EFIDynoTuning Forum

The regulator for the same year truck with a 4.9L straight six will have a ~55 psi regulator. Ford upped the fuel pressure on the straight sixes to combat vapor lock in the fuel rail due to it sitting directly above the exhaust manifolds.

Yeah, I found an old one from my 4.9 but it would have to be modified to mount up correctly. I'll just run the stock regulator for now.

Failed emissions at idle today. Allowed is 100PPM of HC and she read 239PPM. It is a bit rumpety at idle, so it has to be the cam profile causing it. At 2500RPM, 180PPM allowed and it read 15.

Idle speed is under 700rpm so thinking I need to kick it up a bit to pass. Timing jumps around 15-25 degrees at idle. Any other help? Some have mentioned leaning it out a bit but not sure how to force OL at idle.

2500 rpm 15ppm is good, so the cats may not be hot enough at idle. Also locking the timing at 10 is helpful. I would try a higher idle speed like you said (850-900ish) but they may have a max idle speed requirement...

Awesome, I set the idle to 850 and timing at 13*. at 10 it hunts a bit more I think because the minimum idle timing is 10. Should I lower the minimum or leave at 13?

I'll be having it tested again in the morning. I noted that the engine needs a bit more air and fuel at idle now. Is the flame burning into the exhaust port increasing temps?

Yes, the later burn sends more heat out the exhaust which gets the cats up to temp. 13 will prob still work.

lower the timing to reduce emissions, idling at 6 degrees is fine you just need to kick up the idle air thus the throttle stop would need some love to get the idle stable again

the lower the idle spark the more torque reserve you have

you can also allow more egr at idle too in order to re-burn some of that fuel in the exhaust if you can

Thanks, it passed just fine. Was still a bit rich at idle so guy let me set the hego bias to full lean and it cleaned right up.