To much acceleration

[MaRu]

Hello,

a friend has a 1983 930 Turbo. The car is modified, but we donīt know what exactly was done. For sure the 1 bar spring. Here is the problem. When you hit the throttle the car runs like hell. But when you go off throttle it continues to accelerate for about 1 to 2 seconds. And this is really dangerous. Do you have any idea what can cause this? I was thinking that maybe the throttle body does not close directly? I have no experiences with Turbos, so any inport is welcome!!!

Many thanks

Malte

[flightlead404]

Could it just be a sticky throttle linkage, or the return spring missing, leading to the throttle hanging open?

That's easy to check. Pop off the intercooler, and operate the pedal which observing the throttle valve. Put your foot down, remove it. Does the pedal come up quickly? Does the throttle valve close quickly?

[quattrorunner]

Yes agree, My throttle linkage was hanging up and needed adjustment.

[T77911S]

you need to figure out if the throttle is sticking.
you can do that with the engine off.
have someone floor it and you watch the throttle plate,
you can also get under the car and watch the linkage under there,

if that is not it it may be doing what mine did when it was not running right,
when I let off the gas it seemed to run better.
not sure what my actual fix was but I was running very rich at one time, I have had air leaks and some timing advance issues. (that should narrow it down to about everything).

[quattrorunner]

My issues were at the beginning of the tunnel by the peddle cluster

[MaRu]

It is not the linkage itself. But I havenīt checked the spring on the buffle next to the throttle body. Will do so next week. Thanks!

Another idea: Could it be because of the 1 bar spring which might not operate free. There is a little rattle noise comming from this are while the car runs on idle speed.

Sorry for my bad english!!

[quattrorunner]

It must be something to do with the throttle unless there is a valve type leak. Wasegate leak wouldn't be it though I don't believe.
Perhaps there is something limiting the throttle body from returning correctly?

[Tippy]

Originally Posted by MaRu

It is not the linkage itself. But I havenīt checked the spring on the buffle next to the throttle body. Will do so next week. Thanks!

Another idea: Could it be because of the 1 bar spring which might not operate free. There is a little rattle noise comming from this are while the car runs on idle speed.

Sorry for my bad english!!

Your English is better than, I bet, 75% of Americans!

No, wastegate spring should have no effect.

Mine started sticking behind the pedal. My 87 Carrera 3.2 has a bell crank assembly (not sure if 930's are the same?). It was worn and the linkage would snag on the sheetmetal.

[MaRu]

Thank you very much!!!

I will check everything in detail next week and let you know if I found something.

[Rawknees'Turbo]

Another area to check is where the solid (rod) portion of the throttle linkage passes through a small opening in the engine tin, between engine and firewall (rear seat backs) - rod can hang (rub) on that opening (sounds kinky, I know!!!).

Also, the throttle pivot portion (the bell crank) attached to the transmission needs to be checked for smooth operation.

[911tracker85]

My issues were at the beginning of the tunnel by the peddle cluster

I had a similar issue with my 85 911 NA some time ago. my suspicion is back before I was doing my own work, when the guy at the shop took the car for the normal "test drive to verify work", IE joy ride, he had stomped on the gas pedal and bent the linkage/bracket.

there is a little stop on the back side of the pedal, but it appeared from excess pressure twisting the linkage it allowed the pedal to go too far down. they never got to touch my car again.....

it would briefly stick and if you pushed the clutch it would pop loose. bent the linkage/bracket back in place and all has been well.

even in a NA, pretty scary when the gas stays open.

[Speedfab]

I was just interested in how to achieve too much acceleration... I've been trying all my life and have only managed "almost enough" to this point.

[Mr9146]

Check your distributor

[MaRu]

Good advice! Will do so next week. Many thanks!

[smurfbus]

I had this two years ago and it broke the top end, aargh. I was at the drag strip and after the run when I pressed the clutch revs shoot up and broke a rocker and made 5 pistons contact the valves.

My pedal assembly had a bent or loose arm where the accel pedal converts to the front rear rod. It allowded the arm to bend behind the tunnel and get stuck in there.

Luckily that top end rebuild also revealed worn guides that where supposedly changed 8tmiles ago.

Fix it before next run...

[smurfbus]

Part 26

[quattrorunner]

That was my problem as well.

[Robbbyg]

Originally Posted by MaRu

Hello,

a friend has a 1983 930 Turbo. The car is modified, but we donīt know what exactly was done. For sure the 1 bar spring. Here is the problem. When you hit the throttle the car runs like hell. But when you go off throttle it continues to accelerate for about 1 to 2 seconds. And this is really dangerous. Do you have any idea what can cause this? I was thinking that maybe the throttle body does not close directly? I have no experiences with Turbos, so any inport is welcome!!!

Many thanks

Malte

Hey Malte,
I did this to mine to solve the same problem, (insert a second spring)
A quick return is especially needed if you have a lightened flywheel its a 2 minute job once you get to it.
Cheers

[MaRu]

I checked everything and the ignition distibutor is working fine. The acceleration linkeage is in good working shape as well and all springs are working. I just opened the wastegate and found a pressurespring with an overall lenght of 285mm . Isnīt this a little to much? Does anybody knowas what the standart factory spring lenght is? I have a pressure of up to 1.2 an the gauge (in case it is working good). Could it be the problem, that due to the high turbo pressure the throttle plate canīt close fast enough?

[T77911S]

pressure will not effect throttle plate closing.

are you saying your gauge will read 1.2 bar or your boost is hitting 1.2bar.


I will go back to what my car was doing.
it was creating more power when I would lift from flooring it making it accelerate faster than when I floored it.
you probably have the mixture or maybe the timing wrong and when you floor it, the power is down but when you lift the power is actually higher giving you the acceleration when lifting.
I would look at the mixture first. could be wrong due to air leak, WUR, or what ever.