Question about 2000 Pontiac Grand Prix

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1999 Grand Prix GTP. Catalytic convertor fine.

1999 Grand Prix GTP. Catalytic convertor fine. When you got to wide open throttle it loses power. Super charger pressure looks fine.

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  • Mike LaPres
    Mike LaPres May 11, 2010

    Going WOT sometimes causes a lean condition on a stock programmed PCM. How much power loss are we talking about? A slight hesitation or a complete shutdown? If you aren't running premium fuel that will definitely do it and you WILL ruin the motor by not running premium.

  • pentium22 May 11, 2010

    I hope your not going by the DIC in the dash for your boost.

    Is it gutless, or is it just the normal 3.8 power?



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  • Contributor
  • 32 Answers

Use a scan tool to check for KR.
Check spark plugs / wires.
try a colder range plug if running more boost.

Posted on Jun 24, 2009

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  • Pontiac Master
  • 757 Answers

Make sure it always gets premium fuel...even with premium and especially in warmer weather the GTP will frequently perform the factory programmed KR (knock ******.) In WOT it is also more susceptible to running a lean condition with stock programming.
Things you can do to troubleshoot the problem and give more consistant performance with the GTP is run colder range copper core plugs and/or any brand of cold air intake, or even a stand alone 9" open element cone filter. Both are better than stock and provide more airflow even though the stock airbox was redesigned in '99. What else you can do is not limited to that but a start. Good luck.

Posted on Jun 23, 2009

  • Mike LaPres
    Mike LaPres Mar 16, 2010

    That is actually quite normal for a stock GTP but here are some things you can do to help eliminate the problem;

    Higher octane. For best performance never go lower than 93. At wide open throttle it is more susceptible to have knock ******, a.k.a. spark knock due to a leaner, less than optimal fueling condition that it may create. The stock PCM (engine computer) will reduce engine timing to avoid the knock, hence knock ******, and for every degree of timing reduced by the PCM equates to about a 5 to 6 horsepower reduction in the GTP.
    You can also try the next colder heat range of spark plug. What I recommend for your GTP if it is currently with factory parts are copper core Autolite 605 gapped to .055". They are also considerably less expensive than the plugs recommended in the manual.
    The next thing you should do in any case is clean your MAF. (mass airflow sensor). It is easy to identify by it being the large, rectangular shaped device mounted into the top of the throttle body with two security tab headed screws. Once removed you will see inside of it two tiny diodes. DO NOT TOUCH THEM OR DROP OR HIT THE MAF. The wire filaments for the diodes are very tiny and can break...without the MAF your car will not run. With rubbing alcohol, carefully pour it over the diodes until shiny...or you can also dip it into a cup of it. Allow to dry and then reinstall back into the throttle body making sure that it sits flat and be careful not to strip the threads.

    Air...the GTP needs a lot of air. GM redesigned the box for the air intake but it is still quite restrictive. Changing to a K&N drop in filter and/or drilling holes through the box on the inlet side (in front of the filter only) can make a big difference.

    Another thing that helps is to get it running a little cooler to help reduce the knock ******. Leave the engine cover off and take the weather strip on the back of the motor lets heat out.



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SOURCE: Can I take a super charger out of a Grand Prix GTP

Well, the short answer is "yes". But - it isn't nearly as simple as just bolting the supercharger onto the intake and VOILA!, now you're supercharged. The procedure that you're inquiring about is commonly referred to as a "top swap", and there are numerous parts you will need for both engine as well as the transmission. Why the transmission? Because the GT and GTP use different gear ratios and the GTP has a 4T65HD as opposed to the 4T65E that is in the SE/GT. You will also need to have the PCM reprogrammed to accomodate all of these changes.

HERE is a great website that has a ton of very useful information, regarding this and many other Grand Prix topics.

Hope this helps and thanks for using FixYa!

Posted on Oct 21, 2009

  • 757 Answers

SOURCE: replace thermostat on 2003 grand prix gtp with

The thermostat housing is located in the upper radiator hose. You will see a metal elbow secured by two bolts into what I remember is the upper intake manifold...don't quote me on that but you will see it regardless of whatever I call it. Anyways, GM decided it was a good idea to put stainless steel bolts in there but that makes it easy to strip the threads in the bolt hole so I think it's best when you put your wrench on the bolt to just tap on the handle till you vibrate it loose, then turn it.
When you pull off the housing you'll lose a little coolant and it will create an air pocket which we'll address. It's a 50/50 chance that the thermostat housing gasket will either stick to the housing or the may be torn, cracked or flaking in either case clean both contact surfaces before you replace the gasket. I recommend an oil impregnated poly material gasket.
Note the position of the thermostat in the hole and place the new one in as such.
I recommend a 180 degree thermostat...stock is 195 but the GTP runs better with the 180.
Put on gasket and reinstall the hose/housing assembly, alternate from one bolt to the other so the housing mates flat and cannot cause a leak.
Next, fill the coolant overflow bottle to the "HOT" mark. If the bottle is dirty and hard to see just put a light on top of the bottle...GM didn't mark it very well so if it's not squeaky clean you can hardly see a damn thing.
*IMPORTANT** if your car still has Dexcool in it, DUMP IT. It will eventually destroy the motor.
If not...continue on. Start the car. Go back to the thermostat housing and place a rag on top of, and twist the peacock valve on top of it to let the air out until it starts to get coolant on the rag. Done.

Posted on Feb 27, 2010

  • 166 Answers

SOURCE: how to replace throttle position sensor on a 1995

Remove all parts to access the throttle-body, typically the sensor is on the side with 2 screws.  Remove the wired plug and then the two screws.  Assembly is the reverse being careful to fit the flat piece of the throttle-body into the groove of the sensor. Do not overtighten.
Replace connector and other parts.
Typically the sensor is on the drivers side of the throttle body. May be a torx screw, or phillips (star).
Good luck.
Canada Rocks!

Posted on Jun 13, 2010

  • 10319 Answers

SOURCE: where is the throttle control

The throttle control sensor is called a TPS which is mounted on the throttle body. You will see three wires that plug into it. The throttle body replaces the old carburetor since the engine is fuel injected as you may know

Posted on Jul 27, 2010

  • 757 Answers

SOURCE: belt diagram for 2001 grand prix gtp

Here you go.

Posted on Oct 10, 2010

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I got a 2000 pontiac grand prix gtp the car runs well but the boost level will not go more than 1/4 on the gauge, one mecanic said to change the spark plugs because they are 4 or 5 years old (iridim...

The spark plugs have absolutely nothing at all whatsoever to do with boost levels.

However; change them anyway because new plugs are always better. In the GTP, don't use the iridium plugs, use copper core. I highly recommend Autolite 605's, gap them to .055"

In the GTP, spark knock is a common, performance robbing issue because of the supercharging. You'll lose 5-6 horsepower for every degree of timing ****** that the engine computer will employ to prevent the spark knock. If you use copper core plugs though, this problem will be less likely because copper dissipates the residual heat much faster than iridium, so that only the electrode spark alone can be hot enough to ignite the fuel. The only other difference between the plug types is how long they last. Iridium plugs were the originals only because they last longer...they offer no performance benefit to the GTP.

Now on to your actual question.

There only a few causes for loss of boost pressure in the GTP, all of which are an easy fix.

Supercharger belt slip, disconnected or damaged boost bypass valve hoses, or maladjusted boost bypass valve linkage.

The easiest thing to do first is the boost bypass valve adjustment. This will produce results even if you DO still have belt slip or a leaking hose.

Locate your boost bypass valve. You will find it mounted directly in front of where the throttle body bolts into the intake plenum.
You will see that it is held in place by three bolts. Loosen them in this order; left, right and rear. You will find that you'll need a 4" extension socket to reach the rear one. Hold your socket on that one while you push down on the valve body. As you may notice the mounting bolt holes are elliptical, allowing for the height adjustment. You can use this as a visual reference for how far to push the valve down. You shouldn't push it down all the way, only about a half an inch will suffice.

What the adjustment does is reduces the amount of throttle opening needed to produce boost, by shortening the travel length of the valve lever that is attached to the throttle. When properly set, it will allow about 11 to 11.5 PSI at wide open throttle, or just short of wide open throttle. In any circumstance you may also notice that your GTP is a little quicker from a standing start after the adjustment.

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replace catalytic converter before you do more damage to your car. a restricked air flow out the exhaust will cut hoarse power and build up heat in your engine and will burn out sensors

Oct 28, 2010 | 2004 Pontiac Grand Prix

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Where is the throttle control sensor located on a 1999 pontiac grand prix gtp

The throttle control sensor is called a TPS which is mounted on the throttle body. You will see three wires that plug into it. The throttle body replaces the old carburetor since the engine is fuel injected as you may know

Jul 27, 2010 | 1999 Pontiac Grand Prix

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Where is the fuel pump resistor on a 1999 gtp?

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Location of mass air flow sensor, 2000 Grand Prix GTP

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Feb 07, 2010 | 2000 Pontiac Grand Prix

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