R32gtr sputtering and stalling

[Dose Pipe Sutututu]

Time for a modernisation, throw out the AFM, stock O2s, ECU into the e-waste bin. Rip out the cable throttle, IACV, pedal, etc. into the scrap metal bin.

DBW, e-throttle, modern ECU, CANbus wideband, and the thing will drive better than when it left the factory.

[joshuaho96]

16 hours ago, MBS206 said:

I agree, don't go trusting those trims. As I said, first step is to put the logger away, and do the basics in diagnosis.

 

I spend plenty of time with data loggers. I also spend plenty of time teaching "technicians" why they need to stop using their data loggers, and learn real diagnostics.

 

The amount of data logs I play with would probably blow most people away. I don't just use it to diagnose. I log raw CAN data too, as a nice chunk of my job is reverse engineering what automotive manufacturers are doing.

What basics? With these OBD1 ECUs it's not like the ECU will give you any real clues, it's not really doing any sanity checking of sensors/sensor data. My experience is actually a lot of sensors tend to be the source of the issue first and foremost, and checking everything gives you a direction to investigate. MAF/O2/STFT/LTFT should all kind of make sense. You can try little tricks of the trade like tapping the MAFs to see if it triggers a stumble, things like that. But once you've done a compression test knowing whether you have an air leak or fuel delivery problem is kind of hard to narrow down without sensor data. And you don't really know if all your sensors are making sense unless you can interrogate the ECU directly about what it's seeing for sensor data.

[MBS206]

15 minutes ago, joshuaho96 said:

What basics? With these OBD1 ECUs it's not like the ECU will give you any real clues, it's not really doing any sanity checking of sensors/sensor data. My experience is actually a lot of sensors tend to be the source of the issue first and foremost, and checking everything gives you a direction to investigate. MAF/O2/STFT/LTFT should all kind of make sense. You can try little tricks of the trade like tapping the MAFs to see if it triggers a stumble, things like that. But once you've done a compression test knowing whether you have an air leak or fuel delivery problem is kind of hard to narrow down without sensor data. And you don't really know if all your sensors are making sense unless you can interrogate the ECU directly about what it's seeing for sensor data.

 

The consult isn't even OBD1. It's a Nissan Consult. Proprietary.

 

Re read everything I've said. I specifically say, put down the laptop/tablet. Understand, and review the issue first.

Logging voltages is the same as logging the converted value. Things like O2 that you say to log, is unusable for this, whether it be the voltage, or the value the ECU thinks.

 

The fact you don't know how to diagnose without looking at the computer, is exactly what I've said multiple times is the issue for why techs these days can't diagnose the fun issues with cars.

[Dose Pipe Sutututu]

Johnny's approach, throw all the Nissan electronics into the trash.

Best thing I've done to my shit box, go DBW.

[joshuaho96]

3 hours ago, MBS206 said:

 

The consult isn't even OBD1. It's a Nissan Consult. Proprietary.

 

Re read everything I've said. I specifically say, put down the laptop/tablet. Understand, and review the issue first.

Logging voltages is the same as logging the converted value. Things like O2 that you say to log, is unusable for this, whether it be the voltage, or the value the ECU thinks.

 

The fact you don't know how to diagnose without looking at the computer, is exactly what I've said multiple times is the issue for why techs these days can't diagnose the fun issues with cars.

OBD1 is a catch-all term for pre-OBD2 which could have basically any connector design and protocol. I really don't understand this attitude against using data logging for issues that can be multi-causal and subtle. A no-start situation or something like that sure the scan tool does nothing but if it runs like shit it can often be a sensor issue. When a friend of mine reliably had issues with his N54 not able to stay running eventually I narrowed down the issue to a faulty fuel pressure sensor. Only way I could do that was a scan tool to look at the fuel rail pressure and see shadow codes for fuel pressure. Then check against a pressure gauge.

Is reflexively firing up the data logger probably a bad habit? I guess, it can encourage people to not listen/observe but on these old OBD1 cars just taking a log really doesn't do anything by itself. You still have to synthesize everything you know and think about what it all means.

[GTSBoy]

22 minutes ago, joshuaho96 said:

OBD1 is a catch-all term for pre-OBD2

Only in a market where OBD was a thing. The rest of the world was quite happy to let the US EPA only affect US cars for quite a while.

The* problem with datalogs is that unless you are very familiar with what every trace should look like, on their own and as an ensemble, you can and will see weird shit that can and will lead you astray, not realising that what you are seeing is the normal consequence of various transient inputs.

*Really, "a" problem, as there are of course many other problems too.

Look, these cars are so bloody simple that if it is missing or stumbling, the obvious thing is to break out the old mental diagnostic list and just go do all the things that you know you should. After proving that the plugs are clean and sound, ditto the coil stalks, coils, loom connectors, etc, and then making sure that there is fuel pressure at about the right numbers (while driving!, not while sitting in the garage free blipping it), then maybe you go looking at AFM voltages, manually testing the igniter, putting a scope on the CAS, etc.

Then you're into pulling the injectors for a spray pattern look-see and perhaps a clean, squirting carby cleaner around the inlet manifold looking for leaks, and all the more annoying and esoteric, but still common as muck faults that these things have.

I wouldn't ever bother looking at the trims, as they are usually bullshit on these old clunkers anyway.