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1999 Pontiac GTP sputtering


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ctrad45
User

Jul 10, 2011, 4:31 PM

Post #1 of 10 (2179 views)
1999 Pontiac GTP sputtering Sign In

Hey all!

Got a good one for you!

1999 GTP
Just had all the pulleys replaced.
Had a straight pipe put on.
Car sat for about a year.
160,000 on her.

Car has a slight rattle at idle coming from I think the cone of the supercharger. Under power (around 2500RPMs) the car has a slight sputtering and slight loss of power. Under heavy power the car had almost full power but the sputtering is there. The Service Engine Soon light has been on constantly and blinks during the acceleration and sputtering. The sputtering almost feels like its from the exhaust but I can't be sure. I've heard a few theories but came here for another opinion. This forum has helped me in the past and I hope you guys can help.

Thanks!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 10, 2011, 5:00 PM

Post #2 of 10 (2175 views)
Re: 1999 Pontiac GTP sputtering Sign In

The "check engine" light is an indicator for a system that monitors many electronic functions in the system, also called the "malfunction indicator lamp" (MIL). It can come on for any of hundreds of different causes from any of the systems that the computer monitors. Some are very important and can lead to further component or engine damage and some are emissions related not as serious but still a problem and need to be repaired. The flashing part indicates a severe misfire.

Your first step is to have the computer scanned to retrieve the trouble codes that were set when the check engine light came on. Those codes will give you specific information about what the computer saw and will get you pointed in the right direction to find your problem. With a 1996 or newer and some 95 cars and you have an AutoZone or Advanced auto parts in your area, they will read them for free. Once you have these code numbers, we can be a lot more specific about what your problem may be.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Mr.scotty
Enthusiast
Mr.scotty profile image

Jul 10, 2011, 5:46 PM

Post #3 of 10 (2161 views)
Re: 1999 Pontiac GTP sputtering Sign In

Did the car run fine with no check engine light before you messed with the exhaust?
I wouldn't have made it a strait pipe.
--------------------------------------------------------

Your only as good as your tools!


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jul 10, 2011, 5:50 PM

Post #4 of 10 (2158 views)
Re: 1999 Pontiac GTP sputtering Sign In


Quote
Car sat for about a year.


Wonder if that has anything to do with it? How long does it take for phase separation to occur in the gas tank?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


ctrad45
User

Jul 10, 2011, 8:18 PM

Post #5 of 10 (2148 views)
Re: 1999 Pontiac GTP sputtering Sign In

Taking it in tomorrow. Will report back. Had intermittent issues before straight pipe was put on but not like this. I've heard everything from catalytic issue to supercharger coupler issue to "needs a tune-up".

When I get on it it runs strong if just a bit sluggish with a little of the sputtering. Hmmm...

And not sure about the gas tank thing. Did 2 fill ups with super premium and no change.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 11, 2011, 7:29 AM

Post #6 of 10 (2139 views)
Re: 1999 Pontiac GTP sputtering Sign In

"sat for a year" - just because and if you bought it that way and don't know how fuel was if it was stabilized and I don't think that works so well as claimed, would do a fuel filter just because, would get the moto vac injection cleaning job and add 1/2 of what bottle says of Techron by Chevron injector car. Unlikely to solve a problem but may prevent another.

Damn gas sold is so loaded with fillers including ethanol in most places I wish it was sold by weight AND gallons so you know what you are getting but you really won't. I've asked an oil company and they ain't talking.

Gas has become an issue. Math doesn't add up. Barrel (42 gal) of crude at the docks at today's price is $2.38 a gallon, then costs to handle it, refine it (you don't get 42 gallons of gas out of 42 gallons of crude) - deliver it taxes can be 48 cents depending on location or more and poor station owner's really only get 6-10 cent markup and expensive to have the places.

I really don't think the junk they use as so called additives is aways a good thing but that and whatever junk the mix in does make the gallon but not pure product and doesn't seem to store well,

T



ctrad45
User

Jul 12, 2011, 4:26 AM

Post #7 of 10 (2114 views)
Re: 1999 Pontiac GTP sputtering Sign In

Mechanic says the #4 cylinder is misfiring. Tried moving wires to see if it is the wires and still misfiring. Will have another update today.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 12, 2011, 7:09 AM

Post #8 of 10 (2108 views)
Re: 1999 Pontiac GTP sputtering Sign In

OK: Not a wire, now swap spark plug and note what they look like comparatively. Then on to injection, compression. Be quick with this or it will probably kill converter!

T



ctrad45
User

Jul 15, 2011, 6:03 AM

Post #9 of 10 (2094 views)
Re: 1999 Pontiac GTP sputtering Sign In

Wiring and spark plugs needed. Number 4 wire shot. Replaced temporarily with a used wire. I just don't have the $400 to fix. Probably in a few weeks. Still putters but only when Supercharger engages. Mechanic tells me its the unburnt fuel bogging down the engine and catalytic converter. Says the new wiring and plugs will fix this. Will update when the fix is done.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 15, 2011, 6:29 AM

Post #10 of 10 (2091 views)
Re: 1999 Pontiac GTP sputtering Sign In

Think already said. If you let a misfiring or poorly running engine continue add much bigger bucks to the list of what you'll need for a new converter or more. You seem to know just what the problem is so beg, borrow or whatever to get it done fast,

T







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