Hello guys.

Im new to the isF forum here.

Just bought an 08 blue isF with 93k miles. From my lurking here, I think this may have been viperverns car. (feel free to comment on this as well)

My problem happens something like this:

On most drives the car seems to only give 75% power.
Then, almost miraculously, it will run like it should, seemingly giving 100% and pulling hard.
Then back to 75%...almost like a limp mode . BUT, No CEL, no serious problems (no misfiring, wierd noises etc.) its just not quite as fast as is should be (or sometimes is)

It has run like this since day one.

I have since cleaned the MAF with electronics cleaner and installed a k&n typhoon.

Nothing has changed.

Your help would be GREATLY appreciated.
Im going crazy trying to figure it out.

Thanks Fellow ISF owners!!

 

Have you checked for codes?

 

Your not mistaking the opening of the secondary with this transition are you?

 

+1 Even if you don't see a check engine light, You should still take it to an autoparts store and have them check for stored codes. This would be a great way to start tackling your problem.
After that I'd pull the 2 fuses and reset the computer

 

First thing I would do is reset the ECU and see if that makes any difference. It is a 2008 with 93k on it, that engine isn't exactly "fresh" anymore. If that doesnt do anything you'll have to start delving deeper...

Do you know anyone with an OBDII scanner you can hook up to your car...?

 

This might be the reason if you're not aware of the secondary intake opening.

You should scan for codes as well.

 

i would check if there is any mods installed and if there is any codes.

 

Sounds like a bad oil control valve for the exhaust cams. A friend with a GS460 had a similar issue and switched oil from Mobil 1 to the OEM Toyota oil and his issues went away. Don't ask me why, but I've known him for years and have no reason to doubt what he said.

The other thing you might consider - yes, checking for DTC history is a great idea - is taking an oil sample and sending it to Blackstone to be sure nothing bad is going on internally.

Also, there are a couple of little "oil filters" in the valve covers (I only know this because I was researching what parts to have on hand when I do the valve lash inspection) that go to the oil control valves. If for some reason they were clogged, I could see the problems you are having happening.

 

Thanks for the response! I didnt expect so many helpful people.

Im going to consider all suggestions, starting with an oil change. Ill have the codes read as well.

Update coming soon.

Thanks again guys!
what a great resource you all are.

 

I think you should take out your intake and revert to stock, that way you can diagnose the problem without having an additional variable in place, not that I'm saying the intake has anything to do with it.

 

Yeah, if it was me I would slap the stock airbox back on and see if anything changes. I don't think this is the problem but it could be and it's easy enough to do to help rule it out.

Also, I'm a newer ISF owner too so is there a chance you're just mis-interpretting the powerband? Coming from a string of turbo'd cars I had to get used to this V8. If you do a pull from, say, 2k rpm it'll feel slower/less powerful than putting your foot down when you're at 4k+ rpm.

Again, this prob isn't the issue but is something to consider or keep an eye on the next time things are good vs bad.