Flashing CEL with P0300 and P0303

Rock_Rat

Senior Member
Well, it looks like it's my turn for the #3 misfire. I'll let everyone know what I find out tomorrow. The timing isn't the best with winter on the way but I made it through the summer.

Hoping it's a vacuum line, plug, injector or something simple but I'm prepared for the worst on a supercharged motor with 372,620 miles on it.

Good excuse to install my 315 injectors EVO pump and 2.2 pulley.

Lucky me.
 
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With that many miles do a compression test while the plugs are out. Hopefully it's something simple.


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I am hoping your Huskies manage to beat that damn dancing tree in Palo Alto tomorrow night. It should make for a good game. The Huskies just don't seem to be the offensive juggernaut there were last year, though as CP quipped, nobody sees y'all play on the East Coast.

If you don't have one, get a leak down tester as well. Very handy. Should fit well with all those Klein tools on the bench. Good luck....
 
Labor of love. Good luck with the fix, hope it's quick and painless. Will be checking in.

Hey thanks! I have no problem putting time into this rig.

I am hoping your Huskies manage to beat that damn dancing tree in Palo Alto tomorrow night. It should make for a good game. The Huskies just don't seem to be the offensive juggernaut there were last year, though as CP quipped, nobody sees y'all play on the East Coast.

If you don't have one, get a leak down tester as well. Very handy. Should fit well with all those Klein tools on the bench. Good luck....

Well, kick off is in just a few hours! We'll see how they do. Wife and I might make a trip to Santa Clara this year if they take care of business. Didn't have time to make it up north for a game this year with so much going on in our lives.

So I picked up a leak down tester from Harbor Freight - cheap in many ways! I'm going to try and exchange it on Monday. I could never get the indicator to go to "0" on the yellow band. I'm pretty sure I still got a good reading.

With that many miles do a compression test while the plugs are out. Hopefully it's something simple.
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Oh yea. I'm pretty methodical with my troubleshooting! Numbers looked good for this engine.
 
Swap coils and see if the code follows the coil

Check spark plugs in coded cylinders too while you at it - loose plug, cracked porcelain, etc can all cause this.

:behindsofa:
 
Flashing CEL with P0300 and P0303 - Update

I obviously did all the preliminary things that goes with cylinder misfire codes;

Preliminaries
  • Did a visual/hands-on inspection of all vacuum hoses including fuel pressure regulator.
  • Visual/smell of the oil on the dipstick.
  • Visual for color and possible depletion of the coolant in the radiator and the overflow.
  • Ran it in the morning while cold to check the exhaust. No sweet smell. Had the standard cold engine exhaust "smoke"

Plugs and Wires
  • Next I removed the plugs and did a little more research on the IK22's that those of use with Superchargers
    It's not uncommon for those plugs to fail prematurely due to the wasted spark system. Most fail around 30,000 miles. I only have 15,000miles.
    Read up on the preferred gap for that plug and ran across "many" variations. I gapped to .044 I believe. After reading I think it's best to leave them the way they come out of the box which is .032.
  • Cylinders appear to burning clean.

Testing
  • Time to check resistance on the injectors - all around 14 ohms
  • Coils looked good. A little corrosion on the wire end.
  • Compression check (1,3,5 around 175-180 while 2,4,6 were 185 and better.
  • Next was the leak-down check - no problem, less than a few percent if any.


So that's where I'm at on Friday evening before the Huskies kick off and cut down some trees! I'm pleased with my compression numbers and the leak-down. I do find it odd that on these engines in particular, it always seems to be the passenger side with low compression numbers. I just picked up new Denso IK22 plugs and plan on installing them straight out of the box. (And yes, I know how to gap iridium plugs). I also picked up three Denso coils just in case. I don't think they are bad, but it's always nice to have one on the shelf. Wires should be fine, NGK blue.

So tonight I'll just pull the negative terminal off, watch the Huskies and put it all back together tomorrow and see what happens.

If any of you P0300 P0303 experienced peeps have any more insight, post up!

No O2 sensor problems or MAF problems. Codes weren't there plus I'm running a true wideband gauge (which by the way is spot on with our OBII guages) and numbers are always around 1453.

Sorry for the huge pics. I'll resize them later on.


IK22 Plugs after 15,000 miles. I believe I gapped them to Toyota spec but I believe I should have left them at .032 right out of the box.
P0300 P0303 _ 1.jpg

The drivers side numbers were pretty high at around 190 after eight cranks.
P0300 P0303 _ 2.jpg


The passenger side, however were a little lower at around 175-185 after eight cranks.
P0300 P0303 _ 3.jpg

These injectors are from LCE and are flow tested equalized and only a few years old. The resistance was right where I expected.
P0300 P0303 _ 4.jpg


The final test I did was the leak-down test. I'm using a Harbor Freight gauge and the I couldn't get the indicator to go to "0" on the yellow band. Nonetheless, It never did leak or if it did it was an extremely small percentage. I was at TDC.
P0300 P0303 _ 5.jpg
 

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That is one healthy engine for that many miles. All engines leak a little, never seen one read 0%, but if your compression numbers are that healthy, I wouldn't worry too much about the internals.

How closely did you inspect the plug wires?

I have seen injectors ohm out fine yet be bad.

Losing any coolant? Maybe a coolant pressure test is in order then....
 
That is one healthy engine for that many miles. All engines leak a little, never seen one read 0%, but if your compression numbers are that healthy, I wouldn't worry too much about the internals.

How closely did you inspect the plug wires?

I have seen injectors ohm out fine yet be bad.

Losing any coolant? Maybe a coolant pressure test is in order then....

I guess it's one of the benefits of being an original owner. Needless to say , I've had plenty of years maintaining it!

I didn't look too closely at the wires yet. I think I'll just pick up another set of wires tomorrow. They're not too expensive.

Yes you're correct, I haven't ruled out an injector yet, even though it ohm'ed out OK. Pulling the fuel rail is not on my "Oh boy, let's pull the fuel rail!!!" list. haha. The next time I "planned" to pull the rail was with the fuel tank empty and ready to jump up to the 2.2. Fingers crossed... Keep the thoughts coming...

For now - Huskies need to take care of business tonight. You guys are back in it which is good to see. Bama however, I think is staying where they are.
 
Your Huskies are looking good tonight, in football at least. Belmont is giving them fits on the hardwood. My GF doesn't understand the importance of this football game and is passed out with the dogs (spaniels, not Huskies). Her Florida Gators are just a mess this year.

You may need to find a reader with live data capabilities that can show injector pulse and flow rate.

The one misfire I have had on the 4runner a hole was burned into the bottom of the boot on cyl #4. Honestly, having had both Denso and NGK replacement wires, save a little more $$$ and buy the Sumitomos off Amazon.
 
Flashing CEL with P0300 and P0303 - Resolved and Closed

Ok so the Huskies couldn't fix their problems last night against Stanford but I believe I have fixed mine.

  • Compression checked good and so did the leak-down check.
  • Fuel Injectors all checked good with a meter and they worked while turning the engine over. Visual and resistance check - OK.
  • MAF was recently changed, so I didn't bother to check it. Least likely to immediately give me a flashing CEL and mis-fire codes.
  • Plug wires checked good, no cracks or holes in the boots etc.
  • Vacuum lines all connected.
  • PCV was fine.
  • Coil packs looked fine, but decided to replace them.
  • Visuals for fluids and smoke when starting checked fine.

Plugs looked clean, but much wider than the .043 recommended gap so picked up new plugs.

I decided to install new coils but I don't think that was the problem. I'll just leave the "old" ones as spares.


This morning I replaced all of the plugs and took it for a drive to run the temp up and put a load on it at various RPM's and no CEL or codes.

I shut it down and started it again and took it for another drive. No CEL light or codes.

Engine temp was around 186. Ran RPM's up past 4000 with boost.

I decided to check the gap in the old plugs after 15,000 miles and much to my surprise, they were larger than .043 by a lot! My guess is they were close to .050. If I had any spark at all, it was insignificant. I decided to install the IK22's straight from the box at .032. I hope to get a nice clean combustion and little more life out of these plugs.

If the CEL and codes return, or I begin to hear any pinging or other related issues, I'll open this thread back up, but for now, I believe it's closed.

  • Solution - New plugs at a smaller gap
  • Possible second solution but unlikely - Three new coils

Thanks to [MENTION=99144]19963.4lsr5[/MENTION] [MENTION=69868]LittleCaesar[/MENTION] [MENTION=95183]octanejunkie[/MENTION] for your help. Now you guys need to go fix up my "one season wonders" called the Huskies. Damn they look awful.

Look at the size of that gap after 15,000 miles. That's a .045 gauge in there with plenty of room leftover.
P0300 P0303 _ 6.jpg

Nice to see, but it was only after 10 miles...
P0300 P0303 _ 7.jpg

Even better after 30 miles
P0300 P0303 _ 8.jpg
 

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Glad that cleared up easily! You did a fair amount of diligence for the easiest fix, but better that than a bigger issue. Fresh plugs always make for a spritely update, and new coils can't hurt - tell me you went denso

I know you have an SC but any reason you're not running dual electrode plugs?

Can't help your huskies, bama got my attention this year, they're on fire.

Sent from my Nexus 5X using Tapatalk
 
Good to hear. Does the SC cause the 5vz to eat plugs? I just replaced mine last month (they had been in there for nine years but only 38,000 miles) and for the driver's side the electrode was worn much quicker than the passenger but the gap was almost spot on. Quicker pickup.

I just helped a friend's kid with spark plug removal on his Dodge truck the other day, a 318 with 187,000 miles on the original plugs. We had to use an impact on two of them for removal. No misfires, they were all worn evenly.

The Huskies, I guess, will hope for a bowl game on New Year's Day.
 
I wonder if converting the 3.4 to coil on plug would help the spark plug issue. I thought about replacing my wasted spark with coil on plug on my Saturn to see how it goes.


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Good to hear. Does the SC cause the 5vz to eat plugs? I just replaced mine last month (they had been in there for nine years but only 38,000 miles) and for the driver's side the electrode was worn much quicker than the passenger but the gap was almost spot on. Quicker pickup.

I just helped a friend's kid with spark plug removal on his Dodge truck the other day, a 318 with 187,000 miles on the original plugs. We had to use an impact on two of them for removal. No misfires, they were all worn evenly.

The Huskies, I guess, will hope for a bowl game on New Year's Day.

Apparently so when it comes to an SC. With all of the research I've done on these plugs, they seem to be the plug of choice despite the different plugs that folks have experimented with. You probably already know a lot of this anyway but, here's a few quotes from the NGK website:

"When the center electrode reaches 950°C or higher, pre-ignition (early ignition) occurs, meaning that the electrode serves as a heat source and ignition occurs without a spark. Therefore, output falls and this can reach the level of electrode wear and insulator damage."

"Low heat range spark plugs have center electrode temperatures that rise easily and even at low-speed, they easily reach the self-cleaning temperature, so carbon is not deposited easily on the insulator section.
On the other hand, high heat range spark plugs have center electrode temperatures that do not rise easily, so they are unlikely to reach the pre-ignition temperature even at high speed.
Therefore, this type of spark plug is generally used for high speed, high output engines.
That is why it is necessary to select spark plugs with the appropriate heat range for the engine characteristics, running conditions, etc."

"The discharge voltage rises in proportion to the spark plug gap.
The spark plug gap widens bit by bit as the electrode wears, so high discharge voltage becomes necessary and misfire occurs more easily."

Anyway - An Awesome site with a wealth of information. Good refresher. DENSO SPARK PLUGS

I haven't read of anyone using an alternate 2 step colder plug successfully, or they just never followed up on their post. So until I hear differently, I'll continue to use the IK22. As for the gap, I've seen where Gadget says .043, others say .032, etc. Again, no follow up.

I wonder if converting the 3.4 to coil on plug would help the spark plug issue. I thought about replacing my wasted spark with coil on plug on my Saturn to see how it goes.


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This would be nice. In the meantime, we need a double grounded 2 step colder Iridium plug so it can withstand the heat.

Glad that cleared up easily! You did a fair amount of diligence for the easiest fix, but better that than a bigger issue. Fresh plugs always make for a spritely update, and new coils can't hurt - tell me you went denso

I know you have an SC but any reason you're not running dual electrode plugs?

Can't help your huskies, bama got my attention this year, they're on fire.

Sent from my Nexus 5X using Tapatalk

If you've read any of my "build" you'll see that I'm fairly thorough. The one common thing about the mis-fire code on Cylinder 3 is the need to change an HG. My thought process was: First and foremost, due your research and completely understand all three indications. Then begin to eliminate: Compression, Ignition, Fuel. Eliminated Compression (whew) and began with the next steps.

As for the plugs, the IK22's are proven performers on an SC 5vz. They're designed to prevent pre-ignition due to the increase in heat. I would rather change them out more frequently than risk pre-ignition.
DENSO - I learned this lesson the hard way about using aftermarket on sensors etc. So yes DENSO ONLY! My time and money was still way less than a monthly car payment!
 
Sorry to hijack this thread but apparently I’m too new to create my own. Thanks I’m primarily into Building Cruisers but being a Toyota family I have a few 3.4’s on my insurance plan and have to keep them running. Hence the reason I don’t post too often on this forum :). So I’m pulling the P0303 code on a 2000 4w: 5-speed. I’ve changed the wires, plugs, checked the coils and all ohmed within spec. Took one off another good running 3.4 for good measures and no change. I’ve checked the resistance on the passenger side injectors and I have 14.5 in #1, 15.7 in #3 and 14.4 in # 5. The book calls for. Max of 14.2 at 68 degrees. It’s a bit colder but not sure how that affects the code. So is the #3 reading far enough out of spec to be the culprit? Also, if I reset the codes and the motor is cold, it runs like a top until it gets up to operating temp. Then the check engine light starts flashing and everything goes south. Lastly, I checked the compression and it’s 195-200 on all 3 passenger side cylinders. Truck has 230k on the odometer. Look forward to feedback on next possible steps. This is not an area I have expertise in so I appreciate any thoughts. Thanks. Jim.
 
Sorry to hijack this thread but apparently I’m too new to create my own. Thanks I’m primarily into Building Cruisers but being a Toyota family I have a few 3.4’s on my insurance plan and have to keep them running. Hence the reason I don’t post too often on this forum :). So I’m pulling the P0303 code on a 2000 4w: 5-speed. I’ve changed the wires, plugs, checked the coils and all ohmed within spec. Took one off another good running 3.4 for good measures and no change. I’ve checked the resistance on the passenger side injectors and I have 14.5 in #1, 15.7 in #3 and 14.4 in # 5. The book calls for. Max of 14.2 at 68 degrees. It’s a bit colder but not sure how that affects the code. So is the #3 reading far enough out of spec to be the culprit? Also, if I reset the codes and the motor is cold, it runs like a top until it gets up to operating temp. Then the check engine light starts flashing and everything goes south. Lastly, I checked the compression and it’s 195-200 on all 3 passenger side cylinders. Truck has 230k on the odometer. Look forward to feedback on next possible steps. This is not an area I have expertise in so I appreciate any thoughts. Thanks. Jim.

Disregard the above post. I pulled an injector from a spare motor. Swapped it and it’s working great so far.
 
Same thing!!

Sorry to hijack this thread but apparently I’m too new to create my own. Thanks I’m primarily into Building Cruisers but being a Toyota family I have a few 3.4’s on my insurance plan and have to keep them running. Hence the reason I don’t post too often on this forum :). So I’m pulling the P0303 code on a 2000 4w: 5-speed. I’ve changed the wires, plugs, checked the coils and all ohmed within spec. Took one off another good running 3.4 for good measures and no change. I’ve checked the resistance on the passenger side injectors and I have 14.5 in #1, 15.7 in #3 and 14.4 in # 5. The book calls for. Max of 14.2 at 68 degrees. It’s a bit colder but not sure how that affects the code. So is the #3 reading far enough out of spec to be the culprit? Also, if I reset the codes and the motor is cold, it runs like a top until it gets up to operating temp. Then the check engine light starts flashing and everything goes south. Lastly, I checked the compression and it’s 195-200 on all 3 passenger side cylinders. Truck has 230k on the odometer. Look forward to feedback on next possible steps. This is not an area I have expertise in so I appreciate any thoughts. Thanks. Jim.

Unbelievable.. same exact situation.. 98 4runnet 5z engine.. 275k .. just replaced wires,all three coils, plugs,both o2 sensors,maf,tps and 6 new fuel injectors!! We have had this truck for 20 years and would like to keep for another 20!! After replacing all of the above this weekend.. runs awesome for ten-15 minutes then the s$$t hits the fan.. flashing cel missfire cylinder 2..let it cool down and it the cycle continues.. at my wit's end.. what does the ECU do after running for 10-15 minutes?
 

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