89 911 turbo Loosing power at 100mph

[TDH888]

Hi guys ,

After replacing both fuel pumps , fuel pump relay , overboost switch & the yellow relay , i experienced another problem . The car can accelerate fast and freely revs until redline , but it seems its loosing power when it hits 100 MPH at 5th gear the car feels its loosing boost or fuel . It looses speed w/o shutting down . I try to regain speed by down shifting to second gear and it accelerate's hard from gears 2nd to 4th gear . But when it reaches 100 mph at 5th gear the problem arises again .

Thanks in advance,

Tdh888

[T77911S]

squeeze the rubber elbow from the AFM to the down pipe. if it is soft it is collapsing and restricting air flow. they are not that expensive.
it may be that yours is just starting to go.
when they are really bad it cuts out in lower gears once on boost.

[patina]

Does it exhibit the same issues in 4th gear at say, 80mph?

[TDH888]

Hi guys ,

Thank you very much for your reply . Patina it does not happen at 4th gear at 80MPH . T77911S if its not much of trouble pls post a picture of the specific rubber elbow from the down pipe . The car does not loose boost at lower gear it accelerates like a scalded cat .
Anymore suggestions/ comments from other fellow members .

Thanks in advance.

Tdh888

[Jeff NJ]

Do you have an AFR gauge or boost gauge that works well? (many stock ones are iffy)

if so, what do those numbers show?

[Ken911]

Sounds like you need to measure the fuel flow. There are steps in the manual for that. You could either have a bad pump, clogged filter, or clogged fuel tank strainer. The other problem with loosing fuel at peak load could be detonation and all the subsequent issues with that. If it's a boost leak check the recirc valve that plugs into the same elbow meantioned above. It's plasic and somewhat unreliable. most people replace them with a billet version.

[TDH888]

Hi ,

Sorry I dont have an AFR gauge or another boost gauge Jeff , will try to look for one. Ken911 i have a new fuel filter , both fuel pumps are brandnew as well . Hi Ken if its not that much trouble can you post a picture of the recirc valve that plugs in to the elbow .
By the way my car is bone stock .

Thanks in advance,

Tdh888

[Ken911]

I dont have a pic of that your car is a 964 turbo which is set up differently than mine. If you look at the rubber elbow that goes from the air flow meter. It has a little black plastic valve with a vacuum line attached. I believe thats the one.

[patina]

Originally Posted by Ken911

I dont have a pic of that your car is a 964 turbo which is set up differently than mine. If you look at the rubber elbow that goes from the air flow meter. It has a little black plastic valve with a vacuum line attached. I believe thats the one.

89 is not a 964.

[Ken911]

Originally Posted by patina

89 is not a 964.

Oh ok I thought that's when they changed to the different recirc valve.

[Ken911]

Originally Posted by patina

89 is not a 964.

Oh ok I thought that's when they changed to the different recirc valve.

[TDH888]

Originally Posted by Ken911

Oh ok I thought that's when they changed to the different recirc valve.

Hi Ken , Patina

Patina , Ken is right . Thanks for the picture Ken , may I ask were the recirculating valve is in the picture ?

Thanks in advance ,

Tdh888

[Ken911]

ok sorry for the sideways picture for some reason when they get posted from my phone they come out that way. on a 930 the recirc valve is that large magnesium block with the blue rag in it. Whick shouldnt be a problem since your car is not a 964. the elbow in question is in the lower left of the picture coning from the AFM to the recirc valve.

[somoney311]

The red circle is the elbow they are talking about the white circle is the recirculating valve.

[MBruns]

Have you looked at the intake manifold to intake port nuts, they will loosen up.
Mike Bruns

[T77911S]

the one in red above.
just make sure its not soft before you start down other roads.

just thinking with the longer pull in 5th that it may have enough time to collapse. lower gears on boost time is shorter and it may not be soft enough to collapse.

fuel flow would be next on my list. flow more so than pressure. needs to be checked at the return side or out of the FD.
1500cc/ 30 sec I do believe

[TDH888]

Thank you guys for the replies and comments , will just update you to what the mechanic found out .

Best regard ,

Luigi

[TDH888]

Originally Posted by T77911S

the one in red above.
just make sure its not soft before you start down other roads.

just thinking with the longer pull in 5th that it may have enough time to collapse. lower gears on boost time is shorter and it may not be soft enough to collapse.

fuel flow would be next on my list. flow more so than pressure. needs to be checked at the return side or out of the FD.
1500cc/ 30 sec I do believe

Hi guys ,

How can you say if the elbow is hard or soft . Is it normal if one can pinch it or if it’s new you can’t pinch it .
I checked the elbow of my car and you can pinch it specially at the angle of the bend .

Thanks in advance ,

Luigi

[Ken911]

It should be pretty stiff

[T77911S]

Mine is a few years old and I can squeeze it but I can't squeeze it closed with one hand.