Thread: "Christine" free-revs to redline at start-up

I am perplexed by this one. At start up, a (mostly) stock 94 SE-R free-revs, freewheels, deadmans, etc.- up to the point I turn off ignition (7000+rpm), with foot nowhere near throttle pedal.

Details you need to know to help.
1. Lowport running rough.
1a. Battery removed
2. Air intake, MAF, throttlebody, upper intake removed to get at injectors
3. 2 injectors replaced with factory o-rings
4. Re-assembled and doublechecked.
5. Free-revs up to "Holy Crap", and I shut it down. Sometimes it stumbles a few times at @3000rpm, but continues up and a shut down.
6. Disabled cruise control by removing cable from T-body.
7. Throttle body LOCKED closed.
Still runs free up to the point I shut it off.

Any Ideas? I thought of a couple. If an injector is stuck open, where is the air coming from with the T-body shut? If there is an air leak, where is the fuel coming from? As an "oldschool idiot" as someone recently put it, I am familiar with free-revving in a carb engine, but with FI? It doesn't make any sense. Thanks for any and all help with troubleshooting, Chuck

pressurize the intake manifold with about 10 psi and listen for leaks. You can make a pressure tester pretty cheap with a PVC cap and a tire valve stem.

I've had that happen before...turned out to be the brake booster vac line had come loose from the intake manifold. Like posted above, sounds like a vac leak.

Same thing happened to me, the o-ring gasket on the MAF came loose and jammed open the throttle plate, weird.

Definitely a vacuum leak. Go back over your installation and make sure everything is plugged in on the intake.

Thanks for all the replies. I'll go back and check all vac connections again, as I agree and believe it was something I had my booger hooks into that is causing the problem. But, where is the fuel coming from? If the TPS is not signaling for more fuel, where is it coming from? Is it the start-up loop that is causing the dump of extra fuel? That's still my quandary. I know I will find haters, but I'm an old 5.0 guy and I like to keep the education process going for myself. Never stop learning is my motto........ Thanks, Chuck

leaking injector?

When you have no vacuum signal to the FPRit will raise fuel pressure and support some extra air. Now if it's revving up and bouncing off the rev limiter, then something else is going on as at that point the MAF would have to see the increase in airflow to command more fuel. If it's just revving very high with no load, then I would still put my money on a bog vacuum leak.

<----- Also a 5.0 guy

I still think it's something with the throttle plate, but you said it's locked close, which is bizarre. Here's what I'd do, open up the intake so you can view the throttle plate, then have a friend start up the car for a second and see what it does.

Thanks to all who responded. After dinner and a few beers, I once again set out to hunt for the elusive vacuum leak. I removed the intake tract again and cleaned the MAF, unhooked the accel cable and tried to start it...... Running smoothly at 1500.... Weird. Hooked up throttle and cruise cable and started her up for a run around the block. It farted and started running up to redline again.... Hmmmmmm.
I checked the throttle cable and blade, sure enough there was a tiny amount of tension on the TB. I think and beer think. I had had a four pound plumbers wrench hanging on the throttle mechanism, calling it LOCKED....(not) It was held open by the sheath. When I played with the throttle cable and sheath, the sheath popped back into the firewall by 3/8 of an inch. All of a sudden there was slack in the cable assy. I adjusted the stops on the throttle assy and it works fine. Runs like it should now. So, even a four pound wrench could not overcome the tension of the cable and sheath itself.
Bad on me for not being 100% sure and unhooking EVERYTHING. Just goes to show, it's always something.
Once again, thanks to all for their ideas. IT'S ALIVE!!!!!
Thanks, Chuck