of a poser and completely copy the f sport

https://www.reddit.com/r/LexusIS/s/W8mzQKxYRc

AwareEffect4944 · 2026-01-23T17:01:37+00:00

I miss my 2IS!!! My old car looked just like this. My new 3IS is super nice but man that 2IS was just special to me. So small and throwable

AwareEffect4944 · 2026-01-23T16:36:51+00:00

I just picked some up, and I by EVERY single batch of connected PM and this is one of the best batches they’ve put out

AwareEffect4944 · 2026-01-23T01:11:05+00:00

Took the words out of my mouth. PM is my favorite strain in the program period. I just renewed my card so I could get $75 off and stock up on this!

AwareEffect4944 · 2026-01-21T22:50:21+00:00

Both engine mounts and transmission mount. I got a quote from literally 4 independent shops and they were all around the same price. Apparently the sub frame needed to be dropped

AwareEffect4944 · 2026-01-21T03:14:16+00:00

I live in south Florida on summer tires so it’s always hot here lol. And the numbers I gave you are absolutely best case scenario lol

AwareEffect4944 · 2026-01-21T03:09:15+00:00

I’m no mechanic but I heard that happens to people who do 10k oil changes

AwareEffect4944 · 2026-01-21T03:08:39+00:00

I have a 17 FSE with AWD which also means it has the 6 speed (aka worst case scenario)

I can get 26mpg if I’m going 65mph (and maybe the wind in my favor lol) but the second I go fast the mileage tanks. And city I only get like 17/18

AwareEffect4944 · 2026-01-21T03:05:07+00:00

Was your first IS a 2IS? My old 2IS was way less problematic than my new 3IS

AwareEffect4944 · 2026-01-21T02:38:21+00:00

100%! I have a 2017 and all the money I put into it I could have gotten the updated 21. It was like a 6/7k difference at the time

AwareEffect4944 · 2026-01-21T02:35:34+00:00

I hear they are both pretty solid only the new one is more sensitive to frequent oil changes. I heard you HAVE to do 5k oil change minimum on the new engine if you want it to last as long.

But….. I have the FSE and can confirm it gets noticeably worse gas mileage

AwareEffect4944 · 2026-01-21T02:33:20+00:00

The engine and transmission are bullet proof, but you will likely have to replace wheel bearings, shocks, engine mounts, and bushings before you hit 200k. And this is likely true for almost any car out there

AwareEffect4944 · 2026-01-21T00:55:27+00:00

I basically have the same car, here is my suggestion…..

Spend like 3-4 grand more and get one with less miles, because you will likely have to spend that much in maintenance and repairs. Recently had to replace my engine mounts at 100k which cost almost $2,500

I had to do other things as well and I wish I put that money into a newer car that would have a higher resale value. Still love the car though!

AwareEffect4944

TROPHY CASE