Fuel System Problem Question
01-28-05, 04:05 AM
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Fuel System Problem Question
Well, My 90 NA is doing some funny things and I thought I'd share some symptoms and my thoughts and perhaps you can help me pinpoint the things that need replacing now.
The car has no problem starting, its a very poor start though, cranks good fires and sputters bad and barely makes it to about 800rpm and stays there. The car floods often and is getting bad milage(worse than usual) which is leading me to believe the car is running quite rich. In the last week the car has also developed a hesitation, it occurs usually while holding a slight acceleration. I get no codes, but I do get a quick CEL at startup, its only on for a second and registers no codes.
The car is completely up to date on its tune up type maintenence (plugs, wires, fuel filter, clean K&N, new O2 sensor, etc...)
My guesses as to the cause of the problems are:
Fuel Pump
Pressure Regulator
Injectors
Engine Timing (not sure if it would be this, FSM says its possible)
ECU (again not sure, FSM says possible)
If you have any related experience or a better guess than I please let me know so I can arrage to buy the **** needed to fix this.
The car has no problem starting, its a very poor start though, cranks good fires and sputters bad and barely makes it to about 800rpm and stays there. The car floods often and is getting bad milage(worse than usual) which is leading me to believe the car is running quite rich. In the last week the car has also developed a hesitation, it occurs usually while holding a slight acceleration. I get no codes, but I do get a quick CEL at startup, its only on for a second and registers no codes.
The car is completely up to date on its tune up type maintenence (plugs, wires, fuel filter, clean K&N, new O2 sensor, etc...)
My guesses as to the cause of the problems are:
Fuel Pump
Pressure Regulator
Injectors
Engine Timing (not sure if it would be this, FSM says its possible)
ECU (again not sure, FSM says possible)
If you have any related experience or a better guess than I please let me know so I can arrage to buy the **** needed to fix this.
01-28-05, 07:27 AM
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A worn out TPS can do that.
Using test lights or voltage at idle readings will get your idle setting perfect, but you could still have a worn out TPS resistor.
-The golden test:
Unplug the TPS connector.
Clip a cheap analog (needle type) VOM on the orange & black pins.
Set it to the 1K scale.
Hold off the throttle & work the short range TPS plunger in & out.
You should see a smooth sweep from ~0 to ~5K ohms.
Any bad spots or drop outs in the stroke - it's bad & will give fuel cuts at part throttle.
(Before you toss it, try spray contact cleaner between the sleeve & plunger.)
- Then set it:
Find the fast idle (warm-up) cam & back it off so the throttle sits on the hard idle stop.
Adjust the setting to 1K ohms.
While holding off the fast idle cam, open & close the throttle a few times to see that the 1K setting repeats.
The upper (long range) TPS is self adjusting.
You shouldn't have to mess with it.
Its job is to tell the ECU how to run the MOP.
-
-
Using test lights or voltage at idle readings will get your idle setting perfect, but you could still have a worn out TPS resistor.
-The golden test:
Unplug the TPS connector.
Clip a cheap analog (needle type) VOM on the orange & black pins.
Set it to the 1K scale.
Hold off the throttle & work the short range TPS plunger in & out.
You should see a smooth sweep from ~0 to ~5K ohms.
Any bad spots or drop outs in the stroke - it's bad & will give fuel cuts at part throttle.
(Before you toss it, try spray contact cleaner between the sleeve & plunger.)
- Then set it:
Find the fast idle (warm-up) cam & back it off so the throttle sits on the hard idle stop.
Adjust the setting to 1K ohms.
While holding off the fast idle cam, open & close the throttle a few times to see that the 1K setting repeats.
The upper (long range) TPS is self adjusting.
You shouldn't have to mess with it.
Its job is to tell the ECU how to run the MOP.
-
-
Last edited by SureShot; 01-28-05 at 07:29 AM.
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