help, funny rich condition while cruzing.
Thread Starter
single digit dreamer
iTrader: (6)
Joined: Mar 2002
Posts: 9,757
Likes: 4
From: omaha ne
help, funny rich condition while cruzing. i need some help here, i have had this problem for a long time and now, have put many mods on the truck and the problem has stayed prety much the same.
while cruzing along i will be in closed loop and be at 14.7 or so to one with the 02's rapidly switching and all of the sudden it goes way rich, wide band shows 10-1 and stock 02's go way rich also. this would last about 2-5sec and then slowly recover, maybe do it once a min or so. i could see the duty cycle go up too so the computer is asking for the fuel for some reason.
so far this hasn't really effected me, WOT works fine and idle is fine.
now i am trying to run it in open loop, drop the 02's run some leaded race gas... suprizingly it runs prety well, somehow learns to idle well and drives great, the wideband shows prety close to 14.7-1 a/f ratio most of the time even.
the problem i have is now it still does the go rich thing every now and then but it stays rich for a very long time, i am seeing it at 10-1 for about 1/2 of the time i am cruzing, fueling goes corect at WOT or idle and is corect the other 1/2 of the time.
i was thinking about going with race gas all of the time but not if i can't fix this problem. anyone have any ideas?
while cruzing along i will be in closed loop and be at 14.7 or so to one with the 02's rapidly switching and all of the sudden it goes way rich, wide band shows 10-1 and stock 02's go way rich also. this would last about 2-5sec and then slowly recover, maybe do it once a min or so. i could see the duty cycle go up too so the computer is asking for the fuel for some reason.
so far this hasn't really effected me, WOT works fine and idle is fine.
now i am trying to run it in open loop, drop the 02's run some leaded race gas... suprizingly it runs prety well, somehow learns to idle well and drives great, the wideband shows prety close to 14.7-1 a/f ratio most of the time even.
the problem i have is now it still does the go rich thing every now and then but it stays rich for a very long time, i am seeing it at 10-1 for about 1/2 of the time i am cruzing, fueling goes corect at WOT or idle and is corect the other 1/2 of the time.
i was thinking about going with race gas all of the time but not if i can't fix this problem. anyone have any ideas?
On The Tree
Joined: Dec 2001
Posts: 137
Likes: 0
From: Atlanta, Georgia
Parish my guess would be CAT over temp, dumping fuel in there to cool them down, you might wanna try going in and turning that setting off, and see if it doesn't stay @ 14.7:1 also you can try going down to 14.2:1 , mileage will suffer slightly but the engine will run cooler and you'll have cooler exhaust temp.
TECH Regular
Joined: Nov 2003
Posts: 434
Likes: 0
From: Dallas
Maybe the reason it lasts longer in open loop is because the fuel trims are no longer making corrections as they do in closed loop.
Have you logged STFT's and LTFT's when this happens in closed loop?
Thinking about causes for the "go rich" condition... so far I've got:
- intermittent signal from O2 sensor or MAF (short, loose wire, bad sensor, etc.)
- cruise section of the VE table needs fixing
Can you isolate the condition to a specific rpm and MAP range? Look at the cruise range of the VE table (roughly MAP 30-60 and RPM 1200-2800). There are some big jumps in there (up to the MAP 55-60 transition) and some dips with increasing rpms. If your rich condition tracks with one of the large MAP transitions or one of the rpm dips, the VE table may need adjusting in that area. My stock VE table no longer works well in the cruise range either - I have adjusted several of those points for smoother throttle and to get rid of a little part throttle KR.
The VE table explanation also agrees with your analysis of the fueling conditions (ok at WOT and idle, but not PT cruise). According to gameover from hptuners, the PCM uses 3 ways to determine fueling under normal circumstances (i.e. no limp mode, etc.): steady MAP, unsteady MAP, and WOT. He says WOT and steady MAP use mostly the MAF, and unsteady MAP uses the VE table plus the MAF plus the last few MAP/MAF readings to determine fueling. So idle (steady MAP) and WOT are both fueling mainly from the MAF reading and you have no problems. But your cruise (unsteady MAP) has the fueling issue, which is where the VE table is used more.
Sorry so long-winded. Hope this helps...
Have you logged STFT's and LTFT's when this happens in closed loop?
Thinking about causes for the "go rich" condition... so far I've got:
- intermittent signal from O2 sensor or MAF (short, loose wire, bad sensor, etc.)
- cruise section of the VE table needs fixing
Can you isolate the condition to a specific rpm and MAP range? Look at the cruise range of the VE table (roughly MAP 30-60 and RPM 1200-2800). There are some big jumps in there (up to the MAP 55-60 transition) and some dips with increasing rpms. If your rich condition tracks with one of the large MAP transitions or one of the rpm dips, the VE table may need adjusting in that area. My stock VE table no longer works well in the cruise range either - I have adjusted several of those points for smoother throttle and to get rid of a little part throttle KR.
The VE table explanation also agrees with your analysis of the fueling conditions (ok at WOT and idle, but not PT cruise). According to gameover from hptuners, the PCM uses 3 ways to determine fueling under normal circumstances (i.e. no limp mode, etc.): steady MAP, unsteady MAP, and WOT. He says WOT and steady MAP use mostly the MAF, and unsteady MAP uses the VE table plus the MAF plus the last few MAP/MAF readings to determine fueling. So idle (steady MAP) and WOT are both fueling mainly from the MAF reading and you have no problems. But your cruise (unsteady MAP) has the fueling issue, which is where the VE table is used more.
Sorry so long-winded. Hope this helps...
