total frustration, rough running
05-13-2011, 06:52 PM
#1
total frustration, rough running
Cayenne, 6 cylinder, 2004, 136 kms (90K miles) runs intermittently. This has been ongoing for 3 weeks. Typically on highway, sometimes after 2+ hours vehicle runs rough and accelerator unresponsive. Then lunges ahead and goes for a while until reoccurance. 3 weeks ago dealer replaced fuel pumps ($1700), same symptoms next day. The other night after 4+ hours of driving started again and eventually quit. After restarting would go 100 yards and quit again. Had to limp home, next day would not idle, today runs fine at dealer???, no reoccuring codes. Been to dealer 3 times with no luck. Anyone have similar experience?
05-13-2011, 07:07 PM
#2
Instructor
I know you said the dealer changed the pumps but the next time it happens try pulling the relay for the drivers side pump and see if it will continue to run.
Did they replace the fuel filters? How about the check valve? Here are the instructions on how to test the fuel pressure...( i stole this from deilenberger on the site)
You need a $25 kit from Harbor Freight (or the same sort of kit from other vendors for 2-5x the price), and it takes about 5 minutes. You'll need one flat-blade screwdriver, a small needle nose for removing some fuses and the fuel gauge kit.
Steps involved:
- Depressurize the system by pulling fuses 13 & 14 in the fusebox under the hood (do NOT drop these down into the fusebox.. PITA to retrieve..) then cranking the engine over (if it starts let it die..)
- Connect gauge
- Reinstall fuses
- Start truck - check gauge reading. Should be 4 Bar.
- Unplug fuse #13 - truck should keep running, pressure shouldn't change
- Plug fuse #13 back in
- Unplug fuse #14 - truck may stall and pressure may drop to zero.
- Restart truck - (with fuse 14 still out) - truck should restart and pressure should be 4 Bar.
Both pumps were now checked. The fuse/shutdown may be the opposite depending on the fuel level in your fuel tank (they automatically shut down the pump in the half of the tank with lower fuel level.) As long as it will run (it may need to be restarted) with only one pump at a time connected (via the fuse) - your pumps are both working.
You can also check bleed-down pressure - this is how much the system pressure drops after turning the ignition off. The system is supposed to stay at 3-Bar for at least 10 minutes. Mine fails this miserably, meaning I probably have a bad checkvalve. Hence my question to Michael.. If it's only $40, it's not worth me dicking around with warranty and the dealer.
Did they replace the fuel filters? How about the check valve? Here are the instructions on how to test the fuel pressure...( i stole this from deilenberger on the site)
You need a $25 kit from Harbor Freight (or the same sort of kit from other vendors for 2-5x the price), and it takes about 5 minutes. You'll need one flat-blade screwdriver, a small needle nose for removing some fuses and the fuel gauge kit.
Steps involved:
- Depressurize the system by pulling fuses 13 & 14 in the fusebox under the hood (do NOT drop these down into the fusebox.. PITA to retrieve..) then cranking the engine over (if it starts let it die..)
- Connect gauge
- Reinstall fuses
- Start truck - check gauge reading. Should be 4 Bar.
- Unplug fuse #13 - truck should keep running, pressure shouldn't change
- Plug fuse #13 back in
- Unplug fuse #14 - truck may stall and pressure may drop to zero.
- Restart truck - (with fuse 14 still out) - truck should restart and pressure should be 4 Bar.
Both pumps were now checked. The fuse/shutdown may be the opposite depending on the fuel level in your fuel tank (they automatically shut down the pump in the half of the tank with lower fuel level.) As long as it will run (it may need to be restarted) with only one pump at a time connected (via the fuse) - your pumps are both working.
You can also check bleed-down pressure - this is how much the system pressure drops after turning the ignition off. The system is supposed to stay at 3-Bar for at least 10 minutes. Mine fails this miserably, meaning I probably have a bad checkvalve. Hence my question to Michael.. If it's only $40, it's not worth me dicking around with warranty and the dealer.
05-13-2011, 10:19 PM
#3
Burning Brakes
sounds like bad gas, but fuel filter then fuel pump should resolve. Dont run anything but premium octane....
Spark plugs are next.......Ive had my pig since 06, and have 110k miles. No issues as of yet in regards to what you described but please keep updates rolling.
Spark plugs are next.......Ive had my pig since 06, and have 110k miles. No issues as of yet in regards to what you described but please keep updates rolling.
05-14-2011, 07:29 AM
#4
Since the problem began I've had spark plugs, air cleaner and as mentioned earlier fuel pumps changed. Records do not indicate fuel filture or check valve change. I will follow up with dealer. I would estimate I've put through at least 5 tanks of fuel, all high octane.
One other point that may not be significant is the problem resurfaces at about the 1/4 tank level???
One other point that may not be significant is the problem resurfaces at about the 1/4 tank level???
05-14-2011, 08:01 AM
#5
Instructor
Sounds like the Check Valve. I would replace that. The fuel filters are supposed to be lifetime but with your problems I would replace them....I would also throw in a bottle of techron on the next fill up.
Trending Topics
05-24-2011, 06:26 PM
#9
Picked up Cayenne last Thursday evening and since that time have put on about 1200 kms or 750 miles without reoccurance and running fine. Had a look at catalytic converters and they were definitely plugged. Diagnosis was completed as mechanic took vehicle for extensive drive while hooked up to computer. Post catalytic converters temperatures were found to be well in excess of normal. Thus the answer.
Therefore I can only conclude the original diagnosis of fuel pumps failure and replacement ($1700) was unnecessary and a rush to the wrong diagnosis???
What if any options do I have at this point going back to this dealer remembering after the fuel pumps were replaced it didn't last 1 day I was stranded again???
Has anyone been in a similar situation?
Thanks in advance.
Therefore I can only conclude the original diagnosis of fuel pumps failure and replacement ($1700) was unnecessary and a rush to the wrong diagnosis???
What if any options do I have at this point going back to this dealer remembering after the fuel pumps were replaced it didn't last 1 day I was stranded again???
Has anyone been in a similar situation?
Thanks in advance.
