stumped on fueling problem
11-13-2010, 06:54 AM
#1
Staging Lane
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stumped on fueling problem Sorry for the following novel, but I'm stumped and looking for ideas here.
2004 a4 vette with patriot 243's milled to 59 cc's, morel lifters,torquer2 cam, 3600 stall, vararam, hsw interface, ford svo 30# injectors, fast 90 intake, ported ls2 TB, lg pro longtubes with no cats, meziere ewp, and deleted rear o2s.
The car was tuned about four years ago and tweaked over the years like we all do
and has run pretty good with few issues until recently. it has run a best of 11.07 at 123 on motor and 10.54 at 131 on a 100 shot(hasnt been sprayed in two or more years) and been driven frequently on nice days.
Now it randomly starts running like crap. Some days it wont happen, but frequently it will start having fueling issues on the bank1 o2. What i mean by fueling issues is the bank1 trims(and always bank1) will suddenly go 10-20% richer or more(per my hp tuners scanner) than bank2 trims. when it does this the only code it throws is p0172(bank1 rich). You can immediately hear the change in the exhaust note, performance suffers badly and the car bucks at all rpms. There is no rhyme or reason to when it happens and i cant reproduce the malfunction under any particular conditions(sometimes it goes days without screwing up and sometimes only minutes)and when it is not malfunctioning it runs like a raped ape.
so far i have:
1.put three different sets of new gm o2s on it.(i switched o2s side to side also and the bank2 sensor does not fix the bank1 issue), so i am leaning away from sensor issue.
2.changed all plugs
3.switched over all injectors and fuel rail from my firebird(firebird runs with no issues from either set)
4.checked for vacuum leaks from behind the MAF to where the intake seals to the head without finding one(logged vacuum with the scanner and it is steady at idle)
5.checked fuel pressure at the rail and get 62-63 pounds at wot and 57-58 at KOEO( pump was changed three years ago when i fixed my leaking tank, less than 15000 miles since)
6.replaced the MAF with a known good one and took the HSW interface out of the loop(damn, that didnt work either!)
7. replaced the battery(it was bad, but didnt change anything)
8. checked the o2 harness for chafing or burnt wires(none found)
9. the car does not have a miss or throw misfire codes at all and sometimes, but not always, the "issue corrects itself" while driving and may or may not come back that day.
Somebody point out what i'm missing here. Thanks, Dave
2004 a4 vette with patriot 243's milled to 59 cc's, morel lifters,torquer2 cam, 3600 stall, vararam, hsw interface, ford svo 30# injectors, fast 90 intake, ported ls2 TB, lg pro longtubes with no cats, meziere ewp, and deleted rear o2s.
The car was tuned about four years ago and tweaked over the years like we all do
and has run pretty good with few issues until recently. it has run a best of 11.07 at 123 on motor and 10.54 at 131 on a 100 shot(hasnt been sprayed in two or more years) and been driven frequently on nice days.Now it randomly starts running like crap. Some days it wont happen, but frequently it will start having fueling issues on the bank1 o2. What i mean by fueling issues is the bank1 trims(and always bank1) will suddenly go 10-20% richer or more(per my hp tuners scanner) than bank2 trims. when it does this the only code it throws is p0172(bank1 rich). You can immediately hear the change in the exhaust note, performance suffers badly and the car bucks at all rpms. There is no rhyme or reason to when it happens and i cant reproduce the malfunction under any particular conditions(sometimes it goes days without screwing up and sometimes only minutes)and when it is not malfunctioning it runs like a raped ape.
so far i have:
1.put three different sets of new gm o2s on it.(i switched o2s side to side also and the bank2 sensor does not fix the bank1 issue), so i am leaning away from sensor issue.
2.changed all plugs
3.switched over all injectors and fuel rail from my firebird(firebird runs with no issues from either set)
4.checked for vacuum leaks from behind the MAF to where the intake seals to the head without finding one(logged vacuum with the scanner and it is steady at idle)
5.checked fuel pressure at the rail and get 62-63 pounds at wot and 57-58 at KOEO( pump was changed three years ago when i fixed my leaking tank, less than 15000 miles since)
6.replaced the MAF with a known good one and took the HSW interface out of the loop(damn, that didnt work either!)
7. replaced the battery(it was bad, but didnt change anything)
8. checked the o2 harness for chafing or burnt wires(none found)
9. the car does not have a miss or throw misfire codes at all and sometimes, but not always, the "issue corrects itself" while driving and may or may not come back that day.
Somebody point out what i'm missing here. Thanks, Dave
11-13-2010, 07:16 AM
#2
The only cause of that code (P0172) that I do not see on your list is a check of the EVAP cannister (assuming you have one). A EVAP cannister that has been saturated can cause a rich condition.
If you listed fuel filter, I missed it, but with your fuel pressure it would not seem to be a factor.
If you listed fuel filter, I missed it, but with your fuel pressure it would not seem to be a factor.
11-13-2010, 07:43 AM
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Staging Lane
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The only cause of that code (P0172) that I do not see on your list is a check of the EVAP cannister (assuming you have one). A EVAP cannister that has been saturated can cause a rich condition.
If you listed fuel filter, I missed it, but with your fuel pressure it would not seem to be a factor.
If you listed fuel filter, I missed it, but with your fuel pressure it would not seem to be a factor.
11-13-2010, 08:31 AM
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First, check for fuel in the oil to make sure it's not contaminated. You've done a pretty thorough job with the checklist, so now you need to isolate the conditions that are setting the DTC. Believe it or not, it's not random and more than like getting set under indentical conditions each time.
- Pull the freeze frame data from the DTC to see what operating conditions the code was set at. You can also use the scan tool to monitor the O2 voltage to see how it's switching and when it goes rich. Here are the conditions for this DTC:
* The engine coolant temperature is between 50°C (122°F) and 115°C (239°F).
* The barometric pressure is more than 74 kPa.
* The mass air flow is between 5.0 g/s and 90 g/s.
* The manifold absolute pressure is between 26 kPa and 90 kPa.
* The intake air temperature is between -20°C (-4°F) and 90°C (194°F).
* The engine speed is between 400 RPM and 3,000 RPM.
* The TP sensor angle is less than 90 percent.
* The vehicle speed is less than 137 km/h (85 mph).
- Even though you swapped injectors, pull the plugs from the driver side (after the code is set) and see if one plug is fouled. If so, that injector is leaking and not sealed correctly.
Intermittent problems are tough to chase. I would check the entire intact tract from air filter foward for restriction, leaks, and loose connections, etc. Also make sure the MAF is installed correctly with the arrow pointing in the correct direction. Once you determine the exact conditions the DTC is set, verify the fuel pressure inside of those conditions. It could be the fuel pressure regulator.
- Pull the freeze frame data from the DTC to see what operating conditions the code was set at. You can also use the scan tool to monitor the O2 voltage to see how it's switching and when it goes rich. Here are the conditions for this DTC:
* The engine coolant temperature is between 50°C (122°F) and 115°C (239°F).
* The barometric pressure is more than 74 kPa.
* The mass air flow is between 5.0 g/s and 90 g/s.
* The manifold absolute pressure is between 26 kPa and 90 kPa.
* The intake air temperature is between -20°C (-4°F) and 90°C (194°F).
* The engine speed is between 400 RPM and 3,000 RPM.
* The TP sensor angle is less than 90 percent.
* The vehicle speed is less than 137 km/h (85 mph).
- Even though you swapped injectors, pull the plugs from the driver side (after the code is set) and see if one plug is fouled. If so, that injector is leaking and not sealed correctly.
Intermittent problems are tough to chase. I would check the entire intact tract from air filter foward for restriction, leaks, and loose connections, etc. Also make sure the MAF is installed correctly with the arrow pointing in the correct direction. Once you determine the exact conditions the DTC is set, verify the fuel pressure inside of those conditions. It could be the fuel pressure regulator.
11-13-2010, 08:36 AM
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I had a similar problem that ended up being a bad injector. When you swapped over the injectors to the firebird did you run it for a minute or drive the car a while with them. In my case it seemed to run OK at idle or in open loop - accelerating. I think 7 out of 8 cylinders had a good air/fuel mix in open loop in my case.
But cruising on the highway small throttle inputs would make the car buck badly sometimes. In closed loop I think the O2 readings made the computer add fuel to the bank with the bad injector. So then 4 out of 8 cylinders would run badly. The injector duty cycle was 2x more on the bad bank when the problem happened.
It also came on gradually. When it started out I could still drive the car but it got worse over time.
But cruising on the highway small throttle inputs would make the car buck badly sometimes. In closed loop I think the O2 readings made the computer add fuel to the bank with the bad injector. So then 4 out of 8 cylinders would run badly. The injector duty cycle was 2x more on the bad bank when the problem happened.
It also came on gradually. When it started out I could still drive the car but it got worse over time.
11-14-2010, 06:57 PM
#6
Staging Lane
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i hate threads that end without the solution in them for later searching, so i'll post mine lmfao. F***ing msd coils. Had two coils on the driver side that intermittently weak. they never went all the way out and threw a misfire code but they were definitely the problem. cant dog them too much, they were 4 years old and they sure were a pretty red. replaced all eight with my old stock coils and my bitch is back on attack! thanks for the suggesions guys,
Dave
Dave
