Multiple cylinder misfire P0300, 301, 304, 305, 308

My truck is running really bad. i've changed the plugs, coils and fuel filter. the check engine light is on and flashing. It started running bad all of a sudden while driving. Can anyone help with solving this problem? it was starting right up but now it's harder to start and barely stays running when started. It's a 2002 with the 4.7 engine. Please Help!!!!

 

Sorry to hear about your Cylinder Misfire codes. Bummer man. The spark is probably good considering the work you've already done, so next step is to check the air flow. I'd clean the MAF Sensor, and clean the butterfly valve. Maybe replace your air filter if it is due. Tons of video resources for DIY on YouTube for that procedure, very easy to do yourself. Last thing would be to check your fuel injectors. I've never attempted this, and would talk to a professional mechanic about it. Good luck!

 

thanks. I'll try those steps.

 

Not sure, but I’ve a hunch about ‘Clogged’ fuel injectors becoming a problem more and more on our model Tundras. I see many one time commentors come through and state their situational problem similar to yours and they go through the checklist of doing everything as you stated. They never come back and tell us what happened.

Anyways, it sucks to have to clean your injectors if that is the problem but its not hard. You can remove them yourself or let a shop do so. Either way they should be sent to a fuel injection cleaning service where the injectors are sonic cleaned in a bath, tested, then rebuilt with new screens and o-rings.

Costs about $25 an injector for the cleaning service rebuild if you DIY. Add the mechanics labor if they do the pull out and reinstall.

Edit: Maybe bad fuel pump?

 

At that price I'm wondering if your better off ordering the new and improved injectors from dirty deeds? I'd probably go that route.

 

And the added benefit of not having to wait a day with down time on the truck while your injectors are getting cleaned. Win win.

Anyone have personal experience with these 12 port injectors?

 

Hey bud,

What brand coil packs did you replace the OEM with? Did you keep the old ones around so you could swap them back in and see if that solves your issues?

On that same note, which plugs did you use?

Let us know what you learn through this.

 

Shotgunning parts at a modern vehicle to fix a misfire is very foolhardy and expensive. Sounds like you need a fuel pressure guage to confirm proper fuel pressure and a scanner so that you can watch O2 sensor readings and misfire graphics.

 

Are these the coil packs that were installed on the vehicle? I would be surprised if the DENSOs failed.

 

A few years ago, one of my OEM Denso packs went bad and was replaced by an aftermarket. This past summer, when doing my valve cover gaskets change, I noticed about 3 of the OEM’s were cracked on the side body so I decided to replace all of them as I had the money.

The pic above are the ones I ordered and is a fantastic price for Denso. The cheap China ones are a little les$ but the reviews suck (surprise!).

I am selling a few of the old ones in the ‘for sale section’ mainly as emergency replacements for buyers to keep on the truck. They still work fine and I’ll be keeping 3 just in case. They may last another 100k?

 

What component sends the initial electrical pulse/signal to the coils, could that be checked?

 

I have always had good luck with Denso products. And that is a really good price, maybe I should just go ahead and order them for my next tune up now. I was wondering what the OP had used in his rig, and if he did the tune up himself or had a shop do the work.

 

Sure thing bud. We’ll see what the OP put in.

Looking back at receipts, the shop charged me $100 for the aftermarket coil (rip off), but this was the first time my truck ever had a problem since 02’. I was able to limp back to the shop for the quickly needed repair.

Best aftermarket price I could find was around $40 made in China. Figured an extra $15 for OEM was well worth it as Denso is the best in the world.

 

1) Check fuel pressure
2) If you have a scanner check fuel trims, MAF readings and misfire counts
3) Check exhaust back pressure (restricted catalytic converter will cause misfires)
4) Has your timing belt ever been replaced? I've seen a lot of people incorrectly route the wire harness to the crank sensor. It needs to be behind the gap in A/c compressor bracket, if its in front it can eventually rub through and may not necessarily cause a crank sensor fault, I've seen this cause misfires many times.

The most common things I've seen on this engine causing misfires are: bad coils, carbon tracked spark plugs, occasionally a bad injector but if you have four misfires I would consider injectors unlikely (not impossible, though) unless you have contaminated fuel and sediments in fuel rail. I would check for rodent damaged wires also, but that usually sets a circuit fault with coils and injectors. I did have one of these engines have a burnt valve, but on multiple cylinders not likely.

Also, Denso is a good choice for replacements.

 

What is a good scanner for the diy’r to purchase for this? Something less than $200 range.

 

I would have to look into that. The cheap ones I have seen might give you freeze frame data from when the fault occurred. You may be able to read some basic data but likely not a misfire counter in that price range. The misfire counter is great because you can just swap coils and see if the misfire follows the coil. If feasible, you can even do that with an injector. A fuel pressure gauge would be needed for fuel pressure check. Back pressure gauge gets screwed into an oxygen sensor port. Or, just remove O2 sensor or disconnect exhaust and see if it runs better (yeah, it will be loud). Honestly, if a DIY'r is that determined to fix it, instead of shotgunning parts and buying cheap scanners, I would pay a reputable shop to diagnose it. Unless it gets into serious diagnosis (pinout tests, disassembly, removal type stuff), should be 100-200 to diagnose. I know that doesn't really answer your question, if I see something I will let you know. There is probably something out there, maybe even a blue tooth OBDII connector you could get for your phone. Perhaps someone else can chime in with a suggestion for a decent cheap scanner.

 

Thank you. And paying someone in this case sounds like what needs to be done. I see many people throwing money at parts only to not come to a solution. I’ll wait to see what others say per a decent scanner. Maybe the limit for me may be $500 to step up to a proper scanner.

 

Took my truck to my mechanic and he went through all of the same steps that I did and couldn't figure out the problem. He said it was the crankshaft position sensor and then changed his mind. The truck will no longer start and run. it is very hard to start and when it does start, it runs very very sluggish for about 10 seconds and shuts off. I've had the truck towed back home but I need a mechanic to take it too. any suggestions for mechanics in the Atlanta area? I'm really frustrated right now. When my mechanic checked the fuel pump, he said that he didn't hear it running and i didn't hear it running either but he didn't suggest to replace it because when he disconnected something under the hood, he saw fuel passing through. Just because fuel is passing doesn't mean that there's enough pressure to keep it running, correct? I dont know if i'll go back to him with any future issues. He went from a bad cranshaft position sensor to blown head gasket to possible fuel pump issue to injectors, etc... Just all over the place instead of saying he wasn't sure. Some one please Help me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I'm lost at this point. What should I do? Toyota dealership?

 

You are correct about the fuel. Just because there is some pressure or volume does not mean that there is enough to keep in running good. You’re just gonna have to find a better mechanic who knows how to use a fuel pressure guage properly and possible a lab scope if there is a sensor issue.

 

OK everyone. PROBLEM SOLVED!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! BAD GAS. after replacing plugs, coils, fuel filter, fuel pump the Toyota service center found the issue and is working on it now. Initially they said I might have blown my engine but this was impossible because I barely drive the truck. after testing it, it was the gas. hope this helps everyone else.

 

Glad you got it running. Bad gas made me immediately think of this clip...

https://www.youtube.com/watch?v=AynXoLjYrKc

 

HAHA! Billy's best movie in my opinion.