LexusLoyal

I have a 2002 LS430 UL, with 135k. A few weeks ago my check engine light and VSC light came on, also the car began to idle rough, I ran the code and it was P0301, Cylinder 1 misfire. I attempted to troubleshoot the problem myself, i replace the spark plug, the coil, cleaned the MAF, added fuel injector cleaner to the gas tank on two occasions, but none of this helped, it still idles rough and check engine light is still on. Now I'm thinking it may be the fuel injector or maybe head gasket is blown, either way I think I will have to take it into the shop. Does anyone know how much it'll cost to replace a head gasket. What else can be the problem? Can I still keep on driving it?

GLIDESUL

Try the fueL injector in cylinder #1

V8_Fan

If the HG is blown, you will be losing coolant. Is the coolant in your bottle remaining at the same level? What brand/grade of gas are you using? Name brand (Chevron 91 or Shell V-Power) or no name cheap gas? Some cheap no-name stations in town here were caught selling gas with a much higher ethanol content than the 10% limit. Too much ethanol destroys the engine seals, can cause the early demise of a motor. I also would have guessed a bad coil pack. Are you sure you changed the coil for cylinder #1, or did you do #5?

PS: I presume you are using the OEM denso plug and coil?

Jabberwock

As a low cost diagnostic test, you might try swapping the movable parts - plug, coil, wires etc between the #1 and an adjacent cylinder and see if the error code moves to the adjacent cylinder that got the parts or if it stays with the #1 cylinder.

LexusLoyal

The coolant is at the same level, I use BP premium gasoline, a few months ago I did tank up with regular, but since then I must have tanked up atleast 5 times with premium BP gasoline.
I'm sure I changed the coil pack on cylinder 1, it is the first one on the right, closest to the bumper when looking at the car from the front. As for spark plug and coil they were OEM denso plug and coil. As for swaping the coils out with other cylinders, that was the first thing I did and I would still get cylinder misfire code and engine would run very rough.
Today I ran the codes again, and got more codes:
P0300 Random multiple cylinder misfire
P0301 Cylinder 1 misfire
P0302 Cylinder 2 misfire
P0171 System to lean (bank 1)

I was gonna go ahead and change the injector on cylinder 1, but now it seems that cylinder 2 is having problems, and I'm not quite sure how I should address the P0171 System to lean (bank 1) code?

This is the fourth Lexus that I have owned, and I have never had these problems before, I must say I am slowly losing my faith in Lexus.

abs

I once had an intermittent misfire on a couple of cylinders in a GM 3.8 V6 engine - after replacing ignition modules and fuel injectors I discovered that the upper intake manifold was leaking and allowing a small amount of coolant into the cylinders near the throttle body. The leak was slow so no noticeable coolant consumption was occurring. Also, at high RPMs the I would not get any error codes on my OBD-II scanner. At lower RPMs, I would get the misfire codes consistently. The best way to tell if this is the problem is to pull out the spark plugs and see if they are fouled with a brownish crust on them (residue from the coolant). If they appear clean, this is probably not the issue. If it was bad gas, you would see the problem on multiple banks/cylinders, not just Bank 1. If it was a bad fuel pump or fuel pressure regulator, I'm thinking that more cylinders would be involved . . . Lastly, it is unlikely that multiple coil packs would go bad all at once, although not impossible. A bad tank of gas should impact multiple cylinders in both banks as well.

How many miles on this vehicle? Did you recently have any work done on the car?


Always try simple things first:

1. try a high quality fuel injector cleaner (Chevron w/ Techron is tops)
2. try adding isopropyl alcohol to absorb and burn off any water in the fuel (just in case)
3. check plugs for fouling
4. verify fuel pressure in the fuel rail at varying RPMs are in spec
5. swap coil packs to ensure they are not the culprit
6. last option check for small coolant leaks into the cylinder (due to a failing gasket) by disassembling upper engine

Good luck,

Andrew

LexusLoyal

Car has 137k on it, I had water pump replaced, timing belt, and head gaskets less than 1 yr ago. I already used high quality fuel injector cleaner, Techron, replaced spark plugs, and coil. I think the next step will be to check for coolant leaks and verify fuel pressure in the fuel rail. Can a coolant leak be responsible for misfire in cylinder 1 and 2 and Bank 1 being too lean? I guess what I'm asking is, would Bank1 being lean be responsible for misfire in both cylinders from a coolant leak?
Thanks for the advice guys, I'll keep you posted.

abs

If there is an internal coolant leak and it's getting burned up in some of the cylinders, it can eventually cause error codes to be set on the O2 sensor. Apparently some of the chemicals in the coolant can foul the O2 sensor and cause lean readings. As I think about this, I also had a head gasket go on a 1999 Northstar engine (Cadillac Deville) and one of the symptoms was an error code for the O2 sensor on that bank.

If you still have your old spark plugs, I'd take a close look at them for the brown crust I've mentioned. This is one way to test the cooling system. Your other option will be to do a pressure leak down test.

Keep us posted.

Andrew

nc356

iTrader: (1)

I had exact same codes, on same cylinders! 2004 LS430, 115,000 miles. Always Shell or BP or Texaco.
Dealer first swapped all the parts around; codes stayed same. They ran FI purge 3 times; the dead miss got better, but only a little. So: pulled the fuel rail and replaced # 1 injector. problem gone. mileage up about 1 mpg.

Playdrv4me

Ahh the infamous Northstar headbolt failure. I had hoped that I would NEVER have to see ANYTHING coolant related on a Lexus product, so I certainly hope that LexusLoyal's problems does NOT end up being a headgasket.

I have to admit though, everything being reported here is par for the course with early H/G failures on the Northstars (although on the Northstar it isn't actually the headGASKET per se that fails, but rather the bolts pulling out of the block over time to the point that so much coolant is flowing into the cylinders the car overheats almost instantly), ESPECIALLY the PO3xx series codes, and the lean code.

LexusLoyal

So here's the update on my misfire issue. I went ahead to replace the fuel injector in cylinder 1, cleared the codes, but they came back, so I finally took the car to the shop since I was running out of option, already replaced fuel injector, spark plug, coil, and cleaned MAF, so I was running out of option and thinking it may be the head gasket. The shop replaced the fuel injector connector for cylinder 1 and all the codes cleared, no more check engine light. Only light I have on now is VSC and i think that's due to my worn out gas tank cap that I will have to replace, hopefully this weekend.
I'd like to thank everyone for their input.

Playdrv4me

Wow! Glad to hear it was a simple, if somewhat hard to track down fix!

abs

Wow! I've never heard of that happening before. Glad to know the issue is fixed. Thanks for sharing.

Andrew

Jabberwock

Glad it was something relatively minor in the end.

abs

You're right about the bolts pulling out although in my experience and that of most others who have had the headgasket leak on the Northstars, the failure mode includes exhaust gases from the combustion chamber leaking out into the coolant system under pressure and in turn causing the cooling system to overpressurize. In turn, the safety release on the overflow cap allows coolant to escape at a fast rate which results in the car overheating (no coolant left). It is very unusual for these engines to hydrolock due to a failed head gasket seal. Also, nobody really knows which fails first, the gasket (due to oxidation/rusting) or the bolt threads. Regardless, the head bolt threads are almost always damaged (and if not before the bolts are removed certainly they are afterwords) and the head gasket is almost always in poor condition and oxidized heavily. As you can tell I researched this issue extensively and lived through 1 failed Northstar with the headgasket problem. What a catastrophic engineering failure for an otherwise excellent engine.

Andrew