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Firebird wont idle well, or dies like the fuel is being cut off.

Tiny
TRAY BOY
  • MEMBER
  • 1991 PONTIAC FIREBIRD
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 150,000 MILES
I have a 91 firebird v6, had an oil leak for years, got it fixed it was the oil filter, then I noticed my oil pressure went through the roof! The guage stayed maxed at 80. Then after changing the spark plugs, my problems started. It wont idle well, or when giving it gas the rpm's slowly go down till it dies. Changed the fuel filter, ign. Module, distributor, rotor, fuel pump relay, plugs and wires. No change. Messing with the fuel pump or injectors will be my last resort, as it was running fine before this. This bothers me-- when turning the key on "Before starting the car" the oil pressure gauge goes all the way to 80 without the car running? Could the oil pump switch cut off have anything to do with my problems? Thanks for any help. Tracey
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Wednesday, July 27th, 2011 AT 5:15 PM

48 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Shouldn't be any oil pressure without the engine running. Maybe a problem with the sending unit--gage or wiring circuit. Use an analog gage inplace of sending unit, just to double check oil pressure.

Use a gage and check fuel pressure. Any applicable mil codes? You can check those yourself.
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Wednesday, July 27th, 2011 AT 5:26 PM
Tiny
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Thanks, you talking about an oil sending unit? I can't find anything like that at the auto store? To check my fuel pressure, I'm pretty sure I have to remove the entire manifold, also to get to the injectors and the valve. Not good. Mainly focused on the crazy oil gauge. When it runs for a bit, It will drop to around 60 before it dies. Im not an experienced mechanic, lol
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Wednesday, July 27th, 2011 AT 6:02 PM
Tiny
JDL
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The oil pressure switch is N7 in the diagram. If mfi should be a schrader valve on the fuel rail, I'll see if I can find a picture.

Do you know how to check for applicable codes?
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Wednesday, July 27th, 2011 AT 6:30 PM
Tiny
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No sir, I'm learning by doing. There has been no computer hooked up to this car. I would love a pic of where the fuel valve tester is! I do know where the oil pump switches are, is the oil pressure switch different? Is that what sends the signal to my dashboard gauge? Thanks for the help!
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Wednesday, July 27th, 2011 AT 7:06 PM
Tiny
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My bad, they are called pressure switches, not pump. I know theres 2 of them, one has something to do with cutting the fuel off. Its located right by the oil filter I changed.
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Wednesday, July 27th, 2011 AT 7:13 PM
Tiny
JDL
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As far as the oil pressure switch, it handles both, oil pressure gage and redundant power supply to the pump.

To check for mil codes, you use a jumper wire between the A & B terminals at the datalink connector. Then, turn the key, just till the dash lites come on, no further, no crank. The mil on the dash should start flashing, you count the flashes to get the codes. Your looking for two digit codes. An example, code 12 would be 1 flash a slight pause then two quick flashes. May flash three times before moving to next code, if there are any others?

The data link connector should be lower edge of dash, driver side. The picture is just to show location of A and B.
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Wednesday, July 27th, 2011 AT 7:40 PM
Tiny
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OK! Much thanks! Assuming a jumper cable is just a plain straight piece of wire, I will try this, and I sure think the fuel oil pressure switch may be my problem. If I don't blow me or the car up, I will get back to ya. Thanks so much!
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Wednesday, July 27th, 2011 AT 7:59 PM
Tiny
JDL
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Use a piece of automotive wiring at data link connector or a paper clip. A small piece of wire usually works best for me. Not a jumper cable.
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Wednesday, July 27th, 2011 AT 8:14 PM
Tiny
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Okay, , appears to be flashing 12 over and over again. One flash, then 2 quick ones, then pauses and repeats. Going to try to look this up in case I don't hear from you for a while, and Thank You for the tip!
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Thursday, July 28th, 2011 AT 3:45 PM
Tiny
JDL
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Code 12 should mean diagnostic mode. If no codes after that, you don't have any codes. You always have the code 12 first.

As far as the oil pressure switch, my database seems to show something different than your post? Databases are not always correct.
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Thursday, July 28th, 2011 AT 7:22 PM
Tiny
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Ive got to check the fuel pressure, its running, but not well and not for long if I stop peddling the throttle. If you could find that valve, Ill tear off the manifold if I have to. Ive just been told its on the fuel rails, and they are hidden mostly under the manifold.
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Thursday, July 28th, 2011 AT 8:49 PM
Tiny
JDL
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The schrader valve shouldn't be hidden, follow the fuel lines. Sorry, I haven't found a picture. If I found one, it would probably just be generic. With tbi, you splice into the fuel supply line, sometimes, I splice in at the fuel filter. Just be sure, no pressure on fuel line before taking any lines loose.
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Thursday, July 28th, 2011 AT 9:04 PM
Tiny
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I found this picture. It wouldn't make sense to cover the schrader valve. #4 is the schrader valve, #7 is the fuel block, #3 is the fuel rail.
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Thursday, July 28th, 2011 AT 9:12 PM
Tiny
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Yes I found it, its at the very back of the manifold, a chrome looking cap like a bike tire. I'll mess with that soon, I just started it, here's what happens, I unplugged the oil pressure switch, the gauge goes to 80 and stays at all times. When plugged up, its down to zero before I turn the key, then when power goes on, but not starting the car, it goes to 80, then after dying or me shutting it down, but key still to power, the gauge jumps all over, down to 40, back up, back down, just like it wants to play, or is bored? Lol Like there's a short or something. Hope this info helps. Ive got to take a break for a while, the heat is killing me. Thanks again for the photo!
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Thursday, July 28th, 2011 AT 9:37 PM
Tiny
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Sorry when I say jumps around, I meant it moves slowly up and down like its ran by pressure fluctuating. With the motor off but key on after dying.
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Thursday, July 28th, 2011 AT 9:42 PM
Tiny
JDL
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Use an analog gage just to double check oil pressure.
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Friday, July 29th, 2011 AT 4:58 PM
Tiny
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I changed the oil pressure switch, the gauge is behaving normal now, stays at zero till I start the car, then goes to 60 like it always used to. Didnt have gage to test it. I can also hear the fuel pump prime when turning the key. Im going to try to borrow a fuel pressure tester, there just to expensive Im not working right now. The car always runs a bit better in the morning when its cool. After all this, I guess it will be time to check the injectors. Is there a sensor for heat that may be messed up and killing the car or fuel?
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Sunday, July 31st, 2011 AT 11:40 AM
Tiny
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If it is a temp issue, there is the coolant temp sensor? I can't say that is your problem? Glad you got the oil gage working like it should.
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Sunday, July 31st, 2011 AT 4:01 PM
Tiny
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Well thanks, but here's the new problem, I'm putting the fuel test on hold for now. When I turn the key to power, the temp gauge is 0, as soon as I start to turn the motor over, the temp gauge goes to 260 and beyond, Ive also heard the radiator fan come on shortly after getting it running until dies. What sends the signal to the temp gauge? Ive surfed around, can't find a solution. Ive checked another car, it does not do this. Sorry to keep bothering you. I really need to get this car running.
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Sunday, July 31st, 2011 AT 7:10 PM
Tiny
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Im speaking about the engine temperature gauge
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Sunday, July 31st, 2011 AT 7:13 PM

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