Hi,
I run a shop in my hometown and although I do own a 2003 Cobra and through the years we have built a few we have never experienced something like this before. Also we haven't done many in the last years, but we been working on this particular vehicle for quite some time now. Decided to ask first, because maybe someone has experienced something similar and would point me in the right direction instead of doing a lot of troubleshooting and testing.
The car is an 2003 with rebuilt engine with stock compression 2.8H KB, small Comp Cams, headers, exhaust and was previously running dual Ford GT pumps with dual FPDM. Let me give you some background, he rebuilt the engine because around 5 years ago he lost it due to a bad CCRM. It went bad, there were no fans, overheated and then started many problems that prompted a full rebuilt. It overheated a few times until the previous shop found the issue with the CCRM. When replaced the fans worked fine, but it was already toasted. Fixed the engine and since that time he has been having some electrical problems, like eating alternators easily, stock, modded, rebuilt ones, PA, etc. All of them die...
Fast forward to me working on the car... he came first for a tune. We did the tune and although I noticed some funky stuff with the voltage and the fuel pressure and AFR we were able to give it back and it ran fine for a while. Then another alternator die, he changed it but the car was inconsistent. Like from run to run it was loosing 4-6 tenths and 4-6 mph for no particular reason. Just like that from run to run it was gaining and loosing. Told him to bring it back. First few runs on the dyno and it was fine, yes it had the usual returnless issues when trying to push it hard like unstable fuel pressure and it looked like the alternator was dying again as it was loosing voltage and when loosing voltage the fuel pressure went like crazy and the same for the AFR.
Decided to do a full return fuel system and installed new alternator and thought that everything was going to be fine now... wrong! Even with the fuel pressure steady and in place and voltage from the alternator and the battery in check, the car is doing the same crap as before with the AFR all over the place... even without making any changes on the tune the AFR is different from run to run on my dyno wideband and on the one in the vehicle as well. It can go really rich, then somewhat lean, the oscillate all over the place, plus the datalog shows a voltage loss, even when at the alternator and the battery it stays over 13.5 on the whole run and the fuel pressure is good and steady. Also the gauges go like crazy, the datalog quits at around 3700 rpms and there the last view you can see the voltage dropping like to 10.8-11.3 volts and the AFR goes all over the place. It can go to lean or rich when this happens.
Any idea of why the voltage at the battery and alternator is fine but low at the ECU? I know this is why the gauges go all over the place and datalog quits. I tried a run with no datalogger running and the gauges don't go like crazy but the afr goes all over the place after 3700 suggesting that it probably is still droppjng at the ECU level.
Anyone has dealt with something similar or has any pointers on where to check?
Thanks guys!
I run a shop in my hometown and although I do own a 2003 Cobra and through the years we have built a few we have never experienced something like this before. Also we haven't done many in the last years, but we been working on this particular vehicle for quite some time now. Decided to ask first, because maybe someone has experienced something similar and would point me in the right direction instead of doing a lot of troubleshooting and testing.
The car is an 2003 with rebuilt engine with stock compression 2.8H KB, small Comp Cams, headers, exhaust and was previously running dual Ford GT pumps with dual FPDM. Let me give you some background, he rebuilt the engine because around 5 years ago he lost it due to a bad CCRM. It went bad, there were no fans, overheated and then started many problems that prompted a full rebuilt. It overheated a few times until the previous shop found the issue with the CCRM. When replaced the fans worked fine, but it was already toasted. Fixed the engine and since that time he has been having some electrical problems, like eating alternators easily, stock, modded, rebuilt ones, PA, etc. All of them die...
Fast forward to me working on the car... he came first for a tune. We did the tune and although I noticed some funky stuff with the voltage and the fuel pressure and AFR we were able to give it back and it ran fine for a while. Then another alternator die, he changed it but the car was inconsistent. Like from run to run it was loosing 4-6 tenths and 4-6 mph for no particular reason. Just like that from run to run it was gaining and loosing. Told him to bring it back. First few runs on the dyno and it was fine, yes it had the usual returnless issues when trying to push it hard like unstable fuel pressure and it looked like the alternator was dying again as it was loosing voltage and when loosing voltage the fuel pressure went like crazy and the same for the AFR.
Decided to do a full return fuel system and installed new alternator and thought that everything was going to be fine now... wrong! Even with the fuel pressure steady and in place and voltage from the alternator and the battery in check, the car is doing the same crap as before with the AFR all over the place... even without making any changes on the tune the AFR is different from run to run on my dyno wideband and on the one in the vehicle as well. It can go really rich, then somewhat lean, the oscillate all over the place, plus the datalog shows a voltage loss, even when at the alternator and the battery it stays over 13.5 on the whole run and the fuel pressure is good and steady. Also the gauges go like crazy, the datalog quits at around 3700 rpms and there the last view you can see the voltage dropping like to 10.8-11.3 volts and the AFR goes all over the place. It can go to lean or rich when this happens.
Any idea of why the voltage at the battery and alternator is fine but low at the ECU? I know this is why the gauges go all over the place and datalog quits. I tried a run with no datalogger running and the gauges don't go like crazy but the afr goes all over the place after 3700 suggesting that it probably is still droppjng at the ECU level.
Anyone has dealt with something similar or has any pointers on where to check?
Thanks guys!