1uz stumbling, "hissing sound" from manifold

[spf_lexus]

My UZ has always had a very low idle of 300-400rpm but always smooth and composed. Over the past week, the car idles down to 400rpm after warmup, and then misses constantly and sometimes stalls. If I raise the idle with the gas pedal (at stoplight) it still misses, but less often. I am thinking maybe I have a fuel injector thats failing? I have a fuel rail mounted pressure gauge and it usually reads 35psi at idle. If I shut the car off, and then pull the throttle body, I can hear a distinct "hissing & spraying" sound until the fuel press. drops down to zero. Im sure its a fuel leak as the fuel pressure proves this. I did consider the fuel reg as a possible leak but the sound is coming from inside the manifold, no sound near the reg/return line. I also notice some pinging at 4k and up so I have not boosted to redline yet. The sound is like a loose exhaust flange/hardeware until i lay off. Also sounds like gravel hitting the exhaust. I have new iridium plugs, coils, wires, dizzys, caps. I have zero vacuum leaks and running w/o MAF sensor does not change the issue.

Any help appreciated guys

Sean

 

[spf_lexus]

It has to be an injector thats sticking. Why else would fuel be spraying w/ the power cut? I guess i'll use a sethescope and listen to each one tomorrow. If that doesnt work i'll test the resistance and/or test light. I thought about replacing all 8 but at $40 each, I need to narrrow it down.

I did backprobe a couple injectors for a school assignment, maybe the pin fit has loosened up?

 

[spf_lexus]

Just adjusted my TPS and the smooth idle is back but i'm still hearing the miss. Mostly when I lay off the gas. Could this be a sticking injector thats causing fuel to dump into the exhaust causing the Pop Pop Pop that i'm hearing? This must have just failed because I used to maintain 35psi rail pressure for at least an hour before it would start to drop, now I have maybe 2 minutes before its completely zero'd.

 

[spf_lexus]

Just tweaked my tps again and now i cant drop gears, shifts are hanging, and I have a stumble pretty much everywhere. Gotta be the tps out adjustment or faulty.


Any ideas on the leaking injector?

 

[cribbj]

Sean leaking injectors are pretty common on first startup, but I can't speak with any experience about having them leak once the engine has been up & running for awhile.

What you'll need to figure out is whether it's leaking due to an accidental earth on the trigger lead, or if it's leaking due to a mechanical problem with the injector itself.

First you have to find which one is leaking, and a couple of noid lamps might be of some help with that and/or the stethoscope as you mentioned. Mechanically sticking injectors have a different sound than the rest. They don't have a clean snap when they open/shut.