S70 engine revs to 4K and beyond at start up?

NYSmoosehoove · Post by **NYSmoosehoove** » 20 Apr 2019, 16:07

Long time lurker here—
One year owner of previous s70 t5 98 and recently procured my second.
After making numerous fixes to the new model I have but one problem;
Engine turns over at start but very hard,
Then— as if my foot was on the peddle, the engine revs up past 5k in a matter of seconds.
I recently made several repairs to the new car,
I bypassed the heater core, using the 5/8ths U-hose method,
I replaced the PCV system entirely, as well as the radiator, thermostat and housing, coolant resivoir, maf, and the lower radiator hose as well as the upper two coolant hoses and the cars air filters.
I changed the throttle body gasket, and the boost pressure sensor behind the air filter.
Additionally I changed the spark plug leads to oem and added a new spark plug cap.
From my research I’ve deduced that perhaps my issue is a knock to my TPS sensor? Or perhaps an issue with my vacuum lines?
I started the car once in neutral and it seemed to curtail the excessive and unstoppable revving for a few seconds more than when starting from park.
I’ve also noticed that there’s a bit of a gasoline smell in the engine bay when the key is in second position. (Fuel injectors were changed to white tops from my old model, but they look all in place and the correct depth in each port)
I changed the relays in the main fuse box, and thought perhaps there could be an issue with the fuel pump relay, or again vacuum lines in some capacity—
I have the computers from my old model and have considered swapping them as well.

Any ideas?
Thank you all-
Z

Sommerfeldt · Post by **Sommerfeldt** » 20 Apr 2019, 23:58

It sounds most of all like your throttle body is stuck open. Have you checked? Also look and see if you disturbed something when you changed that gasket, and make sure it’s even and sealing.

Any codes?

- S

Post by **RickHaleParker** » 21 Apr 2019, 15:13

(Fuel injectors were changed to white tops from my old model

What was in there before?

Orange - 315cc/min
White - 350cc/min

NYSmoosehoove · Post by **NYSmoosehoove** » 21 Apr 2019, 15:23

Sommerfeldt wrote: ↑20 Apr 2019, 23:58 It sounds most of all like your throttle body is stuck open. Have you checked? Also look and see if you disturbed something when you changed that gasket, and make sure it’s even and sealing.

Any codes?

- S

Unfortunately, it’s been raining in NY where I am the last two days so I haven’t had a clear opportunity to take it down the the throttle body again, I’m thinking tomorrow that will be my first course of action.
On the note of codes, I can’t run the car enough to read them. There’s no CEL at start up, just normal service light, and srs which goes off after one second. The ABS control module is done for and I plan to swap it, so that light is on as well, but probably unrelated from what I understand, as the car ran fine despite its issues when I test drove it before buying.

NYSmoosehoove · Post by **NYSmoosehoove** » 21 Apr 2019, 15:25

RickHaleParker wrote: ↑21 Apr 2019, 15:13
(Fuel injectors were changed to white tops from my old model
What was in there before?

Orange - 315cc/min
White - 350cc/min

Also whites, just not as clean and the o-rings seemed to be getting up there in age, they were most likely the originals.

Post by **RickHaleParker** » 21 Apr 2019, 15:39

I think you got something dumping fuel in the intake or cylinders. When you start it up, the excess burns off.
I would dope the fuel with tracer dye and track down the fuel leak you smell in the engine bay.
You sure them injectors are not leaking.

Sommerfeldt · Post by **Sommerfeldt** » 21 Apr 2019, 16:53

You shouldn’t need to run the car to read codes, though the ECU might not have time to set any.

You could have something dumping fuel in the cylinders, as RHP says, but you’d still need lots of air to rev up and keep revving. Check the TB and move on to injectors, since those are the things that have changed.

And see if there are codes.

- S

Post by **RickHaleParker** » 21 Apr 2019, 17:49

Sommerfeldt wrote: ↑21 Apr 2019, 16:53 You could have something dumping fuel in the cylinders, as RHP says, but you’d still need lots of air to rev up and keep revving.

Fuel dump + Intake Air leaks. For example: Leaking Intake Gasket, fuel runs down from Fuel Rail passes the intake gasket, accumulates in the intake ports. Start it up and you got excess fuel and air.

First figure out where all the extra fuel is coming from. He is smelling fuel .....

Sommerfeldt · Post by **Sommerfeldt** » 22 Apr 2019, 01:02

RickHaleParker wrote: ↑21 Apr 2019, 17:49 Fuel dump + Intake Air leaks. For example: Leaking Intake Gasket, fuel runs down from Fuel Rail passes the intake gasket, accumulates in the intake ports. Start it up and you got excess fuel and air.

First figure out where all the extra fuel is coming from. He is smelling fuel .....

And what happens if you put your foot on the gas pedal before you start the car...?

Better to check the easy things first, then see if more complicated stuff is going on.

- S

NYSmoosehoove · Post by **NYSmoosehoove** » 24 Apr 2019, 16:31

Hey folks,
Problem solved—
And by that I mean the engine bay caught fire... looked like one of the vaccuum hoses that runs off the intake manifold had broken, and additionally the gas smell was most likely liquid build up where the injectors sit.
Started her up after a little work on the throttle body and WOOSH.
That’s that story.

Next up— a 2000 SE hopefully.