Power FC Car won't idle with injectors set to 100%
Thread Starter
Post quality not quantity
Joined: Feb 2001
Posts: 521
Likes: 0
From: Durham, NC
Car won't idle with injectors set to 100%
I'm posting for a friend, and this involves a little bit of general engine troubleshooting tech - so please move the thread if needed, I don't feel right posting it twice:
93, 42k on motor, good compression after ATF (3, 120psi bounces on each rotor)
Good exhaust pulses when it turns over and runs
100k on the chassis (and probably the injectors)
downpipe, high-flow, pfs catback
pfs intercooler and intake
crane hi-6 and crane coils for leading plugs
trailing plugs stock coils
PFC, of course
The car started hesitating at high rpm operation at some point in time,
We decided the plugs might be worn, so he changed them out.
He knows how to change plugs. It was done correctly.
After changing the plugs, the car refused to even start, and floods to the point it loses compression.
We went through standard diagnostics on the car, and identified that (DUH!) there is too much fuel being delivered.
Plugs are fouled and wet when the injectors were set to 100% (we though the fuel pressure regulator was hosed).
So, we cut the injectors from 100% down to where the car would idle (not the fuel maps in the PFC).
We have not, nor will not drive the car in this condition (and was undriveable after it got a "pro" compression check, then it "died" and needed ATF and diagnostics began)
Fuel pressure checks out to be correct, regulator functioning, as is the solenoid (According to the FSM).
We have spark on all 4 plugs (might need new plugs after being ATF'ed a few times, but it should at least run)
Fuel pump relay and resistor okay
Idle speed control is okay
MAP plugged in and reading vac/pressure according to PFC monitor
Question: Can the PFC lose settings?
We are looking at the injectors page, set to stock 550/850
and the car just WON'T idle or start if you set the injectors to 100%. If it is 50%-60%, it will start, run, and idle and rev.
If we adjust the injectors a bit higher where it idles roughly, it will backfire, LOUDLY...like there is a big globule of fuel hitting the warmed up exhaust.
I also observe that injector duty cycle changes during idle, and gets wild when it about dies (at a higher injector % setting on the PFC)
I understand basic fuel injection and know the stock ECU back and forth for the most part, and understand tuning, but I'm not quite familiar with the PFC setting, and only have the reference manual from Apexi. As I understand, this menu is a relative function to the stock injectors, and if you change the size you enter the cc size and change percentages and ms delay correction factor. So, if we change the % with the stock injectors from 100% down to 50%, it should be SEVERELY altering duty cycle to only a little bit open to barely get the car running. Idle is pretty rich as it is....
So I think the primaries are flooding - either something electrical??? or they just are due to be balanced. I wanted to tear into the car and undo the primary rail and run the fuel pump to see if they are leaking, but the car is sequential, and with no garage to store it in, we decided against any further "tweaking" to definitively find out what is wrong.
Any thoughts as to why this is? Is there an electrical gremlin causing the injectors to stay open and flood (the car has 100+K, so it is possible the injectors died)
A.F.
93, 42k on motor, good compression after ATF (3, 120psi bounces on each rotor)
Good exhaust pulses when it turns over and runs
100k on the chassis (and probably the injectors)
downpipe, high-flow, pfs catback
pfs intercooler and intake
crane hi-6 and crane coils for leading plugs
trailing plugs stock coils
PFC, of course
The car started hesitating at high rpm operation at some point in time,
We decided the plugs might be worn, so he changed them out.
He knows how to change plugs. It was done correctly.
After changing the plugs, the car refused to even start, and floods to the point it loses compression.
We went through standard diagnostics on the car, and identified that (DUH!) there is too much fuel being delivered.
Plugs are fouled and wet when the injectors were set to 100% (we though the fuel pressure regulator was hosed).
So, we cut the injectors from 100% down to where the car would idle (not the fuel maps in the PFC).
We have not, nor will not drive the car in this condition (and was undriveable after it got a "pro" compression check, then it "died" and needed ATF and diagnostics began)
Fuel pressure checks out to be correct, regulator functioning, as is the solenoid (According to the FSM).
We have spark on all 4 plugs (might need new plugs after being ATF'ed a few times, but it should at least run)
Fuel pump relay and resistor okay
Idle speed control is okay
MAP plugged in and reading vac/pressure according to PFC monitor
Question: Can the PFC lose settings?
We are looking at the injectors page, set to stock 550/850
and the car just WON'T idle or start if you set the injectors to 100%. If it is 50%-60%, it will start, run, and idle and rev.
If we adjust the injectors a bit higher where it idles roughly, it will backfire, LOUDLY...like there is a big globule of fuel hitting the warmed up exhaust.
I also observe that injector duty cycle changes during idle, and gets wild when it about dies (at a higher injector % setting on the PFC)
I understand basic fuel injection and know the stock ECU back and forth for the most part, and understand tuning, but I'm not quite familiar with the PFC setting, and only have the reference manual from Apexi. As I understand, this menu is a relative function to the stock injectors, and if you change the size you enter the cc size and change percentages and ms delay correction factor. So, if we change the % with the stock injectors from 100% down to 50%, it should be SEVERELY altering duty cycle to only a little bit open to barely get the car running. Idle is pretty rich as it is....
So I think the primaries are flooding - either something electrical??? or they just are due to be balanced. I wanted to tear into the car and undo the primary rail and run the fuel pump to see if they are leaking, but the car is sequential, and with no garage to store it in, we decided against any further "tweaking" to definitively find out what is wrong.
Any thoughts as to why this is? Is there an electrical gremlin causing the injectors to stay open and flood (the car has 100+K, so it is possible the injectors died)
A.F.
Injectors cannot operate correctly above 85%. Injectors have an ON/OFF time. When they are at 100% they never go off. If he needs to run more fuel he needs to upgrade his injectors so they dont run at more than 85%.
Zoom Zoom,
He is not talking about 100% duty cycle, but 100% flow rate
where the injectors are set up. Injector pulse timing correction
menu.
I have responded to him on the list previously.
He is not talking about 100% duty cycle, but 100% flow rate
where the injectors are set up. Injector pulse timing correction
menu.
I have responded to him on the list previously.
Full Member
Joined: Mar 2002
Posts: 192
Likes: 0
From: earth
i have a similar problem with my car and noticed that my car knocks higher at wot with the rate at .00 for the primaries and secondaries. my injectors are stock 550/850 with both at 100%. when i adjust the rate on my pfc to .04 for both the primary and secondary, the knock levels go down. is that safe? i'm a tuning newbie and would like someone to helpppp. i left the settings like that for a while since my knock levels were lower, but am i damaging my engine in any way? my only mod is just a cold air box.
Thread
Thread Starter
Forum
Replies
Last Post
trickster
2nd Generation Specific (1986-1992)
25
Jul 1, 2023 04:40 PM
alphawolff
1st Generation Specific (1979-1985)
17
Nov 17, 2015 05:57 PM
