I understand what you're getting at, but obviously if the engine is pinging then the ECU can't retard the timing enough to correct for it.

 

Precisely, and the ECU can retard quite a bit, and that can easily be measured through ODBII. The last time I played with ODBII on a 3RD gen the ECU could retard by ~12degrees.

 

Right, and I agree. But I think where we're diverging here is what happens if the ECU can't retard enough to create a silent condition in the knock sensor.

From the path you're going down, I'd guess that you're thinking the ECU will stay at max retard (so, -12*). I'm thinking that the ECU will give up and "home".

If the ECU stays at -12*, then I agree that a) you should be able to verify that via OBD II; b) if running Seafoam clears the carbon deposits, then you should of course see the timing shift within the range where the ping was occurring.

That said.. I know that I can make my engine knock by shifting my timing 3* via my SMT piggyback, and it won't clear itself up. If the knock sensor was affecting the timing, then I don't think this would be the case. I'll admit though that this may be an issue with how the SMT (or any piggyback) is
doing it's job.


It's all good. and yeah, it'd be cool to figure it out for real.

 

kinda off topic, but how can you check to see if your o2 sensor needs replacement?

 

Ok then. Why not?

Carbon is extra stuff in the combustion chamber. Correct?
And anything in the combustion chamber, taking up space will increase the compression. Correct? If it were extra metal around the valves instead of carbon, it would still take up space in the cylinder, and therefore increase compression.
Now if you want to argue that the carbon is creating hot spots that cause the predetonation then fine, but I'd like to hear your explanation as to why more carbon Not = more compression.

 

I was referring to this statement, admittedly out of context.

If you are simply reciting the obvious that compression goes up and cylinder volume decreases then go right ahead.

 

Mine is still fine. I did another treatment to both the intake and the injectors about 2k miles after the first and got some more gunk out. Not as much smoke as before, but still got some. Maybe you have just loosened up the crud and you need to blow it out. My mileage has stayed consistent. About 16.5-17 around town (sometimes 15 if I'm up and down hills alot or heavily loaded) and about 18 on the highway...

I have about 4k on the odo since the first treatment...

 

Ok, so what were you trying to say then?
That (regarding the original statement) reducing the compression ratio would increase power/gas mileage, or ??
I was just stating a theory as to why his gas mileage might go down.

 

Uh oh guys
I just did the treatment and now my engine wont start...it cranks, but doesn't fire. I poured half the bottle into the oil (since a whole bottle is good for 10 quarts) and did a 1/3 of a pint into the brake booster line (VERY slowly) and now my engine wont start!!!!
Should I let it sit longer or what? HELP!

EDIT: ok, I waited another 10 minutes and it starts....cranks a few times more than normal, but thats prolly cause I was trying so many times earlier. Should I not have poured into the oil AND the brake booster line? Or are these symptoms normal?
The idle does seem alot smoother now, on the bright side.

 

Did you pour it in with the engine stopped? You're supposed to pour it in with it running...

If you poured it while it was running, then did it stop while you were pouring?

 

It was running when I poured it in....it kept surging like it was going to stall but I guess thats normal since the line was disconnected. It seems fine now, I haven't tried to start it in a half an hour but last time I did it worked. Just scared me at first...after reading Oly's story I was REALLY nervous about this stuff...but, so far everythings ok. My engine's been acting a little funky ever since I got back from Big Bear so that might have something to do with it. (lower rpm's when cold, higher rpm's when hot)
Figured I'd give the Seafoam a try and see if it helped the RPM's at all...I haven't driven it yet but when I do, hopefully all goes well.
This stuff is kinda scary

 

Ok, drove it around, heres what happened:
After waiting a half an hour, it started up like a champ, and drove smoother than before. I was thinkg, wow, this stuff is amazing! Well, I get home, stop the engine, and decide to start it up again to make sure its still ok.
NADA. The engine cranks but wont fire. Ok...so now I crank it a little longer and finally it BARELY catches and idles REALLY low at about 400 rpm's. I give it a little gas and the rpm's shoot up and stay at 1,000 but then slowly drop back down.
Any ideas whats happening here???? I think I need to pay my mechanic a visit This isn't my day.

 

Sounds like you had some underlying problems that are acting up...

 

Have you had your intake off recently by chance?
It sounds like an intake leak.

Or it could be a symptom of running lean.. . .depending.

 

That's what I'm afraid of . If I were running lean, I would be throwing a code right? There's not CEL on. I drove her down to the gas station to fill up and she started just fine right after that. Drove the 3 mile trip home, stopped the engine, cranked it again, and it started. Tested it 3 more times and it started right back up each time.
Does this stuff take awhile to settle in or something? Cause now, after driving around and filling up with gas, everything seems ok.

 

Was the tank REALLY low? Could have been bad gas...

 

No, it was just under a quarter full. I could've easily gone another 75 miles or so. The whole engine bay is caked with dirt, I've already cleaned my K&N filter today so I think I'll move onto my TB and maybe the MAF as well. See if that helps...I'm debating about adding the rest of the Seafoam to see if that helps the idle but I dont want another episode like this.
Sorry to rain on the Seafoam parade...for what its worth, while driving the engine did seem more responsive and smoother. Hopefully it helps my mileage.
Thanks for the input/help so far!

 

True.

CORRECT.

Sure, it'll boost your compression...but you don't have the same amount of carbon buildup in each cylinder, hence the compression ratio will be slightly off in each cylinder and therefore your power pulses in each cylinder will not be balanced. Which is why racers cc their heads, balance pistons, rods and cranks.

In addition, carbon holds heat and causes the predetonation that was spoken of previously. If you want to go against common wisdom and build up the carbon in your cylinders, go ahead. You'll find though, that it doesn't just build up in your cylinders, but also around the intake valves, decreasing the flow into the cylinder.

If you think carbon buildup is the holy grail to finding an extra horse or two, go ahead find some long chain carbons and toss 'em in your tank. You might try dissolving them in toluene or acetone first.

Me? Naw....I try to make my engine last as long and run as smooth as possible and keep the $2-4K for a rebuild doing other things. So far, my strategy seems to be working for me.

 

trying the seafoam reatment as we speak on a 2000 tacoma 2.7 with 68 k on it

 

im a believer , smoother idle, more throtle response thats just from a trip around the block