New User---NEED HELP.

[alsho92]

okay heres the deal
i bought a 92 SHO 3 weeks ago, well out of the three weeks it has been running properly 1 week, 1st week it was missing on cylinder 3 and 5 so i changed out the plugs and plug wires....hooray, that was fun!, then it ran well for about a week, now yesterday i changed the oil, i ran gunk brand motor flush through it for five mins and then i drained it, i added 4.5 quarts of valvoline 5w-30 synthetic and .5 quarts of valvoline motor oil stabalizer, and put a motorcraft filter on, i get her all put back together add a bottle of valvoline fuel system cleaner, then i take her for a drive, well i get out of my neighborhood and i open her up....and...... NOTHING there is no power what so ever. its acting like its running on four cylinders again but the engine wont throw any codes,



question one.... does the yamaha motor have a cam timing technology like the honda vtec? is that why there is a change in engine tone at 4K RPM?


question two.... after my oil change when i open her up at 4K RPM there is a LARGE hiss but only at 4K and above, my guess is that it is a vacuum line somewhere but i have checked the lines and they all are good, i replaced quite a few of the lines, my exhaust butterflies work fine......im stumped...please help




:hopeless in huntsville:

 

[220ksho]

Sounds like an intake manifold leak. Double check that everything's re-connected and torqued down.

No, the SHO motor does not have variable valve timing, but it does have a variable length intake. That is what you hear at 4k.

Jeff

 

[jelloslug]

You either left the vacuum line off of the little black canister on the back of the manifold or one of the lines that go to the secondary actuators. At 4000 RPM there are 6 vacuum operated butterfly valves that open (1 for each cylinder). This open the short, high RPM tuned runners that brings the torque curve back up so it makes power in the high RPMs.

 

[alsho92]

just cleaned intake mani gasket and put some gasket sealer on it, i let it dry and then i took her for a spin.... still hissing, all my vacuums are good my butterflies open and close fine......im stumped

 

[jelloslug]

How does it idle? Did you remove the plug wires? Some manuals have the spark plug wire routing wrong. Also bad grounds will cause major headaches (it did on mine). Make sure all the engine and DIS ground are clean and secure.

 

[F-22 Raptor SHO]

DId you put the plug wires on right? you do know the chilton's manual is not correct as far as locations of the wires?

 

[alsho92]

Update:

well out of all FREAKIN things it was the mufflers......under the hood is solid i have the sucker apart 5 times this past week, so i know what goes where, so i knew everything was functioning properly, so i rev the car and plastic pieces shoot out my muffler, that got me thinking so i just cut the sorry a-holes off took her for a spin and voila! she runs like a deamon again!

 

[jelloslug]

Could you tell what (or where) the plastic piece was? There was another guy here that chased a similar problem for quiet a while and it was a chunk of broken cat stuck in the exaust pipe.

 

[alsho92]

Ya it was one of my cats, it had the platinum wire mesh stuck in there too....i just gutted the pipe, gonna order a catless y pipe, then put some mufflers or just one muffler back on, the car sounds like a possesed retarted kid right now...