1985 Pontiac Firebird Car hard to start

Tiny
AXL4U2000
  • MEMBER
  • 1985 PONTIAC FIREBIRD
Engine Performance problem
1985 Pontiac Firebird V8 Two Wheel Drive Automatic 55k miles

Hello,
My trans am is very difficult to start. When it finally does it feels like it wants to die again but once you give it gas it gets going but the engine shakes and it is very rough. Once is in gear it goes fine and the shaking goes away. I turn it off and it starts right away but still shaky on idle. I let it cool down for 10 mins and it's hard to start again. I noticed a little puddle of something perhaps gas underneath the air intake on top of the manifold right next where two fuel lines come in. My mech told me it could be a bad sensor but not sure. Can you please help?
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Monday, November 24th, 2008 AT 10:52 AM

17 Replies

Tiny
RACEFAN966
  • EXPERT
Ok it is an 85 Firebird with only 55k so gas on the intake is not a sensor this car has a carburator and I think the leak is from that somewhere. So my first question has the carb ever been rebuilt? If not sounds like it is time. If it has never been rebuilt then you can not adjust fuel mixture so it is probably running lean. You can test this with some carb cleaner (NOT STARTING FLUID) and as it is idling spray a bit in the carb and see if it will idle better if so that answers it. I also would like to know if you have an open air cleaner or the original one? If you would like to rebuild it yourself get back to me as I have done lots of rochester carbs and they are very misunderstood. Let me know what you would like to do from here. Thanks
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Monday, November 24th, 2008 AT 11:21 AM
Tiny
AXL4U2000
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I forgot to say it is a MFI not carburated. Sorry about that.
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Monday, November 24th, 2008 AT 11:33 AM
Tiny
RACEFAN966
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Ok my bad I should have asked most are carb. Either way we can do this. So which side of the engine is the leak on and have you checked the injectors for any leaks? Have you checked the fuel pressure regulator for leaks? Lets get this leak found first as this is not good. Then we go from there if the problem is still there after the leak is fixed ok. Get back to me. If you need to send a pic of where the leak is at then go for it. Thanks.
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Monday, November 24th, 2008 AT 11:40 AM
Tiny
AXL4U2000
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Thank you. Well the leak appears to be on the passanger side. If you look at the engine from the front you will see the fresh air intake hose going into the engine's plenum. There are two pipes that go into the plenum right next to the TPS. I can see a drop of something hanging from one of those two pipes right underneath the fresh air intake hose and a little puddle right underneath those pipes on top of the plenum right underneath where the hose and the fresh air flap assembly meet. I have not check the fuel pressure regulator how I do that. Another thing I noticed before this problem started was when I open the gas tank to put gas there was a lot of pressure out almost like the gas cap wanted to fly out of my hand and a lot of smell of gas. I replaced all vaccum hoses with the exception of the ones leaving the EGR and the vapor canister ( they still look in good shape )
The problem started last week with high RPMs on idle, then hard to start, then after it started when you give it gas started to splurr and car died. Now I can get it to start after few times but then engine shakes and on idle the RPM eventually jump to 1500, I put it in gear and shkes go away and then RPMs are in the 500-600 range. Turn the car off and it starts right away. I let it cool down for 10 mins and it is hard to start again.
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Monday, November 24th, 2008 AT 12:15 PM
Tiny
RACEFAN966
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Ok first lets put a new gas cap on it, it should not hold that much pressure sounds like one problem is the gas cap is bad. Now as for the leak what is it coming out off that area is it fuel as there should be now fuel lines hooked to the throttle body the pressure line and the return line should come up to the fuel rail that attaches to the top of the injectors. As for testing the fuel pressure regulator hook up a fuel pressure tester and pull the vacuum line from the regulator the fuel pressure should jump about 10 psi if it does it is working. If you have a valve to hook the fuel pressure tester too you can do a running test on it to see what the fuel pressure is doing when driving. One more question when was the fuel filter replaced last?
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Monday, November 24th, 2008 AT 12:58 PM
Tiny
AXL4U2000
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I did buy a new gas cap and it was done last week before the problem started. When was the gas filter replaced? I bought the car maybe 3 months ago and I have not replaced it. Don't know when the previous owner did so.
I had this starting problem before but since I had aon old battery I never got it to start before the battery went dead. Usually car did not start, my mech towed the car and when they dropped the car it would start fine so he couldnt figure out the problem. He had me replace the alternator but problem continued every two weeks or so thats why i'm not taking my car to him ever again. Now problem is worse and everyday I'm just killing my brand new battery and starter trying to start the car
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Monday, November 24th, 2008 AT 2:10 PM
Tiny
RACEFAN966
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Ok on the gas cap did they give you a vented one or a pressure cap. Your vehicle needs a vented cap or it will build up pressure on the tank could be part of you running problem too. As for fuel filter I would replace it either way as you have no knowledge as to when it was done last. GM likes to have new ones it seems once a year. Then we need to test the coolant temp sensor. What you need to do is give me the resistance (ohms) at a known temp and I will look it up and see if it is in spec. As for the fuel leak it maybe at the fuel line meaning it needs a new oring and I would buy that at the dealer. With low miles it makes me wonder when it was run last. If it has been a long time then you will have to bring it back from parked. I would also run some seafoam through it too to clean the fuel system.
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Monday, November 24th, 2008 AT 3:17 PM
Tiny
AXL4U2000
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I think I got a non-vented cap but I will switch to the other kind and get the fuel filter replaced. Seems like you and my new mechanic share same thoughts on what it could be wrong with the car as he told me that it may be a problem with the coolant temp sensor. I will take the car to him tomorrow and will share the results.
Thank you so much for your help! Excellent service!
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Monday, November 24th, 2008 AT 4:09 PM
Tiny
RACEFAN966
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No problem you are quite welcome and thanks for your support too. Let me know how it goes ok. If you need more help or have more questions then just ask ok.
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Tuesday, November 25th, 2008 AT 10:53 AM
Tiny
AXL4U2000
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Well my mechanic said that he needs to replace the entire fuel regulator and he said that part cost like 220 bucks plus labor he said total of 500 bucks. Im kinda suprised because I looked up it on line and the most expensive one I found was 95 bucks.
Any suggestions?
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Tuesday, November 25th, 2008 AT 4:38 PM
Tiny
RACEFAN966
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Yea replace it yourselft. It isn't that hard should take more then about 30 min. Or so. If need help to do that just let me know and I will look it up and see what I can tell you about doing it yourself.
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Tuesday, November 25th, 2008 AT 9:18 PM
Tiny
AXL4U2000
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Thank you for your help. Its just too much gas going and seems like its not going back to the tank. If it is a plugged return line or a bad fuel pressure regulator how I check for that?
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Tuesday, November 25th, 2008 AT 10:50 PM
Tiny
RACEFAN966
  • EXPERT
Ok first you need a fuel pressure tester for injection and you find the service port on the fuel rail looks like a tire valve. Then you start the car and record the fuel pressure then unplug the vacuum line from the regulator and it should go up about 10 psi if it does it is fine as far as its operation. Your fuel pressure on this vehicle should be 30 to 40 psi and 40 to 47 psi with the regulator vacuum line unpluged. Let me know how it goes. Have a Great Thanksgiving.
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Wednesday, November 26th, 2008 AT 10:18 AM
Tiny
AXL4U2000
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Ok I replaced the fuel regulator and I think that corrected the gas issue. It started fine, no gas leak and real quick but today I went for lunch at work and it was just not starting until I tried for a few times and at the last time I just kept my hand in the switch and it started but maybe 10-15 secs later. I tried again and it started ok. I drove it for a few and park and try to start it again and it worked fine.
Someone told me it could be the distributor as once before ( yeah this happens once in a while before the gas issue ) I got no spark but then the car gets moved such as towing it and when they put it down it starts fine. Maybe new module and coil?
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Friday, November 28th, 2008 AT 3:28 PM
Tiny
RACEFAN966
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It could be a module. Does go along running fine and just shut off sometimes?
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Saturday, November 29th, 2008 AT 9:31 AM
Tiny
AXL4U2000
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Thank you for the advise. I replaced the ignition module and it starts just fine now. I am replacing the coil as well just to be safe.
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Wednesday, December 10th, 2008 AT 11:41 AM
Tiny
RACEFAN966
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Yea that would not be a bad idea as one can take the other out. Anyway thanks for your donation and glad to hear it is running good now. If you need any thing more just ask.
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Wednesday, December 10th, 2008 AT 8:16 PM

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