1JZ code 25 *fun* need advice

[NecroCyde]

Hey guys,

I have searched a ton both on the forums and google and done a lot of digging on this to figure this out cause as i really want to take this thing to the strip.

I have my 87 Supra Targa, was 7MGE and and is now 1JZGTE Auto, originally wanted the auto for drag racing, 5 speed would be more fun right now yes.

1JZ wouldnt run due to 4 stuck intake valves, received a very recently rebuilt head from Slow_SC3 and fired right up, runs and idles great. (2jzgte HG and ARP headstuds)

Car has china y-pipe and 3 in dp, 3 inch 5zigen exhaust, gutted cat. 2.5 inch hardpipes to 24x12x3 FMIC, good couplers and tbolts all around. Driftmotion cone filter on a pipe to the stock accordian. Walbro 255 pump installed with 12 v rewire

Stock boost at 11 psi, sometimes 12. Car ran great, very strong, twice as fast as my 7m auto car with 60-1 ct26 and bunch of other goodies.

Got a CEL shortly after i got the car driving, couldn't pull the codes for the life of me, spoke with Aaron at DM and he suspected the batt pin for the ECU was not getting a constant 12 v for memory. Tracked this down and it looked like the black yellow at EA2 was getting continuity to the ign switch pin??? batt pin got no power. Corrected this and ran a fresh primary wire from black yellow to the batt pin on the ECU. Memory restored, idle improved a bit, cold weather starts idle up properly, etc. CEL light took longer to come on but still did, retrieved the code, 25, too lean AFRs, damn.

Did a bunch of digging and searching and it sounded like most of the people with this problem had bad o2 sensors, so i ordered up a NTK 24137 for a 92 supra as many use that as a local option due to them being same sensor, just a longer lead.
Was very careful installing it, kept things clean and torqued everything to spec, also checked to find any looseness on the y pipe, everything is tight. Car fired up and sounded a bit better still, but after a quick road test, CEL, code 25, at 2500 rpm in 2nd gear after about 30-45 seconds. Car sometimes has a bit of breakup/hesitation at 2500 rpm under higher loads. A bunch of the various supra code breakdowns pointed at the o2 sensor as well.

Hoping to race the car at the strip, i was going to throw caution to the wind, but decided against that, this many years of work and hungry wallets and lean+turbos=bad changed my mind.

Aaron said exhaust leaks, I have several new exhaust gaskets in, some new hardware and everything is tight. Exhaust manifolds got torqued to spec, turbos tight. Several new hosetechniques hoses on the intake side, clamps and everything is tight. While waiting for the o2 sensor i swapped in 4 new coil pack connectors as the clips were broken, they are easy, so easy i have the other 2 on order even though there fine. The starter connector, not so easy.

stock boost, no fuel tuning, rebuilt ecu, 91-94 octane gas all the time. I have driven it a decent bit and it runs and feels fine, cars temp is great and cool. (2jzgte waterpump, jza70 koyo replacement rad, fresh coolant and thermostat)

Not sure what to do next, heard bad injector o-rings can be a cause, but no fuel leaks. I have freshly cleaned and flow tested 440 cc injectors (JDM 2JZGTE) with new o-rings done by DM i am considering throwing in if say my injectors are not doing so good either, but worried 440s with no fuel tuning will cause further issues. I am considering getting an AEM wideband right away since i need one anyway to see where my AFR's really are at. If i was running dangerously lean, would i not hit fuel cut? A bad water temp sensor may do it, but its not throwing a water temp sensor code and i don't want to just throw more sensors at it.

What do you guys think? Put in 440s and see if we are good or maybe throw code 26, too rich? New o-rings on the stock 370s and see? Something else i am missing? HALP! I wanna see what this thing does on the track! Just don't wanna melt it either.

Thank you so much everybody!!!

 

[525gte]

Did you reset the ecu after you made repairs and new o2?.

You can also use a 89 ford mustange 3wire o2 as a replacement as long as you have the correct bung in the down pipe it will prob be half the cost as the stock toyota replacement. You can also ck the voltage of the vf wire to see if the computer is pulling ot adding fuel. Its a 5v deal. 2.5 is nochange infueling. And if I remeber right 5 is adding as much as it can

Putting the 440s in will make the car pig rich also wih out a fuel controller

 

[jetjock]

OX. Nuff said.

 

[NecroCyde]

Ox? What do u mean? Also yes I did reset the ecu, the battery was disconnected during replacing the o2 sensor, it was $118. What else can we try? Thanks.

 

[jetjock]

Well, you can try not swapping parts you paid too much for. That code is set based on what OX is doing. Problem is you have to determine whether OX is bad or just doing what it's told. It's the old chicken or the egg thing...

 

[f00g00]

Injector O rings are a possibility. You can pull the rail and check the big ones on the base, if they are missing or cracked they can suck in air and run lean on that cylinder
I had a similar condition years ago on a 7MGE where it had twisted O rings and was running codes 24 and 25 rich and lean. It was sucking in air and th ox sensor was over compensting and putting In too much fuel.

 

[NecroCyde]

Well considering many of the supra code breakdown pdfs and websites and peoples threads on code 25 lead people to a misreading or bad o2 sensor (20+ years of exhaust might wear something) i figured replacing it like they did may be a good place to start. I wanted to race in a few days, so i had to pay that to get it in hand for $118 CAD. Hindsight being what it is we could have looked elsewhere first, but that's the information i could find at the time, now its new and cant be ruled in is what we can at least take from swapping it.

If the ecu wasn't getting OX or VF it would throw code 21 not seeing the o2 sensor at all. So lets look at this engine itself. Is it normal to hear fuel rushing through the rail itself when the fuel pump is running? If not bad o-rings maybe a great place to start as they are sucking air causing that sound, as f00g00 says, not all but a few cylinders may be sucking in air if those particular injector o-rings are wrecked. Would probably make sense to just put new o-rings in on the 370's first rather then go straight to untuned 440's. Again 20+ year old o-rings that sat for years when this engine wasn't in a car and then wasn't running can very well be trashed enough they leak under fuel pressure and/or vacuum when the engine is running. I'll get some prices on o-rings tomorrow. Thanks for your help guys!

 

[f00g00]

The bottom of the fuel rail itself has a big rubber seal where it seats to the head. It is possible that the rail was installed without one or two. The O rings that are on the injector are so the fuel doesn't leak from the rail, they are side feed so there is an O ring above and below the feed, if they were bad fuel would be leaking.
You can verify the bottom seal on the rail itself without pulling the rail if they are at least there or not where it mounts to the intake manifold. There is a small gap there where you can see it

 

[NecroCyde]

Awesome, thanks for clarifying! I will check those and probably replace them, would also make sense if the o-rings in the rail with the injectors were bad enough to let air in, fuel would be coming out pretty good too of course, my bad.

 

[NecroCyde]

Well, you can try not swapping parts you paid too much for. That code is set based on what OX is doing. Problem is you have to determine whether OX is bad or just doing what it's told. It's the old chicken or the egg thing...

Ok from the diagnostic plug i get from 0.1 to 1.0 of a volt, fluctuates normally, goes higher during revving. Coolant temp sensor has good resistance, just redid my fuel return line. I am going to check my plugs to see if i have any signs of running lean. Maybe try 4644 / BKR7E plugs at 0.028-30 gap.

Also, if the head has been milled 3 times and i am running a 2JZGTE HG, could the comp ratio be a bit higher causing the car to run a bit leaner? (relative i know with how much they removed from the head) I am also going see if anybody has an exhaust sniffer and see what it says well.

 

[Poodles]

Well considering many of the supra code breakdown pdfs and websites and peoples threads on code 25 lead people to a misreading or bad o2 sensor (20+ years of exhaust might wear something) i figured replacing it like they did may be a good place to start. I wanted to race in a few days, so i had to pay that to get it in hand for $118 CAD. Hindsight being what it is we could have looked elsewhere first, but that's the information i could find at the time, now its new and cant be ruled in is what we can at least take from swapping it.

If the ecu wasn't getting OX or VF it would throw code 21 not seeing the o2 sensor at all. So lets look at this engine itself. Is it normal to hear fuel rushing through the rail itself when the fuel pump is running? If not bad o-rings maybe a great place to start as they are sucking air causing that sound, as f00g00 says, not all but a few cylinders may be sucking in air if those particular injector o-rings are wrecked. Would probably make sense to just put new o-rings in on the 370's first rather then go straight to untuned 440's. Again 20+ year old o-rings that sat for years when this engine wasn't in a car and then wasn't running can very well be trashed enough they leak under fuel pressure and/or vacuum when the engine is running. I'll get some prices on o-rings tomorrow. Thanks for your help guys!

As it's already stated, it's the cushion rubber rings at the bottom of the injectors that seal to the intake manifold that would be the leak to allow a lean condition (though under boost it's more likely to be a rich condition).

Ok from the diagnostic plug i get from 0.1 to 1.0 of a volt, fluctuates normally, goes higher during revving. Coolant temp sensor has good resistance, just redid my fuel return line. I am going to check my plugs to see if i have any signs of running lean. Maybe try 4644 / BKR7E plugs at 0.028-30 gap.

Also, if the head has been milled 3 times and i am running a 2JZGTE HG, could the comp ratio be a bit higher causing the car to run a bit leaner? (relative i know with how much they removed from the head) I am also going see if anybody has an exhaust sniffer and see what it says well.

No, comp ratio will do nothing to air/fuel ratio.

You're looking everywhere but where you should be. You're either actually lean, or you're getting a misreading. Yes, it's for the 7M, but it's all basically the same (much like OBD2 codes): http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=27

AFM on the 1JZ would obviously be the MAP sensor in this case.

 

[NecroCyde]

As it's already stated, it's the cushion rubber rings at the bottom of the injectors that seal to the intake manifold that would be the leak to allow a lean condition (though under boost it's more likely to be a rich condition).



No, comp ratio will do nothing to air/fuel ratio.

You're looking everywhere but where you should be. You're either actually lean, or you're getting a misreading. Yes, it's for the 7M, but it's all basically the same (much like OBD2 codes): http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=27

AFM on the 1JZ would obviously be the MAP sensor in this case.

everywhere but huh? Not really dude. Ive poured over those same tsrm's your stating and the code listings for both 7ms and 2jz's and tested voltage at the diagnostic plug, 0.2 to 1.0 volts with variation between the two (like the manual says), tried a spare coolant temp sensor as well. So if in your honest experience and opinion, one should be replacing those bottom o-rings, then i will do it. We cannot be misreading or getting a bad reading from a new o2 sensor unless by some crazy chance its defective. Replacing the fuel return which was of concern is correct as something affecting fuel pressure could cause injectors to lean if they are not being fed properly, now its rock solid. Checking your plugs for lean isnt wrong, because that would be indicative of an engine actually running lean or if they are fine, just the ecu thinks the car is lean. (you would have to check plugs in this fashion on a carb engine, for example) Im also considering seeing if anybody has an exhaust sniffer.

But i digress, i just want to clarify what your saying, are we taking about the insulators that rail sits on or the bottom injector o-rings that is the area of concern, just in case i have to order something as i have new o-rings on my 440s i could use.

Because i cannot:
1. smell a fuel leak
2. see one
3. hear a vac leak either at idle or revving.
4. cannot smell, hear or see any exhaust leaks either, everything is tight.

Thanks alot for your help.

 

[f00g00]

Did you look at the rail where it meets the intake manifold and verify the rail cushions are all there? Just get a strong flashlight and check them. If they are there then I would rule out the rail as the two o rings on the injector would be leaking fuel if any were bad.

 

[NecroCyde]

ok, so they all appear to be there, some look better then others in overall shape. I am going to replace them, going to start digging for a part number, any chance 7M ones work? Anybody know a number? Going to try and order local so i can get these here sooner, Monday is a stat day, so Hopefully i can have them here for wednesday night for install.

Thanks guys.

 

[f00g00]

7M and 1J are not the same but 1J and 2J are so get for a 2J. There is also a pintle ring insulator at the very base of the injector and I am not running them on mine with no problems. the numbers are 23291-75010 for the pintle insulator and 23291-76010 for the base insulator.

 

[NecroCyde]

Thanks for those numbers, little research dug those up for me, i remembered that since north american 2jzgte's have sidefeed rails, the injector o-rings and insulators work as well. (i remembered people put 550s in their stock rails, durrr, just need the resistor)

Im hoping i can order local through the parts store to get this going for friday night races, anybody have a napa or beck arnley number? Rock Auto has listings but only for california models and not, lol, not too descriptive. One question though, if i truly was running that lean, would i not be hitting fuel cut all the time before the engine tried melting itself?

Thanks guys!

 

[525gte]

I just bought a standard large o ring kit for my 440s. And I was able to replace all mine just fine, did not have to order any special rings. I may be wrong but I dont think onrinfs are your problem. If your getting more than 1v at the o2 its more than likey bad.
I would lean more towards an injector not working properly. ? What's the vf reading at idle. Or maybe a stuck fpr. Making base pressure higher. In turn making car rich

 

[Radial]

My 1J fpr failed on me last year. resulting in fuel beein injected through the vacuum hose and fuel pressure was 55psi+
AFR's was 9:1 at WOT with lots of hesitation.

I think the high fuel pressure forced the fpr to leak through the vacuum hose.
A quality fpr with gauge is money well spent anyways.

 

[NecroCyde]

Alright, the fuel rail insulators are totally fine, still soft, flexible and supple, I wiped things off and put it all back together nice and tight.
One fun thing that happened was one wire snapped off my rear cps plug, wires next to the housing were worn out and then the other snapped too. Front one isn't too healthy either and the IAT wires are the same. Got new cps plugs and terminals inbound and new iat terminals as well, the housing is discontinued, but ill order from a connector housing website generic, thanks Jeff!
I highly doubt this is causing my code 25, but it sure as hell cant be helping anything.

I am going to ohm out my injectors and see if there are any out of wack and if they are, I most likely will just slam those 440's in. I'll then get a wideband and put that SAFC Neo in that I have to adjust them. Eventually I really want a good standalone, the new haltech or a AEM.

What else do you guys think?

Cliff notes:
Code 25 for lean AFRs

New o2 sensor
Tried different coolant temp sensor
no exhaust or intake leaks
fuel rail and injector O-rings good
New fuel return line
diagnostic plug reads OX1 voltage from 0.1 to 1.0, at idle staying more towards 0.1 but then when revving moving around from 0.3ish to 1.0.
no code 21,22 of 26 either.

I know ECU's can go bad going ultra rich and dumping fuel into the engine, this ecu is supposed to be rebuilt and im wondering if they can go lean at all, wish I could get my hands on another 1JZ auto ecu to test.

Thanks a lot guys!

 

[525gte]

How are the wires for the water temp plug.