2002 Grand Prix Lag/Bogging at Wide open throttle

[Great Santini]

My 2002 Grand Prix GT 3.8 non supercharged auto with 90,000 miles under hard accelleration at wide open throttle will lag, hesitate, bog down and make a slight detonation sound. There are no trouble codes and the check engine light does not come on. Fuel pressure and supply are fine. Runs fine otherwise the problem is only under hard acceleration.
Thanks for any help

[grandprixgtx00]

does your exhaust smell funny or anything? I would have the Cat checked out. with your year and mileage it would be covered under the 10 year 120K extended warranty

[Great Santini]

I had considered the cat but there is no abnormal "hiss" sound and no abnormal odor. Aceleration and power seem normal as long as the throttle isn't pushed all the way to the floor.

[BNaylor]

Read this at link below and reconsider since you probably have an issue with the CAT converter.

Click here

[Great Santini]

Thanks for the information on the problem with the catalyctic convertor ( I never received that letter from GM ) , I think the wise thing to do is have it replaced and see if that takes care of the problem.

[GPFred]

I experienced the same thing driving my 00 GP to Kentucky. Turned out that the fuel filter was partially plugged and the MAF sensor was dirty. I would try that before spending several hundred on a new CAT. Filter is about $10 and the MAF Sensor cleaner is about $4 a can. GOod Luck.

[grandprixgtx00]

Originally Posted by GPFred

I would try that before spending several hundred on a new CAT.

as previously stated 01-02 Grand Prixs had a recall on their catylatic converters...and have an extended warranty of 10 years or 120K miles. Since the OP has an '02 Grand Prix with less than 120K miles he could get the Cat replaced free of charge.

please see link Bob (Bnaylor) has provided

[Great Santini]

I replaced the filter when I first noticed the problem, it made no difference but it felt as though the engine was starved for fuel so I checked the pressure while driving duplicating the problem with an extended hose on my pressure gauge that is why in the original post I stated the "pressure and supply are fine" That was a good Idea though. I checked for trouble codes and took data readings with a scanner which showed no problem.

I have located the document sent to dealerships about the extended warranty on the catalytic converters. The warranty is not for all 2002 Grand Prixs, only vehicles with a serial number between 2F100019 and 2F276927 are apparently covered, mine is above 2F28++++ so I will have to speak to the service manager about getting it done under warranty.

The converter alone lists for nearly $500.00.

[SNKPWR]

i am having similar bogging issues that have slowly become more noticeable on my 02 gt...but since i just turned 200K on Monday I guess I have to pony up for a new cat myself?

I'm guessing an aftermarket downpipe with ubend delete and high flow cat would be less expensive and a performance upgrade huh?

[i3o2Matt]

I'd check the plug wires too...if they are shorting out at all that could cause it too. i just replaced plugs and wires on a friend's '98 and she had the same symptoms and the new wires cured the problem. Then again, the cylinder 1 wire was rubbing against the metal fan shroud and had worn down to the inner protector...

[SNKPWR]

actually today i start getting some erratic trans behavior so i think that is my prob...

[tblake]

A plugged cat can also seem to cause high shift points. I think I would take it in to the dealership and see if they will replace the cat under warrenty before considering spending money and replacing anything else.

[SNKPWR]

well i started getting hesitation in the trans from a stop, and erratic acceleration (not engine related) through first...after the shift to second it does much better...i'm thinking something with the torque converter lockup, i'm going to search now...

[Great Santini]

I have removed the converter and cut the front cone open to inspect why it was plugged up.. the letter from General Motors said they were extending the warranty because the insulation at the front cone was disintegrating and the debris plugged the brick. Guess what? That is exactly what happened in mine. I spoke with Pontiac Customer service twice and showed the converter to the service manager at my local dealership. The warranty is not for all 2002 Grand Prixs, only vehicles with a serial number between 2F100019 and 2F276927 are covered, mine is above 2F28++++ so they refuse to cover it. The car was built in June of 2002, the service engine light never came on, I have a theory that GM changed the programming on the EPROM so that the newer models would not set a code when the converter plugs up. If my theory is right.... shame on you General Motors!!!!
To say the least I am very dissapointed that GM covered millions of units, mine obviously had the same defective converter installed when the car was assembled but was not covered.
I have a Magnaflow 23405 direct fit assembly being shipped and should arrive tomorrow. The service manager at the dealership said they have had problems with the aftermarket converters setting a code and turning on the service light. Has anyone had a problem with Magnaflows?

[BNaylor]

Originally Posted by Great Santini

I have a Magnaflow 23405 direct fit assembly being shipped and should arrive tomorrow. The service manager at the dealership said they have had problems with the aftermarket converters setting a code and turning on the service light. Has anyone had a problem with Magnaflows?[/color]

Not just the Magnaflow brand but many other aftermarket converters especially hi-flow may give a P0420 DTC which is a CAT converter efficiency issue. I had my Intense PCM module programmed in my GTP to inhibit the P0420 DTC from setting or you can use a 02 simulator connected to the post CAT 02 sensor electrical connector. This is the Magnaflow Hi-Flow 2.5" in/outlet converter. Same issue in our modded Olds Alero with a Magnaflow Hi-Flow 2.5" in/outlet. Plus both have real headers.