SR20 wont rev over 2400

[SRSmith]

Good evening guys and gals,

Yeah, I know you're all thinking: Another thread like this! Use the search button! But please, just hold on a second. :)

As stated, my s13 SR wont rev above 2400 rpm or so. After warming up it can rev all the way up for short periods. Its also running rich. Also, the car seems to be quite warm in the engine bay, but the temp guage says everything is normal. The car idles fine and when it does rev up feels totally normal.

From my resaerch this usually points to the MAF. So I bought a new one but the problem still persists. I had a similar problem with my foxbody and it turned out to be a vacuum leak. I pretty sure this isn't the case here as I dont have the usually whirring sound. Also, once the engine warms up the car can rev all the way up for short periods of time. I don't think its a CAT issue as the car doesn't have one :O

Do you guys have any suggestions? I spent a good chunk of time looking for solutions but I can't find an instance like mine.
Thanks in advance

[nisileighty]

CAS timing or coolant temp sensor


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[SRSmith]

Wow, thanks for the speedy reply.

Both of those would explain the heat and the rich air/fuel ratio.

Would they explain the rev limit? The car runs just fine till it hits 2400 rpm. When it does hit 2400, it drops sharply down like its controlled electronically.

Thanks

[Kingtal0n]

Any nissan engine I think made around 90's will limit RPM to 2500~ when the maf is disconnected.

This is the only thing that causes this condition.

It means the ecu is in limp home mode. So you can limp the car home... and get the maf working....

[SRSmith]

Yes, I have the car at home.
I got a new MAF but the problem still persists.
Does the ECU have to relearn the new sensor? Or do I have a wiring issue?

Thanks

[z31andrew]

What do you mean the engine can "rev all the way up for short periods of time" ? Do you mean it revs to 2500 for short periods of time or past that? You say it's running rich, how rich? Is your Fuel pressure regulator working properly?

CAS timing could be off, check that. Also make sure all wires going to the MAF and CAS are in good shape. Have you checked your o2 sensor is operating properly? What ECU are you running? Where is you air filter located in regards to the MAF? Lots of things to check here man

[SRSmith]

Yes, sometimes when the engine reaches operational temperature it will rev all the way to redline for short periods of time.

[SRSmith]

Heres what it sounds like:
https://drive.google.com/file/d/1YNs9BWIMeSb9CaK3gj4aYoTasbIjMhR-/view?usp=drivesdk

Im checking the cas timing right now.
All the wires look good. The plugs are soaked on oil. The air filter is attached to the MAF. Stock ecu.

Thanks for the help.

[z31andrew]

Your drive is private, i can not view it without permission.

Plugs soaked in oil calls for bad rings, recommend you do a compression test if that is the case.

[SRSmith]

Made it Public.
Wierd, I pulles the plugs and now they're bone dry.

[SRSmith]

Alright, I checked the timing and everything looked great. I made the mistake of removing the CAS sensor and now its idling a bit high. I know I need to fix that, but I don't think that the CAS sensor was the problem.

Next I figured out how to pull codes from the ecu. I'm getting codes 11 and 12, CAS and MAF respectively. Im willing to bet that 11 was just caused by my messing with the CAS sensor. Im pretty sure the problem is with the MAF, but as a new one didn't fix the problem Im thinking if might be wiring related.

What do you guys think? What perplexes me is why I was suddenly able to rev to redline when the car was warmed up. One of those times I took it for I drive and the engine ran perfectly.

Is there a way to test the MAF wiring? I dont have a multimeter but I could get one and learn how to use it. Or do you think I should turn my attention to something else besided the MAF sensor and wiring?

Thanks again

[Kingtal0n]

2500rpm limit is maf

If it sometimes does and sometimes does not

its ECU/Wiring most likely

simply replace the wiring and or computer.
Wiring is 3 wires for stock maf sensor.
There is a fourth "wire" called shielding which grounds at the computer,
because this wire is a ground and because it cover the signal wire "like a sheath"
It is very common for the wire to become cut and the ground to touch the signal intermittently

My approach for most cars would be:
1. goto junkyard and pull some shielded wire out of a common foreign cars like Toyota etc... (I keep a bag of them handy nowadays) inspect them thoroughly
2. install new shielded wiring for maf (or other sensors)
3. change plug for sensor or verify the plug is good somehow

Only thing left after that is computer

finally CAS control timing and needs to be set with a timing light
you cant just stick it back in and hope its close
even just 3 or 4 degrees off can be disaster, will run awful or knock or both

[SRSmith]

Thank you very much for the detailed reply KingtalOn.

Ill try it out and get back to you guys. When I find a solutuon I'll post it so those with similar problems in the future can find it.

Thanks again

[SRSmith]

Here's the results:
There are three wires running to the MAF. The black (ground) and White (signal) run to the ECU. The third wire is black and white and is the power wire. I was getting power, so I only redid the two wires to the ECU. It turns out that it was the signal wire that was at fault.

Runs like a charm now!
Thanks to everyone for the speedy help.