manteuffel

Hey,

Today, this morning, the infamous CEL came on. I was like WTF... this a 30k miles new car.
My '04 6speed is probably one of the early ones built since I bought it on Dec 03.
It's been at the dealer once for squeals and noises on the Brembos: they fixed and replaced whatever it was at no cost.
During that visit, I mentined that my car hesitated while accelerating during very light throttle conditions... they told me that it was fine and not to worry about it. Obviously, I kept on noticing the hesitation for a few more months until I decided to take the matter on my own hands.
I did got horrible MPG too, around 19-20 in city, 26 in hgwy. It was real bad for a car rated at 29-30 mpg. It got to a point in which I was getting better MPG on my Z06 Corvette than the TL in city driving... Another thing, the TL tailtips were black as you wouldn't believe it...

At any rate. I had har other cars in the past that showed similar symptoms and I decided to decarb the engine this past Friday. After I did the decarb of the engine the car felt much better, I mean, it came alive again, the da** hesitation was pretty much gone and the car mpg went up about 21 (from 19 or so)
Them two days later, as I was saying at the beginning of this post, the CEL came on. What I did? I drove down to the Advance Auto Parts store to have the codes pulled out with their scan tool.
Here are the codes that I got:
-random cylinder missfiring,
-missfire 1
-missfire 2
-missfire 3
-missfire 4
-missfire 5
-missfire 6
-oxygen sensor 1 bank 1 stuck on lean.
The missfire codes were history, probably from when I decarb the top end since I made it drink the seafoam until it stalled, so I wasn't too worried about them but the O2 sensor stuck on lean worried me a lot.
What does oxygen sensor stuck on lean mean? Very simple: it means horrible MPG, hesitation during acceleration and uber-rappy performance all over the powerband.
Why all that? Simple, because when the PCM sees a lean condition at the O2 sensors, it tries to compensate it and throws more gas to correct the lean condition, and the more gas it poors, the more unburned crap sticks all over the top end of the valves, heads and combustion chamber and less and less gets burned completely so its a vicious circle because those nasty uburned carbon deposits are like small sponges that absorbe the mist of air/gasoline mixture that is coming in from the injectors/intake. This means that the more carbon deposits are on the top end, the more and more gas gets trapped on the sponges and less and less actually goes into the combustion chamber so less and less gets burned and the O2 sensor sees that the mixture is very lean because all the gas, instead of going down to the combustion camber, gets stuck all over the carbon deposits. So, the O2 sensor is telling the computer to compensate and to send more gas, and that is therefore, ruining the MPG, the engine performance, the cats and who knows what else...
So, I inmediatly knew that the PCM had to be reset (not reflashed) so it can re-learn the new fuel trims for the carbon-free top end after the decarb so I told the guy at the auto store to clear the codes and reset the PCM... so he did.

After that, I drove around and my average went up from 21 to 24-25 mpg. The car felt completely different that after the decarb, no hesitation at all, smooth as it used to be when new... very nice.

So, you might be wondering what on earth a decarb is and how do you do it?

***Remember, this is an explanation is of what I did, so try it at your own risk!***

Here it is how I did it:
1)Go to the auto store and buy 2 cans of a product called SeaFoam... dont try cheap aerosol cans, get SeaFoam: it is the real deal... it works like a charm and you'll see it.
2)Go to a deserted location, you'll understand why later.
3)Pop the hood, remove the plasitc engine cover.
4)With a pair of pliers, open the clamp that secures the PCV hose. The PCV is the hose that goes from the left side (passenger) of the front engine bank to the left side (passenger) of the big aluminum intake manifold that is at the top of the engine.
5)Get a small cup or container, about half the size of a regular glass.
6)Fill it up with SeaFoam.
7)Get inside the car and start the engine.
8)Let it achieve operating temperature. (5-10 mins if it was cold)
9)When engine is at normal temp, pop the hose from the PCV, pop the end that attaches to the V, not the side that goes into the manifold.
10)You'll feel the car accelerating to compensate and you'll hear a loud hissing noise coming from the hose. don't worry, that is normal.
11)Take the cap and make it suck slowly the SeaFoam thru the PCV hose. very slowly, you don't want to stall the engine yet..
12)Go the 1st cup (not bottle) slowly and once its empty. reconnect the hose and fill the cup once again.
13)Pop the hose and sink the hose into the seafoam until the engine stalls. It should stall right away. <# DO NOT #> restart the engine.
14)Reattach hose.
15)Wait for 10 minutes.
16)Fill the cup once again.
17)Restart the engine, it will take several tries and once it does, there will be a lot of hesitation for a few seconds and after that, you'll be giving a new meaning to the words "smoke screen". In short, the fumes coming out of your tailpipes will be absolutely EXTREME... so, be prepared for that.
18)Let it sit for a few seconds and then, close the hood and take it for a spin. Make sure you do several acceleration runs, do slow progressive accelerations combined with hard ones. Drive until no more fumes come out of the back. The time might vary for you, depending on how much crap there is in your engine.
19)Repeat the steps 13, 14, 15, 16, 17, 18 and 19 until the SeaFoam can #1 is depleted.
20) If still see a considerable amount of fumes coming out with just one can, let it rest for a while before you go with the can #2 and you'll need to get a third one as well.
21)Now, use a funnel to dump the entire SeaFoam can #2 into the gas tank.
22)After that, reset the PCM. Either unplug the battery, pull the fuse or have it reset at the auto store. Whichever way you want. Just make sure the PCM loses its memory so it has to relearn the new fuel trims. VERY IMPORTANT!
23)Enjoy the newly discovered power in your TL. Make sure you repeat this procedure every 5k miles or so, gas is pretty dirty around here.

Enjoy.

G.

Phesto

whats a good milege to try this...............I have 18k 03tl-s

manteuffel

You can do this at any time. Obviously, with less than 1000 miles, is probably too early, but with 18k on the clock it is a perfect time to do it.

This procedure will work for any TL generation, actually, it will work for any car with an internal combustion engine. (gasoline, not diesel!!)

BTW, this will greatly help your car pass the emissions test if you have to put it on the rollers to do the sniffer test .

G.

Phesto

Good idea about the emissions test................I may still have a problem with my RT cat

manteuffel

this should clean most of the engine internals, including cats. Specially if you poor the seafoam until it stalls. Remember that most of it won't be even burned after you try starting the engine. The non-burnt seafoam that goes into the headers and cats cleans the carbon from there pretty good too.

G.