1998 Pontiac Grand Prix trouble

pes1952 · 03-04-2008, 12:51 PM

My car is missing badly. I had a computer read out that mentioned the Emissions System VAP. My Service engine soon light seems to stay on and when you take the gas cap off, you can hear a constant low pressure sound in the tank. Can anyone help. Thanks.

cardoc · 03-04-2008, 01:07 PM

Goodafternoon pes1952
The sound in the tank is the fuel pump running,a normal sound.As for your miss more info is needed.Under what cicumstances does it miss,under a load idling etc.If you run it with the gas cap off it will set an active code and turn your SES light on.Do you have any other info from a scan tool.Could be something as simple as bad spark plugs or wires.
Good luck,Cardoc

pes1952 · 03-04-2008, 01:20 PM

The sound in the tank is present when the engine is not running. The miss is under a load between 30 - 40 mph. I have new wires and plugs. I don't have any additional information but, the service engine soon light is on sometimes and sometimes not. I noticed when the light is not on, I can't hear the sound in the tank when I take the cap off. I also have had trouble putting gas in the car, there is a back pressure that keeps me from filling the tank. Thanks.

cardoc · 03-04-2008, 01:56 PM

It sounds like you need shop help/a good tech with a scan tool.You may have more then 1 problem.Your noise in tank may be a bad check valve in fuel pump bleeding fuel pressure back into tank but that wouldn't affect the slow fueling problem.A fuel pressure gauge will show this.Did all this start at the same time.A miss like you describe could be fuel or spark related.Are the fuel filler and vent tubes damaged.One large tube,one small both leading to fuel filler.Was the skip there before new plugs and wires?
Good luck,keep me posted .
Cardoc.

**bruiser** · 03-04-2008, 03:25 PM

If you don't have a code reader or scan tool, run by Autozone and have them pull the codes. Be sure to write them down and post what they are.

BUDFAN8 · 03-04-2008, 11:50 PM

most of the GM motors around that time until recently are having bad problems with the intake gaskets leaking. my 01 grand prix did it too. slight miss not enough to hurt power but it was irritateing.

check to see if your antifreeze level has gone down any or if your getting moisture out of your tailpipe also check and make sure your oil isnt milky looking. if this is the case there is now a "problem solver" intake gasket set.

the originals are plastic and rubber the plastic kinda dryrots and therefore leak the new ones are aluminium and rubber and will hold up alot longer.

03-04-2008, 12:51 PM	#1 (permalink)
pes1952 Registered User Join Date: Mar 2008 Posts: 2 OS: vista sp2	1998 Pontiac Grand Prix trouble My car is missing badly. I had a computer read out that mentioned the Emissions System VAP. My Service engine soon light seems to stay on and when you take the gas cap off, you can hear a constant low pressure sound in the tank. Can anyone help. Thanks.

03-04-2008, 01:07 PM	#2 (permalink)
cardoc Registered User Join Date: Apr 2007 Location: Ct. Posts: 198 OS: win xp sp2	Re: 1998 Pontiac Grand Prix trouble Goodafternoon pes1952 The sound in the tank is the fuel pump running,a normal sound.As for your miss more info is needed.Under what cicumstances does it miss,under a load idling etc.If you run it with the gas cap off it will set an active code and turn your SES light on.Do you have any other info from a scan tool.Could be something as simple as bad spark plugs or wires. Good luck,Cardoc

03-04-2008, 01:20 PM	#3 (permalink)
pes1952 Registered User Join Date: Mar 2008 Posts: 2 OS: vista sp2	Re: 1998 Pontiac Grand Prix trouble The sound in the tank is present when the engine is not running. The miss is under a load between 30 - 40 mph. I have new wires and plugs. I don't have any additional information but, the service engine soon light is on sometimes and sometimes not. I noticed when the light is not on, I can't hear the sound in the tank when I take the cap off. I also have had trouble putting gas in the car, there is a back pressure that keeps me from filling the tank. Thanks.

03-04-2008, 01:56 PM	#4 (permalink)
cardoc Registered User Join Date: Apr 2007 Location: Ct. Posts: 198 OS: win xp sp2	Re: 1998 Pontiac Grand Prix trouble It sounds like you need shop help/a good tech with a scan tool.You may have more then 1 problem.Your noise in tank may be a bad check valve in fuel pump bleeding fuel pressure back into tank but that wouldn't affect the slow fueling problem.A fuel pressure gauge will show this.Did all this start at the same time.A miss like you describe could be fuel or spark related.Are the fuel filler and vent tubes damaged.One large tube,one small both leading to fuel filler.Was the skip there before new plugs and wires? Good luck,keep me posted . Cardoc.

03-04-2008, 03:25 PM	#5 (permalink)
bruiser TSF Enthusiast Join Date: Jul 2005 Posts: 1,975 OS: xp	Re: 1998 Pontiac Grand Prix trouble If you don't have a code reader or scan tool, run by Autozone and have them pull the codes. Be sure to write them down and post what they are.

03-04-2008, 11:50 PM	#6 (permalink)
BUDFAN8 Registered User Join Date: Apr 2007 Posts: 205 OS: XP	Re: 1998 Pontiac Grand Prix trouble most of the GM motors around that time until recently are having bad problems with the intake gaskets leaking. my 01 grand prix did it too. slight miss not enough to hurt power but it was irritateing. check to see if your antifreeze level has gone down any or if your getting moisture out of your tailpipe also check and make sure your oil isnt milky looking. if this is the case there is now a "problem solver" intake gasket set. the originals are plastic and rubber the plastic kinda dryrots and therefore leak the new ones are aluminium and rubber and will hold up alot longer.