Built SR20 blacktop holding itself at 5k RPM

[J_raw]

Drove car for a 2 days after getting it out of the garage on a nice day for first time since winter. 3rd day of driving while heading to the car started idling at 2.2-2600 rpm, hunting. Limped it home and checked TPS voltage which was good. Checked maf by unplugging and car wanted to die so figured that was good. After a while of testing it went away and I took it for a spin in the neighborhood. This is when things went awful, car now revs to 5k regardless of throttle input. Ordered a new IACV gasket which is what I’ll pull and clean and test next, ordered an CTS aswell. Not finding any vacuum leaks. Any other suggestions? Am I clearly missing something?Mod list here

* S13 SR20DET Black top
* Block machined by D&D Engines
* 86.5mm CP Pistons
* Manley rods
* King main and rod bearings
* Tomei oil pan
* ARP headstuds
* Tomei headgasket
* Brian Crower 272 cams
* New Springs and retainers
* New Rocker arm stoppers
* New timing chain
* New chain tensioner
* Tomei 740cc injectors
* Walboro fuel pump
* Greedy style intake manifold
* ISR FMIC kit
* Flex-a-life dual fans
* Tomei exhaust manifold
* Garrett GTX2867r turbo

Nismotronic tuned.

Car has run great for some 8k+ miles now. Drove it all last season.

[jedi03]

check voltage of tps and also try adjusting the iacv and see if idle changes...additionally check for leaking injectors and vacuum leaks...looks like good fun build to me!

[brndck]

do not start your engine.

pull your charge piping and look at the throttle plate. its super common for the pin to crack and the screw(s) to fall out. the screw can then get sucked in to the intake manifold and fuck shit up on its way out.

[slider2828]

@brndck. I have heard horror stories of that little screw grenading engines.... Do you normally tack that in place?

[brndck]

On mine we removed one screw and welded the hole, then removed the other screw and welded up the hole. You could prob remove both screws at the same time but we did it this way just to be cautious and make sure the Plate didn’t move.

[J_raw]

check voltage of tps and also try adjusting the iacv and see if idle changes...additionally check for leaking injectors and vacuum leaks...looks like good fun build to me!

Thanks, will check for injector leaks. And yes 400whp on a conservative tune, fun when it’s running!

[J_raw]

do not start your engine.

pull your charge piping and look at the throttle plate. its super common for the pin to crack and the screw(s) to fall out. the screw can then get sucked in to the intake manifold and fuck shit up on its way out.

Well this is outright terrifying. Hopefully I see two screws when I look. Thank you!

[brndck]

Yeah it happened to me at a drift event. I was off throttle and all the sudden revs went to redline. Shut the car off. Came to a stop. Started it up and revs went straight to redline again. Shut it off and pushed into the pits. Checked everything, throttle cable and linkage we’re fine, no blown hoses. Pulled the coupler off the throttle body and the screw was just sitting there, in front of the plate. SO SO fortunate it didn’t get sucked in. One of my friends had the same thing happen a few months after, except he sucked the screw in and it wrecked cyl 4 on a freshly built engine.

[ultimateirving]

Yeah it happened to me at a drift event. I was off throttle and all the sudden revs went to redline. Shut the car off. Came to a stop. Started it up and revs went straight to redline again. Shut it off and pushed into the pits. Checked everything, throttle cable and linkage we’re fine, no blown hoses. Pulled the coupler off the throttle body and the screw was just sitting there, in front of the plate. SO SO fortunate it didn’t get sucked in. One of my friends had the same thing happen a few months after, except he sucked the screw in and it wrecked cyl 4 on a freshly built engine.


Happened on my first SR. I was at the drag strip and it started making the worst sound after a run. Basically crushed the bolt into little pieces between my piston and cylinder head.

[J_raw]

Update: Throttle plate screws are tight and have not come loose and no obstruction inside throttle body. Removed and clean IACV waiting on gasket to arrive from enjuku. Will have a buddy help test for leaking injectors this weekend. Always open to suggestions until then.

[brndck]

Update: Throttle plate screws are tight and have not come loose and no obstruction inside throttle body. Removed and clean IACV waiting on gasket to arrive from enjuku. Will have a buddy help test for leaking injectors this weekend. Always open to suggestions until then.

Rad. Now THOROUGHLY inspect the rod that the screws go into. Front and back. That is the part that breaks. On the SR, there isn’t really a stop for the gas pedal, and many throttle cables are not properly adjusted, so the throttle body reaches its max, but the gas pedal still has room to go, so all that stress pushes against that one little rod, then eventually the rod breaks, allowing the screw to fall out.

It’s not so much an issue of the screw just backing out on its own.

I guess I should have done a better job explaining earlier.

[brndck]

The rod breaks where the red line is drawn. That allows the screw to come loose.
https://uploads.tapatalk-cdn.com/20190315/ed6be8a2a185d3574d62e2bae854f57f.jpg

[J_raw]

Rad. Now THOROUGHLY inspect the rod that the screws go into. Front and back. That is the part that breaks. On the SR, there isn’t really a stop for the gas pedal, and many throttle cables are not properly adjusted, so the throttle body reaches its max, but the gas pedal still has room to go, so all that stress pushes against that one little rod, then eventually the rod breaks, allowing the screw to fall out.

It’s not so much an issue of the screw just backing out on its own.

I guess I should have done a better job explaining earlier.


Will do, thank you for the tips and picture!

[jr_ss]

Are you certain you have no intake leaks? Take some carb cleaner and spray around the injectors/manifold halves/TB, basically anywhere excessive air can get drawn in.

[singlecamslam]

The rod breaks where the red line is drawn. That allows the screw to come loose.
https://uploads.tapatalk-cdn.com/20190315/ed6be8a2a185d3574d62e2bae854f57f.jpg

So to avoid possible damage when it break, you tack the screw to that rod from the direction of your picture?

[brndck]

So to avoid possible damage when it break, you tack the screw to that rod from the direction of your picture?

We removed one of the screws and welded the hole so the rod is now welded directly to the plate, then removed the other screw and did the same thing.

[slider2828]

We removed one of the screws and welded the hole so the rod is now welded directly to the plate, then removed the other screw and did the same thing.

I guess that would be safest lol but I only have a mig