Engine Misfire

J

Jonny3777

Member
Hi all,

I'm posting this to help anyone that might have the same unusual issue I had yesterday. I was driving home from work (an hour commute) and 10mins from home the car starts intermittently jerking and losing power. I get home and leave to to run idle seems fine 🤔 strange... So I turn off the car I plug in my OBD scanner as I get a P0420 code error every now and then saying the bank 1 threshold is below standard. My cat is fine passed emissions test great a couple of months back plus I use redex in every tank of fuel to keep it clean. So I go for a spin 30mins later and the car judders 4 times before I get to 3rd gear. So back into the driveway I go. My mechanic picked it up on the tow truck today.

I thought it might be the usually cause of a misfire so troubleshooters, spark plugs, fuel injectors, camshaft sensor, mass airflow senor, compensatior cap, fuel pump or filter. None of these were the cause, it turned out to be the DTC. The ECU didn't know where to send the power and caused the engine to misfire. My mechanic is working on it now I'll update you guys if there are any other issues.
 
My 2nd Coupe flased up an amber EML soon after I got it for codes P0420 and P0430 - post-Cat 02 sensors for both banks. It still dorve fine though with no misfire or hesitation.

Anyway during the diagnosis the original 9 year old battery died, so I suspect my problem was one of those random electrcial issues that these cars seem prone to having when the battery is on it's last legs!
 
Worth checking the coil packs - I had a couple of intermittent misfires earlier this year - after changing them (& plugs) not a murmur out of place since
 
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