Richer and Richer at idle with SD tune
03-19-2010, 10:08 PM
#21
Mine does the same thing. There is a vent line coming off of your fuel tank going to the drives side of the engine. There it goes into a valve, then into the manifold. When the fuel tank pressure reaches X this valve is opened and the raw fuel vapors are consumed by the engine. You will see this in your STFT's. They will go lean until they max out if the LTFT is not turned on. I run 80# injectors and with my current fuel pressure setting the PCM and injector combo can not lowed the duty cycle enough to compesate for this.
I am not saying this is the answer, just something to check. To check it disconect the wires going to this valve and watch the WB and STFT's to see if there is a change. If it goes lean I would say this is what is causing the issue.
If the NB cool off too much they will not function properly. I have also seen this issue.
Do you have all the correct injector data? PM me your email and I will send it to you.
Another thing that can cause this is the fuel pressure regulator could be malfunctioning and causing the fuel pressure to increase at idle. You can watch the fuel pressure while it is doing this and see if it is incressing.
NB and WB do not read fuel in the exhaust. They only read Oxygen. If your cam lopes it can drive the PCM crazy because there will be pulses of unburnt O2 in the exhaust stream. You could raise the idle rpm a few hundered rpm and see if the problem goes away.
Just suggestions. Good luck.
I am not saying this is the answer, just something to check. To check it disconect the wires going to this valve and watch the WB and STFT's to see if there is a change. If it goes lean I would say this is what is causing the issue.
If the NB cool off too much they will not function properly. I have also seen this issue.
Do you have all the correct injector data? PM me your email and I will send it to you.
Another thing that can cause this is the fuel pressure regulator could be malfunctioning and causing the fuel pressure to increase at idle. You can watch the fuel pressure while it is doing this and see if it is incressing.
NB and WB do not read fuel in the exhaust. They only read Oxygen. If your cam lopes it can drive the PCM crazy because there will be pulses of unburnt O2 in the exhaust stream. You could raise the idle rpm a few hundered rpm and see if the problem goes away.
Just suggestions. Good luck.
03-19-2010, 11:57 PM
#22
TECH Resident
Thread Starter
Great ideas! I will check fuel pressure and tank vent. PM sent, I'm interested in anything about these SVO injectors, they may be part of the mystery. My idle is at 1200, this engine sounds great, plenty of cam lope there so that could be an issue.
03-22-2010, 11:04 AM
#24
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As Patrick recommended, setting the O2 switching to 450 seems to be the magic number. I had them lower and it did not work as good. At 450 I had to raise the numbers in my VE table because I had it way leaned out. Idle is better, A/F still drops from 14.5 to 13.6 before it stabilizes.
Whenever I reprogram, it takes the tune a while to stabilize. Why is that, is the computer still learning something even with LTFT off.?
Whenever I reprogram, it takes the tune a while to stabilize. Why is that, is the computer still learning something even with LTFT off.?
03-22-2010, 03:53 PM
#25
Even with my switchpoint table tweaks the idle tends to wonder on cold days. Holding the RPM around 2k for 10 seconds usually heats them back up so it idles at 14.7. Here's the numbers I've been using:
LABELS bank
CL Mode Bank-1 Bank-2
0 365 365
8 403 403
16 407 407
24 411 411
32 450 450
40 485 485
48 495 495
56 550 550
64 560 560
LABELS bank
CL Mode Bank-1 Bank-2
0 365 365
8 403 403
16 407 407
24 411 411
32 450 450
40 485 485
48 495 495
56 550 550
64 560 560
