Porsche 951 stumble after let go of throttle
#1
Porsche 951 stumble after let go of throttle
I am having the following issue and can't figure out what is wrong.
It all started when i was driving and have been able to stay at 15psi boost till red line. Yesterday i heard a pop and lost power. I could not get any boost and ran very rought. I then parked it and went shopping. When i came back after 20-30 min it would not startup. After about 15 of trying to start i found that the boot came off the throttle body to the intercooler section. I was able to get it home by babying it home. Then after checking all hoses and connectirs car tried to start but would not stay running. I was running 1 level colder plugs (ngk bpr7es). I cleaned them then car start then die shortly after. I put back the old (ngk bpr6es) and now car runs but has a hard time driving and staying up. I have noticed that it happens when i let go the throttle. Like when switching gears. If i keep revs up while changing gears then car doesn't stumble or try to die. But if i'm at throttle (3-4k) then let go then try to give it gas again the car acts like the plugs are fouling. Misfires, pops, stumbles, no power. Then i press clutch then rev engine till it clears up. Any help would greatly be apreciated.
I tested ohms of dme temp sensor. I had to also bypass dme relay and car only works this way. I have resolder everything icould on the dme and klr. I have the dme cover off and have noticed that the thick metal sections (ignition) get extremely hot. Is this normal. It burns my fingers if i touch it. I heard it is because of running the relay bypassed.
Here is a video of issue and also how vac goes crazy during issue.
http://youtu.be/u5SOXiV8PhU
It all started when i was driving and have been able to stay at 15psi boost till red line. Yesterday i heard a pop and lost power. I could not get any boost and ran very rought. I then parked it and went shopping. When i came back after 20-30 min it would not startup. After about 15 of trying to start i found that the boot came off the throttle body to the intercooler section. I was able to get it home by babying it home. Then after checking all hoses and connectirs car tried to start but would not stay running. I was running 1 level colder plugs (ngk bpr7es). I cleaned them then car start then die shortly after. I put back the old (ngk bpr6es) and now car runs but has a hard time driving and staying up. I have noticed that it happens when i let go the throttle. Like when switching gears. If i keep revs up while changing gears then car doesn't stumble or try to die. But if i'm at throttle (3-4k) then let go then try to give it gas again the car acts like the plugs are fouling. Misfires, pops, stumbles, no power. Then i press clutch then rev engine till it clears up. Any help would greatly be apreciated.
I tested ohms of dme temp sensor. I had to also bypass dme relay and car only works this way. I have resolder everything icould on the dme and klr. I have the dme cover off and have noticed that the thick metal sections (ignition) get extremely hot. Is this normal. It burns my fingers if i touch it. I heard it is because of running the relay bypassed.
Here is a video of issue and also how vac goes crazy during issue.
http://youtu.be/u5SOXiV8PhU
#2
Also, the old plugs were completely black and wet with fuel.
I tried testing coil but i diconnected the green wire the plug test cable to the green side of coil the pluged a spark plug to the end of coil. Then when i tried to tap the lead wire from the ground side of coil to ground of battery but just burnt cable. But car now runs with same issue and i can run full boost if i baby it.
I tried testing coil but i diconnected the green wire the plug test cable to the green side of coil the pluged a spark plug to the end of coil. Then when i tried to tap the lead wire from the ground side of coil to ground of battery but just burnt cable. But car now runs with same issue and i can run full boost if i baby it.
#4
I have a vac/boost gause and when it idles good around 1,100rpms the vac is around 18. I did notice that when it starts to stall the vac goes from 12 to 5 and jumping. While driving i have to keep the rpms above 3,000 or else it stumbles and dies but not all the time. Can it be the idle valve or o2?
#5
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do you have a maf?
#6
I replaced the old afm box with Guru Racing Chips on the klr and dme, i replaced the FPR to the 3bar one, i installed the AFMLink controller and connected the temp sensor to the old afm cable on port 1 and 4, also replaced the afm air box with a new metal jboot and air filter. It was working fine for 2 weeks until this boost poped the silicone boot that goes on the thorttle to intercooler pipe.
I tested the coil, dme temp sensor, then tps (i did the ohms testing from idle to WOT and ohms show correctly. If i keep car above 3000 rpms i can run normal and can even boost to about 11psi and runs strong but as soon as i let go the throttle and try to accelerate again it stumbles and tryies to die.
Can this be a vac leak? My vac/boost gause shows from 20-18 vac when idle...thats is if its running fine because if i let go of throttle and let it idle some times it dies.
I tested the coil, dme temp sensor, then tps (i did the ohms testing from idle to WOT and ohms show correctly. If i keep car above 3000 rpms i can run normal and can even boost to about 11psi and runs strong but as soon as i let go the throttle and try to accelerate again it stumbles and tryies to die.
Can this be a vac leak? My vac/boost gause shows from 20-18 vac when idle...thats is if its running fine because if i let go of throttle and let it idle some times it dies.
#7
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#8
Here is what the spark plugs looked like while the car would not start. These are 1 level colder plugs as is recomemnded when running 15+psi boost, car would try to turn on but would die right away and could not get it to run. I switched them out for normal ngk bpr6es and now car runs but has the issues listed above.
#10
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#11
under the hood only mods are:
Vitesse turbo upgrade but that involved an cone engine air filter as well as 83 lb injectors and a new chip and I believe MAP and MAF as well
Battery disconnect switch
Hose temperature gauge
It's set to idle at 800 but hen I'm idling at a standstill, the idle will drop dramatically, usually I can "recover" it by giving gas but when I'm shifting down from 2nd to neutral off the highway that's when the idle drop occurs.
Never when I'm giving gas only when I'm in neutral...still sound like vacuum lines/hoses?
Vitesse turbo upgrade but that involved an cone engine air filter as well as 83 lb injectors and a new chip and I believe MAP and MAF as well
Battery disconnect switch
Hose temperature gauge
It's set to idle at 800 but hen I'm idling at a standstill, the idle will drop dramatically, usually I can "recover" it by giving gas but when I'm shifting down from 2nd to neutral off the highway that's when the idle drop occurs.
Never when I'm giving gas only when I'm in neutral...still sound like vacuum lines/hoses?
#13
Make sure TPS is adjusted properly. Electronically verify idle-switch. Use Clark's Garage procedure to disable idle-valve and and manually set idle to 900rpms. Idle should now not drop below that.
What is idle-vacuum and MAF-voltage at idle with warmed up engine?
What is idle-vacuum and MAF-voltage at idle with warmed up engine?
#14
I did a smoke test (feeding fog into the intake while blocking off the air filter) and there was a small amount of smoke emanating from the throttle body (for which i ordered the paragon seal kit) but TONS of smoke coming from the air oil separator.
First of all I didn't know the AOS was even part of the vacuum system but that aside I just replaced it with a nused one that I checked thoroughly for cracks and I sealed the hoses on there really tight so I'm flabbergasted as to that being the major source of the leak
any thoughts?
First of all I didn't know the AOS was even part of the vacuum system but that aside I just replaced it with a nused one that I checked thoroughly for cracks and I sealed the hoses on there really tight so I'm flabbergasted as to that being the major source of the leak
any thoughts?
#15
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First of all I didn't know the AOS was even part of the vacuum system but that aside I just replaced it with a nused one that I checked thoroughly for cracks and I sealed the hoses on there really tight so I'm flabbergasted as to that being the major source of the leak
any thoughts?
any thoughts?