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Code P0300 Misfire


TONYUBALDO

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Good Afternnon guys,

well recently my car has been acting up for about 2 weeks..but this time its worstbcuz i cant drive my car too far without stalling and with out no power when i press the gas. After turning on the car the rmps go a little bit over 1,000 rmp and once i put it on reverse or drive the rmps drop. After driving my car for about 15 to 20 minutes my car drives fine. once i turn it off and wait about 5 minutes or so and try to turn it back on it feels like the car wants to turn off.

I tried driving my car like that and it drives really slow i even tried floring it and it feels the same. it feels like it stalls and has no balls. i replaced the Spark plugs from autozone and used Autolite. the old ones i took off where gapped at like .040 i dont know if that makes a difference??? so i put the new ones and gapped them at .050.

(i really think my sons tricycle could go fastrer dan my caddy) :(:(

the codes i was getting are these

P0300 - Random Misfire

p0420 -Catalyst System Efficiency Below Threshold (Bank 1)

P0463 Fuel Level Sensor Circuit High Input

(is this the reason why my fuel gauge always is acting crazy?? some times when i have a 1/4 of gas in my car is always marking like if i have a full tank?? its just bouncing up and down???)

i really need some help im stressing out bcuz i dont know where to start..i went to a shop to see how much the catalyc converter would be and they gave me an estimate of $300. im not sure if its clogged or something. but this one time when my car astared acting liek this i looked under the car and i could see some smore coming out from the cat or from where the cat goes connected to too. i dont remember.

any help?? thanks guys..

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I took the ALL CAPS and STRESSING out of your thread title

In 2002 GM had problems with their CATS, they clog up, you may be able to go to the dealer and have it replaced, they will solve the NO POWER problem. GM had been replacing them under warranty, I think they have an 80K mile warranty. My 2002 Monte Carlo had NO POWER with its clogged CAT and GM replaced it free.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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ONCE you replace the CAT, you can continue with the P0300, its possible the P0300 is being caused by the back pressure

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I took the ALL CAPS and STRESSING out of your thread title

In 2002 GM had problems with their CATS, they clog up, you may be able to go to the dealer and have it replaced, they will solve the NO POWER problem. GM had been replacing them under warranty, I think they have an 80K mile warranty. My 2002 Monte Carlo had NO POWER with its clogged CAT and GM replaced it free.

my car has 127k i think it passed its warranty lol...... is it still posible that my cat is clogged up even if it stars stalling and feels like has no power once in a while. because when my car usually cools down i can turn on the car and i have no problem with it. but once it hits driving temp and turn it off thats when it starts acting up. unless the cat is super super hot and when it cools down it stops doing that?????? i dont want to go and spend money for a new cat if thats not the problem. any suggestions???

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CALL GM and see if they will replace the CAT, it was a defective part, they had a LOT of bad CATS.... THAT is a known fact

To check the fuel pressure, get a fuel pressure gage and connect it to your fuel rail, look for 42 to 45 PSI

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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My 2002 had both the 300 and 420 code... plugged cat...

If the car is off both the GM and Federal emissions warranties replace the cat with an aftermarket one less then half the price and just as good (as the one that you replaced)

Edited by OynxSTS

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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My 2002 had both the 300 and 420 code... plugged cat...

If the car is off both the GM and Federal emissions warranties replace the cat with an aftermarket one less then half the price and just as good (as the one that you replaced)

ok guys i ordered my cat this past friday it should be arriving at the shop today. It was $240.00. i was thinking of changing tboth oxygen sensors what do you guys think?? and also putting new ac delco plugs and boots???? right now i have autolite in my car.......

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We just had another member have a misfire with Autolites, I only use AC DELCO, as is recommended

You cant change the boots by themselves, its part of the ignition wires

I would wait to change the O2 sensor, until you change the CAT, they are expensive to buy (about $90)

As Greg mentioned your he had a 420 and 300 with a clogged CAT, Id wait till I change the CAT

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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We just had another member have a misfire with Autolites, I only use AC DELCO, as is recommended

You cant change the boots by themselves, its part of the ignition wires

I would wait to change the O2 sensor, until you change the CAT, they are expensive to buy (about $90)

As Greg mentioned your he had a 420 and 300 with a clogged CAT, Id wait till I change the CAT

Should i change both of the o2 sensors??? or just the one before the CAT???

my car has no wires it has coils..so i have to change the coils in order for me to put the new rubber boots ???? arent the coils expensive??

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We just had another member have a misfire with Autolites, I only use AC DELCO, as is recommended

You cant change the boots by themselves, its part of the ignition wires

I would wait to change the O2 sensor, until you change the CAT, they are expensive to buy (about $90)

As Greg mentioned your he had a 420 and 300 with a clogged CAT, Id wait till I change the CAT

Should i change both of the o2 sensors??? or just the one before the CAT???

my car has no wires it has coils..so i have to change the coils in order for me to put the new rubber boots ???? arent the coils expensive??

Unlike the Cat, I would ONLY use GM parts for the plugs and the O2 sensors...

On my car the dealer ONLY replaced the Cat... neither of the O2 sensors were repaced.

caddy.jpg

Easin' down the highway in a new Cadillac,

I had a fine fox in front, I had three more in the back

ZZTOP, I'm Bad I'm Nationwide

Greg

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I would wait on the O2 sensor, if you still have a code after the CAT we will determine which one it is.... as Greg said a plugged CAT caused the O2 sensor code

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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good night guy,

well i took my car to get the CAT changed and yes my cat was clugged up...when i was driving back home the car was running fine i was about 1 blovk away from my house and the car it starting stalling and it felt like it had no b*lls if u know what i mean. i got home looked under the car and WOW the new Catalyc converter was super super red it was like glowing..i got the codes again and these are the ones that came back

p1574 Stoplamp Switch Circuit

p1860

p0300 multiple misfire

p0463 Fuel Level Sensor Circuit Voltage High

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good night guy,

well i took my car to get the CAT changed and yes my cat was clugged up...when i was driving back home the car was running fine i was about 1 blovk away from my house and the car it starting stalling and it felt like it had no b*lls if u know what i mean. i got home looked under the car and WOW the new Catalyc converter was super super red it was like glowing..i got the codes again and these are the ones that came back

p1574 Stoplamp Switch Circuit

p1860

p0300 multiple misfire

p0463 Fuel Level Sensor Circuit Voltage High

Years ago, I had a resonator collapse inside and block the exhaust exit on a 66 coupe. It sounds like you have a bad resonator DO NOT drive the car like that with the CAT glowing red. You will destroy the new cat. Its possible that the banging on the exhaust system cleared the blockage. I am not 100% sure you have a resonator, check it out

The other thing that I can think is that your FPR is bad or you have leaky injectors, given the P0300. Dont drive the car you will destroy the new cat

You should check your injectors, lift the fuel rail, and turn the key to ON not START to pressurize your fuel rail, see if any injectors are leaking

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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See this

http://answers.yahoo.com/question/index?qi...09200831AA55Lc6

The leaky injector probably burned out your old CAT

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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good night guy,

well i took my car to get the CAT changed and yes my cat was clugged up...when i was driving back home the car was running fine i was about 1 blovk away from my house and the car it starting stalling and it felt like it had no b*lls if u know what i mean. i got home looked under the car and WOW the new Catalyc converter was super super red it was like glowing..i got the codes again and these are the ones that came back

p1574 Stoplamp Switch Circuit

p1860

p0300 multiple misfire

p0463 Fuel Level Sensor Circuit Voltage High

Years ago, I had a resonator collapse inside and block the exhaust exit on a 66 coupe. It sounds like you have a bad resonator DO NOT drive the car like that with the CAT glowing red. You will destroy the new cat. Its possible that the banging on the exhaust system cleared the blockage. I am not 100% sure you have a resonator, check it out

The other thing that I can think is that your FPR is bad or you have leaky injectors, given the P0300. Dont drive the car you will destroy the new cat

You should check your injectors, lift the fuel rail, and turn the key to ON not START to pressurize your fuel rail, see if any injectors are leaking

good morning,

well yesturday i was asking alot of questions to the guy who was getting the job done. and he told me that i do have a ressonator. its right after the CAT.

do i need to get a fuel pressure gauge to pressurize the fuel rail?? or what do you mean??? can you explain to me a little bit more on how to do this???

thanks soo much

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A couple of things can cause that RED CAT, raw fuel is one, check your fuel pressure regulator, by taking off the vacuum hose and looking for fuel at the nipple, with the engine off then on, reving the engine to see if it spits fuel from the regulator. If it spits fuel it is bad

By lifting the fuel rail and supporting it with something like wood or holding it while someone else turned on the KEY to ON NOT RUN, the fuel pump will pressurize the fuel rail. When it is pressurized, if an injector is leaking you will see fuel leaking from one of the 8 injectors when the rail that they are attached to is pressurized. If any leak make a note of which ones leak.

You have to eliminate these potential causes first

One trick, I just read about, hook up a fuel pressure gage to the scrader valve on the fuel rail, turn on the key to pressurize the rail, you should see 42 to say 45 pounds. Turn off the key and watch the gage and see if the pressure drops, record how long it takes to drop, mine holds pressure for quite some time only dropping to about 20 in an hour. This test is not 100% reliable, and it is not a substitute for what I said in the above two paragraphs.

See what you find. Are you doing your own work or having work done?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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A couple of things can cause that RED CAT, raw fuel is one, check your fuel pressure regulator, by taking off the vacuum hose and looking for fuel at the nipple, with the engine off then on, reving the engine to see if it spits fuel from the regulator. If it spits fuel it is bad

By lifting the fuel rail and supporting it with something like wood or holding it while someone else turned on the KEY to ON NOT RUN, the fuel pump will pressurize the fuel rail. When it is pressurized, if an injector is leaking you will see fuel leaking from one of the 8 injectors when the rail that they are attached to is pressurized. If any leak make a note of which ones leak.

You have to eliminate these potential causes first

One trick, I just read about, hook up a fuel pressure gage to the scrader valve on the fuel rail, turn on the key to pressurize the rail, you should see 42 to say 45 pounds. Turn off the key and watch the gage and see if the pressure drops, record how long it takes to drop, mine holds pressure for quite some time only dropping to about 20 in an hour. This test is not 100% reliable, and it is not a substitute for what I said in the above two paragraphs.

See what you find. Are you doing your own work or having work done?

ok well i just got back and i checked the fuel pressure regulator witht he iigniton to on and than turned on the car and there no gas leaking from that nipple nor any gas spit fromt he regulater after turning on the car.

oh before i forget when i turned on the car to test the FPR i herd a rattleling noise where the new cat is at. im getting scared lol...i only drove it home yesturday it was only like 6 blocks home. not that far.... :(

here are some pics i took.

post-10243-1252523168_thumb.jpg

post-10243-1252523182_thumb.jpg

Edited by UBALDO2002
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A couple of things can cause that RED CAT, raw fuel is one, check your fuel pressure regulator, by taking off the vacuum hose and looking for fuel at the nipple, with the engine off then on, reving the engine to see if it spits fuel from the regulator. If it spits fuel it is bad

By lifting the fuel rail and supporting it with something like wood or holding it while someone else turned on the KEY to ON NOT RUN, the fuel pump will pressurize the fuel rail. When it is pressurized, if an injector is leaking you will see fuel leaking from one of the 8 injectors when the rail that they are attached to is pressurized. If any leak make a note of which ones leak.

You have to eliminate these potential causes first

One trick, I just read about, hook up a fuel pressure gage to the scrader valve on the fuel rail, turn on the key to pressurize the rail, you should see 42 to say 45 pounds. Turn off the key and watch the gage and see if the pressure drops, record how long it takes to drop, mine holds pressure for quite some time only dropping to about 20 in an hour. This test is not 100% reliable, and it is not a substitute for what I said in the above two paragraphs.

See what you find. Are you doing your own work or having work done?

ok well i just got back and i checked the fuel pressure regulator witht he iigniton to on and than turned on the car and there no gas leaking from that nipple nor any gas spit fromt he regulater after turning on the car.

oh before i forget when i turned on the car to test the FPR i herd a rattleling noise where the new cat is at. im getting scared lol...i only drove it home yesturday it wa sonly like 6 clocks home. not that far.... :(

6 blocks home and it was glowing red?

It started OK then as you got home it ran rough with no power?, is that typically what it did in the past?, before you did the CAT?

Do you have a fuel pressure gage?, check the pressure and the drop over time

If you are leaking that much fuel it wont hold any pressure,

You are also going to need to consider that your resonator or muffler system is collapsed

My guess is fuel because of the misfire,

How good did it run when you first picked the car up last night?,

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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That photo above is of the fuel rail, each injector has an o ring, be careful of the tips not to touch them or lean them on anything and DONT try to clean them at all

Are you mechanically inclined?, are you going to attempt to pick up the fuel rail yourself?

We will need to find a photo of your fuel rail to help you, this is a delicate job

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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A couple of things can cause that RED CAT, raw fuel is one, check your fuel pressure regulator, by taking off the vacuum hose and looking for fuel at the nipple, with the engine off then on, reving the engine to see if it spits fuel from the regulator. If it spits fuel it is bad

By lifting the fuel rail and supporting it with something like wood or holding it while someone else turned on the KEY to ON NOT RUN, the fuel pump will pressurize the fuel rail. When it is pressurized, if an injector is leaking you will see fuel leaking from one of the 8 injectors when the rail that they are attached to is pressurized. If any leak make a note of which ones leak.

You have to eliminate these potential causes first

One trick, I just read about, hook up a fuel pressure gage to the scrader valve on the fuel rail, turn on the key to pressurize the rail, you should see 42 to say 45 pounds. Turn off the key and watch the gage and see if the pressure drops, record how long it takes to drop, mine holds pressure for quite some time only dropping to about 20 in an hour. This test is not 100% reliable, and it is not a substitute for what I said in the above two paragraphs.

See what you find. Are you doing your own work or having work done?

ok well i just got back and i checked the fuel pressure regulator witht he iigniton to on and than turned on the car and there no gas leaking from that nipple nor any gas spit fromt he regulater after turning on the car.

oh before i forget when i turned on the car to test the FPR i herd a rattleling noise where the new cat is at. im getting scared lol...i only drove it home yesturday it wa sonly like 6 clocks home. not that far.... :(

6 blocks home and it was glowing red?

It started OK then as you got home it ran rough with no power?, is that typically what it did in the past?, before you did the CAT?

Do you have a fuel pressure gage?, check the pressure and the drop over time

If you are leaking that much fuel it wont hold any pressure,

You are also going to need to consider that your resonator or muffler system is collapsed

My guess is fuel because of the misfire,

How good did it run when you first picked the car up last night?,

once i started my car it was running smooth i even felt like it had more powere because the cat wasnt clogged anymore. once i came to a red light and it turned green i would step on the gas and i could feel the difference but once i got close to my house it started stalling. the car had the same symtoms and when it had the clogged cat. the guy told me i have a resonnator but that is to keep the noise down or some BS like that.

what would happend if the resonator or muffler is clogged up?? will that make the CAT glow red and give it a funny smell???

no i dont have one. i was cheking ont he internet and they are pretty expensive like $100.00 or maybe i can borrow one from autozone..ahaha

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I have this one from sears

http://www.sears.com/shc/s/p_10153_12605_0...+pressure+gauge

if the resonator collapses it will block the exhaust system and act a lot like a clogged CAT

I would eliminate the fuel issue first, if you have an injector leaking fuel, you need to eliminate that

Who put the CAT in?, maybe they have a gage they can put into the front O2 Sensor that measures back pressure in the exhaust system, you need a gage like this to test for exhaust system back pressure. The P0300 must be tracked down, that includes checking the coils, coils not firing will cause unburned fuel also

http://www.sjdiscounttools.com/ta33600.html

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I have this one from sears

http://www.sears.com/shc/s/p_10153_12605_0...+pressure+gauge

if the resonator collapses it will block the exhaust system and act a lot like a clogged CAT

I would eliminate the fuel issue first, if you have an injector leaking fuel, you need to eliminate that

Who put the CAT in?, maybe they have a gage they can put into the front O2 Sensor that measures back pressure in the exhaust system, you need a gage like this to test for exhaust system back pressure. The P0300 must be tracked down, that includes checking the coils, coils not firing will cause unburned fuel also

http://www.sjdiscounttools.com/ta33600.html

ok well likeBodybyFisher said ima start off with checking the fuel pressure. i should be going to the store 1st thing tomorrow morning and buy the pressure tester. what would be more accurate to use the pressure tester on the scrader valve on the fuel rail??? or lifting the rail to see if any of the injector leak?????

i called this shop about the cat and told the guy me that i should also check the FPR or maybe i had a leak on an injector. he said that the fuel pressure regulator doesnt have to leak every time.

. I dont know guys......

so bodybyfisher do i do the test with the car on or off?? or just the key set on ON without turning the car on???

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