mhawker

I have had my 4 Runner SC'd since it's birth in 1999. It was plagued by a "power band" effect for some time and I thought I had it fixed when I cleaned the MAF. That DID make a big difference, but not in the main problem.

What I get is sometimes the truck is very fast and some times it feels like it's being choked. Using my many minutes of education it feels like the engine is retarding the timing and then when the revs get going, it kicks in. Possibly hearing a "knock" so it retards the timing until the knock goes away?

If anyone has ever ridden a dirt bike, it's the same feeling you get when the bike gets in it's power band. You know, it's accelerating along and there is a noticeable "jump" in power.

Any ideas?

Mike:wtf:

rimpainter.com

I think you answered your own question. The knock sensor is most likely retarding the timing under boost.

mhawker

Great, I'm brilliant! Now, is there a way to fix it other than injectors, piggy back computer etc?

It's something I can live with, but if anyone has run across this and a fix, let me know.

Mike

Dr. Zhivago

Nope, not really.

Sorry to be the bearer of bad news, but there is just so much evidence to support the need for the additional items to make the TRD S/C run correctly.

My .02
Dr. Z

Gadget

If you want yours to run as powerful and seamless as mine install the following mods:

Walbro 190 LPH pump
ND 305cc injectors
Split Second ESC1 (if you have a front O2 sensor)
Split Second FTC or a UNICHIP

I just got back from some dyno tuning on my UNICHIP on a loading Mustang dyno. It is upto 240 HP on the Mustang which consistantly prints about 20 HP less then a DynoJet dyno. I think I can get some more out of it, but I need to get some road time on it and then tune again.

No pings, no hesitation, lots of torque all through the ROM range even without boost. This thing is a true joy to drive!

Next, my new engine...

Gadget

www.GadgetOnline.com

ManyMods

I am just wondering whether this is possible. A lot of us who have GM 350ci motors switch out knock sensors. i.e.: The LT1 motor uses one design of knock sensor and the LT4 uses another that is, shall we say, less sensitive to sound. Using the the noisy LT4 HD timing chain would set off the LT1 knock sensor and cause spasmodic timing retard. Since we know that the knock sensor is a microphone, would it be possible to find one, perhaps from a V8, that would be interchangeable?

So it follows that maybe you are not getting knock, the timing is being retarded by some other erroneous sound that perhaps is coming from the SC. My performance/ acceleration also ramps up when the rpms get into the sweet spot of the motor/SC. BUT ... I don't hear any knock and right now I don't even have any pre-ignition. Of course, some people think that knock is the same as pre-ignition.

BTW, since I repaired the very slight vacuum leak that I had my mpg has gone up by almost 2-mpg = 17.2 at my last fill up. That's quite a difference for a vacuum leak that didn’t even set a trouble code.

FattyCBR

Mike-

I definitely notice a strong increase in acceleration at part throttle once I pass 4k rpms. My take on it is ecu programming being less than optimal for the sc below 4k. I have only noticed knock 1-2 times at lower rpms so I don't think it's knock related.

Peter-

This past weekend I recorded 21 mpg on one fill up and several right around 20 mpg (this was over 1100 miles of highway driving). I think my poor gas mileage this past winter (17 mpg hwy) was due to winter gas as other people have said.

rimpainter.com

I get between 16 and 16.8 MPG consistently (mixed driving). Yeah, I am a leadfoot at times, but c'mon. I dont understand how people can be in the 20's for gas mileage!

mhawker

I'm not sure if it's knock or not, but I have a feeling that engine's electronics will hear knock before I would.

The one thing I notice is that the engine is always faster on cooler days and more consistantly inconsistant on hotter ones. I also noticed when I cleaned my MAF and reset the computer, I don't think the truck has ever been that fast. Or, it was running so bad before I cleaned it, that it was just the change I noticed.

I need to carry a bag of ice with me for the intake manifold like the weekend drag racers!

Anyway, thanks all for the input. Gadget, your advice, as always, is gospel. Great to hear about your truck's results! My priorities have changed a bit recently (1st baby coming- the shock is still sinking in ) so I sold the fuel mods I had waiting for installation. Although I know it would be better with them, my truck has never had a pinging problem.

An interesting "pinging" side note: when I cleaned my MAF and reset the computer, after about 50 miles, I was actually getting pinging. Then, after the computer adjusted a bit, the pinging went away and I haven't heard it since.

Thanks again everyone.

Mike