Austin1991

Hi
I do not think I have ever posted. So if this wrong I apologies in advance
so I have my very first 928
it is a 1983 automatic. 4.7 L-jetronic.
I have invoices from the previous owner of the work they did at a Porsche dealer. Aug of 2013
the car had at the time 55719 miles
I bought it April 2020 with 61400 Miles
I am just now getting around to drive it for fun. when I test drove it I did not push the car because it was not my car at the time.
no I realize it is very much under power from a stand still.
Here is what they replace at the Porsche dealer.
Air flow Sensor 612.00
Fuel Filter 38.00
Thermo Valve 36.00
Fuel Pump Relay 128.00
Temp Switch 123.00
Timing Belt (the works) 1400.00
Spark Plugs 45.00
and they noted on the invoice that they clean the injectors
I am getting spark on all the plugs. and I am also getting voltage at all the injectors i tested them with light
with the the labor it all adds up to almost 7000.00
I am at a lost of what to look for to try to figure this out
any help would be grate
thanks in advance

Speedtoys

Low power, as compared to what?
The 928 is -not- a quick stoplight go-car.

It's a high speed GT car.

FredR

I would find out what the 0 to 60 time is for your model year and then go see if it can achieve such. You may just be expecting too much and getting somewhat underwhelmed as a consequence.

Given it is a 1983 model I assume it has the three speed box- correct? They are not noted for rapid initial acceleration- a friend of mine over here chucked the three speed box out and transplanted a 4 speed transaxle unit with the Porsche LSD unit fitted - that made him much happier. The 4 speed boxes are not exactly low ratio never mind the 3 speed.

That being said I have never studied the ratios actually in play.

Walt Simpson

Along with your 0-60 benchmark, what are your shift point RPMs and corresponding speeds from a dead stop while starting out in Drive? Also, have you experimented with manually shifting the Auto?

atb

Depends on where the O/P is located. The North American models got the 4 speed automatic, but we needed it. Our 4.7L (L-Jet/239 HP) was nothing compared to what everyone else got (4.7L CIS / 300 HP).

The O/P really needs to do a dyno run before assuming the car has issues. As stated, the 928 is not quarter miler.

Remember, your 928 is a 1983 model, that's 37 years old.

Here's some specs to put that in perspective comparing your 928 to a 1983 Toyota Camry (which it totally destroys and should), and a 2020 Toyota Camry.

1983 Porsche 928S (4.7L 8 cyl / 239 hp) 0-60 7.0s 1/4 Mile 15.4s
1983 Toyota Camry (2L 4 cyl / 92 hp) 0-60 12.4s 1/4 Mile 18.60s
2020 Toyota Camry L (2.5L 4 cyl / 206hp) 0-60 5.8s 1/4 Mile 14.1s

Short acceleration is not where your 928 shines.

Now put all three cars on the freeway. Accelerate to 135mph. (I don't think either of the Toyotas will get there, but let's give them to benefit of the doubt).

Then, hit the cruise control.

Your 928 will do that all day every day.

Petza914

Also, check your ignition timing to make sure it's right.

Austin1991

Thanks everyone for taking the time to read and answer my post.

My 0-60 is about 15 seconds. I have to put the accelerator all the way to the floor to get it going. It will pick up speed as it gets moving.
I do own two other mid-80's Porche 911's and this doesn't seem normal.
Transmission fluid is on the money.
The car starts right up from a cold start or at operating temperature, and holds 800 rpm while idling.
When the car reaches operating temperature, the rpms drop to 150-200.
The car will not stall or try to die. It idles smoothly, even at low rpms, when it's warm.
I checked the timing, and at 3000 rpms, the timing is right at 21*.
Now here is the crazy part...I cannot get the car to go over 95 mph with the gas pedal to the floor. But I also notice that I cannot get the rpms to go past 4200 as I'm driving or if the car is in Park. Manual shifting does not seem to make a difference. Can it be that even though a lot of work has been done, the spark plug cables could be my problem?

I am in the Kansas City area. If anyone on this forum knows of a good, independent Porche shop, I would appreciate it. Or I can keep trying any suggestions.

Thanks again for your time and help.

atb

Definitely something is wrong with 15 sec 0-60.

Its a long shot but are you sure your throttle body is opening fully?

Petza914

At 3,000 rpm and the vacuum lines disconnected from the distributor your timing should be somewhere between 25-31 degrees depending on engine type and model year, so you're quite a few degrees retarded and why the car is running like that with no power. Bring it up to 25 or 28 degrees with the lines disconnected and see if it runs much stronger with better throttle response.

19psi

Sounds like cam timing might be off a notch. I'd check to see if all the marks line up.

Austin1991

Hi
thanks for the info
I will move the timing to 25-28 degrees here is my question I only saw a 20 mark
so do I just take a guess. Or should I see a 30 mark
my eyes are not what they used to be

also I did take the intake manifold off

to spray some cleaner

I pushed on it by hand and the truth is
i remember it open, but I do not know by how much.
is there a way that I can check it with out removing the manifold?

and if I have to remove it
is it suppose to open all the way vertical
and if it doesn’t what should be my plan to adjust it

on an other note.
i am not a person that knows a lot about posting on line
but I always think how nice it is of people to help
and I will never understand why in places like YouTube people give thumbs down to a video
when someone was. Just trying to help


thanks. For helping

atb

Very Long thread on a similar issue:

https://rennlist.com/forums/showthre...&referrerid=93

In the end, the O2 and rotor replacement did the trick, although when the old ones were put back in the original condition do not replicate itself.

Regardless, the thread has a long and methodical checklist on chasing down the issue.

Speedtoys

"Regardless, the thread has a long and methodical checklist on chasing down the issue."

The issue hasn't even been identified yet. Just "its slow".

Heck, so many people thought RX8's were slow, they got their money back.

Properly driven..a stock RX8 will still lap most of the cars out on a track day in an advanced group.

My 928 is "slow" too, next to a miserably low geared American V8 next to it.

atb

Not entirely true, he stated the engine won't rev past 4200rpms.

The thread I posted had a similar symptom, except the O/P in that posting identified that it wasn't able to rev past a certain rpm because it started to miss, like hitting a rev limiter.

This sounds like timing or fueling to me. Originally I thought it could be an intake restriction, like the throttle body wasn't opening all the way, or maybe the AFM flapper was getting stuck, but typically even when intake air is restricted an engine will still rev, it will just take longer to get there.

You've got no argument from me on complaints that a 928 "feels slow" on acceleration My prior post shows how a 2020 Toyota Camry with a 2.4L 4 cylinder will give a GTS a run for its money on 0-60 and 1/4 mile specs.

Speedtoys

*refreshing browser does great things*

This thread was two lines of garbage text, and a few days of posts were missing.

Looked like when I try to print threads...*grr*

Thank you ATB.