sj408

iTrader: (6)

Hey guys, so i have a boosted na-t single turbo running a MAP based aristo ecu (thanks ali)

2 days ago i started to have slight misfire on takeoff and the whole time trying to boost.

last night i took it all apart, cleaned out spark plug holes, checked plugs and found 1 cracked boot.

Wrapped boot in electrical tape and reinstalled.

Now my idle shoots wayyyyy high when i start and doesn't come down....

Im assuming my manifold didn't seal??? Guess i never realized on MAP based a leak would cause high idle.

Do you guys use a gasket or rtv on the throttle body mount?? or both??

Previously had a metal gasket with grey rtv in there but wondering what's ideal.

HiPSI

iTrader: (2)

If there is a leak in the intake manifold it will cause the engine to idle high. Leaks pre throttle body in the intercooler will not cause high idle.

Sounds like something might of gotten caught in the intake manifold when you tightened everything up causing it to leak. I did this exact same thing with a vacuum hose that got stuck between the upper and lower runner. I would take the manifold apart, look at the gaskets and reinstall.

sj408

iTrader: (6)

Yeah gonna yank it apart, sadly nobody has a new throttle body mounting gasket local.

Anybody just using rtv there? mines been reused like 6-7 times and re rtv'ed.

t2d2

iTrader: (8)

I don't know about the SC300, but AutoZone and NAPA both carry the throttle body gasket for the SC400. I just did mine today. Felpro #60893. Is the 300's throttle body different?

I can't imagine why silicone wouldn't be sufficient, though. All it has to do is form an air seal.

HiPSI

iTrader: (2)

I would fear using to much RTV and it being sucked into the intake. I would order new OEM gaskets from Curt at elmhurst or locally and call it a day.

Ali SC3

iTrader: (10)

I have seen ones I take off where people use RTV on that gasket. I never like it that way, I always clean everything down and use a new gasket. a new gasket will seal without any rtv, there is not supposed to be RTV there at all, its just a quick fix for not getting a replacement gasket. if the old gasket has parts of the metal that is exposed as in the rubber coating has started to come off of it its toast, and you are pretty much relying on the rtv at that point.

did you ever manually adjust the idle. if you had a problem before with the coil causing a lower idle, and then raised it manually, fixing the coil could cause the idle to rise some. but if you made no adjustments its more than likely an air leak.

t2d2

iTrader: (8)

Shoot, if I had known that I would have thought better of reassembling the intake manifold with its gaskets starting to flake away the surface coat... I guess I'd better order a new set! I didn't use any RTV, instead hoping they would seal up as well as before once tightened down. Resulting whine from that area indicates I was wrong.

sj408

iTrader: (6)

Yeah it idled like stock nice and quiet, then all the sudden i had misfires and now i gave myself a leak hehe

The gasket for the throttle body is 100% metal so i assume it's old and toast. Can't find any gaskets local and they wanna order one for 75$..... and it looks quite a bit different the the one i think is in there.

Im gonna hit toyota and i guess if not them should i slather the gasket in rtv? or just use rtv? or clean and use just the metal?

Ali SC3

iTrader: (10)

normally a stock gasket is metal with a black coating which is a rubber viton coating, seals very well and on one of the sides it will have a raised edge of the same coating stuff all around the opening to seal and make up for imperfections.

now when the black stuff starts to flake off thats basically the coating that does the sealing. its still possible to tighten the gasket down still if there arent many imperfections or the flanges are perfectly straight still (not warped at all)... it may or may not leak really depends. I like to change it when I see the rubber flaking off. if not I reuse it and I have reused them many times with no problems.

generally in a pinch you should be able to use RTV on both sides of the metal gasket, its just a bit messy to clean up later. just make sure to not use a ton of it or else it may block some passages when you close it together, like the idle air from the IACV come out right at the flange and you wouldn't want to block that.

t2d2

iTrader: (8)

I may have actually gotten lucky. While doing all the manifold stuff, I had also removed the EGR valve and block-off plate (for the previously done EGR Delete) to run a coolant line straight through where it normally connects to the EGR. I didn't re-seal it when putting the block-off plate back on, so I re-did that this weekend with RTV on both sides of the metal gasket. I think that's where my vacuum leak was coming from, rather than the manifold gaskets, in which case I dogged a sizable bullet! The old silicon never seats quite right once disturbed... The whine seems to be gone, along with the grumbly low end responsiveness typical of vacuum leaks.

I'll still be ordering new manifold gaskets for next time I dig into that area, but as long as there's no previously used silicone gunk messing up the mating surfaces, it seems like slightly worn metal/rubber gaskets can still do the job. Also, as I recall, mine were just flaking at the outside edges, not along the raised part through the middle that does the bulk of the sealing. That's probably the surest indicator of whether a gasket is reusable. The EGR gaskets were bare metal and presumably never had the rubber coating -- I can't imagine they would have been that fully degraded on both sides to have no lingering traces of rubber.

Are the factory throttle body gaskets all the metal/rubber variety? The old one I scraped off in pieces was in such poor shape, I assumed it was the original one. But it was some sort of papery cardboard material. My IAC Valve gasket is also paper. Those seem like fairly unlikely "routine maintenance" items, unless someone really took care of the car somewhere along the line. And I suspect my water inlet filler gasket isn't original, being just a metal washer and not an o-ring. That would make a lot more sense to have replaced during a tune-up and/or coolant flush. They were also too lazy to put a new o-ring on the thermostat, instead sealing the housing with silicon ... leaked like crazy when I first put it back together before realizing how compressed the o-ring was.

Ali SC3

iTrader: (10)

most of the gaskets are the metal type with the rubber. there area few of the other kinds but the IAC should be the metal/rubber kind. someone didn't get the gasket kit. I have even used the eristic brand gasket set for the top end and its identical looking to the oem ones, and the whole kit is reasonable you can get it on ebay. on the sc400 I wouldn't use their headgasket, but the rest should be fine. for the 2jz they actually make a decent head gasket, but the jury is out on that one also.

t2d2

iTrader: (8)

The various gaskets are only a couple bucks each through Sewell with the CL discount. That's going to be tough for any kit to beat, I would think.

fried_rice

iTrader: (20)

New gaskets are cheap, they can be purchased locally from any of the national auto parts suppliers. If you have to use a used gasket, and fear it may leak, you can use Copper Spray-A-Gasket.

Ali SC3

iTrader: (10)

Oh and I have had that same leak at the egr thing before. it needs new high temp silicone every time more or less, leaks like crazy if you just try and use the old stuff and tighten it back down.

I did have an idea of cutting an extra egr gasket off of an extra 2jzge or 2jzgte lower runner intake gasket (egr gasket is connected to intake gasket normally) and using that to seal the other side of the block off plate instaed of RTV, but haven't gotten there yet on my main motor.

t2d2

iTrader: (8)

That's good to know, i.e. that it wasn't just mine acting that way. It would be nice if there were some way to coat the metal EGR gasket with a durable rubber surface so silicone wouldn't be necessary... On the other hand, how hard would it be to cut a chunk of rubber with the necessary heat resistance characteristics (?) to the same shape as the EGR gasket?