Multiple Misfire - P0301, P0303, P0304

rudecuban · November 13, 2012

I have a 2000 Es300 that started missing and the check engine light started flashing. I drove it over to Auto Zone and they found multiple misfires for the #1,3,and 4 cylinders. I have changed a few coil packs over the years and thought this was the problem again, but find it hard to believe all 3 went bad at once. the car has 188,000 miles on it and i have changed the plugs within the last 30,000 miles. When i got back home i popped the hood to have a look for a vacuum leak and happened to notice the exhaust manifold was bright red : ( i assume this was caused from the misfiring issue. Wondering if anyone has some direction for me to start before i take it into the shop. I would rather try to fix this issue myself before i take it in. Any help would be greatly appreciated and many thanks in advance.

lenore · November 13, 2012

When you changed plugs did you use OEM or Bosch..? Bosch are bad...Otherwise start the process of moving coil packs and see where the code changes.

rudecuban · November 14, 2012

I replaced the plugs,old ones were denso, I replaced with ngk iridum, I also ohmed out the coils that were getting the error codes and compared them to the ones that were not throwing the code and they all had the same ohm readings I switched the coil paks around and will have to see what error codes come up next..so far I have the same issue, I will keep on posting of what I find. I have searched many forums and found this problem hard to diagnose and nobody seems to give a solution. Also cleaned the MAF sensor

lenore · November 14, 2012

One other thing, did you look with a flashlight into the connector (spark plug) end to see if you had any corrosion? That could cause missfires also.

92ES300RFD · November 15, 2012

I have a 2000 Es300 that started missing and the check engine light started flashing. I drove it over to Auto Zone and they found multiple misfires for the #1,3,and 4 cylinders. I have changed a few coil packs over the years and thought this was the problem again, but find it hard to believe all 3 went bad at once. the car has 188,000 miles on it and i have changed the plugs within the last 30,000 miles. When i got back home i popped the hood to have a look for a vacuum leak and happened to notice the exhaust manifold was bright red : ( i assume this was caused from the misfiring issue. Wondering if anyone has some direction for me to start before i take it into the shop. I would rather try to fix this issue myself before i take it in. Any help would be greatly appreciated and many thanks in advance.

I had the same issue and it was one of the 3 O2 sensors and now the car runs fine once again.

rudecuban · November 17, 2012

I will post what the shop finds out. I checked the ohms of the o2 sensors, along with the heater relay for the o2 sensors,also checked ohm readings at the injectors,cleaned throttle body. Still runs rough and misses. I also looked over the vacuum lines.

MCoop · December 5, 2012

Do a search on Oil Control Valve.

kakarot · January 1, 2013

I have a 2000 Es300 that started missing and the check engine light started flashing. I drove it over to Auto Zone and they found multiple misfires for the #1,3,and 4 cylinders. I have changed a few coil packs over the years and thought this was the problem again, but find it hard to believe all 3 went bad at once. the car has 188,000 miles on it and i have changed the plugs within the last 30,000 miles. When i got back home i popped the hood to have a look for a vacuum leak and happened to notice the exhaust manifold was bright red : ( i assume this was caused from the misfiring issue. Wondering if anyone has some direction for me to start before i take it into the shop. I would rather try to fix this issue myself before i take it in. Any help would be greatly appreciated and many thanks in advance.

Here are the cause of miss-fire start off with the simple and easy fix first.

It could be any of these symptom: fuel injector, vacuum leak, weak gas pump and spark plug wire/spark plug, ignition coils, EGR, MAF ect..

Using the multi meter to check resistance is fine but it does not tell you if you have enough spark. Use a spark tester to test if you are getting the correct spark. When I did my spark test my cylinder 1 failed right away not enough spark and it was weak once I start to crank the engine.

I have the same error code and it turn out to be a bad spark plug that has corrosion on please removed spark plug 1,3,4 and inspect for damage and corrosion.

I aslo replace the ignition spark plug boot sometime those are worn, crack or the spring inside the boot is not good anymore that you can't tell.

Use die-electric grease to help the rubber end to make good contact when installing spark plug wire/spark plug.

After all that is done and you still experience the same issue move to the next symtom alway do the easiest first.

I hope this will help you out let me know if you have others questions.

Make sure you use OEM when replacing stuff.

MrScott · January 30, 2013

I have a 2000 ES with 190k miles and I just went thru something very similar. I noticed that once I was in the car, it would not start acting up until I had come to an idle (after 30 mile freeway drive) or if the engine had warmed up. I was getting various bank 1 misfires when I had the codes read. Troubleshooting, I moved around the coil packs to see if I could narrow it down to the bad one (brother is Mr. Badwrench) and ended up changing what I thought was the bad one. Of course engine cool, and part changed, it started fine. Wasn't the fix. After highway traffic and stopping back in city traffic it would idle like a dump truck again. So my next venture was to change the Oil Control Valves and filters (originally did 1, but decided to rule that out so replaced both). I double checked the wiring harness and all the connections. The P1349 error code I was getting went away, but then I was getting error codes for knock sensors, wiring, or connection. The symptoms mirrored those of the Oil Control Valves, but with both replaced, obviously not the problem. I've heard horror stories of sludge for this generation of ES300 so by process of elimination I decided to add a cleaner to the oil, remove the oil pan and change the oil. ( I attached pics just as a visual reference for you.) I have not had an issue since. I *think* that due to changing the company where I have my oil changed... the product being put in the car probably changed as well. My brother said it's is *best* to use the same type oil throughout the life/ownership of the car. And thinking back, it's not possible to get that good of a price on synthetic.

Upon pulling the oil pan, I noticed a very nice coat of varnish (which I still don't understand) and some gunk/sludge build up. Considering I've had this car since new, and knowing how hard I am on cars, I felt it was better than expected. What did surprise me, was the amount of Gasket Seal that was broken loose inside and was clogging up the intake screen. This in turn inhibited the intake of oil and resulted in reduced oil pressure for the Oil Control Valves to work as they were designed.

I also found a kick !Removed! post by GoldenStateSilverSport for IACV cleanup. I owe him many thanks. After doing this... my car is like new. I had forgotten it ran this well. I've started saving for the speeding ticket I know is on the horizon. So Kudos and a Case to him.

Last weekend, I verified - will still do 145mph. :snoooorrrtttt: the windows bow out more now than they did years ago at this speed. LOL Certainly thrilling, but nothing compared to jumping out of a perfectly operational airplane.

Hope this helps 10% of what GoldenGateSilverSport's post helped me at least.

:cheers: Please let me know if it does help.