1994 Ls400 Will Not Start

[BogeyJH]

I've been battling an non-starting issue with my 1994 Lexus LS 400 with no success to date. I'm at the end of my rope and considering taking it in to the dealer for service (ugh!), so I'm turning to the forum for suggestions.

The issue first presented when my wife was on an errand and called to say the car wouldn't continue to run after starting it and that the check engine light was on.

I went to rescue her and was able to get the car to start, but it would only run with higher RPMs. Even then, it wouldn't consistently run no matter what I did. I managed to get the car home, which was not far, but I must have restarted it a dozen times in less than a quarter mile to get there.

The next day, it wouldn't even restart. It would catch, indicating the coils were firing, but would die immediately.

Using the tutorial from LexLS.com, I read check engine trouble code 14, which indicates a problem with the Ignition No. 1 Signal Circuit (left/driver side). According to the service manual:

"No ignition confirmation signal 1 to ECM (Engine Control Module) for 8 - 11 consecutive Ignition 1 signals."

Possible causes I checked:

• Igniter No. 1 - verified good including power source
  
• Primary and Secondary Coil No. 1 - verified good including coil wire
  
• Crankshaft sensor - verified good
  
• Camshaft Sensor No. 1 - verified good
  
• Engine Control Module - verified good (rebuilt last year and sent back for warranty service when this problem presented to eliminate ECM as a suspect)
  

I reset the ECM (sometimes referenced as ECU) by pulling the fuse, and verified the code was cleared (check engine light flashes ~4 times per second). All that is required to trip trouble code 14 again is to turn the ignition switch to the ON position without cranking the engine.

Any suggestions are welcome.

[landar]

It would appear, from your description, that coil #1 is out. A very common issue for your year. I would try swapping the two coils and see if the code switches to 15. How did you verify that coil #1 was good?

[BogeyJH]

It would appear, from your description, that coil #1 is out. A very common issue for your year. I would try swapping the two coils and see if the code switches to 15. How did you verify that coil #1 was good?

Thank you for your input landar.

Coil was verified good using 3 tests.

1. Primary coil verification was performed by measuring the resistance between the terminals of the ignition coil connector.
   
2. Secondary coil verification was performed by measuring the resistance between terminal 1 of the ignition coil connector and the high-tension terminal.
   
3. Used an igniter bypass test detailed on YouTube -
   
   

Test 1 and 2 verified the coil independently. Test 3 verified the coil in circuit.

I'll consider swapping the coils later on when I get back to the car.

The thing that is throwing me is the fact that code 14 is tripped without turning the engine over. Just switching the ignition to ON is all that is necessary for the computer to display the trouble code.

[landar]

Despite best efforts, static tests (like DC resistance) are not always telling. If the engine runs but runs really rough, like it is only hitting on half the cylinders, then I would really suspect spark. The distributor cap, rotor, or main coil high voltage wire could also be breaking down. Any significant reduction in high voltage could cause the problem. You might see a spark with your igniter bypass test but that does not confirm proper high voltage is being delivered to each spark plug. Don't let the code coming up (without running) throw you off track. Could be that it really was never completely cleared. Verify proper spark right at the plug(s).

[BogeyJH]

landar, I really appreciate the input.

FYI, the code trips after a verified clearing of the ECM - after resetting the ECM with the E1 / TE1 jumper in place, the check engine light flashes ~4 times per second indicating that it is cleared; remove jumper and turn ignition on and get code 14.

I am desperate enough to try swapping the coils at this point even though it isn't logical to me, but I will be the first to admit that I am definitely not an experienced automotive troubleshooter.

[landar]

Bogey, I have been around a lot of years and troubleshot lots of systems and I can tell you the biggest downfall in finding the root cause is "assumption". Assume nothing, let everything be suspect. You can eliminate things one at a time but there can also be wrong assumptions made even then. As you can imagine, it is extremely difficult to troubleshoot your situation from a forum. I have not heard enough information to be able to offer much pinpoint advice other than check the spark. Rather vague but thats where I would begin. In general, I tend to try to separate the problem into two distinct areas: spark and fuel. If you were to spray some starter fluid into the intake while it was trying to run and the engine suddenly takes off, then fuel delivery is the issue. Else, it is probably spark. The last part of the equation is timing and compression but these are not as common.

So, can you describe the operation of the vehicle in more detail? You have said in your first post that you can get it to run at high RPM's. Does it run very rough(like shake, rattle and roll)? Or is it smooth once you get to higher RPM's? That kind of detail is important when troubleshooting. You might even consider taking a video of the engine attempting to run and upload it for us.

[BogeyJH]

landar,you're a heckuva guy to offer your time and expertise to this forum.

Since day 2 I can no longer get the car to start at all, so no video of it running is possible. It seems to catch when cranking (that point where you normally release the key), but will not run.

Additional info:

• When I limped it home on day 1 it ran smoothly at higher RPMs, but died suddenly and often.
  
• I'm pretty certain there isn't a fuel problem since when cranking I can smell gas (flooding due to no start). I would think that Is a safe assumption.
  

I had thoughts that maybe it jumped timing, but haven't gone there since it isn't likely.

I've also had thoughts that it may be the distributor, but swapping the coils per your suggestion would definitely precede that action since it is much simpler and might eliminate or confirm the coil as the culprit

[curiousB]

I would stick with the ignition theory for now. It is a chronic issue with these cars so is a good path to start down on.

Pick up one of these and see if you have spark on each bank:

http://www.jbtoolsales.com/lisle-20610-inline-spark-tester/

A bad coil will kill 4 cylinders and make it run rough or not at all (on a cold engine that was a little hard starting anyway).

[landar]

Actually, "not running at all" is good. It is almost always easier to resolve a problem when it is completely dead. The spark tester which curiousB shows could help with spark diagnosis. The Toyota vehicles have a rather deep well for the spark plug due to being OHC engines and I doubt you could use this tool on a particular plug. However, the good news is that your "no start" will allow you to test each coil for spark and you will not even have to remove them. Just remove enough plastic to gain access to the coils then take a spark plug wire and spare spark plug and hook the plug up to the coil output. With the spare plug grounded on the engine chassis, you should see a blue flame jump the gap when you crank the engine. An orange flame would mean "low" high voltage (it will still raise your hair but may not be enough to light the fuel mixture in a compressed cylinder). You might even plug the wire into one of the distributor ports to see if high voltage is making it through the rotor and out.

[TLCAUTOREPAIR]

I'm curious if the timing belt was replaced recently. I've seen the wire going to the crank sensor damaged by the serpentine or timing belt if it's not routed properly after a timing belt replacement. That could give you a code without cranking the engine because the ECU is looking for continuity on that circuit when the key is turned on.

[IanRShearer]

I had a similar problem, sudden cutout, rough running, almost no power. I found abraded wires rubbed by the timing belt and thought that was going to be the fix, but the problem was still there.

Turned out the left hand/ drivers side HT coil was failing, It was a little out of spec. on the resistance test, but looked fine.I didn't really think that was the problem, but changed it.

The coil lives fairly close to the exhaust, and runs in a hot environment, so tends to fail more than the other coil. I found a replacement right hand coil and changed the mounting brackets over.

My car would start, though, and run rough, so symptoms not quite the same.

[IanRShearer]

Also, this post has a diagram

http://www.clublexus.com/forums/ls400/456163-code-14-a.html

If the code 14 comes up the minute the ignition is turned on, then the IGF1 signal must be missing, thats a positive voltage from the ignition relay, through the low voltage coil on the ignition coil, and through the igniter. Should be checkable with a multimeter, and might just be a bad connector. The difficult bit is identifying the correct wire on the connectors.

I would check for 12v on both sides of the coil first, then compare voltages at the igniters, as your no2 igniter is working ok. You basically have 2 identical systems to compare, swap things with

[VBdenny]

I must be lazy but I'd take the car to the dealer and have them do the diagnostics. All comes down to time vs money and which you have more of at the time. Probably cost you 75 bucks to have them figure out the issue. I would not go to any aftermarket place as they don't know what they are doing half the time.

[BogeyJH]

I've been quite busy lately, so I haven't been back here to let you guys know the final fix for the LS400.

Back in November 2011, ASI repaired the ECM using low ESR capacitors for all the the original ammonium salt electrolytics.

When the ECM was returned for warranty service (November 2012), ASI fixed a problem they found in an area not related to the trouble code 14 (ignition circuit). After re-installing the ECM, I continued to have non-starting issues.

All troubleshooting led me right back to the ECM. The bottom line is that the ECM ignition circuit would function normally when disconnected from the load of the igniters, etc., but once it was reconnected, it could not drive the load. This condition was not detectable using the recommended diagnostics from the service manual, which test the ECM without the load of the igniter and incorrectly specified replacement of the igniter #1. Swapping the igniters proved that was an incorrect resolution. The problem was finally identified by using an oscilloscope and connecting a T-pin into the IGT1 signal at igniter #1 to identify the bad signal under load.

I returned the ECM to ASI with detailed info and they located an issue in the #1 ignition circuit, repaired it, and sent it back. They paid for shipping to and from since they had not fixed the described issue previously. I re-installed the ECM (again) and the ol' girl cranked right up.

Thanks again to you all for your valuable input, my wife is happy to have her car back up and running.