Wednesday, March 21, 2018

Tutorial on Spark Plugs plus LS400 Update

This is a simple procedure but I figured I would post a write-up for anyone that may not know how to do this or be doing it wrong.

I also wanted to update my readers on my car, The Chariot. Recently I ran into some trouble but, again, was able to sort it out quickly. I was driving along just fine when all of a sudden, the car lost what seemed like 85% of its power (causing me to have to limp it home) and also didn't really want to respond to the gas pedal if I went past about half. It would respond but it would take a second for it to actually start accelerating faster so that was weird. See if you can guess what it was.

Everything here applies to all cars that have spark plugs. You need to buy a spark plug tool which is a hollow socket with a magnet inside of it to pull the spark plug out. I had lost the one I bought so I used one without a magnet and came up with a very simple way to fish the old spark plugs out, which can be a pain if they're deep like on this LS400. The trick is simple. I simply grabbed a vacuum hose that I had lying around and tested to see if it would slide onto an old spark plug. In fact, the hole was perfect - big enough but small enough to where the hose is able to hold the spark plug in once you slip the hose on the tip. It's time consuming but just go slow and have patience. Look down into the engine to see where the plug is sitting and do your best to aim the hose hole onto the plug. Press down whenever you feel like you're close. You will probably miss a bunch of times but you should feel your hose slip onto the plug when you get the angle right. Then you can just pull it out.



The first thing you have to do is remove the covers to get access to the spark plug wires. When you disconnect the spark plug wires from each spark plug, you will have access to the spark plug itself.

It is important how hard you tighten the spark plugs when you put them back in. More on that later.




These are the covers on the LS400. It's time consuming if it's your first time but it's not hard. You have to take the air intake and ducting off to get access to the spark plug covers. You also have to take the distributor covers off as well which are the triangular covers. Everything is held on by 10mm bolts and comes out in order from the ram air intake, then the round air intake itself, followed by the MAF sensor and elbow, and then the large ducting which goes to the throttle as well as to some other hoses. How many depends on if you deleted your ACV yet or not (there is a tutorial on this site).

Take your time with the ducting.


Be careful and go slowly when you take the main piece off. You should have the clips for the big connecting hose off. You have to take your time wiggling this large plastic piece off of the throttle and also the big hose. Take your time! Move it side to side and pull. Eventually you can pull upward to take it off the throttle opening. As for the big hose, turn it back and forth as you pull the two pieces apart. Carefully. You should have already disconnected any other hoses there.

Once you get the covers off, you're ready to change the spark plugs one by one. This way you won't get the wires mixed up which is important for the timing on the engine.

Start from the left and go right on the passenger side and right to left on the driver's side. Take the spark plug wires off one at a time. They're held in by little clips so take the wire you're working on out of the plastic clip(s). They just hold the wires in place. When you take the boot off, go slowly because you don't want to damage it if it's dry rotted at all. Depending on how long it's been, its pretty easy to take out each boot or plug of each wire.

Use your hands and not pliers or something. Hold on to the rubber boot at the base, start applying even pressure by starting to pull on it (don't just rip it out - apply strong but not too strong, even force) and attempt to start moving it side to side a little bit. My spark plugs hadn't been touched in 220,000 miles (incredible) and they were pretty easy to take off. They're somewhat stuck so you will feel it when they're free and they should pop out with a little extra pull.

You now have access to the spark plug. Go ahead and take it out. Remember, you're doing one at a time and you should line them up as you do so. The reason is so that if you find one with a serious problem, you know which cylinder it came from. One of the spark plugs I took out had fresh oil on it and even though a little is normal if they haven't been changed in a long time, it was good to know which cylinder it was in.

The type of socket I used to loosen and tighten my spark plugs. This one isn't magnetic.

Putting the new spark plug in is simple but like I mentioned above, there is a proper way to do it so please do it like this.

Go ahead and start tightening it knowing there's a certain point that you have to stop at that you will be able to feel so pay close attention. After you do a few, you will know the exact feeling. They tell you to "hand-tighten" it before you turn the socket a half-turn or 180 degrees. I don't like that term because it implies that once you can't turn it with your hand is when you do it but that's wrong. When the spark plug hits the bottom as you are tightening it, you will feel it. The force needed to turn the socket anymore will increase two or three times. It is at this point that you turn your socket 180 degrees or a half turn. At this point, it should be in good. But you have to stop because over tightening spark plugs can range from being kinda bad to really bad.

Onto the update with my car. Initially I thought that the catalytic converter was clogged simply because of how much power and response the car lost. After a back pressure test and some diagnostics, I was told that my car still has the original timing belt and water pump.

That wasn't the only original parts I found in there. This 220,000 mile supercar was still running on carbon-deposit-and-oil caked original Denso spark plugs.

At that point, neither I nor the mechanic knew what exactly the problem was but eventually a check engine light came on. That's what was messing with me initially - there wasn't even a code!

What happened was that the car regained enough power from the spark plug change to be drivable and the code for a bad oxygen sensor in bank 1 (sensor 1) only comes up if the car senses a bad O2 sensor for a certain continuos amount of time, which is what happened.

Today I got the sensor changed out at Muffler Man, a shop I have come to love. The people are honest and one of the main guys that run it was nice enough to show me their project car and talk to me about cool s*** for a while. Here's a sneak peak. You can expect a small article on this 600 horsepower 1988 Camaro and the shop. They put a lot of work into it and it shows.


Amongst all of this, something happened that I have never experienced, heard of, or even thought was possible. When I changed the old spark plugs out for Denso Iridium ones, the engine sound changed.

It makes sense now that the O2 sensor has been changed out, the ECU is able to set the proper fuel ratios and all of that good stuff, and the engine sounds smooth. However when I first changed the spark plugs and the engine was running weird, I literally thought I had a different problem because the engine note changed from a smooth V8 to a mean V8.

It's such a huge difference that I couldn't believe it wasn't being caused by some issue. The noise, that is. The car sounded like a truck before I fixed the O2 sensor. It just turns out the LS400 sounds mean as hell stock if it's well maintained.

I believe my O2 sensor got clogged by carbon deposits from Seafoaming the car. I'm not saying anything bad about the product because it works well on the right engine but even though it was probably because it wasn't able to burn up fully due to the old spark plugs, the fact is I believe carbon deposits got sent downstream and killed it. That's not to say it wasn't on its way out anyway.

I am saving money to change the timing belt and waterpump as soon as possible. Unfortunately I have to drive it because there isn't even busses where I moved and the wife and I need to work. I believe the timing belt will hold up for another few weeks if its done 200k+ already.

I know some people would say I'm stupid but when I get that done, I think I will have put three grand into this car when a running one costs a thousand.

But here's the thing. Most of the mechanic work I did myself so this vehicle will be completely up to date on anything that would need to be changed. From the top of my head, I already did...

I fixed a few leaks but you can probably see the residue I need to clean.

The power steering pump, ACV delete, radiator, alternator, vacuum hoses, coolant temp sensor, engine temp sender, spark plugs, complete fluid change using Mobil 1 synthetic, front brake pads, rear brake pads and rotors, and upholstery work on the inside. I've been dealing with mechanical things but I do have the hood hinge I need to fix the way my hood sits. I also have the radiator support which is the last casualty, if you will, of the minor accident the car was originally in.

So I've paid three grand and I would pay that much more. Of course, I would be mad as hell if it was right after this. But the car is very special to me. I bought it so I would get better working on cars and I did. At the same time, I always liked LS400s but after driving this car, I knew I was going to keep it. Initially I planned on getting it running and flipping it but it turned out to be the best car I've ever had.


In a way, I'm glad I was able to fix all of this stuff right away. But I have to tell you - it was pretty bad breaking down every couple of months! Luckily me and my wife are getting through it and the Chariot is surviving and getting stronger. Thanks for reading, everybody.

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