(Long post) Rough idle/low power...suggestions?

achilles100

New Member
Jun 23, 2010
8
0
0
Mesa, AZ
Folks,

I have a 91T with 89,000 original miles, no modifications. HG done at 40K by previous owner. I have not yet done a retorque in the 2 months I have owned it.

That being said, since I took possession of the car, it has had an extreme shake at idle. The entire car bounces around and the shifter goes crazy moving around. Tach does not bounce. It stays steady at about 800rpm or so. However, the car also is very sluggish off the line. To the point that it feels like you are accelerating in third, when you are in first. It's no rocket ship at speed either. I have to shift from 5th to 4th just to accelerate on the highway. I can maintain speed in 5th, but not speed up. Coolant gauge stays rock solid well below halfway, and no coolant loss. Oil pressure is fantastic. No smoke of any kind, ever, out the exhaust. Did not pass emissions when I bought it. But Champion iridiums and NGK wires cleared that up and it passed with flying colors. FYI, the described problems existed before and after the plugs/wires. Interestingly, the idle is not so bad when cold, but as soon as the vehicle reaches operating temperature, the roller coaster ride begins. Quite comical really. Also, the turbo seems to struggle to build boost, and does so slowly, only reaching maybe 4 or 5psi as indicated on the gauge. (see exhaust leak below)

OK, what have I done?
-Champion iridiums (I couldn't find any other brand on quick notice and needed to pass emissions and wanted iridiums, so we'll see how they last)
-NGK wires (firing order is correct, I was very careful)
-Timing checked using TSRM instructions and is perfect
-All vacuum hoses checked for leaks and proper connections, and intake monifold/throttle body/EGR gaskets checked - no leaks found after careful analysis. Accordian hose is intact.
- One bottle of Techron fuel cleaner ran through the tank.
- Verified with a smoke test that the exhuast manifold gasket is leaking at the #6 cylinder area, and possibly the turbo to manifold gasket as well. Fairly sizable leak...enough to hear clearly.
- No codes active or stored

I'm not a rookie to Supras, so throw me what you have and I'll go check it out this weekend and see what I can find. I have done quite a bit of searching on these forums and racking my brain, and I am mostly looking for a diagnostic path to follow so I don't waste alot of time or money running in circles. I know I haven't checked everything I really should before posting, but I'm trying to knock this out quickly so I was hoping you all could fire off some thoughts for me.

Thanks in advance for any suggestions you have!

Aaron
89T
91T