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1996 Lexus Es300 1Mz-Fe Loud

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check engine light is on, but no codes that relate to anything exhaust, but car is really loud!

I have codes P0300 P0301 P0303 P0305 P0115 P0135

(indicating misfires in cylinders #1 #3 #5 the back row)

I just got new spark plugs put in but it is still loud!

Why aren't any exhaust codes showing up on CEL? There's obviously a hole in it from the sound!

I have the CarMD tool (cannot turn off CEL though), which comes with this online support thing, and it suggested either spark plugs or fuel injectors (I'm also running a quart of Lucas fuel injector cleaner in the gas tank)

Noise sounds more from the front of the car, by the firewall

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Loud exhaust noise at the firewall suggests that the exhaust manifold gasket has gone bad, or the exhaust manifold is cracked. Misfires can be caused by man things, bad coil pack, bad ignition wires, etc. You need to have a good service technician check things out. Good Luck.

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I got the plugs replaced and reset the check engine light. The misfires are gone, however now that catalyst and evaporative monitors will not be ready. What can I do? I drove it for 5 days already, and today I drove 100 miles (50 miles each way). On the way there, I made no stops, just drove 50 miles straight. On the way back, I made one stop almost exactly in the middle. But the catalyst and evap monitors will never be ready!

The evap monitor was ready before I got the new plugs, but the catalyst was never ever ready.

All the other monitors are ready (Misfire, fuel, comprehensive, oxygen sensor, oxygen heater, EGR) and the misfire codes did not come back. However, I still have code P0135 for the O2 heater and the car is still loud. The only code I have now is P0135, but the catalyst and evap monitors are not done yet (I had no evap codes before the reset, so I'm not really worried there)

Also, at 65 mph and above, the car shakes bad (it also shakes not-as-bad below 25 mph). But between 30-60 mph the car is fine. Even over bumps and potholes. At high speeds, the passenger seat shakes noticeably (with nobody sitting in it--I never took it on the highway at that speed with a passenger). I know I need tires and CV joints (due to the telltale clicking sound they make when turned all the way), would either of those clear it up?

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OK, I figured out why my car is so loud (see photos), discovered when trying to change my oil (drain plug overtightened)

Exhaust is broken at the part right in between the oil and transmission pans, the pipe coming from the rear exhaust manifold (for the back row of odd cylinders 1, 3, and 5) is broken and/or rusted off the other thing in between the engine and transmission oil pans. The manifold itself seems OK though.

I don't think the cat is busted because I hit it with a wrench and it did not rattle like marbles.

What is this part called?




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Pix are a bit difficult to see, but having just spent a few weeks wrestling w/ my rear (bank 1) manifold on my 1mzfe, I may be able to venture a guess.

What is broken appears to be the Y shaped exhaust pipe connecting the front and rear manifolds to the downstream pipe that runs into the cat about 2 feet further distal. You'll need to replace this, by unbolting it from both manifolds (12 mm lock nuts that are a bear to get off, use a lot of penetrant and a air impact wrench, or a 1/2 inch socket w/ much leverage) and removing the clamp just below the pipe/manifold connection on the front. Not sure how it's connected to the down pipe, but may be a big ring clamp, if not welded. I bet this piece is quite expensive new, but a trip to the junk yard might give you a good practice lesson and/or prolly wouldn't cost that much to have them take it off. OTOH, midas could do it too for enough money w/ out paying lexus or toyota outrageous labor fees, particularly if you don't want to get dirty on your back.


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Thank you guys so far!

Now I have another question: It appears the 1994 1MZ has a separate front-pipe (ie, you don't have to buy the whole cat), whereas on my 96 I don't see this coming up as available and you have to buy the whole cat

Here is a picture of the supposedly 94-only front-pipe (before the cat):

Another question I have is which brand is better, Eastern or Walker?

(Each cat is about the same price, around $220)

I found the Eastern on RockAuto, and the Walker on Amazon, if that matters

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