1998 Ls400 Won't Start Anymore :(

[Smokey]

My problem started about 2wks ago. One morning I started up the car and it ran really rough and died. I took a different car to work and tried again the next day to find the same result. What I noticed was that if I gave it gas it would run pretty smooth but at warmed up idle it was rough. I searched around online and a few people mentioned its probably bad plugs (100k on oem plugs) so tonight I go pick up some NGK iridiums.

I start with the drivers side bank (easiest access) and replace the 4 plugs. While I was pulling out the front most plug my ratchet contacted the terminal on the fuse box and sparks flew. I was startled but finished the drivers side and tried to start the car and the car started for about 10seconds stumbling then it died. Now it wont start. I checked all the fuses I could see (clear top) and theres a couple block fuses I don't know how to check. All the fuses look good, nothing burnt and the elements look intact.

Trouble shooting so far: I've cranked the engine for a few secs and checked the drivers side plugs and they're all wet. This leads me to believe none of the plugs are firing anymore(even the front most plug, whose coil pack was out). My thought on this was that I could've killed the coil packs from that spark? I'm confused since the motor did start up for at least 10seconds or so. Is there a fuse I'm missing that is causing the plugs not to fire? I'm assuming that spark killed something or blew a fuse that I dont know about. BTW which fuses should I be looking at? The none of the abreviated descriptions make sense to me.

I may go borrow an OBDII scan tool this week if I can find one. I really don't want to tow this to the dealer but I suppose I am due for my yearly raping. Last year was the timing belt. The year before was the starter. etc etc.

thanks for any help in advance.

[curiousB]

Not sure replacing plugs was your best first item to try. Its hard to think through how a plugs would have worked a couple weeks ago and suddenly overnight they are bad. That's not a likely failure mode for a plug.

If you have a voltmeter you could measure the point that you shorted to ground to see if it is at 12V still. If its zero you must have popped a fuse somewhere. At least hopefully it is a fuse as that is a lot easier to replace than a wiring harness.

What model and year do you have?

[Bali26]

Its usually something simple. You might have killed or disconnected one coil causing to run on four cyl.

or maybe put the spark wires on wrong. or blew a fuse.

[SKperformance]

Lock and unlock the car door with the key to make sure the theft system is not active.

How much gas in the tank?

Disconnect the maf and see if it changes.

More than likely it is the crank position sensor ,check it for damage. I don't know where it is you'll have to do a search.

[Smokey]

Thanks guys. The car is a 1998 LS400. The initial reason I thought a plug or two went bad was because of the rough idle but it would run pretty smooth with a little gas (higher rpm). Talking to my uncle he said its probably just a plug gone bad so I attempted to replace them. I've done many plugs before so I figured it'd be easy.

Reading through the forum and talking to another car guy it sounds like i essentially shorted the battery. And now the 120A alternator fuse is in question since it usually blows first with a battery short. I'm looking at the fuse (white body,clear top) and its two metal bands coming together with a little fat spot in the middle. How do I tell this fuse has gone bad? How do I get this fuse out to test if its good. Its stuck in there really tight and my fingers are in pain from pulling.

Good tips guys!

I'll try to just check to see if i still get 12V between the short circuit point..

I'm pretty sure coil packs/wires were plugged in right. I removed/replaced them twice. The only thing I noticed was the coilpack sure seamed alot easier to put in than pull off the old plugs (I assume due to length of time being in there).

Tank is over half full.

OH I was using the Valet key too maybe that was part of my issue???

What is this crank position sensor? My friend said that could be that too. I have no idea what that is. Is it DIYable? Or will I likely need to tow it in?

Thanks again for all the help/tips/ideas. I was ready to have it towed in this morning after being so frustrated with it last night. I'll stick it out this weekend and continue to trouble shoot.

[Smokey]

Well I think all my fuses are good. I checked with a DVM and have continuity and 12V between the fuse terminal and the ground(short point).

Unfortunately the master key won't be home for a few more days so until then I'm stuck unless there are more suggestions or any tips on where the crank position sensor is.

thanks again!

[az735i]

Well I think all my fuses are good. I checked with a DVM and have continuity and 12V between the fuse terminal and the ground(short point).

Unfortunately the master key won't be home for a few more days so until then I'm stuck unless there are more suggestions or any tips on where the crank position sensor is.

thanks again!

Hopefully this helps. Here are the check procedures for the camshaft sensors and the crankshaft sensor, as well as a troubleshooting list. From your original post, it sounds like there is no spark. The camshaft sensor and the crank sensor can cause the problem you are experiencing.

The crankshaft sensor is located behind the crankshaft pulley.

[curiousB]

Well if you measure 12VDC at the point you arced to ground it seems the fuse did not blow. Must be a high current circuit I suppose. Not sure this is good since the fuse is a protection element.

Based on this maybe the arcing situation is throwing you a curve ball and the real issue is some error in the repair you did and the ARC, while annoying, didn't do any damage. Any chance you got plug wires mixed up (sorry I had to ask).

I guess if crank sensor isn't working there would be an error code in ODMII log so maybe should should try that.

Auto parts stores sell these spark test modules to go in serious with plug and wire. Very cheap clear plastic so you can see arc of a spark. At least you could try on a couple plug wires to see if any spark is attempted. Timing maybe be off but at this stage you're not sure if spark is happening but at wrong time, or spark isn't even happening. Knowing which it is might give a helpful clue at this stage.

[blake918]

Based on this maybe the arcing situation is throwing you a curve ball and the real issue is some error in the repair you did and the ARC, while annoying, didn't do any damage. Any chance you got plug wires mixed up (sorry I had to ask).

I think you are on to something. I'm in the middle of changing the valve cover gaskets on my '99. When I was putting the driver's side valve cover back on, I noticed something spark near the battery and fuse box. I tried starting the car, and it would just click. A few tries later it started right up, and everything worked like normal (ran like a top, 14v+ at the battery during idle, went in to gear, etc.) except the speedometer/tach needles didn't light up, although the malfunction lights cycled as the car started. I spent a while longer checking for OBDII codes and checking all of the fuses, and everything checked out. Then, a few tries later, it would just click.

After reading this thread, I decided I'd check (just visually) the wiring in that area and try pushing the wires further in to their harnesses; I did this on the throttle body actuators, fuel injectors, coil packs, etc. I try starting the car after this and everything is back to normal. Maybe the arc was a curve ball, and I had actually snagged something when I was taking the valve cover out since it is a tight squeeze. I think it would be tough for the OP to have the coil packs plugged in wrong, since they are tailored in length to each of the 4 plug locations, but anything is possible. I wonder if he snagged a wire or something like I did, or perhaps mine just needed to sit with the battery unplugged for a while. Who knows. . .

[Smokey]

Ok more update...

I dig some digging and found the master key. I turned it over and it kind of ran and stalled out for about 10s again. Cranked again and no luck so its not the security system.

I think I was checking the camshaft sensor. I couldn't actually get at the plug it was showing me in the picture but I could see on the plug and it had blue/yellow wire. I followed those wires up to a different plug with 4 wires which had a corresponding blue/yellow wire. I metered the blue/yellow wire and got 0.749Mohm. I looked around and didn't find any other blue/yellow wires in the general vicinity so I'm assuming that is the camshaft sensor I metered and it is bad (just low for cold range). I guess the next step is to get an OBDII reader to verify any error codes.

So 2 follow up questions.

1) I was lazy so I didn't want to crawl under the car tonight and check the crankshaft sensor. Maybe tomorrow I'll do that but could both of those go bad? or more likely just one of them going bad?

2) How hard is it to replace these two sensors? is it DIYable? Is there a camshaft sensor on the passenger side bank? az735i, you wouldn't happen to have the instructions to get at these sensors would you?

THANK YOU az735i for the diagrams and everyone else for the tips/ideas/input. At least I have a better feeling about whats going on now even if I end up towing it in :(

Oh I forgot to answer the other questions. I did one plug at a time so there is no issue with mix ups. The coil pack can't be plugged in wrong. It only plugs in one way with a snap to confirm its in all the way. I didn't tug/snag any wires. I generally am pretty careful when working on electrical wires etc. The only hick up was the spark which probably threw me off.

[az735i]

Ok more update...

I dig some digging and found the master key. I turned it over and it kind of ran and stalled out for about 10s again. Cranked again and no luck so its not the security system.

I think I was checking the camshaft sensor. I couldn't actually get at the plug it was showing me in the picture but I could see on the plug and it had blue/yellow wire. I followed those wires up to a different plug with 4 wires which had a corresponding blue/yellow wire. I metered the blue/yellow wire and got 0.749Mohm. I looked around and didn't find any other blue/yellow wires in the general vicinity so I'm assuming that is the camshaft sensor I metered and it is bad (just low for cold range). I guess the next step is to get an OBDII reader to verify any error codes.

So 2 follow up questions.

1) I was lazy so I didn't want to crawl under the car tonight and check the crankshaft sensor. Maybe tomorrow I'll do that but could both of those go bad? or more likely just one of them going bad?

2) How hard is it to replace these two sensors? is it DIYable? Is there a camshaft sensor on the passenger side bank? az735i, you wouldn't happen to have the instructions to get at these sensors would you?

THANK YOU az735i for the diagrams and everyone else for the tips/ideas/input. At least I have a better feeling about whats going on now even if I end up towing it in :(

Oh I forgot to answer the other questions. I did one plug at a time so there is no issue with mix ups. The coil pack can't be plugged in wrong. It only plugs in one way with a snap to confirm its in all the way. I didn't tug/snag any wires. I generally am pretty careful when working on electrical wires etc. The only hick up was the spark which probably threw me off.

I have removal and installation instructions for the driver side cam sensor. Removal is not hard, but it will take some time. I would also check the wiring like Blake mentioned above.