Idle Problem or Fuel Problem?
09-09-11, 10:41 AM
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Idle Problem or Fuel Problem?
Hey guys this is my first post but it may be a tough one to answer.
To start with I have a 1988 S4 Turbo II with 26k original miles.
The emissions were removed by the previous owner. He also said he did some other mods including:
Fuel pump rewire mod (I had to go in and solder the crimp on terminals he left)
Throttlebody mod
I may be forgetting some..
The Engine was rebuilt 3-5 years ago and has been running for about 11k miles since then.
When it was rebuilt by Marval Speed in Dallas TX they installed 3mm apex seals and streetported the motor.
It has an Rtek7 1.7 ECU
Aeromotive FPR
AEM wideband
To list a few..
The car ran great up until I found the first puddle of gas under the car.
After chasing the leak for a week or so all it was a crappy hose clamp the previous owner used on the rubber fuel line that connects the FPR to the Pulsation Dampener (PD).
I replaced the cheap hose clamp and while I was in there I decided to install a banjo bolt to replace the PD, with the Aeromotive FPR installed I thought it wouldn’t be an issue.
The car ran great with no leaks. After fixing the leak and replacing the PD I was boosting on the highway on the way back to my garage to make sure it wouldn’t leak again.
I did one last pull before exiting the highway and everything was fine.
When I pushed the clutch in the and pulled up to the stoplight the car died.
It started fine and the Air Fuel Ratio (AFR) was fine above 1000-1500 RPM, but below 1k rpm the car leans out and dies…
So far I have replaced the fuel filter and installed a brand new walbro 255 pump and I am still having the problem.
The car runs and drives fine above 1500RPM.
The AFR read normal and 10.0 flat in boost.
So at stop lights I have to hold the gas down to keep it from leaning out.
I removed my fuel injectors and made a DIY kit to clean them outside the car. (12dc laptop power adapter with a push button switch and an injector clip solder together HAHA)
They seemed fine and now it idles really low at about 500-700 RPM barley sputtering AFR reading 16-17, if I hold the gas at 1k rpm it will run a decent AFR.
The whole time of having this issue I am noticing a Strange Sputter sound that you can hear when it leans.
If I hold the gas at a steady RPM every few seconds or so you here a sputter that almost sounds like a plug missing but when it does that the AFR leans by 0.5-2.0.
Say if I were to hold the gas at 3k rpm the AFR would read something like 12-13 and when I would here the sputter the RPM drops a tiny bit and it may lean out to 13.0-14.5 AFR for just that hair of a second
I deiced to reinstall the PD and now the problem is worse help!
Before it wouldn’t lean at higher rpm but now just sitting in the driveway at 3k rpm it runs around 13 AFR.
If I give it more gas it sputters more and leans to 14-15 AFR.
Now holding the gas at 1k rpm is a 17 AFR before it was closer to 13.
Today I am going to remove the dampener again and see what that does..
I also plan on testing my Air Flow Meter using a Multi Meter and the factory service manual.
To start with I have a 1988 S4 Turbo II with 26k original miles.
The emissions were removed by the previous owner. He also said he did some other mods including:
Fuel pump rewire mod (I had to go in and solder the crimp on terminals he left)
Throttlebody mod
I may be forgetting some..
The Engine was rebuilt 3-5 years ago and has been running for about 11k miles since then.
When it was rebuilt by Marval Speed in Dallas TX they installed 3mm apex seals and streetported the motor.
It has an Rtek7 1.7 ECU
Aeromotive FPR
AEM wideband
To list a few..
The car ran great up until I found the first puddle of gas under the car.
After chasing the leak for a week or so all it was a crappy hose clamp the previous owner used on the rubber fuel line that connects the FPR to the Pulsation Dampener (PD).
I replaced the cheap hose clamp and while I was in there I decided to install a banjo bolt to replace the PD, with the Aeromotive FPR installed I thought it wouldn’t be an issue.
The car ran great with no leaks. After fixing the leak and replacing the PD I was boosting on the highway on the way back to my garage to make sure it wouldn’t leak again.
I did one last pull before exiting the highway and everything was fine.
When I pushed the clutch in the and pulled up to the stoplight the car died.
It started fine and the Air Fuel Ratio (AFR) was fine above 1000-1500 RPM, but below 1k rpm the car leans out and dies…
So far I have replaced the fuel filter and installed a brand new walbro 255 pump and I am still having the problem.
The car runs and drives fine above 1500RPM.
The AFR read normal and 10.0 flat in boost.
So at stop lights I have to hold the gas down to keep it from leaning out.
I removed my fuel injectors and made a DIY kit to clean them outside the car. (12dc laptop power adapter with a push button switch and an injector clip solder together HAHA)
They seemed fine and now it idles really low at about 500-700 RPM barley sputtering AFR reading 16-17, if I hold the gas at 1k rpm it will run a decent AFR.
The whole time of having this issue I am noticing a Strange Sputter sound that you can hear when it leans.
If I hold the gas at a steady RPM every few seconds or so you here a sputter that almost sounds like a plug missing but when it does that the AFR leans by 0.5-2.0.
Say if I were to hold the gas at 3k rpm the AFR would read something like 12-13 and when I would here the sputter the RPM drops a tiny bit and it may lean out to 13.0-14.5 AFR for just that hair of a second
I deiced to reinstall the PD and now the problem is worse help!
Before it wouldn’t lean at higher rpm but now just sitting in the driveway at 3k rpm it runs around 13 AFR.
If I give it more gas it sputters more and leans to 14-15 AFR.
Now holding the gas at 1k rpm is a 17 AFR before it was closer to 13.
Today I am going to remove the dampener again and see what that does..
I also plan on testing my Air Flow Meter using a Multi Meter and the factory service manual.
09-09-11, 03:41 PM
#2
Compression test the engine before going any further. If you've lost some compression on a rotor, idle can suffer, but you may or may not notice any real reduction in power. Above 1k RPM, the ECU advances timing, so compression related idle problems can be hidden above that point.
You'll need a standard compression tester with the schraeder valve removed from the end. Hold the bleeder button, and watch the needle bounce as the engine cranks. Hopefully you'll see 3 even bounces per rotor of about 90+ psi. Holding the throttle plates open, having the engine warm and the battery fully charged will ensure accurate results.
You'll need a standard compression tester with the schraeder valve removed from the end. Hold the bleeder button, and watch the needle bounce as the engine cranks. Hopefully you'll see 3 even bounces per rotor of about 90+ psi. Holding the throttle plates open, having the engine warm and the battery fully charged will ensure accurate results.
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