I'm still having what I thought was a transmission problem on my 06. I'm now thinking its a fuel/air/spark problem.

I'm experiencing rpm drop and power loss under 2000rpm. Typically in third and 4th gear at low speeds. I never experience it under hard acceleration or higher speeds. The RPM will drop and get sluggish while accelerating but jump up where it should be if I give it a little more gas.

The only CEL code I've ever got was P2198 (A/F sensor stuck rich) It was on two separate days and went off on its own both times. I was having this problem weeks before the code and now weeks after. The issue comes and goes, some days it's there and some days it's barely noticeable.

Supposedly the plugs and PCV valve were changed prior to me buying the car 6 months ago, but the PCV doesn't look like it was changed. I'm going to pull the plugs and make sure they are the correct plugs and aren't fouled.

So far I've cleaned the MAF and Throttle body with CRC cleaner. The back side of the sensor was crusty with carbon, but seems to be good. (The car immediately dies if I pull the plug). I only cleaned the TB from the front. I didn't take it apart.

I don't know what else to do other than a top engine clean and start replacing things one by one. (Plugs, PCV, A/F sensor on the manifold, MAF, etc...)

Anyone ever experience this or have any advice on what else to check?

 

Is your air filter new/reasonably clean?

 

Yeah, it's a couple months old.

 

Well with the GS300 a top engine clean would be a good idea, and maybe clean the throttle plate again, especially around the edges. Unless you're also having rough idle, the spark plugs are probably fine. And if you're in doubt about the PCV valve it would be a good idea to replace it since they're only like $15 or so

Yeah it sounds like a really annoying problem, but hopefully a good cleaning will take care of it!

 

Not sure if you know these 2006 GS300 have a carbon buildup issue. A few years ago the dealer would rebuild the entire engine for free. Has your engine ever been rebuilt or cleaned out?

Your engine maybe clogged up with carbon, this is what I would do. I would let the car idle for about 10 min to build up heat. Pull out all the spark plugs and pour a small amount of ATF fluid or marvel mystery oil into each spark plug hole. This will coat the tops of the pistons and hopefully leak into the rings aswell. Next I would buy about 3 cans of Mopar combustion chamber cleaner and spray 2 cans inside of the spark plug holes, and into the intake manifold aiming trying your best to reach the valves. Put the old plugs back in and let the products soak overnight.

Next morning I would remove all the spark plugs, get an air compressor with a tiny spray trigger and blow out all the fluids that are left inside of the combustion chamber. Put the old plugs back in and start the car put dont give it any gas. The car should smoke like crazy, allow all the smoke to burn off at idle.

Next heat up the car once again and spray 1/2 a can of mopar into an empty intake port while running. Allow the engine to almost stall while spraying, half way into the can stop the engine and let it sit for about 20 min and repeat the process and finish off the bottle. Once finished I would then install new oem denso spark plugs, pcv, air filter, and new engine oil.

 

Well, I think I'm giving up. I replaced the plugs, PCV, thoughly cleaned the Throttle body, performed the top engine clean service, and had the transfluid exchanged.

Today (two weeks later) its back to running poorly. This morning on the highway (45-50mph), I felt something, looked down, and sure enough the rpm was bouncing back and forth from 1-2000rpm. It only lasted about 5 seconds, but long enough to know the issue isn't gone. Then, this afternoon, It felt sluggish at times like it was in too high of a gear or was losing power.

I can't figure it out. I think I'm just going to try trading it in for something else.

 

Consider having someone check it first before you sell... Who knows, it might be something real simple!

 

Did you at any point hook up a scan tool and check for stored codes and/or look at live data readings?

 

Toyota checked. The only stored code was from a misfire from a cold start months ago. I haven't checked the live data myself. I thought about getting the software and mini vci, to check myself, but I have no idea what I would be looking for, if I have to interpret the data myself. I guess it won't hurt to try.

 

Sounds like your crankshaft senor position is about to go bad.....im 70 -80% positive

 

 

Just got it installed, all problems gone. No more rough idles, bouncy rpms, dead spots,.and miss fires.

 

What do you mean by "dead spots"? I want to see how closely related our symptoms are.

Did you have trouble starting? I read that's a symptom but mine starts no problem.

Did you have symptoms before you got the CEL for it? Mine hasn't thrown a code for it.

 

I had these symptoms before i got a the check engine light.

Before my car would sometimes have a hard time starting, it will take longer than usually till it starts.

Sometime my engine would not accelerate when driving around 40 or 60 mph..the engine would kinda bogg and the rpm needle aould just bounce

Also my rpm needle bounces up and down when the car is cold. It doesn't happen to much when its warm up but it still does alittle when warm.

 

Also one more thing, my car would use to drop down to 500 to 400 rpm when coming to a complete stop then it would go back to 600

I see that you also have the same problem that i had before where the rpm would drop and lose power at lower speed around 15 to 40 mph but will pick up once given more gas....sounds exactly like my problem lol

You could also have a bad camshaft senor...