Hey guys,

I have a 1997 ls400 that is giving me quite a headache. The car has about 140,000 miles and was running great one day it started running kinda rough not too bad, so I changed the plugs, wires, caps and rotors and the problem went away. I drove it for like 2 miles and the misfire came back. It has gotten very bad, I get codes for random misfire as well as misfire codes on multiple cylinders. Like I said I've changed everything, I've checked for vacuum leaks and cannot find any, someone said the igniters were no good and needed replacing. I replaced them to no avail. Same problem. Sometimes the car will not even start at all an when it does it smokes white beyond belief and smells like straight fuel. Guys I'm stumped, any help would be appreciated

 

Have you changed the coil? It is normally the one on the passenger side opposite the battery tray.

 

At night when it is dark with the engine running, look for sparks due to the wires arcing. I'm not sure if by igniters, you mean coils, but the coils can easily be tested to see if in spec. Also, you can clean the crank sensor if it is dirty. It's not that hard to get to. Mine had a good layer of sludge. Keep us in the loop.

 

I haven't changed the coils but I measured the resistance and I believe they are in spec, the wires are brand new so there shouldn't be any arcing but I've tested spark and it's got a strong spark. I'll check out that crank sensor and let you know

 

I had a misfire on my 97LS400 that was more subtle than what you're describing. It occurred after I had replaced one of my coils. If I was in "D" and stopped occasionally I would feel a stutter in the engine. If I was in "N" it wouldn't stutter at all. If I was in "D" and moving I didn't notice anything, it seemed fine. I troubleshot it using a spare coil that I subbed in for each of the two coils.

The resistance measurements are difficult on the coils, I think it's the secondary where the spec is so low you can make it pass or fail just by how well you're touching your multimeter probe to the measurement points.

Couple ideas:

1. If you're getting multiple misfire CELs, do they trace to any one particular coil?
2. Have you checked for air leaks? In particular check the air tube just downstream of the MAF sensor, when it cracks it's not always visible.

Hope that helps

 

They do not trace back to a specific coil, I checked the maf and intake no cracks, no vacuum leaks that I can find, and no arcing when I ran it at night. Now about the crank sensor. Where is it exactly is ther a good picture or diagram someone can show me? I think I know where it is but I'm not sure. I only get like an hour of daylight after work which doesn't leave me much time to work on it after so sorry about the slow responses and thanks for the help so far

 

Saturday update:
I finally got a chance to work on the car, checked the crank sensor it was a little dirty so I cleaned it but it didn't help. Do these sensors go bad often? And would that sensor going bad cause my problems?

 

A simple approach, what gas was put in?

 

recheck your caps and rotors, might have a crack, letting spark jump..... also take a look at the mass air flow sensor... clean it with carb cleaner, if necessary. AND do check the gas like RA said

I sure hope you didnt get diesel fuel in it......


.

 

Well the cap and rotors are brand new and no there was no diesel fuel put in. Of that I'm positive, I've Put high grade fuel in it and it doesn't help. I've tried a few different places but as of right now no luck. Now the car has started running smoother it still misses but is running better, but the exhaust is completely white an smells like fuel. I have a flashing CEL now so I'll have to get the code checked

 

Other than smoke, sounds like mine did for 3-4 months until the fuel pump went out totaly. BTW miss-fire error codes were for the even side, if that helps. Generic replacement on ebay $36 looks exactly like the OEM without the bracket ( takes 3minutes to put that on), local shop wanted $200.
Pull seat back and sound deadening mat off you may hear it cutting out. Probably due anyway.

 

even a new one could have a crack, I even thought about putting the old ones back on to see if it made any difference.

 

Ok so I've double checked everything and the caps are fine, and now the car is only giving me 1 set of codes, misfires on cylinders 4,5,6. Ive ruled out vacuum leaks, spark igniters, plugs, caps, rotors, wires. Now I haven't replaced the coils yet because I'm not sure a bad coil(s) would cause misfires on only 3 cylinders. Can anyone shed some light on that?

 

I had a problem like this on my windstar. I end up replacing the camshaft synchronizer for the timing of the fuel to the cylinders. I would look in that direction.