More 2JZ woes.. Sputter/misfire at low throttle and low RPM..

[ifyouaint1sturlast]

Car currently starts and runs fine, drives fine, no codes, just changed the plugs.. everything is gravy. One last remaining gremlin. At anything like 0-25% throttle at around 2-4k RPM the car sputters really badly. Above that it gets better, not gone, but a lot better. I recently had a TPS issue where the computer would give me a TPS code even though everything was in spec. That's gone, I reset the TPS and everything seems fine now. The TPS is exactly where it used to be from the factory and everything checks out to spec.



My notes..
-MKIII Supra (91) with Aristo 2JZ-GTE, completely stock except aftermarket single turbo
-TPS is correctly set, and calibrated, and reads 100% correctly according to TSRM
-There are no codes stored in the ECU
-Car idles fine but does have an intermittent misfire "pop" every 10-15 seconds
-Could it be caused by higher fuel pressure due to "12v mod" on my pump? (read 'whats changed')
-Revving in neutral reproduces the problem as well
-Seems to only happen at < 25% throttle and < 4k RPM (although doesn't really go away completely above that)

Things I've tried..
-Tested TPS resistance and voltage
-Changed spark plugs
-Fresh gasoline

What's changed since running correctly..
The car ran perfectly until Febuary of this year when I tore down the harness to make a fully rebuilt custom harness. It was just messy, done incorrectly, and everything of the sort. I've since made my own harness from scratch, ran everything exactly how the factory harness ran it (all grounds to same locations, power to same locations, etc..). The car runs again, doesn't throw any codes, everything seems perfectly fine. However, it did sit for almost 5 months ..

Finally, the last thing I did was run straight 12v to my fuel pump (Denso TT pump) instead of how it was hooked up. It was hooked up to factory wires and resistor. I learned that the factory wiring is rated for far less amperage than the TT pump pulls, so I did the "12v mod" temporarily until I purchase a fuel pump controller or the 2JZ fuel pump computer.

What I'm going to try next..
I will test o2 sensor voltage and resistance tomorrow. I was thinking of pulling the fuel rail and cleaning the injectors. The thought is that maybe pulling the fuel lines allowed some debris in there that is clogging an injector.

Finally I was going to hook up my AEM wideband (finally) and see what's going on. I'd need to get a bung welded to the downpipe though.

Will get a video up tomorrow.



Any tips? help? suggestions?


Thanks all.

 

[525gte]

my car did this also.. and it says that you adjusted tps? back to stock. did you use a volt meter to calibrate it? on my car if i mess with the idle screw (at all) or if the tps is out even the slightest bit it will have the same syntoms yours has.. maybe take a 2nd look at tps. also reck the wiring to it since it says you rebuilt harness

 

[ifyouaint1sturlast]

Sounds good man thanks. Your car is 2JZ?

 

[gurley0916]

What are your plugs gaped at? anything lower than .028" produces that intermittent miss at idle. To make that go away you need a little fatter idle A/F or just live with it. There is nothing wrong with that slight miss as it would be fine above 1200rpm when driving. But for the other case for you having it be from 2-4K I would say check your A/F when the gauge is installed it will tell you alot. If your not giving the ecu a o2 signal it will burn leaner. At least mine did until I emulated the signal with the LC1 wideband.

 

[ifyouaint1sturlast]

They were pre gapped at .032", and it's not a slight miss it's a sputter..

 

[525gte]

They were pre gapped at .032", and it's not a slight miss it's a sputter..

oh mine is a 1j.. but mine was not a sputter.. mine was a snap crackel pop

 

[IBoughtASupra]

Get out of here you cheapo 1JZ owner.

 

[ifyouaint1sturlast]

Agreed.

 

[te72]

They were pre gapped at .032", and it's not a slight miss it's a sputter..

Never trust a "pre-gapped" plug.

I would think your timing hasn't been altered (being 180° out of phase?) in any way since the tear down? Mine will sputter a bit at idle once in a while, but it runs fine, so I never bothered with it. I may have missed it, but the coils on JZ engines seem to be a weak link in the ignition system for many people. Are they free of cracks? Remember that electricity will travel the most convenient path, and if you have cracks in your wiring, it can play all sorts of tricks on you.

 

[kneedragger85]

I doubt it's the coils as he would be sputtering in boost and not under 1/4 throttle. My question for you is are you running stock fuel (minus the pump and 12v mod) and if so did you keep the pulsation dampener?

 

[ifyouaint1sturlast]

Let me take you guys through my day..

Tested the motor by pulling the injector clips one by one. They all did the same thing and lowered the idle except for #5 did nothing. All it did was remove the intermittent pop when I removed clip #5.

Removed the intake manifold and injector rail. I then cleaned the injectors as best as one can clean injectors at home. I increased fuel pressure to around 80psi and pulsed them manually. I noticed the spray patterns (into a glass jar) were all very different. I then ran drained the rail and capped the ends, I poured fuel system cleaner into the rail and let it sit for 30 minutes. I hooked up the fuel line and pulsed each injector one by one, letting out all of the injector cleaner then some fuel. I then pulsed each injector again into the glass jar and the spray patterns appear to have more atomization and more similarities between all six than being all unique.

After putting it all back together I can't tell if I've fixed anything because my ISCV appears to have taken a shit. Idle starts at 1500 or so and then over the course of 30 or so seconds increases to around 2200 RPM. You can hear it just sucking in air like no tomorrow through the ISCV, and I can get the car to idle decently if I cover about 3/4 of the port on the ISCV.

I just bench tested it and failed horribly. I hooked up the two B+'s to power, and cycled 1-2-3-4 with the ground and it sounded like it wanted to move but never moved at all. I don't hear it clicking when I turn the car off either. I used the chart below.

@KneeDragger: Yes stock, no FPD.. however the car ran great for months without it.

 

[soapra]

check polarity of the coils. recheck your wiring.