So I'm having a little trouble diagnosing this one I'm pretty sure it's a clogged catalytic converter but would like to know what you all think. I know the p0300 is in cylinder 3, 5, and 7 with cylinder 7 having the most misfires. When I try to accelerate quickly there's a rumbling/muffled sound and when I get to 40mph the check engine light starts flashing and it's like I have a lose of power and doesn't want to go over 40mph followed by some popping/bogging feeling but not like a loud backfire. When I'm in drive and come to a stop if feels like it's bogging and wants to Stahl I also have a strong rotten egg/sulfur smell. I've replaced o2 sensors and cleaned the fuel injectors any opinions or advice would be much appreciated!
NEED HELP 2009 saab 9-7x 5.3i p0300 and p0420
- Thread starter help-i-own-a-saab
- Start date
If you think your cats are clogged, take out your upstream O2 sensors, and try driving it. Yes it will create more check engine lights, and will be noisey, but its a cheap test. If it drives better, you may have your answer.
3, 5, and 7? Since its a 2009 model, it will have AFM/DOD. Problem is, thats on cylinders 1, 4, 6, and 7. With 7 having the most misfires, I would check the rockers to see if the AFM/DOD is your problem on #7. 3 and 5... Could be Spark Plug, Coil, or?
3, 5, and 7? Since its a 2009 model, it will have AFM/DOD. Problem is, thats on cylinders 1, 4, 6, and 7. With 7 having the most misfires, I would check the rockers to see if the AFM/DOD is your problem on #7. 3 and 5... Could be Spark Plug, Coil, or?
The most reliable Diagnostic Tool for investigating a "Poisoned" or Clogged CAT is to point an Infra-Red Camera at it and View-Save & Post the Image along with the Temperature Reading using an inexpensive Laser Thermometer here at GMT Nation:
I'm in the process of taking the upstream 02 sensor off now or possibly even unbolting the catalytic converter from the exhaust manifold and then driving it to see if there's a difference.
I checked the coils and plugs and even replaced the plugs but no change. Wow thank you I'll have to look into that I honestly didn't even think of that because I thought it was all related to the catalytic converter being clogged and the back pressure being the cause of the misfires. It just through me for a loop only being 3 out of the 4 cylinders that where misfiring. But I'll definitely look into that thank you!
corky
Member
If you pull the first oxygen sensor and put in a back pressure gage you can tell and when ever my truck feels like its missing its usually a bad coil. One of the reasons my cat wes clogged is due to fact that the inside of my exhaust manifold was breaking up in to flakes and clogging the cat so if you replace your cat maybe take a peak up into the exhaust manifold and see what it looks like.
Mooseman
Moderator
The clogged cat could also be caused by the misfires. Maybe the clog is causing the misfires, especially since they are all on the same bank so maybe that cat is clogged.
And if you don't have a thermal camera, another tool you could use is an infrared thermal gun. Compare the temps before and after the cats. Temp should be higher after the cat.
And if you don't have a thermal camera, another tool you could use is an infrared thermal gun. Compare the temps before and after the cats. Temp should be higher after the cat.
Thanks for all the advice I really appreciate it, its nice to talk to actually knowledgeable people! When i took it to the muffler shop they told me my brand new spark plugs where shot lol.
I ended up unbolting it from the exhaust manifold and test drove it and found a major increase in performance and no misfires in cylinders 3, 5 and only 2 were recorded in cylinder 7. So I finished unbolting it and cut the exhaust. You can see the broken pieces inside and when I shake it you can hear it rattling around in there. Now the fun part of trying to find a replacement because nobody around me will weld a new catalytic converter on it because of the angle.
I ended up unbolting it from the exhaust manifold and test drove it and found a major increase in performance and no misfires in cylinders 3, 5 and only 2 were recorded in cylinder 7. So I finished unbolting it and cut the exhaust. You can see the broken pieces inside and when I shake it you can hear it rattling around in there. Now the fun part of trying to find a replacement because nobody around me will weld a new catalytic converter on it because of the angle.
Mooseman
Moderator
Shop around and see what you can find on the used side. Trailblazer SS or Saab 9-7x Aero are also able to be used.
Buick Rainier V8 seem to be the most common V8 GMT360
Buick Rainier V8 seem to be the most common V8 GMT360
The Broken or Shattered CAT Ceramic Insert(s) can indicate Bad Motor & Transmission Mounts (and on occasion... explain the presence of having a Cracked Flex-Plate). So, you might consider performing their R&R if you decide to swap out the Heavy Cast Iron OEM Exhaust Manifolds... For Stainless Steel Headers instead. Thus, This... provides more of an open area within which to work on the Motor Mounts...Too... :>)
"Why is THIS...THUS...? And What is the Reason for THIS THUS-ness?" -- Abraham Lincoln --
"Why is THIS...THUS...? And What is the Reason for THIS THUS-ness?" -- Abraham Lincoln --
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