I bought an 03 ls430 it ran great for a while and then started misfiring. I changed the coil packs and plugs and it didn't do anything. I cleared the codes twice and it started working normally for about 3 to 4 months. Now it's doing it again
The coil packs I put in weren't the greatest and they were cheap . Could this be my issue? Also notice like a black residue on the coil pack. Didn't look like oil because it was only on 1 or 2 of them and was dry on there. Almost looked like the rubber on the end was getting burned in there or something

 

What are the codes? What kind of shape were the old plugs in? How many miles?

You need to determine which cylinders are misfiring and concentrate your efforts there. Since it appears to be somewhat intermittent I would be looking at the condition of the wiring to the cylinders in question...

 

Check the coil connectors for loose wires. Seems to be common for the wires to loosen or be pulled out when handled. If you have certain cylinders misfiring, check those first. Then swap the coil to another cylinder and see if the misfire moves with it.

 

The car has about 280k original miles. the plugs are new and in good shape . Little sludge on them though. Codes p0303 p0306 and p0308. I checked the spark plugs . Two of them were a little loose. Tightened all of them not to hard to strip . Swapped the coil packs. I dont have a code reader on hand. But last time I had this issue I replaced the plugs and coils and cleared the engine and it was fine.

 

I will try that . Is there a starting point or a beginning for all the wires to be disconnected at once . Like the main connector . Sorry my terminology is crap lol

 

Sorry I think I was replying wrong. I pulled the plugs they looked fine. Checked the coil packs they also look fine. Noted: just bought these plugs and coils about 4 months ago. I unhooked the battery for 30 min or so. Turned it on . And have the same issue but with not flashing check engine light. It comes back after idle at pr about 1500rpm. Still shaky and it smells like gas. Noted: this cars catalytic converters are gutted.

 

Faulty coil packs the whole time. Replace all 8 with trq's for 160. Thanks everyone!!!

 

What is trq?

Country of origin?

 

Trusted Reliable Quality Auto Parts logo
TRQ Aftermarket Auto Parts
(many TRQ parts are Chinese)

 

Got them off of 1A Auto . Much better then the bs Orion packs that were In there

 

Little Sludge? Are your valve cover gaskets leaking around the plugs? If so that will cause issues.