Thread: Reaching the thermal sensor on a lowport SR20?

Well this one is probably solved. Someone with more knowledge about loosening stuff on various cars pointed out that I should remove that metal thing that holds the connector. It shouldn't fall off he said so that is comforting and then a long socket. I also learned from him looking from the top when you hang over the engine front side, it looks a lot more normal and doable then silly Japanese and complex.

Now I hope it will come loose easy and that my favourite prying thingy will be long enough to catch that metal clip. Getting that clip and hearing the thermal sensor with a loud click loosening from the aluminium is something to look forward to. Removing the ABS block should be enough. The rest will be a walk in the park

After some researching I'm going to replace my know a bit worn MAF but bought at being 0.7 volts engine not running, for a know bad one. I have three other 0.9 - 1 volt MAF's that I happend to keep. One is from the Nx I own, one from the rust-nx from ten years ago and another one I really don't remember how I got it. I'll test them to make sure it is not my MAF acting up.

But the story is that after dropping my aftermarket air filter in to four pieces with know cracks and glueing that tite, car started but stalled almost directly. Logically this would be from glueing those cracks airtite but the filter is before the MAF so I wonder if that is something that can be expected. Temperature was moderate. With colder days, engine stalls harder.

But it wasn't a real problem to me, the dartyness of the engine is and I believed it would be easy by swapping parts from rust-nx with no dartyness to my Nx but it isn't. So my car stalls a bit when cold but after changing AAC, FICD, AICV, coil and distributor my car has a bit more power and runs very smooth.

Then I changed my orignal fuel pump for a known newish one and from this point or just a bit later I'm not sure, maintaining speed was no longer a problem but my engine went like, oohm, hmm, oohm, hmm at 60 miles per hour and I noticed my fuel meter dropping faster then usual. By filling up my gas tank and using the trip meter and a calculator on my phone I noticed my fuel economy has been suffering from 35.3 to 31.5 and being forced to keep driving home to work I am able to relate this to the oohm, hmm, oohm, hmm which is highly annoying and making me sad since noticing losing a tenner each tank feels like loosing on money worth spending to fix my problem.

But besides thenot appealing idea I had to change my fuel pump and I have three so I did this a couple of times, I expected to ridding being stuck in open loop since I believe this is what is going on, but of course it didn't.

So 'chaning' my air intake made it stall and changing my fuel pump or just after, it went to open loop. My car actually accelerates a tiny bit when it go's oohm and looses speed a tiny bit going hmm. There is no other hint or complaint that is telling me that is open loop besides the bad fuel economy but I'm confident my ecu is acting on something. My o2 has been replaced ten years ago for a NTK and it is exactly like the original besides a Nissan logo so I believe I have the original part. It has about 20k miles on it and it responds very well according to Datascan so I still assume it is not a broken lambda.

After reading several internet pages, one with a sales pitch to MAF repair kits but I lost the link, told me that a broken MAF (one that is still working but is broken, not just worn), can give trouble that looks like low fuel pressure, bad fuel pump, stalling engine and maybe something I forgot but I also did recognize it as a descriptive list of almost everything they could come up with but who knows.

The open loop description is a good read but with an open end, it also said it can be quite hard to diagnose without an engine trouble code and I again lost the web link. But now three things or strictly speaking four things are on my list, swapping MAF, replacing temperature sensor, swapping fpr (but some smartypants decided to put a screwdriver on that screw that is just below the metal fuel line on the fuel rail and that fpr didn't come off yet) and swapping lambda but I have no other lambda.

For the AAC and the power transistor, I learned you want original parts and for the coil, my coil had corrosion on that connector for the coil cable and sanding helped but by visiually and audiably checking spark I couldn't see a difference but that the little lightning was able to go down in a more straight line on the not sanded and not corroded connection and assume from that pint it is better to have a coil that is slightly out of spec (10.5 kOhm instead of 10 kOhm) and for the AAC and power transistor I have pictures.

And here is the placeholder I mentioned before but that was a while ago.

I found a non original power transistor and I confirmed by having only one original power transistor the spark is more audible and and blue. That aftermarket power transistor just isn't good enough to compete with a given power transistor that is original.


The right one has a marking that isn't meaningful to me and I couldn't find the manufacturer of it and the left one is a original.

For the AAC, wow that was a good one. The right AAC is definately non original and for ten years I drove around like, hmm, it drives great but engine is a bit raw and vibrating to my taste. The left AAC is definately original and besides being in open loop which is audible it can be out of open loop at times (not visible on my fuel meter dropping a bit too fast) and my engine purrs like a kitty. The difference is this big that I started to being annoyed about tyre noise and the stiffer then stiff setting of my coilovers. Maybe hard to imagine but it really is this big this difference.


Such AAC part on the right you just can't tell who made it, just like the power transistor.

For completeness here is a picture of the correct AAC, that part is important man.


I'm completely lost about the cold engine stalling and the open loop and or bad fuel economy, it makes me sad. Just because I am aware that changing the termperature senor for a new one is a good step just like changing MAF.

I'm aware this was a long post.

In short, aftermarket power transistors or AAC valves just don't work well enough to compete with original 150k miles or over Nissan parts.

Investigating thermal sensor for coolant and switching MAF for unknown MAF but I have three for stalling.

Thinking about this, I expect the stalling and the open loop modus metuens are seperate problems. One thing is that the dartyness is ten years old. What to expect.

Will post my questions in another tread. Just be sure your iginition is original or good and that the AAC is original or good, driving a SR20 like a new car is achievable!