Misfire on transition from open loop/closed loop, cyl 2,4,6,8
01-25-2005, 08:19 PM
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Misfire, Cyl. 2,4,6,8 I have an 02 TA, 25,000 miles, auto trans, slp long tubes, stock cats, borla, stock internals, the problem is the car will miss on cylinders 2,4,6,8, it runs okay on initial startup, then as i watch the pcm data on a tech 2 the instant the car goes into closed loop it starts missing in cyl 6, it goes completely dead, then 10 sec later cyl 4 misses just as often as 6, so now 4&6 are dead racking up misfires very quickly, if you put the car in gear and slighty brake torque it to 1100 cyl 2 and 8 show misses but not as often as 4/6, after 45 sec it clears up and the car runs fine until you shut it off, it drives smooth, strong, normal, it wont log a misfire the rest of the trip. For example after it has been missing cyl 6 history will be 950, cyl 4 650, 8 and 2 will show 75-100 misfires. IT only logs a po300. ALL this happens with the car not moving.
When the missing is happening the b2s1 o2 is 1007mv and the b1 inj pw is 5.9 while the b2 is 3.5, so the o2 is seeing rich and the computer is trying to pull away fuel, the other o2 values are normal, the plugs are new ac delco (same p/n as stock) the wires are new, the pcm is new, the #4 and #6 coils are new, all 8 injectors were taken out and flowed on a wet injector bench, test perfect mechanically and electrically, i have replaced two injectors, swapped the bank 1 injectors to bank 2, all of this was done one step at a time, the problem remains the same and does not change cyl's,
If i start the car and manually force it into closed loop when it is cold (with the scanner) the car will start to act up, starting with 6, then to 4 and eventually all of bank 2, i had a spark tester hooked up to 6 and then made the car act up and it does have good spark, the plugs from bank 1 look normal but the bank 2 look rich, i have swapped o2s from bank 1 to bank 2, have checked the grounds for the pcm, inj bank 1 and bank 2 (they are differnt locations) both coil banks grounds, it seems like an intermittent but i can make it do it everytime only once per key cycle, the car runs too good when the miss quits in closed loop and also runs normal in open loop, i havent done a compression test because of this, there is no mechanical noises, the ckp has been re-learned when the pcm was replaced and flashed, any suggestions, im running out of patience and money!
When the missing is happening the b2s1 o2 is 1007mv and the b1 inj pw is 5.9 while the b2 is 3.5, so the o2 is seeing rich and the computer is trying to pull away fuel, the other o2 values are normal, the plugs are new ac delco (same p/n as stock) the wires are new, the pcm is new, the #4 and #6 coils are new, all 8 injectors were taken out and flowed on a wet injector bench, test perfect mechanically and electrically, i have replaced two injectors, swapped the bank 1 injectors to bank 2, all of this was done one step at a time, the problem remains the same and does not change cyl's,
If i start the car and manually force it into closed loop when it is cold (with the scanner) the car will start to act up, starting with 6, then to 4 and eventually all of bank 2, i had a spark tester hooked up to 6 and then made the car act up and it does have good spark, the plugs from bank 1 look normal but the bank 2 look rich, i have swapped o2s from bank 1 to bank 2, have checked the grounds for the pcm, inj bank 1 and bank 2 (they are differnt locations) both coil banks grounds, it seems like an intermittent but i can make it do it everytime only once per key cycle, the car runs too good when the miss quits in closed loop and also runs normal in open loop, i havent done a compression test because of this, there is no mechanical noises, the ckp has been re-learned when the pcm was replaced and flashed, any suggestions, im running out of patience and money!
Last edited by Red-Z; 01-25-2005 at 08:40 PM.
01-27-2005, 12:05 AM
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Headers often cause mis-learning at low flows due
to being cold. It would take time for this to unlearn
and the other side's sensor, in the same cold spot,
might do just as poorly. Maybe the passenger's side
is more remote and colder.
If the O2s act too lame too long then the car will just
forget about closed loop, set mixture without trims and
off you go. This might set a code if it happens consistently
enough, or maybe you have already had the codes turned
off that would clue you in about that?
Try a pair of the 'Vette rears in the front positions
and see how that does for you.
to being cold. It would take time for this to unlearn
and the other side's sensor, in the same cold spot,
might do just as poorly. Maybe the passenger's side
is more remote and colder.
If the O2s act too lame too long then the car will just
forget about closed loop, set mixture without trims and
off you go. This might set a code if it happens consistently
enough, or maybe you have already had the codes turned
off that would clue you in about that?
Try a pair of the 'Vette rears in the front positions
and see how that does for you.
01-30-2005, 10:40 AM
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I dont think that the O2's would cause a dead miss like I am having though. I dont see how a poor O2 signal would cause a miss like I am having. I see the point you are giving, but It ran fine for 3 months until now. PLease help, I dont know what else to do!!!!
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02-01-2005, 10:14 AM
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The rear O2s are exposed to colder air (after the cat) and it looks like they have a beefed up heater element if they've been helping people in this situation.
Ben
Ben
Originally Posted by Red-Z
What is the difference between the Vette rear O2s and the stock ones I have now?
02-02-2005, 10:15 AM
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Originally Posted by Red-Z
What is the difference between the Vette rear O2s and the stock ones I have now?
02-02-2005, 09:45 PM
#12
THis may sounds nuts *** off the wall. But last week I had a 99 chevy pu acting the identical way. After pulling my hair out for three and half hours I discovered that the right hand cat had partially melted and was causing the problem. But it did not set a converter efficiency code. Try pulling the front o2 out of the offending side and start the engine with the o2 removed. When i did this on the truck it was able to flow enough exhaust that the misfires went away and it ran perfectly. Ordered a new crossover and the truck was fixed. It is rich on that side becuase in all actuality it is seeing an extreme lean condition.
