Hey everybody.Got a 95 ls400 with misfire . I put new plugs in a few months ago went with autolite double platinum which were good for about a month or so. Started to misfire but didnt have money to buy the good plugs immediately. Eventually i got some NGKs double plat. but still misfiring. Scanner pulled p300 p305 and p307. Changed cap and rotor with no luck. . I got new plugs/wires cap and rotor. Also the idle is higher than usual when engine starts plus the idle drops while in drive at random. Any suggestions

 

check the plug wires and order. test them with an ohmmeter.

you have something else going on other than the plugs, i run NGK V-power copper plugs in mine and havent had a single problem ever.

 

i pulled plugs 5&7. 5 was black and 7 was white these are new plugs not more thatn a month or two old. also the wires which are also new the wire to plug 5 was slightly burned wha tmigh this indicate. I would post a pic but i dont know how

 

if you are able to down load the photo to your pc, the go advanced (here below) button will let you post it

 

Hey puredrifter, jw if u can tell me what the part number is for the plugs ur running? And how often do u swap them out?

 

As far as testing wires with an ohmmeter what should it read if good and what would it read if bad?

 

Something else is going on as PD suspects. Any obvious oil consumption? Seems to me that 5 is being fouled (no spark or oil) and 7 is lean. Some of the 95-96 have ECM issues.

 

Ok, I have the photos downloaded to my PC but when I click below on "go advanced" and try to insert photo, it ask for a URL for the image. Sorry but I'm new to these forums and haven't yet familiarized myself with it yet.

 

 

this is what cylinder 5 plug looked like it was black but not wet (no oil) the plug wire is shown above

 

 

Can an EGR be cleaned or do they have to be replaced?

 

I suspect you have injector issues at #5 and 7. Curiously, what gas are you using? Some like the Chevron Techron FI cleaner, your choice. Try that and see if there are changes. If you have a bore scope, I would take a look inside the cylinder and see how the piston top is.

The boot concerns me. Since this was new, I suspect that it is seeing higher than average temps and it is arcing. Maybe someone else has a different interpretation...?

 

I just bought athis camera from costco so I will be looking tomorrow if it doesnt rain

 

That's your culprit. A bad boot will not fire the plug but instead find another path to ground and that's how you are getting your misfire. Replace all those spark plug wires and see if it still misfires. If still does, injectors would be next.