P0300 code and a flashing check engine

hello, i have a P0300 code and a flashing check engine, i have checked plugs and coils, new fuel regulator, and clean (old) maf sensor, and check timing

the truck seems to drive fine underload but at idle it runs real bad, also all cylinders are misfiring

previously i had a code that i don't remember the numbers for but it said the truck was running lean i though id have some time to make it to the weekend but on my way home from work it started idling at stops really bad and the engine light started flashing. hope this makes sense cause i need help it's been 2 weeks already

 

Is there only a p0300 or another code too?

 

p0301 ,302,3,4,5,6,7, p0300

 

Flashing cel indicates way too much unburnt fuel and it flashes to get you to let off the throttle. When you say 'checked' various components, you mean tested to be within specs per FSM, correct? Has intake been cleaned along with MAF?

 

starts up fine but starts misfiring after a while, felt fine when i drove, it seems to be more noticeable while idling,

 

the intake has been cleaned maybe 3 months ago while i changed out the starter

 

or sorry the throttle body was cleaned and the air filter had been changed

 

and yes iv checked the spark gap and ignition coils all light the tester, after timming pressure gage was at 210 and fuel pressure was at 45

 

How many miles on the truck? Might be time for new injectors

 

Poor idle is often vacuum lines. Check them all and ensure they all got hooked up after your starter replacement. Also check for cracked lines that would leak.

 

269k. i think my next step would be cleaning the injectors but all injectors have a reading that was all relative to each other i dont remember what the number was, also they all sounded pretty consistent, i have not tried pulling the fuel rail out and checking the spray im not entirely sure how too do that on a v8

 

im also hoping for a vacuum leak but i have not found one yet.... tomorrow hopefully i can perform a smoke leak test.:?

 

This is not the injectors.

When was the timing belt last done? Toyota calls for 9yr/90k miles on these trucks, and belt failure at any significant RPM will brick your engine, it’s low interference. What condition is the belt in, have you taken a 10mm to loosen a timing cover and check?

Check all your vacuum hoses.

Verify all your grounds.

What is the condition of the O2 sensors and wiring? They’re critical to combustion.

 

haha shifty iv actually read all about your o2 sensors rant on one of the forums !
i just checked the timming witch did show off time and iv readjusted that is why i am here now, 02 sensors is what iv been looking into today i havnt gotten to far on checking the o2 sensors yet itll be something ill be checking on tomorrow after work along with getting my hands on a smoke leak test

 

would you happen to know how many or which grounds i should be looking for ?

 

Grounds. Not sure on the 02. I know on mine, I’ve got at least two grounds near the battery. At least one at the forward-most drivers side head up top, by the cam tower. One from the rear of the block to the firewall. There’s probably more than that.

One potential trick you can try - but don’t treat it as “definitive” - is to run a solid 8awg-12awg ground jumper from the negative side of the battery to the block, to a few different places, see if misfires go away.

but don’t treat the vacuum suggestions by @KNABORES earlier as bullshit. Vacuum routing should be on a sticker under your hood if still original, and often times the ends of hoses will crack.’ Sometimes just cutting 1/4” off the ends of the hoses and reseating may resolve issues, since they’re prone to cracking at the ends.

 

Also check intake manifold gaskets.

 

thats a great way too check ground thank youll ill keep that forever in the brain box ,iv checked the hoses as much as i can visually i dont see anything but i keep looking ill have another person look as well, im really hoping its a vacuum leak iv just redid my hole front end from the damn balljoint failure siltation at the end of last year

 

Yeah, you can only use OEM lower balljoints on these trucks. That and many other tips over here: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

Maybe do yourself a favor and put a teaspoon of dawn dish soap in a spray bottle. Fill the rest with water. Spray it around the vacuum hoses and manifold to look for anything out of the ordinary (sucking, blowing, everything most dudes love).

Lots of ways to hunt problems without spending $$. But biggest thing is to check everything is connected as expected. Check batt cables for corrosion inside the sheath ,etc.

 

found my problem, intake plenum gaskets, i guess i either messed up or it wasnt a good gasket i installed years ago when i changed the starter out..
found it doing a smoke test. so i used fuel gauge and compression gauge and smoke test ,. if any one sees this do all these test for p0300 code and all 8 misfires
thank yall for messaging and talking through things,

 

Looking at you @bmf4069, aren’t you having weird multimisfire stuff?

 

Didn't he already have some kind of intake gasket debacle in the past?

 

Yup

 

Yes sir, and I can't find my code reader anywhere. I guess it's time to buy a new one. I don't think it's my IMG; it's not backfiring into the intake lile last time. Well, I mean it could be. It is acting like a huge vacuum leak, and all my vac lines look OK.

 

@bmf4069 I can swing by and read your codes, just let me know. I'll bring the propane too, if you have a massive vacuum leak it should be an easy find.

 

I think I will take you up on that. Whatchya doing on Friday?

 

Not a damn thing, holla at me!

 

smoke test is the pretty great way too find a vacuum leak, and yes i had too remove my intake plenum to get too my starter that was years ago , iv had this truck for 10 years now its been there a lot for me and other people when they've need to use the truck ill have too post it haha

 

also note that no local auto parts will sell me just the bottom plemun gasket only all of the gaskets for the plenum ... so i have too order online and wait.....

 

This is one of those gaskets where you need to be really super careful which brand you buy. bmf above can share his pics if I didn’t already link them. I hate to tell you to splurge on OEM, if you don’t want to pay that much, order from a universally trusted name like Felpro.