I changed my knock sensor on my 2002 rx 300, including replacing the intake and intake manifold gaskets as recommended Also replaced all my spark plugs.
I put everything back together and connected all my vacuum hose as they were before. I started the car with no issues. Shortly after, CEL came on with a P0300 code. I drove a round a bit and it the car seems to "buck" when shifting into gear. It revs up and kicks into gear.
I cant seems to figure out what the issue is. Prior to me changing the knock sensors, the car shifted smoothly with no issues.
The car idles slightly above 1000rpm. But once in gear, it drops below 1000.
I cannot seem to figure out what i did wrong. I torqued down the plugs as tight but not too tight without a torque wrench. I have no issues with start-up so I dont think the plugs are the issue.

Please help!

 

Did you follow the DIY or some one else changes the knock sensors?

My first guess is that all grounds are not connected. Please reverify the steps and ensure all ground straps are connected and are nice and firm. [multiple wires are grounded near the hidden bolt]

Salim

 

Well, it shouldn't be idling that high - that's one thing that's causing it to "buck" when you shift it into gear. As for the code, could be a vacuum leak, bad catalytic converter, bad EGR - a whole host of things. Running rich for a long time could have hurt something, although if it just started after you did all that work I'd go over everything again and double check the vacuum hoses, etc, first. Sounds like you're pretty handy if you could change those rear plugs!

 

Update: I was driving and I had another code come up P0758. (Tried to keep in in first and second gears). I didnt have any transmission issues prior to doing this work, so I think the random misfire (P0300) is putting the transmission into limb mode or something. I had a mechanic listen to the engine. He thinks I need a new gasket because i didnt follow the tightening pattern, and probably crushed the gasket on one side. ( I tightened it from one side to the other).
With regards to the ground wires, I had two on the left side of the intake, which I connected, and one attached to the back of the intake, next to the bracket. Also Attached that. I sprayed carb cleaner on the hoses to detect any leak and found non. So I plan on redoing this gasket.

 

So how many wires did you connect between the engine and there firewall [you cant see them]?

Lust reach back there and see if a wire is pinched.

Salim

 

I attached 2 ground wires from the firewall to the engine. 1 to the intake manifold, and another to the throttle body.

 

Can some one please confirm the wire count. I remember more than one [is it 2 or 3] .

Salim

 

Update: I got everything fixed and working right again. it was the gasket. When I first did the job, I over tighten the intake nuts, also, I used an aftermarket gasket.
So I ordered new gaskets from Toyota via Amazon and borrowed a torque wrench. The torque is 11-ft/lbs. which is very low. Also, you have to tighten the gasket in the correct pattern. Zig-zagging from front to back. Everything works fine now. on cold start, the rpm is about 1800.
Thanks for the response and support.

 

Are you sure about the pattern .. it is counter intuitive .. normally you go center out, even on both sides. If you have a reference please share.

Salim