So, I have been working on getting my 393W conversion up and running (see THIS THREAD ). I have it all installed and finally got to start it for the last time last weekend.
Well, it started immediately (the good news), but it has a severely rough idle (the bad). I have put in a base tune using the Moates tuner; mainly adjusting for the displacement, MAF and injectors. It wouldn't be so concerning if it were just and idle issue, but it also has an intermittent loss in RPM if I bring it above idle. It does seem to smooth out above idle, but there is almost a shudder, and loss in rpm. It quickly recovers and does it again without a real steady pattern. It seems to affect both banks evenly, and at the same time.
So, in attempting to diagnose this issue, I have verified a few things:
One other odd thing I noticed - I happened to pull my upper intake off very shortly after shutting the motor off and noticed little puffs of smoke wafting from the lower intake - is this normal? Makes me think that the vales may not be seated right, but I am not sure. I don't hear any noise in the valvetrain. If it were the springs; I would only expect to see issues at higher rpms, right?
Starting to grasp for straws right now...
Any and all ideas are welcome.
Thanks,
Eric
Well, it started immediately (the good news), but it has a severely rough idle (the bad). I have put in a base tune using the Moates tuner; mainly adjusting for the displacement, MAF and injectors. It wouldn't be so concerning if it were just and idle issue, but it also has an intermittent loss in RPM if I bring it above idle. It does seem to smooth out above idle, but there is almost a shudder, and loss in rpm. It quickly recovers and does it again without a real steady pattern. It seems to affect both banks evenly, and at the same time.
So, in attempting to diagnose this issue, I have verified a few things:
- fuel pressure is good while running
- compression test when cold had all cylinders between 160 and 165psi
- no vacuum leaks (only have the FPR and PCV attached, so that's easy to check) - also tried leaking a little mapp gas around the intake
- vacuum guage shows the needle moving from about 15-18" of vacuum corresponding to the erratic idle, but also has a high frequency, low amplitude bounce overlaid on it (any thoughts?)
- no KOEO codes as I have all the emissions stuff disabled through the tune
- coolant is circulating properly, so temp should be good
- all sensors hooked up that I can possibly think of
- I retuned for the stock MAF just to see if the 73mm C&L cal I was using was incorrect (no difference)
- pretty sure I purged any air from the fuel system/rails
One other odd thing I noticed - I happened to pull my upper intake off very shortly after shutting the motor off and noticed little puffs of smoke wafting from the lower intake - is this normal? Makes me think that the vales may not be seated right, but I am not sure. I don't hear any noise in the valvetrain. If it were the springs; I would only expect to see issues at higher rpms, right?
Starting to grasp for straws right now...
Any and all ideas are welcome.
Thanks,
Eric
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