Knocking when starting the car

[spundall]

I have a 2001 Pontiac Grand Prix GT 3.8L V6. Out of now where I started my car and there is this terrible knocking noise coming from the motor. When initially started the whole car shakes. I let it idle for about 5min to see if it would go away but it didn't. Haven't driven it since it happened. Please give me some sort of idea as to what this could be. Please note that I am a woman.

[richtazz]

Did the car do anything odd the last time you drove it prior to this happening? Examples, odd noise, hesitation, stalling, steam from the exhaust, etc....

[BNaylor]

Also it would be helpful for the mileage on your GP and when was last the tune up? Do you ever get a SES light?

It could be a clogged fuel filter. Best to check the basics such as fuel and ignition (spark plugs and wires). Other possibilities crankshaft position sensor, MAF sensor and worse case a clogged CAT convertor. 2001 - 2002 Grand Prixs were delivered with flaky CAT convertors and GM extended the warranty on CAT to 10 years or 120K miles, whichever comes first.

[spundall]

The only thing was the day before when I started it. There was a terrible smell. I thought my two year crapped his pants but then my husband said he could smell it outside the car as well. It did go away. The only other thing was last week the coolant light came on and we put coolant in it.
Thanks

[spundall]

It just rolled over 100000km

[BNaylor]

Originally Posted by spundall

The only thing was the day before when I started it. There was a terrible smell. I thought my two year crapped his pants but then my husband said he could smell it outside the car as well. It did go away. The only other thing was last week the coolant light came on and we put coolant in it.
Thanks

Can you explain the smell....rotten egg, fuel, burnt plastic?

[spundall]

Rotten Egg

[BNaylor]

Originally Posted by spundall

Rotten Egg

Are you the original owner? GM sent out notices on the CAT warranty and defect. You should have received a letter from GM. If not take it to a GM dealer and have them check out the CAT convertor. It sounds totally clogged up which is what the letter addressed. It should be covered even in Canada. Good luck!

[richtazz]

You probably have a catalytic converter issue. Known issue with 00-01 GP converters. It is possible that the blocked converter backed up exhaust pressure through the EGR passage, cracking the upper plenum and causing the coolant loss as well.

[spundall]

I'm not the original owner. But the CAT Converter would make the engine knock?

[BNaylor]

Originally Posted by spundall

I'm not the original owner. But the CAT Converter would make the engine knock?

Yes. That is one symptom of a clogged CAT convertor because exhaust is blocked. Here is a copy of the letter.


This is a special policy that raises warranty coverages on the converter in case you experience a failure.

Dear General Motors Customer:

As the owner of a 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; or Buick Regal model vehicle, equipped with a 3.4L or 3.8L V6 engine, your satisfaction with our product is very important to us.

This letter is intended to make you aware that some 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; and Buick Regal model vehicles, equipped with a 3.4L or 3.8L V6 engine, may have a condition where the catalytic converter is replaced due to complaints of lack of power or illumination of the Malfunction Indicator Lamp (MIL). This may be due to the front endcone insulation from the catalytic converter breaking away and blocking the front of the first catalyst brick and preventing the free flow of exhaust gas through the converter.

This is not a recall. Do not take your vehicle to your GM dealer as a result of this letter unless you believe that your vehicle has the condition as described above.

What We Have Done
General Motors is providing owners with additional protection for the Catalytic Converter. If this condition occurs on your 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; or Buick Regal model vehicle, equipped with a 3.4L or 3.8L V6 engine, within 10 years of the date your vehicle was originally placed in service or 120,000 miles (190,000 km), whichever occurs first, the condition will be repaired for you at no charge .

What You Should Do
Repairs and adjustments qualifying under this special coverage must be performed by a General Motors dealer. You may want to call the service department at your dealer to find out how long they will need to have your vehicle so that you may schedule the appointment at a time that is convenient for you. This will also allow your dealer to order parts if they are not already in stock. Keep this letter with your other important glove box literature for future reference.

[spundall]

Thanks Guys,

Ok, so if this is what happened and as a result of it it caused something else to happen. I suppose i'm responible for the cost of the additional repairs.

Order of events:
Last week coolant light came on put coolant in
Saturday Rotten egg smell for about two minutes didn't happen again.
Sunday started car engines knocking

[richtazz]

How much coolant did you lose? It is possible you had an upper intake plenum failure, causing coolant to get into the exhaust. The coolant then hit the hot catalytic converter, breaking it's internal grid or clogging it over time. It's a case of the chicken and the egg. Which came first? Either could have caused the other. Normally, when the intake starts to fail, you'll notice a sweet smell from the exhaust, or excessive steam after the car has warmed up.

[spundall]

Yeah I know the smell your talking about from previous vehicle and I never had that smell with this car.

thanks

[richtazz]

Good, then hopefully the converter failed and it should be covered under the extended warranty Bob (bnaylor) described earlier. Take the car to the dealer and let us know how it turns out.