Darius Juca

This is my daily driver,it's the most valuable thing I have in life besides my family and I have been trying to find the problem for a while now.
I am sorry to keep bothering people but I have no choice.

Thanks to John it has been running better but still have problems wich are:

1 rough idle on cold start up wich smoothes out when warm
2 when warm it used to idle down untill allmost stalling then come up to 1100rpm and back down to stalling and back up..not fast but back and forth at a steady rhythem.....seems to have gone away in last few days.

3 this problem is the most important....As it starts to get in the boost sometimes it stumbles before full 15 psi boost and I can see on my narrow band A/F gauge that it dropps to lean so I let off.
Sometimes though it goes in full boost and even pulls like crazy but the power seems to die off as it gets close to 5K rpm..actually it really only pulls till about 4.5 and seems to reach some kind of a governor but the A/F ratio says on stoich an does not drop and it's not a stumble like when the A/F Gauge dropps to lean...more like it's all it has.

Seems like when it's cold it does not act as much and gets in boost and power much eager...just does not pull all the way till 6 .....not even past 5.
When it warms up it starts to act as stated above more and more often as it gets hotter and sometimes it acts up eevn off boost.......
Every time though the A/F gauge dips in lean and sometimes just bonces back and forth between Lean and Stoich at a steady rhythem...rarely it stays on stoich and just drives well and if I slowly gas it it won't dip in the lean...
Funny thing is if it satrts to dip in lean and I ease off the gas it goes back to stoich and I can slowly build boost like that........wich makes mw wonder if it is vacuum leak related becouse if I am in 3'rd and it acts up/dips in lean at say 3k rpm when I let off the gas it goes really up on stoich allmost rich......I have checked and checked and checked again for any leaks and found none.
The ISV is the only thing I could not fully check without removing the manifold.
Could it be the FPR? I have an adjustable one...or a somehow a line to it.
I have recently replaced my fuel pump with a 928 gts one and fuel filter is only 1 year old.........What could prevent fuel from being delivered...the injectors are also with less than 5k miles on them.
I have also noticed that since I switched to FQS 3 adding more fuel it does better but still acts up.
One thing I also notices on the A/F gauge..if I am at idle sitting , when I turn on the lights it goes one bar or two lower in stoich towards lean....not in lean but say from high stoich to mid high to mid stoich......turn the lights off and it goes bach up.
Could it be electrical or vacuum related? please help it's tearing me apart. Thank you.

jimbo1111

Try removing the maf meter and cleaning the hot wire with a mild degreaser. Oil or dirt could effect the performance and drive you crazy.

Ian Carr

what are your fuel reg, pump, and dampener like? new old? If so maybe replacing the reg or pump might help the problem. Maybe your idler pulley is the reason the rpms go up and down so much. I'm not sure what the problem is... Maybe a vacuum leak as well

-Ian

fast951

How old is the fuel filter. Check the vacuum line going to the adjustable FPR. It appears that you are running out of fuel... Too bad you can't see the fuel pressure under load..
Lift the car and check the fuel lines underneath, mainly the line from tanlk to fuel rail..

edit: Send me a SMT log session.. from initial pull till it hesitates...

Darius Juca

I will do an do a log session and send it.
Jimbo what degreaseris good to use? going under car for a fuel line inspection.....I really appreciate your input..and I mean really.

AlexE

That is your best bet.

When I first installed the SMT6 I had some issues as well. The problem is I became fixated of fixing the problem with the SMT6. So I was dumping more fuel in ........and leaning it out at idle trying to fix a problem.

COMPLETELY ignoring basic 944 troubleshooting (bad move)

SO go back to the basics. RESET the fuel maps back to the way vitesse gave them to you. (I am assuming you have probably played around leaning and richening up different cells trying to make it idle properly)...........

SO go back to the way it was set up. I did this and realized I was masking my own problems. Intake leak, bad TPS......... etc

The car may run even worse when you reset your fuel maps back to 0 but the symptoms will be more consistent for us to help you troubleshoot.

I found by playing with the cells close to idle you can make your idle hunt as you describe.........

Good luck

P.S
IF this was a stock car.......
- a rough idle on cold start (up here in the frozen tundra) is normal
- hunting idle (adjust your tps or it could be faulty)
- you may have a vacuum leak

TurboTommy

Darius,
this must be very frustrating.
If it was me, it wouldv'e driven me absolutely crazy!
Why don't you just take it to a shop; a shop that's familiar with 951s and tolerates mods.

If it was a vacuum/pressure leak it would be running a tad rich under load.
It doesn't sound like, by your description, that your air/fuel ratio monitor is dithering.
You really should have a wideband.
It does sound like you're not getting enough fuel in every situation. Idle, for example always needs to be a little rich for smoothness.

jimbo1111

Simple green or even 409 will work. If that doesn't work you could try some carb cleaner. If the air oil separator hose is close to the hot wire. Oil residue could affect the readings. Simply clean it and give it a try.

Darius Juca

Turbo Tommy ..the only shop within 100 miles of here that knows Porsche's is IPC Motorsports but the specialize in NA 911 and 914's...and at 80 an hour just for them to scratch their heads...I went down there and I was more familiar with it than they...They did have some awesome 911 engines...

Alex youre right..I sent John Smt logfiles including a funny thing that happend in log/run 003 ...it actually pulled and pulled hard in log runs 1 and 2 untill slowing after 4k but the turbo did spool up a quick 14 psi.....man does it sound nice... and pulled hard...untill 4k.
But after a few pulls I took it out of gear to let it coast and it died on me!!! I also had to crank it a while to get it back started and when it wold start I had to gas it to keep the rpms past 1200 becouse it would die at idle.....after a few minutes of drving it went away.....my idle acts up sometimes and becomes unsteady dropping very low.
Could it be the fuel sendig unit? Or an NTC sensor not sure what the latter is or where.
Not sure and could be assumption but It may act up more when fuel is low in fueltank...
Waiting to hear from John on the results.