It seems to me I'm getting too much fuel. When the injector sprays it sprays hard and bounces a little off the throttle plate. I keep getting a code 45 and on one of the checks were for the fuel pressure. I rebuilt the fuel pressure regulator and also swapped another one in to see if it worked but was the same both ways. Could my fuel pump be putting out too much fuel? The injector is pretty new and does not leak. Would the fuel pump relay or oil pressure switch cause too much voltage to the fuel pump to cause more fuel to come out? Its a 4cyl.

Does not seem likely that fuel pump would produce more pressure over time - they seem to produce less. Any chance that the pump was replaced ? I was thinking that a V6 pump would not work well in a Duke ( parts store sold the wrong part). The fuel return line could be blocked / pinched, not allowing the press. regulator to work correctly.

Looking at the causes for a Code 45, Has the O2 sensor been replaced ?, since it is a wear item. Check for a broken vacuum line to the MAP sensor. The TPS sensor could be worn. (Better to confirm sensors(s) bad before replacing and less $$$)

Too much voltage to the fuel pump, the voltage could be higher if the alternator was over charging.

I dont know what a code 45 is off hand, but if its an O2 sensor code, thats a generic, anything's wrong with the engine code. Pretty much anything that happens in the engine will effect the exhaust gas either rich or lean depending on what it is. Seeing an O2 code is usually just a symptom of another problem. I really really doubt you are seeing too much fuel pressure though, if you dont know just have it checked, if you dont have a guage, just pull up outside a shop that doesnt look busy and ask real nice, it just takes a second. I forget what its supposed to be off hand, but its lower than 15, the V6 pump puts out 40, FYI

quote Originally posted by StockGT: Does not seem likely that fuel pump would produce more pressure over time - they seem to produce less. Any chance that the pump was replaced ? I was thinking that a V6 pump would not work well in a Duke ( parts store sold the wrong part). The fuel return line could be blocked / pinched, not allowing the press. regulator to work correctly. Looking at the causes for a Code 45, Has the O2 sensor been replaced ?, since it is a wear item. Check for a broken vacuum line to the MAP sensor. The TPS sensor could be worn. (Better to confirm sensors(s) bad before replacing and less $$$) Too much voltage to the fuel pump, the voltage could be higher if the alternator was over charging.

I don't know if the fuel pump was replaced. I replaced the 02 sensor about 9 months ago. This is when the problems were first comming about. Vacuum line to map is new. I've tried 2 or 3 different TPS sensors. New IAC, new coolent temp sensor with new pigtail, rebuilt the throttle body. Just replaced wires and plugs. The engine light doesn't come on when driving now after the plugs and wires but in park and idleing it will come on until I give it some gas. I did put a CS alternator in the car a month or so ago but it was doing this way before then. I need to get a fuel pressure tester and just see how much my pump is putting out.

Sounds like you have already change the most common parts for your problem.

I have read a few post about problems with O2 sensors on Fieros, many have reported Delco and Denso work best. How's your MPG, bad O2 sensors increase your visits to the gas station. Don't rule out the possibility that the "New" part is bad.

Sensors are just part of the Engine control computer system. The connectors and wire are getting old, even when taking care to remove connectors, I still manage to crack some of the old and brittle plastic connectors. Corrosion on the connector is another problem.

Do you have access to an engine scanner ? Some parts stores have a scanner that they will scan the car for you.
Depending on the Year of your Fiero, with a Laptop and OBD1 cable, you could use WinALDL to monitor the engine when running ( WinALDL not for 87&88 Dukes).

add-on: What type of spark plugs ? ACDelco - regular type?

[This message has been edited by StockGT (edited 05-02-2008).]

yes, your fuel pump could be putting out to much fuel. that its job. there is a fuel return for the excess. there is a regulator also. have you actually check the fuel pressure? there may be a ECM issue, where the ECM or a short in the wiring leaving the injector wide open?

[This message has been edited by Pyrthian (edited 05-02-2008).]

ck your presure first to be sure, but if you've already replaced the regulator then about the only thing that could cause too much presure would be a plugged (crimped) fuel return line.

I'm using AC Delco plugs. I swapped an different ECM to see if it would help last year but its the same. I need to borrow a laptop and run Winaldl as I do have a cable.

ly41181 - I have an 87 Duke, does EXACTLY what yours is doing. Extremly bad gas milage and my fuel injector just POURS gas into the TB.. I replaced the fuel injector and O2 sensor. didn't help anything... Does your duke have hesitation or lack of power. especially when first starting off from a stop sign or light. ????

quote Originally posted by Russ544: ck your presure first to be sure, but if you've already replaced the regulator then about the only thing that could cause too much presure would be a plugged (crimped) fuel return line.

Russ is right on here. You need to check your fuel preasure. You are trying to do steps 3 and 5 without doing steps 1 and 2. Always start st the beginning with the simplest tests first.

quote Originally posted by Kyle87: ly41181 - I have an 87 Duke, does EXACTLY what yours is doing. Extremly bad gas milage and my fuel injector just POURS gas into the TB.. I replaced the fuel injector and O2 sensor. didn't help anything... Does your duke have hesitation or lack of power. especially when first starting off from a stop sign or light. ????

Starting off from a stop its slow unless I give it some decent throttle(auto). When I come to a complete stop, sometimes it wants to die. I have a really high idle when I start the car. Up to 2700rpm sometimes. I'll give it a little gas and it will drop down to 2000. When she warms up I have a decent idle at 1100. I've unplugged the coolent temp sensor while the car is running and it will drop the idle by 700 when cold. Used to if i did that the car would die. If I unplugged the MAP it would change the idle, now if I unplug the MAP it will die. Wild.

You say that it looks like is spraying a lot of fuel, on a throttle body this is usually the case. just looking at the spray can't tell you much. as was you said you were going to do fuel pressure will tell the real story. you can also look at you spark plugs, if they are black and sooty then you are running rich. they hould look more tan to brown on the tip. that will give you a better indication of how the system is running

quote Originally posted by Ants87gt: You say that it looks like is spraying a lot of fuel, on a throttle body this is usually the case. just looking at the spray can't tell you much. as was you said you were going to do fuel pressure will tell the real story. you can also look at you spark plugs, if they are black and sooty then you are running rich. they hould look more tan to brown on the tip. that will give you a better indication of how the system is running

The old plugs I pulled out were normal, no evidence of running rich. The car can sit there and idle in park and the check engine light will come on if I let it sit long enough. Thats when I can give it some gas for a few seconds and it will go off.