1JZ code 25 *fun* need advice

[NecroCyde]

How are the wires for the water temp plug.

Good, no fraying or damage at all. How the hell do you de-pin an IAT connector housing?

In other news, all my injectors have resistance at 14.1 to 14.3 ohms, i cant find the 1jz spec anywhere, but they likely are good as they are all that close to each other. I'll ohm out a 440 and see.

 

[NecroCyde]

Don't everybody respond at once......crickets in here.

 

[525gte]

Injectors are good. Can you hook a vaccume pump to the fpr and pull like 20 inches and see if it gets better

 

[NecroCyde]

Don't have a vacumn pump, ill look up what that is, would a bad stock FPR be to blame? you can hear it make noise, fuel rushing sound, sounds kinda like the heater valve. Car had some pretty bad break up issues from 2600-3000 rpm, cleaned up a decent bit when I regapped my plugs down to 0.028.

I'm also going to check my coil packs for any damage, that's likely a side issue though. I'm going to pull apart the glove box and see if the OX pin is actually getting what the diagnostic plug is reading. Money is on now with everything that has been checked that it may be something simple like that, just like the ECU constant power issue. No, I didn't extend the harness.

 

[3p141592654]

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.

The Ox sensor should be switching between 0.1 to 0.9 volts and doing this rapidly (called cross counting). You cannot really measure this with a multimeter, you need a scope, or at least a meter with a frequency (Hertz) mode. The key parameters is not the voltage, but the number of cross counts per minute. What the voltage does as you rev it is meaningless for the most part.

Your code 25 says that the ox sensor is not cross-counting properly. The ECU is adding a lot of fuel relative to what a normal engine needs and still the ox sensor is reading lean (0.1V).

To test you run a warm engine at ~2500 rpm and make sure it is cross-counting fast enough, usually that means at least once per second. If it is not, then find someone with a gas analyzer and measure the AFR out the tailpipe. That will then allow you to know what the problem is.

 

[NecroCyde]

Alright, confirmed, OX at the ecu has continuity to the OX1 pin at the diagnostic plug and gets typical voltage with fluctuation as expected. Time for an exhaust gas analyzer, could i be looking at a bad ecu maybe? The TSRM kinda points this way once you have checked all of the above.

Oxygen sensor is new, wiring good, no vac or exhaust leaks, coolant temp sensor good. Let get the exhaust sniffed and see if the car is actually running lean. Also checked coil packs and no cracking, look good. Pulled two plugs and even at 0.028 they dont look bad, little golden brown further up, little grey/white at the base. tip and porcelain look fine.

 

[3p141592654]

So, you are saying its cross counting as expected? Then the mixture is fine as the ECU is in fuel control. Seems unlikely though given a code 25. Suppose its true, then the next step would be to look at Vf and see how far from the norm you are running.

 

[NecroCyde]

ok exhaust gas analyser reads idle AFRs at 15.0 and revving up to 2500 rpm in the high 13s. This was done at a stand still and not driving/under load.

So a touch leaner at idle but richening as expected as boost comes on. Checked my map sensor connection, wires and line, no change.

Do i by chance have one mechanically bad injector maybe? Bad ecu??

Thanks!!

 

[NecroCyde]

Spoke with Aaron at DM and he thinks bad ECU, borrowing a friends manual one, I'll see how that goes. Any other ideas people?

Thanks.

 

[NecroCyde]

Its not the ECU!!! Condition persists with a known confirmed good manual one, interestingly your car will still drive with a manual ecu, no TC lockup though.

Spoke with Aaron again and we figure bad harness work. He has never had a car get a code 25, even when it was running lean, air leaks everywhere and running like crap. Its as if the resistance is off or something in the line, the ECU gets the voltage, but the cross counts are not correct?!@

I could throw in my 440s and see, if it still thinks its lean with 15% more fuel, something electrical is to blame for sure. My plugs at a 28 gap check a week later at a nice golden brown/tan, looking great, car isn't lean. I shrink tubed my coil stems and replaced the last two coil pack connectors (old ones were not broken) as well for insurance.

I think I'm going to pull the harness and have Dr.Tweak or Kaizen redo it over the winter. Any other thoughts guys? Only thing left is injectors, FPR or map sensor and those are outlandish longshots considering how well this car runs.

 

[525gte]

So have you cked the vf readings yet? And have you put a vaccume \boost pump on the fpr yet ? Maybe the car runs just fine. But the condition triggering the code is at idle only or 1 specific point of rpm I don't think the plugs will tell you . I would also clear the codes and see if it comes back

Did you bye chance remove the fuel dampener?. If its been removed on stock ecu it will cause a wicked lean out at about 2500 if iirc

 

[NecroCyde]

VF readings originally looked fine, I will check again but I didn't see anything out of the ordinary at the diagnostic plug. The code goes away with the key off, but once you start driving again, it triggers again at its trigger point, not when you start the engine again. The stock fuel dampener is still there, on the engine mount bracket. Ill see if I can rent/borrow a vacuum pump.

 

[525gte]

Right are you clearing codes bye disconnecting battery?

 

[NecroCyde]

Absolutely, im just saying the code does not persist after you turn off the ignition and start the engine again, like some codes. It needs its trigger conditions met, even though whats causing them at this point are very likely false. I really suspect wiring, but ill keep digging here. AEM wideband nearly here, that will also help diagnose any lean areas in the powerband.