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1999 Firebird Hard to Start When Hot
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devont07
New User
Feb 3, 2009, 7:07 PM
Post #1 of 8
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1999 Firebird Hard to Start When Hot
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Car Information:
Pontiac Firebird 1999
V6 3.8L around 120,000 miles
Oil has been changed every 3000 miles with mobile 5000, recently changed to penzoil
Coil pack has been changed at 60,000 miles
Last tuneup was around 70,000
Symptoms:
Crackling in tailpipe when letting off the gas pedal, backfiring
Very Hard to start when car is warmed up, large puffs of smoke initially, flooded (Starts on first crank when cold)
Very rough idle, car shakes and rocks when idling
Recent slight knocking noise coming from engine, is audible from tailpipe
Checked:
Fuel pressure - ok
Fuel Filter - ok
Vaccum Hoses - ok
About 6 months ago I started experiencing some major difficulties with my car. One day I went to start the car and it was warm outside, it took forever to get started and when it actually started I got a ton of smoke, it seemed like it was flooding bad. Now that its winter and its cold outside it starts perfect the first time. If i drive it around and it reaches operating temperature, I leave it for about 10 minutes and try to start it will not start properly once again. I brought it to a mechanic and had it checked for the problem, he said there was no major problem and he wasn't sure about the starting, maybe a faulty oxygen sensor or ETS. It idles extremely rough and when i accelerate and let off the gas I get a very loud pop followed by some crackling in the tail pipe. I put a scan tool on the car and checked the coolant temp sensor and the initial value was 34 and after i got it to operating temperature it peaked at 194. The engine only has 120000 miles on it so I wouldn't think its an actual mechanical fault with in the engine and I take very good care of this car. I've had a check engine light twice but it happens very randomly and dissapears quickly, the code is "random misfire".
Oh yea, yesterday I was inspecting the coils for ohm rating and I found one of the terminals on piston 3 was very rusty and the wire lead was even worse. I haven't got to replace the wires yet because of snow but is it possible for a faulty coil connection to cause all of these symptoms?
Any feedback is appreciated.
(This post was edited by devont07 on Feb 3, 2009, 7:12 PM)
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Loren Champlain Sr
Veteran
/ Moderator
Feb 3, 2009, 7:23 PM
Post #2 of 8
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Re: 1999 Firebird Hard to Start When Hot
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If it's been 50,000 miles since the last tune, I'd say it's time for at least spark plugs. Wires, maybe. When the CTS read 34, was that fairly accurate as to ambient temp? What kind of readings are you getting from the MAP sensor?
I'm sure injector pulse width is very high, due to the overfueling. Just re-read post. When you replace the wires, clean that post on the coil with emery cloth or steel wool. Then, use dielectric grease on the wires before you install them. A fuel pressure test would help to see if it's holding pressure, or bleeding off (leaky injector(s).
Loren
SW Washington
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devont07
New User
Feb 3, 2009, 7:30 PM
Post #3 of 8
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Re: 1999 Firebird Hard to Start When Hot
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It was around 34 degrees outside when I tested it yea, I actually wrote down the information from the scanner, the scanner showed 10.3 in.hg at idle for map sensor. I believe the mechanic that serviced my car checked the fuel pressure and he said that it was ok. I will clean the terminals and put on the new wires tommorrow, I will also schedule a tuneup. I will update and let it be known if the new wires fixes the problem. Thanks!
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Loren Champlain Sr
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Feb 3, 2009, 7:36 PM
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Re: 1999 Firebird Hard to Start When Hot
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10.3 is way too low. That will cause the system to go rich. Check for vacuum leaks. The manifold vacuum should be around 17-19hG. The MAP sensor sees a drop in vacuum as if you are under load, accelerating, so the vacuum drops, and it adds fuel. Engine condition and the way it is running, of course, will affect manifold vacuum. But, the low vacuum reading will cause a flooding condition. A cold engine can handle that extra fuel, but a warm one cannot.
The fuel pressure, at this point, isn't my concern. Is the fuel pressure holding after engine shut-down, or is it bleeding off, into the cylinders?
Loren
SW Washington
(This post was edited by Loren Champlain Sr on Feb 3, 2009, 7:38 PM)
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devont07
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Feb 3, 2009, 7:57 PM
Post #5 of 8
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Re: 1999 Firebird Hard to Start When Hot
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Wouldn't the low vacuum cause a check engine light though?
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Loren Champlain Sr
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Feb 4, 2009, 4:02 PM
Post #6 of 8
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Re: 1999 Firebird Hard to Start When Hot
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The vacuum wouldn't cause a CEL, itself. However, the results of the low vacuum might. I would think that it would give you a rich O2 code, however. Also, misfire codes due to the roughness. But, we tend to 'depend' on the PCMs too much. They don't always pick up everything.
Loren
SW Washington
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devont07
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Mar 6, 2009, 3:28 PM
Post #7 of 8
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Re: 1999 Firebird Hard to Start When Hot
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Ok just as an update, it's been a while since I posted on here but so far I've replaced half the spark plugs and half the wires, this included the wire that was very rusted. When I first started the car after replacing the spark plugs it started perfect, no rough idle and had some major power, kind of like back when it didn't have this problem. So I drove it around and parked it at a restaraunt and ate....I came back out approximately 40 minutes later and.....of course it wouldn't start right again and the rough running continued and may actually be worse, it hardly back fired what so ever but after I started it the second time the backfiring continued. UGH!! I'm trying to figure this out myself because I can't afford to put it in a shop at the moment because I need a car to get to school and work. By the way, changing the spark plugs was a major pain in the ass and I've only changed the driver side plugs which I've heard the passenger side is even harder. I've also noticed that when its at idle and I get on it and let off it studders really bad and if I don't give it time to mellow out after the start up it will die on me when I changed into drive from park.
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Loren Champlain Sr
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Mar 6, 2009, 5:15 PM
Post #8 of 8
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Re: 1999 Firebird Hard to Start When Hot
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Please re-read the entire thread and proceed from there. This doesn't sound like a spark plug fix, although they are probably needed.
Loren
SW Washington
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