5.3 C10 Swap Idle Issue

[layinrocker65]

If I’m reading the thread right, your using the stock regulator in the stock early year LS truck rails. The regulator for flex fuel is different than the standard(non flex fuel) ones per online info stating the flex fuel runs at a lower pressure. So changing the regulator or rails to a regular(non flex fuel) setup will test if my theory is right. It will(or should) put the fuel pressure to the standard LS 58psi and if the truck runs normal, it’s an issue with the tune.

[shortboxin]

Originally Posted by layinrocker65

If I’m reading the thread right, your using the stock regulator in the stock early year LS truck rails. The regulator for flex fuel is different than the standard(non flex fuel) ones per online info stating the flex fuel runs at a lower pressure. So changing the regulator or rails to a regular(non flex fuel) setup will test if my theory is right. It will(or should) put the fuel pressure to the standard LS 58psi and if the truck runs normal, it’s an issue with the tune.

Per Bad Luck Garage on youtube, the return style systems are only around 42-50PSI at idle. Granted, the returnless non-flex runs higher than the flex systems, but at idle should still max out around 50PSI. The only way I could test your theory would be to have a returnless system altogether. Assuming that the in tank pump can drive to 58PSI, it would require a swap to a returnless fuel rail and a return filter inline.

Thanks for the idea, but I think there's too much required to test out. I'm thinking of having someone else reprogram a second computer to the flex specs and see how it runs.

Another question for anyone interested... Could there be a problem with the computer not getting any feedback about the type of fuel in the system thus causing an issue like this?