Marlon

...any updates? Enquiring minds want to know...

CarreraX

Well, the fuel flow wasnt what it needed to be so they are putting in a new fuel pump today and I hope to know more later. In a nutshell, it has new plugs, wires, dist caps and rotors and fuel filter. I really dont mind replacing these parts since they are basically maintenance related (although Im pissed since I was told that all maint was up to date!). That didnt fix the problem. I checked the chip and it was stock. We changed out the MAF with one from a perfect running 993 and that also wasnt it. Steve @ Rennsport (Awesome guy!!! I encourage everyone to use his services as much as possible) suggested that the fuel pump(s) may not be providing sufficient fuel so that was checked and a new pump was ordered. That is where Im at right now. I am a very mechanical guy and I have built several SCCA racecars (World Challenge and IT) but I just dont have the time to mess with this as of right now. I wish that I had the time to work on it but I just want to get it done and drive it. Anyway, I will know more later today........Thanks!

Marlon

...cool! Good luck!!!

Marlon

So just to understand again: If you are were in first gear or any gear, the car would not rev past 5400 or so???

mar

CarreraX

Yea but not exactly 5400, it would vary depending on the load. for instance, it would rev to RL at idle. It wasnt bad gas either. I ran 2 tanks out driving it back from New Jersey. It actually ran good without a big load...

MarkD

Clutch slips, RPMS are easy.
Forward progress, not so much.

On a fuel injected engine, fuel pressure and volume are really important.
I am pretty sure that the rev limiter on these cars simply cuts off fuel flow (thought I would guess this is done at the injector). If he "hits a wall" at 5400 rpms, fuel pump is a good guess IMHO.

CarreraX

Well, the best way that I know of to see if a clutch is slipping is to have the car in 5th or 6th on the HWY and stand on the gas. If it is slipping then it will do it now and you will see the rpm increase but not the speed. Anyway, I can feel that the the clutch is a bit high and that was negotiated in the price. Im already planning on doing a clutch/LWF soon so this may just "Force" me to spend the money Uh, gee honey, I have to spend the money on the clutch right now......It also needs a new suspension so that the clutch works right ....He..he...

Marlon

Dang I hope it's a simple problem - usually is! These DME systems have a throttle position indicator that converts throttle plate movement to electric current for the 'brain' to tell the injectors how much coal to shovel on. Maybe the little gizmo is out of wack...

CarreraX

Update, fuel pump didnt fix it. I swapped out the ECU for one from a friends 95 993 and that wasnt it, I swapped the main ECU relay and that wasnt it. Im thinking maybe clogged Cat? Any ideas? My friend did take his cat off for a cat bypass pipe so I will get that swapped out in the next few days. I am also going to revisit the distributors to make sure that they are still in time.........

997Heaven

could the Tachometer be bad ...giving incorrect readings? seen it a lot in airplanes.bad guages...just a thought may be u could R+R it with another car

CarreraX

nope, car is DEF down on power! My 540 wagon pulls harder than the 993.....

Steve Weiner-Rennsport Systems

Hi Marlon:

All 993's still have cable-actuated throttles; no electronics here,...

That technology (drive-by-wire throttles) didn't get deployed by Porsche until 2001.

CarreraX

Has anyone heard of a plugged cat on a 993? If my car has a plugged cat Im certain that it will just get removed without getting a 100 cell one unless there is a HP advantage to do that. And also, I cant thank Steve from Rennsport enough. I have been in touch with him and have called him several times on this car problem. Im sure that I will have it fixed soon enough. I just need to have my car fun in a 540 wagon.......how depressing is that........

Cactus

Keep us updated on this problem and good luck.

Coleman

This is an interesting thread.. I've been pondering what this could be for some time.. you are getting closer at each stage of eliminating parts.. swapping out the ECU proved that the problem lies after that in the chain of fuel delivery.. here would be my next items to check..

Coils- one or both of these could be failing.. not producing enough spark, or not firing half the plugs?

The 5400 rpm issue is an interesting telltale- it's close to peak power so clogged cat is a decent guess as well, it seems as if under load, the system cant cope with getting to peak. If 1 or 2 cylinders were not operating, could this prevent the engine from reaching peak under load? When there is no load, (ie rev in neutral) the system has enough power to hit redline. When it's under load, the load+tax prevents it from hitting redline, as a portion of the energy is being taxed by this unknown problem.

1 or 2 cylinders are not firing. This could be enough tax on the engine to prevent it to reach redline under load. Maybe check injectors. If poor fuel was used in the past, even though you flushed the system, some of the injectors could be just clogged/ messed up-

just some ramblings..

Coleman-