engine misfire 2001 gt

I've read so much about MAF sensor problems as well as CAT convertors needing replaced on these models. I'm wondering if these symtoms point to the culprit.
2001 GP GT, 3800 series II engine ,87,000 miles.This is my daughters car and she tends to drive at the upper limit allowed. On several occasions the car quit and then ran ruff and misfired for a time.The service engine light blinked while this was happening and the engine temp went up higher than normal. Then the engine would smooth out like nothing was wrong. The service engine light stayed on for a time then went out. It comes back on any time the engine goes through the misfire again, which happens sporadically. The gas milage has gone from 22 to 17 MPG. If you rev the engine while in park the engine starts to miss at 4ooo rpm.
The codes that they pulled for me at the parts store were;P0300,P1361,P1362. Has anyone had the same symtoms or can point me in the right direction. Thanks for your help.

Puzzled Dad

I believe you answered your own question but I'd put money on the CAT convertor. The symptoms you have are classic.

Thanks for the reply.I did forget to mention that new plugs and wires were installed a month ago.
Do you know what the codes mean?.You seem to know about Pontiac's.I was a certified Pontiac mechanic back in the 60's when thing weren't so complicated. Still love Pontiacs ,have a 91 Bonneville SSE still in excellent shape.
Also, does anyone know if a second owner of the car is covered for the replacement ? I sure hope so!

Thanks for the reply.I did forget to mention that new plugs and wires were installed a month ago.
Do you know what the codes mean?.You seem to know about Pontiac's.I was a certified Pontiac mechanic back in the 60's when thing weren't so complicated. Still love Pontiacs ,have a 91 Bonneville SSE still in excellent shape.
Also, does anyone know if a second owner of the car is covered for the replacement ? I sure hope so!

Were the plugs and wires changed as a tune up or due to other problems?

P0300 = Random Misfire Detected
P1361 = Bypass Open Circuit Fault related to Ignition Control
P1362 - Bypass Short Circuit Fault related to Ignition Control

The misfire is consistent with possibly the CAT being bad. Misfires will cause the CAT to heat up above specs. If it were one specific plug or wire a more specific code such as P0301 would be generated indicating cylinder #1 misfire and so on.

P1361 and 1362 could be consistent with the CAT but are probably triggering due to variations in the crank position angle which can be caused by misfire. The PCM uses the 18X pulses generated off the Crank Position Sensor in an attempt to put the system into bypass mode. From the 18X pulses, 3X pulses are processed by the ignition control module and then to the PCM module. These codes can be generated due to a defective ICM module or PCM too.

Once the source of the random misfires is resolved the other two codes will probably be resolved.

I'd recommend that you check with the local GM dealer but they should honor the extended emissions warranty on the CAT which is now 10 years or 120K miles, whichever comes first on a 2001 - 2002 Grand Prix regardless if you are not the orginal owner. Good luck!

BTW - I forgot to mention that the dealer can test for excessive exhaust backpressure/CAT by running a low pressure test fixture at the front 02 sensor. The reading cannot be over 1.25 psi.

Thanks again,you must have read my mind about why the convertor can cause an ignition problem.The tune up was not done because of the problem ,it came later. Do you know what the thread type and size is on the O2 sensor?

I know the thread diameter is 18mm, and I believe it's a 1.5 thread pitch, it's course thread metric, which I believe is 1.5. The stupid Delco catalogs don't give specifications anymore.

The typical GM Oxygen Sensor Bung size for sure is 18mm x 1.5 thread.

http://i5.photobucket.com/albums/y186/lizzywiz/o2bung.jpg
18mm X 1.5

If you plan on running the test yourself you will need a low pressure 0 - 5 psi gauge. Backpressure reading should not exceed 1.25 psi.

Great info! Went to the dealer to see if it was under warranty .He didn't know anything about the extended 10 year 120,000 warrenty.Does anyone have an actual copy of the letter that was sent out?Anyone have one over 80,000 miles that was covered and maybe a second owner?

Great info! Went to the dealer to see if it was under warranty .He didn't know anything about the extended 10 year 120,000 warrenty.Does anyone have an actual copy of the letter that was sent out?Anyone have one over 80,000 miles that was covered and maybe a second owner?

Here you go.

************************************************** ****

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.

Back again,thought the problem was fixed.Had the cat convertor(no help from the dealer) replaced with a Magnaflow. The one removed was plugged the honeycomb was all in pieces. The car has more power but the misfire is still there. After it was replaced I drove about two miles ,the car was running great .Then all of a sudden started the misfire.I could here it poping through the intake. The car could only go about 30 MPH.The engine light came on flashing,went about a 1/4 mile and it was like a switched was turned on .It ran fine again and the engine light went out. Have any ideas's ????

Back again,thought the problem was fixed.Had the cat convertor(no help from the dealer) replaced with a Magnaflow. The one removed was plugged the honeycomb was all in pieces. The car has more power but the misfire is still there. After it was replaced I drove about two miles ,the car was running great .Then all of a sudden started the misfire.I could here it poping through the intake. The car could only go about 30 MPH.The engine light came on flashing,went about a 1/4 mile and it was like a switched was turned on .It ran fine again and the engine light went out. Have any ideas's ????

What I do know for a fact is the 3800 is sensitive to the spark plug wires and spark plugs. What brand did you use? Whenever the SES light flashes it indicates a misfire conditon.

Also disconnect the electrical connector to the MAF sensor and test drive it. The PCM will detect no MAF input and revert to pre-programmed air flow values. It won't hurt anything. The idle may be a little erratic until the engine warms up.

Thanks for the quick reply, I checked the plugs they are Delco 41-940 .The wires are new but they are not Delco.
I reved the engine in park and at 4000 rpm it misses,I tried disconnecting the maf sensor ( at least I think it was it? ) and reved the engine and it still missed at around 4000 rpm.Which one is the maf sensor?

Thanks for the quick reply, I checked the plugs they are Delco 41-940 .The wires are new but they are not Delco.
I reved the engine in park and at 4000 rpm it misses,I tried disconnecting the maf sensor ( at least I think it was it? ) and reved the engine and it still missed at around 4000 rpm.Which one is the maf sensor?

The best plugs to use are the AC Delco 41-101 Iridium. If the 41-940 are double platinum they could cause problems. The other AC Delco plug that works is the Rapidfire #14 Platinums. The wires recommended are the AC Delco Premium Silicone 7mm.

The MAF sensor is the square black module located on the top of the throttle body. The PCM has a rev-limiter that kicks in at around 4000 rpms so it will be normal for the cutoff in park or neutral. Try testing on the road with MAF disconnected. If that doesn't work then wires and plugs are the most likely cause.

My MAF sensor gave me a heck of a time this past week, My car had eveyr engine code in it BUT the MAF. So, don't rule it out. Good Luck.

BTW - One other thing......the plugs you are using AC Delco 41-940 are incorrect for the 3800. They are the standard plugs in a GM 3.4L 3400. How did you come about using those plugs? They did not ring a bell so I checked them out for you and found the above.

The AC Delco Rapidfire 14 Platinum or 41-101 Iridiums are the specified spark plugs for your model GP.

My daughter's husband had someone put them in.
I'm going to try driving it tonight with the maf sensor disconnected. I'll get a set of 41-101 and put them in tomorrow. Thanks for your help.
Just puzzeled how it works fine then goes wacky,then fixes itself.
Just and old mechanic missing the days when I could find problems.

Never ending story continuation! Things changed overnight on the page,looks good.
Went for a drive with the maf disconnected, car ran terrible missed badly the whole time. I pluged it back in and continued ,it ran better but it did start misfiring again. It was night time and I noticed that all the warning lights began to flash on and off while the car was popping and running poorly.I mean all the lights ,check engine,low oil level,battery,security and maybe more that I did not see. It may have done this before but I did not notice it in the daytime.Anyway before I got home it started running perfectly again. Could the malfunction be in the computor ? Does the computor have to re-learn and needs to be driven for some period of time? Something is causing the thing to go wacky. Just wondered if driving it with the plugged cat convertor started all this or is ther something wrong with the ECM.

Never ending story continuation! Things changed overnight on the page,looks good.
Went for a drive with the maf disconnected, car ran terrible missed badly the whole time. I pluged it back in and continued ,it ran better but it did start misfiring again. It was night time and I noticed that all the warning lights began to flash on and off while the car was popping and running poorly.I mean all the lights ,check engine,low oil level,battery,security and maybe more that I did not see. It may have done this before but I did not notice it in the daytime.Anyway before I got home it started running perfectly again. Could the malfunction be in the computor ? Does the computor have to re-learn and needs to be driven for some period of time? Something is causing the thing to go wacky. Just wondered if driving it with the plugged cat convertor started all this or is ther something wrong with the ECM.

Well, it sounds like you can rule out the MAF sensor. Hopefully the clogged CAT didn't cause any damage. The PCM does not have to be forced to re-learn depending on the malfunction and will normally clear if all faults are corrected or no further emissions related problems are detected. It should do this after a few drive cycles possibly up to 40. A case variation learn is only is required when you perform major work around the crankshaft, crank position sensor or replace the PCM. The case learn will program the PCM to prevent false misfires.

The other possible problem is the CAT may have caused upper intake/lower intake manifold problems which is common on a normally aspirated 3800. Don't know if this will help but you could hookup an automotive vacuum gauge to a vacuum source on the intake manifold or throttle body. It should read no less than 15 inches on a 0 - 30 hg gauge. Also, check for any possible cross contamination of engine oil and coolant which is an indicator of a manifold leak or UIM/LIM EGR stovepipe damage due to high exhaust temperatures.

Another source of misfire is clogged or dirty fuel injectors. Until you get the correct spark plugs and wires I wouldn't rule that out either. Good luck!

i personally am partial to autolite copper core plugs, they're just as good as anything out there and wont cost you and arm and a leg. I know 606 is the stock range for gtp but im not sure if that differs with the L36

Plugs and wires replaced,vacuum test OK, no contamination.
Is the PCM the same as the Engine controll module?
Took the car out for a drive and it ran better than it had before,got almost home and it started misfiring again. I noticed the engine light does not stay on like it did before.Is it trying to clear itself?I will drive it somemore. Sorry to be a pain but what is a case learn? Thanks again.

Plugs and wires replaced,vacuum test OK, no contamination.
Is the PCM the same as the Engine controll module?
Took the car out for a drive and it ran better than it had before,got almost home and it started misfiring again. I noticed the engine light does not stay on like it did before.Is it trying to clear itself?I will drive it somemore. Sorry to be a pain but what is a case learn? Thanks again.

I'd run it a few days but if the misfire situation doesn't resolve you probably still have the same problem whatever it may be. If the SES light light stays off that is a step in the right direction.

A case learn is performed on a Tech II machine at a GM dealer. Normally it is not required unless the PCM has been replaced or you have had major work done to the engine lower end. The crank position angle is programmed into the PCM. For optimal performance it is recommended but the real reason is to help the PCM monitor misfires both real and false. I seriously doubt that you need a case learn but you may want to check with the dealer and see if any PCM revisions are out and whether it should be updated.

Here's a sample of the procedure.

97-2003 Engine CASE learn procedure:

1. Turn the key to on position
2. Turn Tech II on
3. Select the Diagnostics Menu
4. Select Car Information (Year, Make, Engine, Etc.) (Make sure they enter 1998 as the year.) (Also you will be asked what type of product line/type. It is a single letter code. Which corresponds to the first letter in your VIN)
5. Select Special Functions.
6. Select Variable Crankcase Learn Procedure.
7. Follow On Screen Directions.


The Crankcase Learn Procedure is going to ask the Technician to do the following:

1. Put E-brake On.
2. Make sure car is in neutral or park.
3. Turn engine on
4. Rev Car to Rev Limiter (car will hit limiter at 3,000 RPM)
5. Wait about 5 seconds.
6. Rev Car to Rev Limiter (The car will this time hits about 5,500 to 6,000 RPM)
7. Wait about 5 seconds.
8. Car is done.