top end problem debugging
04-10-2007, 08:31 AM
#1
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Join Date: Aug 2006
Location: Longview, TX
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top end problem debugging
I've noticed a problem that has been steadily increasing in occurrance, now it is 100% of the time since about a month ago.
at WOT in 1st and 2nd gear at about 5200 RPM the right side only o2 sensor drops from ~900 down to 70mV(unheated) at the same time that the engine acts as though it hit the rev limiter, this only lasts 1/2 a second and then it shifts, significant loss of power. So I believe I'm either losing fuel or spark. the injectors barely hit 80% duty cycle at max RPM at WOT, it's been like this for years and they haven't had a problem. I suspected the old opti, and changed that out this weekend as well. I ran some cleaner through the injectors, but no real change has occurred. The speed increase continues after the abrupt bump.
So I'm left pondering a few more things.
A. perhaps fuel pump is going out.
B. Perhaps the right side fuel injectors are dying.
C. Perhaps the PCM is flipping out due to the o2 response even though it should be ignoring them at WOT, but such a huge change could make something happen?
I'm going to hook a fuel pressure gauge back up to the fuel system, this is probably the next step. besides that I'll try to get some more basic data-logs by doing a run up in manual mode and bouncing it off the rev limiter to get a good display of what is happening.
at WOT in 1st and 2nd gear at about 5200 RPM the right side only o2 sensor drops from ~900 down to 70mV(unheated) at the same time that the engine acts as though it hit the rev limiter, this only lasts 1/2 a second and then it shifts, significant loss of power. So I believe I'm either losing fuel or spark. the injectors barely hit 80% duty cycle at max RPM at WOT, it's been like this for years and they haven't had a problem. I suspected the old opti, and changed that out this weekend as well. I ran some cleaner through the injectors, but no real change has occurred. The speed increase continues after the abrupt bump.
So I'm left pondering a few more things.
A. perhaps fuel pump is going out.
B. Perhaps the right side fuel injectors are dying.
C. Perhaps the PCM is flipping out due to the o2 response even though it should be ignoring them at WOT, but such a huge change could make something happen?
I'm going to hook a fuel pressure gauge back up to the fuel system, this is probably the next step. besides that I'll try to get some more basic data-logs by doing a run up in manual mode and bouncing it off the rev limiter to get a good display of what is happening.
04-11-2007, 12:02 PM
#2
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Join Date: Aug 2006
Location: Longview, TX
Posts: 199
update:
gave it a run in manual mode to remove the transmission from the equation, WOT it occurs in both gears as before. non-WOT it does not occur for those RPM's.
This leads me to believe its the injectors dying or the fuel pump. Any thoughts?
gave it a run in manual mode to remove the transmission from the equation, WOT it occurs in both gears as before. non-WOT it does not occur for those RPM's.
This leads me to believe its the injectors dying or the fuel pump. Any thoughts?
04-11-2007, 12:14 PM
#3
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Join Date: Feb 2006
Posts: 302
Hook up the fuel pressure gauge, make sure your pressure is staying up.
04-12-2007, 10:47 AM
#4
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Join Date: Aug 2006
Location: Longview, TX
Posts: 199
well, don't have a fuel gauge, but I swapped all my injectors from one side of the block to the other. The problem is steadily getting worse, and the same side of the injectors failed (o2 sensor read low during WOT, severe loss of power) first.
Since the fuel lines come in on the left side, and the right fails first, I would assume its getting starved for fuel, so it's either the fault of the fuel filter (just replaced it 3 months ago.....) or the fuel pump.
Since the fuel lines come in on the left side, and the right fails first, I would assume its getting starved for fuel, so it's either the fault of the fuel filter (just replaced it 3 months ago.....) or the fuel pump.
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