Join Date Dec 2017 Posts 8 2008 GT500 breaking up past 5000rpm and voltage spikes.

[Pro60modman]

Tuning an 08 GT500 that was a bit of a basket case. Injectors clogged, bad fuel pumps and bad PPRV. Put ID1050X injectors in then saw on the log it maxxing out FPDC and dropping fuel pressure to 10psi by 4800rpm . Deleted the PPRV, maxxed out the FP voltage in areas where pressure dropped and it still dropped to 30psi. Put Deatschwerks 300M pumps in and it now maintains 55psi of fuel pressure at WOT. However it is still breaking up at 5000rpm. Installed new Blue Streak coils from O'Reilly's and TR6IX then BR7EF plugs gapped down to .026" and it still breaks up. Looking at the logs the system voltage is jumping between 12 and 15. Could this be an alternator issue or is the voltage jumping a result of the misfiring? The owner did put an 8 rib alternator on it recently which is incorrect but this issue only shows up at WOT and once it starts misfiring.

 

[SCGallo2]

With bad fuel pumps and clogged injectors, was the fuel filter replaced? I would say the alternator is suspect; I had a newly remanufactured OEM alternator that quit charging at WOT. Also, in 2008 there was a change in alternator type according to build date, so you need to verify the correct type is installed. PA Performance was able to provide me with the correct replacement, and I ordered it with an underdrive pulley to keep alternator rpms down and it has been working well. Also, OEM COPs are the most reliable on our engines.

https://www.svtperformance.com/threads/how-well-is-your-alternator-performing.1159061/#post-15898038