4.7L Code P305 - Cylinder 5 Misfire Detected

I am the original owner of a 2005 Toyota Tundra 4.7 Liter I-Force Crew Cab TRD with 356K miles on it. Recently I had code P305 - Cylinder 5 Misfire Detected pop up. The engine has a slightly rough idle (especially when AC compressor engages while in gear and stopped at a light) but engine runs smooth and code clears above 1,000 RPM.

So far I have replaced the coils (Denso), the plugs (Toyota Iridiums), and the fuel injectors. In addition, I checked the air filter (clean), cleaned the throttle body, and even swap the catalytic converter on the driver's side with a known good one (it is off my other 2005 Tundra - long story). The plugs were clean and the engine is not losing any coolant nor does it burn oil. I ran a bore scope down the front and back of the catalytic converter and the honeycomb is intact with little to no buildup on it. There is also little to no backpressure when I blow air through the cat. Even with all these changes, I have not been able to clear the P305 code or rough idle.

I am running low on ideas so I would like your thoughts. I have a bore scope and have considered pulling the plug on #5 to view the combustion chamber if for no other reason than just marking it off the list. The ECM was changed quite a while ago by Toyota and that seemed to have created as many gremlins as it cleared but I have not heard of the ECM creating an issue with just one cylinder.

Thanks!

 

Thanks! Definitely more items to check out.

 

Check out the "So you wanna buy a 1st gen" sticky at the top of the subforum. It has decades of information as well as links to the Field Service Manual, Wiring Diagrams and other useful, helpful stuff.

 

After changing all those parts and cleaning of TB, have you unhooked battery for say 30 min so when you hook battery back up the ECU can go thru re-learn.

As for the 305 cyl 5 issue, have you swapped with another cyl to see if code follows to that cyl or at least suspect the new fuel injector on 5.

 

I bet you anything your issue is the injector. Didn’t miss where you tried swapping the injector on cylinder 5 with the injector from cylinder 3 or 7?

Nevermind, I see you replaced the injectors.

The only thing that makes sense to me is either:

• Your timing has jumped, or if someone did the cam seals in recent history, they didn't install the service bolt and now the cams are a hair out of time with the rest of the mechanicals (yes, we've seen it, it took 25 pages of thread to solve his problem), or ...
• You have an issue with air getting into the cylinder (i.e. the rubber molded gasket for the intake is bad), or ...
• Maybe you're not getting a hot enough spark to that cylinder? Like, the connector has a broken tab and isn't seating properly? (The wiring for the injectors IIRC is very criss-cross, where there's a shared ground with 1-4-6-7 and 2-3-5-8

Best guesses. You can run with the FSM, but ... if I were you, I'd do your best to check the timing.

 

Also, when was the last time the timing belt was changed? It's required every 90k miles or 9yrs, although it's not unheard of to go 100k/10yr (**IF** you use OEM parts, can't speak to aftermarket, aftermaret parts are shit these days)

You should be on at least your 3rd belt by now. I ask because belt stretch would be another one of the anomalies the FSM (pages above) probably aren't going to know to tell you. Belt stretch could account for a single-cylinder misfire.

Your engine will potentially die if that belt snaps while it's under any meaningful load. Minor interference engine.

 

The timing belt was changed by Toyota at 319k or 37k miles ago so that is probably a low probability.

The cam seals have not been replaced so I would rule that out.

I have not swapped the #5 injector with one of the others but it is easy to do. I kind of gave up on that idea when I replaced the injectors and nothing changed with the rough idle. When I changed the injectors I really looked over the connectors and everything looked good and they snapped in place like they are designed to.

I will keep the intake manifold leak idea on the list.

I will also disconnect the battery overnight to force it to re-learn. Simple to do and I would be tickled if it were that simple.

 

Need to check for compression on that cylinder. A bore scope isn’t a bad idea either. You’ve replaced all of the parts related to it. Intake leak is a possibility. Could have a valve issue though. Compression and leak down test would help determine that.

 

A noid light set can really help diagnose if you are not getting injector pulse to number 5. Harbor freight sells them and I think you can rent from parts stores. Here's the harbor freight link. Just have to determine if one of the pieces will connect to the Toyota style connectors.

 

Yup, stuck valve would be another solid possible.