Oil on spark plugs - misfiring p0300

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Rocket Man

Mark
Supporting Member
Joined
Dec 25, 2014
Posts
26,004
Reaction score
50,862
Location
Oregon
I had a lot of misfires and stuttering on hard acceleration and it got worse and worse. It was plugged cats, the engine couldn’t breathe so it was coughing and choking. It got worse over time, and was worse when it was hot. Once the exhaust cooled it would be fine until it warmed up. Just another possibility.
 
Last edited:
OP
OP
FAUST

FAUST

Member
Joined
Sep 27, 2023
Posts
45
Reaction score
26
I had a lot of misfires and stuttering on hard acceleration and it got worse and worse. It was plugged cats, the engine couldn’t breathe so it was coughing and choking. It got worse over time, and was worse when it was hot. Once the exhaust cooled it would be fine until it warmed up. Just another possibility.
I will add this to the list to evaluate however I can.

These are all free checkups and definitely open my eyes for future possibilities on my other vehicle (09 4cyl Camry).
 

Rocket Man

Mark
Supporting Member
Joined
Dec 25, 2014
Posts
26,004
Reaction score
50,862
Location
Oregon
I will add this to the list to evaluate however I can.

These are all free checkups and definitely open my eyes for future possibilities on my other vehicle (09 4cyl Camry).
I had a shop do a flow test on the cats, it didn’t cost much. There are other ways I’ve heard of.
 

Larryjb

Full Access Member
Joined
Jul 21, 2016
Posts
1,159
Reaction score
1,087
I can't recall, did you replace the intake manifold gasket? If you have air leaks into specific cylinders, unmetered air can enter those cylinders and cause a misfire.

When I had my misfires, I found it was very hard to diagnose conclusively, other than random misfires on one bank only. I may have also had a lean code.

Others say you can flow propane around the intake. I had tried that, but I couldn't get any results from that test. I think some one here did a smoke test. That might work better, but you'd have to have a way to see "under" the intake as well which is tough to do.
 

Larryjb

Full Access Member
Joined
Jul 21, 2016
Posts
1,159
Reaction score
1,087
Check post #12 here:

I didn't have a lean code in the beginning. It was the lean code that led me to change the IM gasket.
 
OP
OP
FAUST

FAUST

Member
Joined
Sep 27, 2023
Posts
45
Reaction score
26
I’ll have a go to look at that.

I just check my transmission fluid - not good. It’s dark and low. I’ll be doing a transmission fluid change as soon as I can.
 

strutaeng

Full Access Member
Joined
Aug 10, 2023
Posts
1,178
Reaction score
2,444
Location
Dallas, Texas
I’ve seen mention of a specific tool for these rigs - do you have a suggestion?

I agree with you 100% - before I became engulfed in this process I spent $100 on blue driver scan tool - it has the ability to see misfires on each cylinder but it’s not live.

I’m trying to do what I can without spending a ton of money on “fixes” that aren’t fixes.

I’m sure y’all have been here before - 3 kids in private school, Mtg, extra curricular, etc. just not a lot of expendable cash.

This forum has been helpful, I’ve learned a ton about the engine and engines in general - for that I am grateful.

Thanks for continued support and brainstorming to help a new wrench turner along.
Understand completely. Yes, same situation here.

I've had the higher end handheld Innova from AAP and it's decent, but kinda of expensive for what you get. It does do the injector balance test and has live data, but not cylinder misfire count.

I tune in to Pine Hollow Diagnostics and he recommended this Topdon dongle. I ordered it and just received it in the mail and was messing with it. It has a lot of features. I didn't see an injector balance test though, but does have cylinder misfire count and a lot of other bi-directional controls. The only drawback is after the first year they charge you like a $60 subscription per year. Still doesn't seem too bad if you are a DIYer.
TOPDON TopScan OBD2 Scanner Bluetooth, Wireless OBDII All System Diagnostic Tool for iOS & Android, Bidirectional Scan, Check Engine Car Code Reader, Vehicle Performance Test, Repair Guides, AutoVin https://a.co/d/hiNlqVM

Another option is the Tech2 clone. That one should do all the functions and covers up to like 2013 models IIRC.
 

Rocket Man

Mark
Supporting Member
Joined
Dec 25, 2014
Posts
26,004
Reaction score
50,862
Location
Oregon
A lot of us here have a Tech 2 clone, in fact there’s a list of members available to help using their tech 2 by area.

 
OP
OP
FAUST

FAUST

Member
Joined
Sep 27, 2023
Posts
45
Reaction score
26
Understand completely. Yes, same situation here.

I've had the higher end handheld Innova from AAP and it's decent, but kinda of expensive for what you get. It does do the injector balance test and has live data, but not cylinder misfire count.

I tune in to Pine Hollow Diagnostics and he recommended this Topdon dongle. I ordered it and just received it in the mail and was messing with it. It has a lot of features. I didn't see an injector balance test though, but does have cylinder misfire count and a lot of other bi-directional controls. The only drawback is after the first year they charge you like a $60 subscription per year. Still doesn't seem too bad if you are a DIYer.
TOPDON TopScan OBD2 Scanner Bluetooth, Wireless OBDII All System Diagnostic Tool for iOS & Android, Bidirectional Scan, Check Engine Car Code Reader, Vehicle Performance Test, Repair Guides, AutoVin https://a.co/d/hiNlqVM

Another option is the Tech2 clone. That one should do all the functions and covers up to like 2013 models IIRC.
Is there a specific brand or website I should look to purchase a Tech II GM scan too from?
 
OP
OP
FAUST

FAUST

Member
Joined
Sep 27, 2023
Posts
45
Reaction score
26
A lot of us here have a Tech 2 clone, in fact there’s a list of members available to help using their tech 2 by area.

I want to get one of these Tech2 clones - it is in fact Christmas season and it maybe the perfect “Christmas wish list” item to give my Wife for ideas this year.

I am just not finding a viable website/vendor to purchase from.

Any ideas?

Sounds corny, but this may work out for Christmas hahaha
 

Forum statistics

Threads
132,307
Posts
1,865,712
Members
96,895
Latest member
EGDinSD
Top