Hey all -

My car has been running a little rough after getting up to temperature, say a 15-20 min highway drive, but starts cold absolutely fine and runs smooth. Only after getting warm does it sound a little "lumpy," for lack of a better term. I swapped the plugs and wires today (changed the coils ~13k miles ago) to see if it would make a difference. It didn't. In the photos, the two plugs on the left were from the front rotor, the two on the right were from the rear rotor. My non-expert opinion believes the black on the tip and insulator mean there's some type of seal problem on the front rotor, which probably hasn't gone far enough to result in a misfire, hence no CEL, but it seems like it may be on the way. Is a compression test the next step? Searching through it seems like a DIY compression test is tough, but can it be done accurately?

Thanks in advance.

 

How old are these plugs?
Your front trailing is fouled over the electrode, so it probably hasn't fired in a while. If that's the case, that might explain the lumpyness. Was the wire securely attached to the plug? Has it been flooded?

You also have this white stuff on the rears, and a bit on the front leading on top of the black stuff. Could just be the gas you're using, but how's your coolant level lately? It's too light to be coolant, but just thought I'd ask. If it's not that, check for vacuum leaks, you might running a bit lean on the rear rotor.

 

All information I should have provided. Plugs had 42k miles on them. No flooding, wire was attached when I took it off and I was sure to hear the click when I replaced them today.

The white stuff on the rear may just be the flash, it's a pale brown in person.

If the one plug not firing would explain the lumpiness, replacing it would have fixed the problem right away, no?

I'll double check the vacuum nipples.

Car has 83k on it.

 

+1
Especially because the trailing plug plays a very large role at idle, more so than the leading plug.

I was going to say exactly what the OP responded. Looks like it could just be the camera flash making the nice light brown colour over exposed to white.


I know you said the coils had been replaced but that doesn't mean one of them hasn't failed. You could also have a cracked connector in the plug lead where it connects to the coil, or even a harness issue.

Yup check for vacuum leaks.
Make sure plugs and leads are tight and on correctly.
Clean Maf
Clean ESS
Reset nvam ram (20 brake stomp)
Check air filter
Any catalytic issues? Has it been inspected?
Buy a HEI Coil tester -- they are cheap and will tell you the health of your coils.
Compression test if you think it needs it. But that's going to cost more than the above recommendations.

 

it says your car runs, and you drove it, and maybe the T1 coil/wire is bad

 

It appears the one totally covered in soot is not firing

 

Update: Just got the call from the dealer - Rotor 1 low compression. I'm getting a new engine - as long as my log sheet is sufficient documentation. I recorded every gas fill up, tire rotation, tire change, brakes, oil change...everything I've done in one excel sheet. Only thing it doesn't have is receipts (which I could argue don't guarantee the work was done either).

 

Uhmmmmm. No receipts.
I dunno good luck please update when you get new info.