P0304 arghh

i have a 2000 3.4 Tacoma.Ive had an issue the last week.I start my truck after sitting for a bit(getting groceries or something),and it runs really rough.Always starts and runs great when cold.I put a new temp control sensor in this morning thinking that was the problem and nope.I then bought a new scan tool and a p0304 #4 cylinder misfire code comes up.I tried swapping plugs(yes they are the right spark plugs)and coil packs around and the problem stays on #4.I have a compression tester coming in the morning to check compression to rule that out so I’d like some input.

 

There's a bunch of ways to tell if an injector is bad, but the best way is to move it like a coil/spark plug. It's lots of work but you'll know 100% for sure its the fault.

Use Rockauto, I've used it in Calgary plenty of times.

Only replace the injector that's failing. They are common on the 3.4, I've changed a few.

I recommend 1 injector, 5 injector oring kits (you'll disturb all others) and the intake plenum gaskets.

https://www.rockauto.com/en/catalog/toyota,2000,tacoma,3.4l+v6,1364723,fuel+&+air,fuel+injector,6224 A new injector is best, don't buy a re-manufactured.

A fuel filter isn't a bad idea either.

 

Already did a fuel filter a few months ago and noticed quite an improvement.Since #4 is the problem,I don’t want to take everything apart twice if I don’t have to so I’d rather buy an injector and replace it rather than swapping them around..At least I think that’s the best way.I have no problem spending money on one injector.

 

in addition to the above... look at the Y shaped vacuum hose at the back of the block and check those little bastard coolant hoses that go to the IAC valve while they are easy to get to.

 

I'm guessing you have a 3.4? I just resolved my P0303 with new plugs. I had one that was shot. Follow the FSM for testing coils and wires. The wires for example need a resistance no more than 25 K ohms. Theres a procedure to check coils below. (The high tension terminals are the contacts that touch the spark plugs and where the plug wire plugs into the coil.)

(c) Inspect the primary coil resistance.

Using an ohmmeter, measure the resistance between the

positive (+) and negative (–) terminals.

Primary coil resistance:

Cold 0.67 – 1.05 Ohms

Hot 0.85 – 1.23 Ohms

If the resistance is not as specified, replace the ignition coil.


Inspect the secondary coil resistance.

Using an ohmmeter, measure the resistance between the

positive (+) and high–tension terminals.

Secondary coil resistance:

Cold 9.3 – 16.0 Ohms

Hot 11.7 – 18.8 Ohms

If the resistance is not as specified, replace the ignition coil.


As for the injectors, I'd replace them all at the same time to be sure that they all flow the same rate of fuel. Heres a link to a company that remanufactures OEM injectors. Theres a core charge and they only accept OEM in return. https://motorwestperformance.com

 

Thanks jj04taco,I swapped coils and a few plugs around just to see if I could get the problem to move to a different cylinder but no change.
I will test everything today following your list.

 

Dude, I love winter, snow and all. I’m in Dallas, and I miss the hell out of weather like that. Working in that would be not so pleasant without a garage however...

Weather here sucks most of the time. Too damn hot and humid. Supposed to be 71 degrees here today. It’s February!

 

I put a new set of plugs in thismorning,new ngk wires should arrive on Friday.Any advice on these readings?

 

New plugs and wires? Did that fix it? If not, try swapping the coils to a different cylinder first. While you have them out test them with an ohm meter too, it’s super easy and pretty quick and definitive. (Mark their original position.). I’d eliminate spark before I go fuel. Then reset your ECU, and see what happens.

I can email you the PDF from the factory service manual if you need diagrams...

I’m not to familiar with those readings on the scan tool. Sorry.

 

Plugs did not change issue,new wires on order.
I swapped wires and coils around and problem stays on number 4 cyl
I chased and cleaned all grounds I could find
Yesterday when I did a hot start leaving the mall,it ran like shit for about 5min of driving then cleared up for the rest of the drive home.Parked it for about 10 min and when I tried to start it it was running like crap again.
Looking at landcruisers and jeeps on Craigslist...lol

 

I found a site from a Timmy the toolmans YouTube page that you can get remanufactured OEM injectors for way less. Sounds like it could be an injector. I’d personally recommend changing all of them at the same time as they are flow tested and matched as a set. Plus no one likes doing all that work over and over. I’ll post it up in a bit...

 

It's running super lean, check the intake tube and the plenum for vacuum leaks.

May need to figure out how to hook a fuel pressure gauge up.

 

Why do yo say that? I had the intake tube off to change plugs and it appeared fine.havnt checked the plenum.I find it weird I can drive it for hours with no issues then after shut off for 10min or so,the problem arises.And why it went away on the drive home is strange.Anyways,I’m going to give to a mechanic.

I should mention that I had a 0171 code come up a while ago.I cleaned maf sensor,throttle body and new fuel filter and it seemed to solve the issue.

 

Bishop is referring to the fuel trim info on your scan tool. (I just googled STFT and LTFT... because I didn't know what that was.) Here is some info that came up. This is all news to me and pretty cool information. What scan tool to you have? I'd love to have that same information...

EDIT: From same article:

• P0171: system too lean (bank 1)

https://www.autoserviceprofessional...-works-and-how-to-make-it-work-for-you?Page=2

Also here's the link to the place to get OEM injectors...

https://motorwestperformance.com

 

Thanks,I’m learning this stuff also....or trying to,lol..
Scan tool is a Innova 3030

 

Dude, this is why I love forums. Sometimes you may have a little knowledge or learn new stuff. Then, when helping someone you do some digging and learn more stuff. All this fuel trim is new to me too, but man, how useful is that info eh? But actually being able to diagnose the issue with all of that info seems to be a challenge in of itself...

 

LT 14% means its adding 14% more fuel then normally set, this means lean.

Ideally you want +/-10%, anything more can trigger codes and implies a fault.

With lean, it can be a MAF, vacuum leak, fuel injectors, fuel pump, or valves. Also failing o2 sensors but less likely.

 

Thanks.

 

Ok,today I threw in the towel and booked an appointment with a real mechanic.lol..I’ve never needed to rely on a mechanic before so I’m pretty frustrated but I keep looking at pictures of @kmcmahon5 ’s build which is strangely keeping me positive...maybe once the issue is sorted out I will build it up..

 

Nothing to be ashamed of, in fact you may have made his job easier. I have dibs on injector issues...