Hello! I recently bought a 2012 Toyota highlander 3.5 v6 4WD and I notice a rough idle at start up on a cold engine with some vibration that goes away as the engine gets warm.
The car has approx 100k miles and i don't have a scanner yet so no codes that I know of. I shift into neutral from park or drive and the vibration goes away. Once the engine is warm it idles smoothly at 800 rpm and sounds great. While driving down the road, car drives great, no weird sounds or anything. Only happens at idle on a cold start.
I've changed the air filter which was filthy and probably never changed, I cleaned (probably poor) the throttle body, spray cleaned MAF, and ran some royal purple through it. It was a bit better after all of that but still persists. I will have another go at cleaning the throttle body because It was very very dirty.
I've considered pulling a spark plug to see but I will clean the throttle body more thoroughly and see how it goes.
Any ideas? Thanks!
An update: Upon further inspecting the engine, I hear what I think is a whistling sound when the engine is running. It sounds like it's coming from around the ABS control module (or the pump?). It also appears that there is a trail of grease or oil that comes from the edge of the module and runs down below the engine. Would a leak from that module cause a vacuum leak??
Get yourself a scan tool and check the live data. It can give you a good idea of what is wrong.
Any affordable ones you could recommend??
It depends on how much you want to spend but the Bluedriver is a good one for the price and what you can get out of it.
After some plugging around, I found the PCV was very fouled up and replaced that. That fixed the poor idle however under a load I still get 5-10% positive long term fuel trims whereas short term fuel trims hover around 0 most of the time.
I tested the maf with ignition on and engine off, both before and after extensive cleaning, and it reads 0.65g/s with engine off.
Manual states that any reading above 0.55 g/s means you should replace the maf.
How true is this?
Your fuel trims are fine. Check the MAF reading when you put the car in drive and put your foot on the brake. If it is about 3.5 g/sec, I would not worry about the MAF sensor.