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Misfire mostly at idle 2000 DTS


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Hey guys, I have a pretty heavy misfire at idle usually only when I am stopped at a stop sign or light, the SES will flash after I start pushing on the gas leaving the stop light but only for less then 30 seconds then it returns to just being steady on. I forgot to pull the codes from the built in OBD reader before erasing them, can do that tonight because it will be throwing a code shortly again, but I did get codes from my craftsman scanner:

P0137 HO2S-12 Circuit Low Inpute Bank 1 Sensor 2

P0303 Cylinder 3 misfire detected

P0420 Catalyst system low efficiency

P01133 HO2S-11 Bank 1 Sensor 1 insufficient switching

not worried about the 420 most likely caused by the misfiring over the years, replaced the converter years ago and need to do it again looks like.

I was reading from Logan on this post #11 that the manuals for 2000-2003 do not have a specific p030X code just the generic P0300. I state this 1. due to the fact my scanner pulled a 303 which I guess could be rubbish and 2. I replaced the rear bank Ignition control module already where cylinder 3 is located, when I did that about a month ago, it got better but never went away and now its back with a vengance!

So, any advice or perhaps intution with the O2 sensors causing something like this, before I start throwing money at parts would be greatly appreciated!

thanks,

koushka

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I would pull the coil pack for that bank. (firewall side unfortunately) and check it for cracks in the housing. just went through the same with my 01 eldo. coil was bad and was misfiring on cylinder 4. replaced plugs and wires(COP), then the coil. voila, runs like new

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Did you change plug and boot on #3 while in there changing the coil bank?

Either could be faulty - possible leaking injector on cylinder #3 or plug could be going bad due to coolant fouling on the intake side.

You'll pull a standard 0300 misfire from the display but your code reader may be able to read the cylinder

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So I am cheap and played the switch around game, I pulled the plug cleaned it, just seemed normal maybe running lean with a carbon deposits, I switched the boots from cylinder 3 and 7 around, I put my old coil pack in and cleaned the ground to the coil pack and I will see how it goes from here. I pulled the codes again after resetting them from previous post and all I had was the general P0300 code. I will update in a day or two see how it runs for the next 100 miles or so. Cylinder 3 boot seemed to have oil around the top of it, maybe that is causing my issue.

thanks for all the info guys, appreciate it.

koushka

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If the P0300 came back after you worked on the ignition and cleared the codes, the problem was still there when you were done.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Yep, the P0303 and P1133 came back. I wonder if its the O2 sensor acting up on me that is causing this or a dirty injector. Blast! I just don't want to spend the money till I know it will fix it, I suppose 1 plug won't hurt :D

thanks again,

koushka

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Its not an o2 sensor causing a misfire. Did you switch the plug and boot as a pair. I have had many engines with misfires 2000+ and the delco plugs seem and look fine. I replace them or move them as a pair to another cylinder and find a bad spark plug.

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A bad oxygen sensor will eventually ruin a cat. After you fix the miss, I would change the oxygen sensor. When all the codes are gone except the P1133, you can replace the cat.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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  • 2 weeks later...

Installed brand new spark plug, misfire continues. So to recap, I switched the boot, the coil pack and now the spark plug to no avail. That leaves the injector, should I replace that next or try some cleaner in it first, or should I give up and take it in *gasp*.

Again thanks for the help.

koushka

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Well, thought about it and I think I will swap an injector for another cylinder and see if the misfire follows or clears up. Any words of wisdom on the removal of the fuel rail and getting to the injector?

koushka

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A few screws, then it pulls up. The injectors are held in by O rings, so be careful not to damage any of them.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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  • 7 months later...

I have a 2001 cadillac seville sls. got it from an auction. has 91000 miles. It keeps throwing pcm p0300 codes, engine light, and idles rough at stop signs and when parked.

the plenum had a air leak. replaced it. some vacuum hoses cracked so i replaced those. there was a cyl 2 misfire code so i looked and there was alittle oil in around the spark plug so i cleaned it out and put all new spark plugs. but when i took the coil pack off it touched the engine while it was still hooked up and made a spark noise and i tested it and two of the things didnt have any juice going to them so i got a new coil pack from the junk yard and put it on. i cleaned the throttle body and egr valve. i put a new fuel filter on. after all that it seemed to run excellent until i drove it half mile when the light came back on and it started idling bad again. checked the fuel pressure regulator and its fine as far as i can tell. the fuel pressure is low though. it says 35 psi. it does jump when i put the throttle down and when i take the tube off of the fuel pressure sensor it jumps up to 40psi or so. when i turn the car to the on possition the fuel pressure tester kinda slowly makes its way to 35psi. What does this mean? i took the fuel pump out to look at it and the filter packet thing on the bottom of the fuel pump looks kinda blackish like maybe its dirty and making bad fuel flow or something. not sure why im getting low fuel pressure but worse of all this p0300 code is killing me. it says that on the dash but autozone's tester was more specific and told me it was p0304 (cyl 4). any ideas? please help. Thank you.

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