Fuel cut, or something simular, at 1PSI.. STUMPED
08-24-09, 05:24 PM
#1
Fuel cut, or something simular, at 1PSI.. STUMPED
So it's a Newly built 88 turbo 2.
NO emissions. Replaced tps with a GOOD unit and set to 1k ohms.
I can use full throttle up until about 2200 or 2300 rpm right when boost is just starting to build, it does this with the FCD plugged in or not, or even if i unplug the MAP sensor all togather. so i am pretty sure it's not that.
It happens long before the 2ndary injectors so it's not a problem with them.
And it's kinda odd that even with the ECU not knowing that i was hitting boost, it still starts stuttering like fuel cut, but maybe it's something else,
i also tried:
removing the KNOCK sensor temporarily, no effect.
i do have a VAC LEAK at the LIM which i dont feal like like pulling the turbo off right now to fix as a new turbo is on the way, i just wanna get some breakin time without hitting the FUEL CUT at low PSI.
NO emissions. Replaced tps with a GOOD unit and set to 1k ohms.
I can use full throttle up until about 2200 or 2300 rpm right when boost is just starting to build, it does this with the FCD plugged in or not, or even if i unplug the MAP sensor all togather. so i am pretty sure it's not that.
It happens long before the 2ndary injectors so it's not a problem with them.
And it's kinda odd that even with the ECU not knowing that i was hitting boost, it still starts stuttering like fuel cut, but maybe it's something else,
i also tried:
removing the KNOCK sensor temporarily, no effect.
i do have a VAC LEAK at the LIM which i dont feal like like pulling the turbo off right now to fix as a new turbo is on the way, i just wanna get some breakin time without hitting the FUEL CUT at low PSI.
08-24-09, 07:17 PM
#3
well no, it doesn't, it's not that bad of a vac leak, not bad enough to keep the car from idling, it just has a bouncy idle.
I have ohm'd the Airflow meter, and it is ok, but when i ohm'd the fuel pump relay c and d were ok, but a to b and E to F is off, so i'm hunting a replacement in my heeps of left overs, i should have one, i'll let yall know if this is the fix if it is, it sure seems likely, as you know all turboII's run a high voltage when the car goes into boost, but then again it still did it with the boost sensor unplugged. kinda puzzling
I have ohm'd the Airflow meter, and it is ok, but when i ohm'd the fuel pump relay c and d were ok, but a to b and E to F is off, so i'm hunting a replacement in my heeps of left overs, i should have one, i'll let yall know if this is the fix if it is, it sure seems likely, as you know all turboII's run a high voltage when the car goes into boost, but then again it still did it with the boost sensor unplugged. kinda puzzling
08-24-09, 10:24 PM
#5
The fuel pump relay should be switched by load condition, not boost. Load is calculated from a number of things, but primarily airflow from the AFM.
And the atmospheric pressure sensor is used to small fuel adjustments. The boost level & RPM determine how much fuel initially, then other factors come into play to vary the mixture.
Have you pulled engine codes yet? It should save you a lot of time if there is something malfunctioning.
And the atmospheric pressure sensor is used to small fuel adjustments. The boost level & RPM determine how much fuel initially, then other factors come into play to vary the mixture.
Have you pulled engine codes yet? It should save you a lot of time if there is something malfunctioning.
08-24-09, 11:04 PM
#6
no check engine light, how ever i 've never gotten codes in this car even with the O2 sensor not plugged in, so maybe the light is burned out, i'll have to look into that, whats the best way to make the check engine light come on?
atmospheric pressure sensor checks out fine.
atmospheric pressure sensor checks out fine.
08-25-09, 03:13 AM
#7
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when I forgot to put a hoseclamp on my AWS valve the car would drive just fine, except for it sounding like it was bridgeported. underboost it would hit 1 psi then it would hit a brick wall. once I found the leak the problem went away.
the only other time I had that symptom is when the HKS F-Con I was using was set to rich.
the only other time I had that symptom is when the HKS F-Con I was using was set to rich.
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08-25-09, 04:19 AM
#8
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cat
a blocked cat converter will stop it from making boost, took mine to the dyno one day and only made 1psi with a gt35r took it back a week later after punching out the cat and problem solved.
08-25-09, 02:48 PM
#11
actually, now that i read your thread, it sounds A LOT like a boost leak. my friend's eclipse had this exact same issue. turned out one of his hose clamps broke off on his FMIC causing a massive boost leak, but no issues at atmospheric pressure.
08-25-09, 10:05 PM
#14
So i made up a led resistor combo for checking my codes, and i have none, but i can verify that it works by unplugging the tps, and it throws a code, and then unplugging various sensors and watching it through the code, but then i unplug the boost sensor, and no code at all... but that doesnt make sense... ive regulated compressed air into it and it's works and is accurate.
08-26-09, 12:31 AM
#15
yeah boost sensor unplugged wouldn't cause a fuel cut... you're setting the TPS at 1 volt at idle right and not 1 ohm right? Doesn't really even sound boost related cause 0 psi or 7.5 psi it shouldn't hit a fuel wall. is this problem throttle position related? like will it run fine at <half throttle acceleration? that vacuum leak wouldn't cause this problem either. you have a spare AFM or ecu maybe?
08-26-09, 09:23 AM
#16
lol. actually i may have set it to 1k ohm, let me go redo that, and last night i back probed the ECU for the boost senor at pin 2b, and the ground for the same at 2c, and read 2.25v at idle, and 2.56 or there abouts when hitting the fuel wall. let me go do my tps again...
EDIT: so TPS was at .86V, so i dialed it back up to 1.00 flat, problem still exsist..
Next fuel filter( just because it's been a year) and fuel pump rewire, as i can only get 9.XX volts at any time.
EDIT: so TPS was at .86V, so i dialed it back up to 1.00 flat, problem still exsist..
Next fuel filter( just because it's been a year) and fuel pump rewire, as i can only get 9.XX volts at any time.
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