livinfree

This is a 98 LS400, 148K. I've only had it about 6 months. Its been doing this ever since I got it. Runs fine even while throwing codes. I get about 18MPG in the city and on gets 31.5MPG on long highway trips. However...those codes....usually starts in stop and go city type driving. I'll notice a slightly lower idle that's a little rough. Once I get that I know that soon it will start running rich and I'll be smelling gas. Once I smell gas I know the CEL and VSC lights are gonna come on soon. Sometimes they will go off quickly, sometimes it will take a few days. I have replaced the plugs. I think I got the NGKs...not cheap. Today I dumped in a can of Seafoam injector cleaner and also switched coils on cylinder 7 and cylinder 3 so see if I start getting a P0303 instead of a 307.

One other detail I finally resolved today involved the air intake collector (I think that is the right name). One of the nipples for a hose going from the head to the collector had broken off. Previous owner had tried to epoxy it and yeah that didn't quite work, so I repaired that properly today.

Do you guys have any other ideas?

PureDrifter

iTrader: (10)

check the coil on cylinders 3 and 7, cam sensors (voltage tests, search for it, do bank 1 (driver's side) first), and if all of the above test out perfectly fine, come back.

DirtyLex

Interesting, im having the same problem on my 97 ls400. Only had it for a couple months and all of sudden this happens. Im afraid to drive it now until i fix the problem.

AutoZone printout for this code shows:

Cylinder 7 misfire detected.

Probable Cause:
Large Vacuum Leak
Fuel System Concern
Ignition System Concern
Engine Mechanical Condition

bornpeace

When was the last time you change spark plugs? Do what PD suggested, also check ur spark plugs. I had the same problem and spark plug cure it. Check coil connector make sure is not loose in cylinder 7 and 3

DirtyLex

i actually bought ngk platinum plugs when i was checking the code at autozone.
i havent put them in yet. hopefully tonight! thanks

bornpeace

In case you dont know, cylinder number 7 and 3 are on driver side. #7 is the last one close to the firewall, #3 will be the second from front of engine just after oil fill hole.

bornpeace

i recommend iridium rather than platinum. iridium are also recommended by your manual. I know they are expensive but you will have more 60,000miles without the need of new plugs

ROLEXUS400

iTrader: (2)

Take p.d.s advice and it wouldnt hurt to check compression anytime their is a missfire, and plugs are already out of engine. Heres a lil chart incase you didnt already have it

DirtyLex

Thanks for input.

Ive changed the plugs and also the air filter while i was at it. There was also a vacuum line that was crimped that i replaced. Vacuum line ran from side of intake across engine and down to the frame. It was a metal pipe that it connected to.

Cylinder 7 also has like a very tiny bit of white fluid around the plug. It was definitely just a tiny bit and i only noticed it in cy #7. This plug was also the hardest one to get out.

So i started the car and it seemed fine until i started to drive it. Same problem! At low rpms it just is not running right. the CEL doesnt come on till i start to drive it, once i give it some gas. Then the TRAC light starts to blink rapidly. One the car is warm and its parked at idle, it drops to around .500 rpms and in the exhaust i can hear like a misfire i think.

So whats recommended next, new wires?

thank you

enoggin

Hi...i"m having the same issues with my ls... I was having the same issue about 6 months ago. I cleaned the throttle body and it seemed to go away. It has now come back again. I changed the plugs (they were due anyway) and it didn;t make any difference.

Any ideas?

ef8sir1988

iTrader: (2)

I to just got the same problem but in cylinder 8. My mechanic say he thinks that the coilpack is starting to give out.