clue to rough idling problem?? (pics)

DaMoNe6969 · #1 01-06-2005, 04:37 PM

1990 Supra turbo a/t, about 17 in/hg vacuum at idle
I got my car parked for winter But I decided to start it up and let it run for awhile today to get fresh antifreeze and fuel line antifreeze through the system.. And once again, it started to miss and stumble.. (a problem thats been off and on for about 8 months..Ive posted the problem before to no luck)
After checking EVERYTHING.. again.. Just for the hell of it, I pushed on my intake manifold (see first pic), and wouldnt you know it, Idle smoothed Right out.. I didnt have to put a lot of pressure on it..

So I gently pulled back on the manifold, like this.. And the idle got much worse..

I checked some of the manifold mounting bolts.. (the ones I could see) and TB mounting bolts.. and they seemed to be tight.. Im hoping this sheds some light on my intermittant rough idling problem...

Anyone figure This one out??? Any ideas where to start?

projectsupramk3 · #2 01-06-2005, 05:11 PM

Now that is weird, I've never seen that one before. I guess the first thing I would do is go to Toyota and get all new gaskets for the intake. Remove the old ones and replace then reinstall. How much does it moving when you push/pull on it by the way?

DaMoNe6969 · #3 01-06-2005, 05:13 PM

I just went and checked again.. To get to idle to perfectly smooth out, Ive got to push pretty hard.. Enough to rock the engine about 1/2" to 3/4".. As soon as I let go, the idle starts to stumble, and the more I pull back, the worse it gets.. even the weight of my arm pulling will cause it to get worse

DaMoNe6969 · #4 01-06-2005, 05:14 PM

I checked my boost gauge, it reads about 17 in/hg vaccum at idle.. with about 13,000kms on the rebuild..

MKIII87Turbo · #5 01-06-2005, 06:34 PM

Its an intake leak. Retorque all the nut/bolts and see if that works. If not then you'll have to take the intake off and install a new gasket. The torque wrench is your friend for this. Don't use a ratchet to tighten it and think it will be good enough. The gasket has to have equal pressure across it to work properly.

projectsupramk3 · #6 01-07-2005, 12:20 AM

It's a paper gasket, it's not that big of a deal if you've used a ratchet before. Common sence is a must I assume, I have seen people strip the wussy alum threads trying to put there body weight into it. The car is close to 15 years old now anyway so replacing the gaskets is basic maintanence by now. Don't try and re-compress a 15 year old half discentregrated gasket.

DaMoNe6969 · #7 01-07-2005, 05:59 PM

Quote:

Originally Posted by projectsupramk3

The car is close to 15 years old now anyway so replacing the gaskets is basic maintanence by now. Don't try and re-compress a 15 year old half discentregrated gasket.

The engine was just rebuilt summer before last, so the gaskets shouldnt be that old.. But after seeing the way he (guy who rebuilt engine) stripped my exhaust manifold on with big bolts.. (not mani studs) Im kinda scared to look at the intake manifold..

well, either way, i'll change the gaskets out.. 13 ft.lbs for all the intake manifold studs correct??

projectsupramk3 · #8 01-07-2005, 09:50 PM

Yup you got it, 13ftlbs...
http://www.cygnusx1.net/supra/librar.../em/EM_53.html
If it's been rebuilt by the shady guy I'd be willing to be he stripped most of them out, and the few that were holding are now letting go. If there all stripped out it's helicoil time, it's not fun at all.

DaMoNe6969 · #9 01-13-2005, 02:38 AM

Well I had to heli-coil the exhaust mani. studs.. It was fairly easy, I used a 90degree angle drill and a chopped down drill bit, made drilling them easy w/o removing the head..(finding a heli-coil kit was a lot harder than installing it)

But it looks like the manifold side will be a little more complicated..
well, it'l give me somethin to do anyway.. Toyota called today and both gaskets are in ($35 for both + my 15% discount for being a SONIC member)

But anyways, thanx once again for your input project, and MKiii

BTW, quick question.. im gonna replace my plugs while its apart, and there seems to be a lot of controversy over wether or not to gap NGK iridium or platnium plugs.. They come pre-gapped, but not at the toyota recommended gap..
So whats your opinion?
and what plugs do you recommend?

HeyMyEngineLopes · #10 02-16-2005, 06:35 PM

Quote:

Originally Posted by DaMoNe6969

BTW, quick question.. im gonna replace my plugs while its apart, and there seems to be a lot of controversy over wether or not to gap NGK iridium or platnium plugs.. They come pre-gapped, but not at the toyota recommended gap..
So whats your opinion?
and what plugs do you recommend?

Greetings, I'm curious as to what plugs you chose; and the opinion regarding gapping. I'm considering the Iridium since my car is still apart as well.

Thanks.

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