Huge power loss in GSL-SE
03-01-09, 09:24 PM
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Huge power loss in GSL-SE
I have an '85 GSL-SE. I am having a huge power loss and idle issue. I have an S4 engine and throttle body with a small street port and racing beat street port exhaust. I have the correct exhaust for the 6 port. I am running two GSL-SE injectors with the stock ECU. The engine only has 16,000 miles on it. The injectors were rebuilt same time as the engine. Overnight my car completely lost power and does not idle over 500 RPM's until the car is completely warm. It will die if you don't hold the accelerator down. Once the car is warm it will not die but still idles low. Acceleration is incredibly slow at all RPM's.
I cannot figure out what is wrong. I have replaced the spark plugs and wires. The oil has recently been changed. I replaced the fuel filter. I conducted a compression test. Each rotor has great compression. I also conducted a fuel pressure test. The pressure is at 68 lbs from the fuel pump and 40 lbs through the regulator. When accelerator is pressed the barn door opens in the mass airflow sensor as do the flaps in the throttle body. I can't think of anything else to check. Does anyone have any ideas???
I cannot figure out what is wrong. I have replaced the spark plugs and wires. The oil has recently been changed. I replaced the fuel filter. I conducted a compression test. Each rotor has great compression. I also conducted a fuel pressure test. The pressure is at 68 lbs from the fuel pump and 40 lbs through the regulator. When accelerator is pressed the barn door opens in the mass airflow sensor as do the flaps in the throttle body. I can't think of anything else to check. Does anyone have any ideas???
03-01-09, 09:45 PM
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I did. Each rotor had great compression. The bump test was showing 35-40 for each rotor and the test with the compression button released showed 90 on each rotor.
03-01-09, 10:51 PM
#5
are those compression numbers on a warm engine?
I ask because the S3 and S4 13B blocks were essentially the same and for a 13B block, compression numbers should be in around 110psi.
my rebuilt S3 13B got me 125psi on all faces, 5psi higher than what the FSM mentions as a completely healthy, brand new engine. 85psi is the limit IIRC
I ask because the S3 and S4 13B blocks were essentially the same and for a 13B block, compression numbers should be in around 110psi.
my rebuilt S3 13B got me 125psi on all faces, 5psi higher than what the FSM mentions as a completely healthy, brand new engine. 85psi is the limit IIRC
03-01-09, 11:00 PM
#6
No distributor? No thanks
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How are you testing your fuel pressure? If you're able to test at the firewall hardline and have 2-3 feet of hose, strap the gauge under the wiper and go for a drive. You may well find that the pump can keep up at idle, but the pressure will drop under load. I had a clogged fuel pickup screen in the tank (I could fill it with gasoline in the driveway, and it wouldn't leak out) that also killed the pump in short order. A clogged filter or weak pump would also show up in a test drive with a fuel pressure gauge under the wiper.
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03-02-09, 05:23 AM
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I don't have much time before morning PT but I'll respond best I can for now
Checked that. That flapper appears to open just fine. The more gas, the wider it opens.
[QUOTE=are those compression numbers on a warm engine?
I ask because the S3 and S4 13B blocks were essentially the same and for a 13B block, compression numbers should be in around 110psi.
my rebuilt S3 13B got me 125psi on all faces, 5psi higher than what the FSM mentions as a completely healthy, brand new engine. 85psi is the limit IIRC[/QUOTE]
The engine was not warm. I'll do it again if it will make a difference.
[QUOTE=How are you testing your fuel pressure? If you're able to test at the firewall hardline and have 2-3 feet of hose, strap the gauge under the wiper and go for a drive. You may well find that the pump can keep up at idle, but the pressure will drop under load. I had a clogged fuel pickup screen in the tank (I could fill it with gasoline in the driveway, and it wouldn't leak out) that also killed the pump in short order. A clogged filter or weak pump would also show up in a test drive with a fuel pressure gauge under the wiper.[/QUOTE]
I checked it according to the FSM, but I will try to do it while driving down the road. Good idea.
[QUOTE=1 of 2 things happening here.
1) lost your leading spark
2) lost power to one of the injectors [/QUOTE]
All plugs have spark. I am runing an MSD ignition box with wires going from the coils directly to the leading plugs. I am positive all plugs have spark.
[QUOTE=have you double checked your wires to see if you installed them correctly? sounds like you might have reversed the leading/trailing.[/QUOTE]
Double and triple checked. That will really mess things up.
[QUOTE=also, another thing to mention is a clogged converter(s). do you have a conveter? [/QUOTE]
No converter.
Checked that. That flapper appears to open just fine. The more gas, the wider it opens.
[QUOTE=are those compression numbers on a warm engine?
I ask because the S3 and S4 13B blocks were essentially the same and for a 13B block, compression numbers should be in around 110psi.
my rebuilt S3 13B got me 125psi on all faces, 5psi higher than what the FSM mentions as a completely healthy, brand new engine. 85psi is the limit IIRC[/QUOTE]
The engine was not warm. I'll do it again if it will make a difference.
[QUOTE=How are you testing your fuel pressure? If you're able to test at the firewall hardline and have 2-3 feet of hose, strap the gauge under the wiper and go for a drive. You may well find that the pump can keep up at idle, but the pressure will drop under load. I had a clogged fuel pickup screen in the tank (I could fill it with gasoline in the driveway, and it wouldn't leak out) that also killed the pump in short order. A clogged filter or weak pump would also show up in a test drive with a fuel pressure gauge under the wiper.[/QUOTE]
I checked it according to the FSM, but I will try to do it while driving down the road. Good idea.
[QUOTE=1 of 2 things happening here.
1) lost your leading spark
2) lost power to one of the injectors [/QUOTE]
All plugs have spark. I am runing an MSD ignition box with wires going from the coils directly to the leading plugs. I am positive all plugs have spark.
[QUOTE=have you double checked your wires to see if you installed them correctly? sounds like you might have reversed the leading/trailing.[/QUOTE]
Double and triple checked. That will really mess things up.
[QUOTE=also, another thing to mention is a clogged converter(s). do you have a conveter? [/QUOTE]
No converter.
03-02-09, 08:15 AM
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Oh right. I didn't mean to make it sound like it was an assumption. I have pulled each plug and watched it spark. It looks pretty strong. I also have the second gen fuse box so no more fusible links. All my fuses are good though.
03-02-09, 10:06 AM
#14
So you have spark, you have air, and you think you have fuel because the fuel pressure test checked ok----good. From here I would test to make sure that both injectors are working. There are also injector grounds near the vent/vacuum solenoids. Make sure there is good connection there. Also, you checked fuel pressure, but what about fuel volume?
The fact that your 7 runs a little better when its warm causes me to think that it is fuel related. When the car is cold it demands a lot more fuel, etc.
Mike
The fact that your 7 runs a little better when its warm causes me to think that it is fuel related. When the car is cold it demands a lot more fuel, etc.
Mike
03-02-09, 12:22 PM
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So you have spark, you have air, and you think you have fuel because the fuel pressure test checked ok----good. From here I would test to make sure that both injectors are working. There are also injector grounds near the vent/vacuum solenoids. Make sure there is good connection there. Also, you checked fuel pressure, but what about fuel volume?
The fact that your 7 runs a little better when its warm causes me to think that it is fuel related. When the car is cold it demands a lot more fuel, etc.
Mike
The fact that your 7 runs a little better when its warm causes me to think that it is fuel related. When the car is cold it demands a lot more fuel, etc.
Mike
03-02-09, 07:37 PM
#19
I would do a pin test at the ECU. The procedure can be found in the FSM.
Trochoid has a link in his signature.
That way you can find out if there are any abnormalities one of them being a loss of ground from one of the injectors. The clips become very brittle over time and corroded. I have had it happen on several SE's and found it through the pin test.
Trochoid has a link in his signature.
That way you can find out if there are any abnormalities one of them being a loss of ground from one of the injectors. The clips become very brittle over time and corroded. I have had it happen on several SE's and found it through the pin test.
03-02-09, 08:57 PM
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For some reason trochoid's links aren't working for me. I'll see if I can find an FSM elsewhere or see if my Hayne's manual covers it. Thanks Doc.
03-02-09, 09:37 PM
#21
03-03-09, 03:36 PM
#25
I would disconnect the exhaust to see if maybe the muffler or a presilencer has broken up internally and restricted the flow. if that checked out look into the fuel volume/pressure under load, there is a small cone strainer BEFORE the fuel pump on the SE it may be blocked and it will look like the pump is weak.