Clogged Catalytic Converter / P0300 Code
 

After months of dealing with a P0300 code, my car went into Limp or Safe Mode while on my way home. It wouldn't go over 40mph and 2500 RPM's. I drove it to the dealer, they conducted an initial test, then a compression test. I was told it was a clogged Catalytic Converter causing a P0300 code. When the first Check Engine Soon light was received, I changed the entire coil pack, all spark plugs, cleaned the MAF sensors and checked for vacuum leaks without no success. Has anyone ever heard of clogged Catalytic Converters causing a P0300 code

Any mods on the car? Miles? not sure about miles but I thought federal emissions equip. warranty was 10 years?

If the diagnostic was indeed correct, another investigation is needed to find why the catalytic converter had become clogged in the first place.

I have approximately 92,000 miles. I have an ARK Grip exhaust and K&N Cold Air Intakes. The Warranty is seven years and eighty thousand miles.

It could be due to the oil consumption issue, I'm switching to Motul. Some people claimed that their consumption issues were completely gone after the switch.

Get test pipes, never worry about clogging again.

During the initial p0300 occurence, you may have been sending un-burned fuel into the cats due to the random misfire. This could have slowly started to clog the cats. Since you changed the entire coil pack, all spark plugs, cleaned the MAF sensors, and checked for vacuum leaks, this may have eliminated the initial root cause, but the secondary symptom has not yet been resolved. With the lower than normal flow out of the cats, this may be causing another random misfire.

This is all just a guess.. Let me know your results though. I had this code thrown without any symptoms. I did the same procedure as you and the code went away for several months, but it has returned without any symptoms again. Could possibly be my car is experiencing the same issues.

The P0300 code started in August without any symptoms, it went into Limp Mode in October. I drove my car to the dealership on Friday and was told it was the Catalytic Converter the following Monday after a compression test. I was told the part would be in on Tuesday and my car would be ready on Wednesday. On Wednesday, instead of telling me my car was ready, they called to tell me the car was misdiagnosed and that it was my timing chain. The service consultant said my timing chain was off twelve degrees.

I'd be pretty wary about this misdiagnosis; what else are they going to misdiagnose. I had serious doubts about random misfire events caused by clogged catalytic converter(s). Mistimed camshafts might be a slightly better candidate, but I'm skeptical at timing chain; it is unlikely for a timing chain to jump/stretch causing twelve degrees out of timing. I suppose I'll believe it when it's fixed and it doesn't come back.

Gixxerman, did they mention how or why your timing chain was off by 12 degrees?

I've had my car back since Friday, all is well. I bought the car with 65,000 miles on it, I can't speak for what the previous owner did to the car. I'm not a mechanic so I had to take the dealer's word (we all know they're theives).

Of course they asked me if I did anything like excessive high RPM revving, I don't drive it any harder than normal.

If you were still within the factory RPM limit, I do not see why high RPM revving would cause your timing chain to go off by 12 degrees. There must be something else involved.

What normally keeps a timing chain in spec?