All other cylinders between 120-130 lbs. Uploading pics was being a pain this time.

 

anyone know what the difference might be if its not warm and throttle not open?,,did mine several months ago like that 160-170

 

Technically your PSI spread is slightly over the limit but on a 300K engine its probably not significant in reference to your problem. That said, all of your readings are low and the engine is well worn.

If you are absolutely certain that you have ruled out ignition problems (checking spark quality at the plugs, misting in the dark, etc) then this is most likely your spider. The throttle backfire implies an ignition or timing problem. This can be spark or timing (CMP retard (worn gears or timing chain) or a jumped chain. I don't think that the cam value you captured is this parameter because it will almost certainly not be zero on a high mileage engine. One of the best tests is a fuel delivery balance test where each injector is fired in turn without the engine running, recording the pressure drop at the shrader, charging the rail between readings. Given your fuel trims, you would likely see low delivery on #4 and #5. I use a seperate control box to do this along with a fuel pressure gauge. That high end scanner might be able to do this. That scanner may also be capable of a cylinder drop test where each injector is disabled in turn on a running engine to watch the rpm drop. Whatever you do dont replace that spider with a low cost aftermarket spider as a trial because the OEM spider may get detroyed upon removal and if thats not the issue and cause new problems.

Next, fixing that O2 sensor issue is relatively easy but since this problem is on both banks that is probably not the whole thing

Your rear O2 sensor implies a dead cat which was likely killed by fuel issues or coolant leaks. A cat can die with no restriction which will not cause the truck to run bad just not pass inspection and worse for the envioronment. If you are developing excessive back pressure then that can cause problems, usually poor performance under a load. There are tests for this.

If you are going to need to tear down the top of the engine for a spider, you should do the LIM gaskets, one of the top known issues on this engine. If so you use the high end Felpro set. If you oil has ever looked milky or you have coolant loss then this is indicated. They are likely bad on a 300k engine.

BTW, I am not knocking high mileage, my Toyota work truck is at 301K. I did a head repair on that one at 155K but at over 300K I would go new block or crate rebuild after the next major issue.

George

 

Man those toyotas can go forever, only thing that bothers me about doing the lim gaskets is pulling the distributor. If it was my race car with an old school small block I wouldnt hesitate. Its basically the same block just 2 cylinders lopped off i guess. I'll keep ya posted on what I can figure out on the above mentioned tests. I'll figure out if the scanner can do it. I appreciate you taking time from your world and going through the diag. processes with me.

 

No problem, glad to help. Keep me posted.

George

 

Replaced the lower intake gaskets today and the spider. Put the plenum on and decided to chek for fuel leaks before we really buttoned everything up. Strong smell of fuel. One of the lines was leaking where it connected to the main unit. Gotta return it and get another one. It was a reman but it didn't have the clips that hold the injector in the lim. Guessing it was an updated design. Crazy how thise lines have to ben around to find their home.They just snapped in. Everything went really .well considering I've never done it before. With the exception of a shiity part fresh from the shelf. Stay tuned lol

 

SUCCESS!! Ordered a NEW spider and bracket. It came in yesterday and got it together. Started right up and ran smoothly. Smoked like hell for a few, but I expected it as it cleaned itself up.We ran into a small issue routing the spider lines. After watching the video that came with the part it showes 2 different routes. We gad trouble fitting the plenum as it was hitting the plug on #3 injector a little. We tinkered with that and was able to get the plenum pretty flush and walked it down the 1/16 inch. Got lucky with the fuel lines at the rear of the plenum, my 5/8 wrench was just short enough to get good bites on the lines. Someone had been in the motor before as the lower intake gaskets had been updated to the new gaskets. The ports for the coolant were very crappy looking and deteriorating. Its a good thing I took the extra time to do the lower as well. Thanks again GeorgeLG for walking me through the diag. process. Hopefully others will find this thread useful.

 

Congratulations on taking a diagnostic approach to find a targeted fix. Glad I could help.

George