1994 ls400

Ok, in my quest to do everything possible to reduce high NOX before the smog test coming up in April, I am considering replacing the distributor cap, rotor and ignition wires which have never been replaced. Meaning they are 21 years old. One mechanic opined that because the wires are so old they might not be delivering the optimal current (?) that keeps things fired up. So fuel might not be burning as efficiently, etc. I don't know the details of how things work on an engine, and I also know it would be great (at this late stage) to replace a lot of things on this car, but I am only interested in replacing what absolutely needs it, when it needs it, if I get something out of it (like a better chance of passing smog). The car starts/runs fine. Another mechanic told me that he did not think that that repair would help much at all with smog test results. I was quoted $500 for the job, so it's not cheap. Anyone care to weigh in on this theory? And no, this is not a job I can do myself. Not a DIYer.

 

NOX is EGR related. Cleaning that up will get it to pass. From the sounds replacing the worn ignition components is also a good choice.

 

NOx is related to high temp combustion, and like mentioned above EGR is what is suppose to take care of that.
If there was an ignition problem then the HC would be out of spec. So you will not accomplish much with caps etc for the Nox. So EGR, and of course the ecu plays a role in the control of that as well.

The quote of fuel not burning efficiently, is wrong, as its burning nicely to create the high Nox. If it wasn't burning then you would have the high HC readings. Did you get a print out of air fuel ratio?

 

No disagreements with everything above.
But FYI, you have TWO caps and TWO rotors - just don't be surprised if you see that on the bill.

 

Thanks everyone. Ok, sounds like it would be a good idea to replace these things but it won't help at all with the smog test. I plan on doing a pre-smog check to see if the new fuel dampener has helped with reducing high NOX. I have a little time to try to get this figured out. Yes, from what I have read, EGR, which I guess I will need to look at if the pre-smog comes back still showing high NOX. And no, I don't have a copy of my last smog test results (I barely passed). I will check back with more info once I get the pre-smog done.

 

Is your lower EGR pipe going to the Pass exhaust manifold leaking? Mine started leaking and caused a bad sputtering every time I was on the gas that got so bad that it triggered a CEL and I had to fix it because it was starting to affect the fuel economy of the car by about 2-3 mpg, and when these cars get 20mpg avg, that's pretty noticeable!

I had the crack welded for 20 bucks and its working great now, power seems to be increased as well.

This is a common problem on LS400s I found out soon after purchasing mine back in October 15'

A new pipe is $120 or so or you can just have it welded and it should last the life of the car. Be sure to get the gaskets for them as well, I went OE for these since they were both available at the dealer for a good price (10 bucks total for both i think)

Plug wires are $65 for Denso OEM on Rock Auto, $6.99 x 8 for NGK Iridium plugs at a local parts store, and the Caps ($12 each) and rotors ($5 each) Rock Auto aren't too expensive. So most likely $150 in parts.

I replaced my wires and caps/rotor recently after a timing belt job with some from a salvage yard LS400 that i noticed had recently done all the ignition components, I could tell since the TB/WP had a date stamp of 10/2014 on it, so i opted to get those parts for about 40 bucks from that car.

My car is pretty efficient on the highway now, averaging 27mpg on a recent trip to CA.

All these little things will affect the overall emissions the car puts out, so if you haven't done it in 21 year, then its LONG overdue. You could do it yourself, all you need is a screwdriver and 8/10mm socket wrenches (plugs wires and cap/rotors), the EGR pipe is a lot more involved and I would recommend a mechanic to do this, even though I did it myself but that ended up taking me a couple days after stripping one of the pass. side catalytic converter bolts.