Thread: '91 SE-R - Engine Wants To Take Off

Some good things sorted out thus far. It isn't an intake leak, as I can "choke the engine out" by blocking the throttle body. Fixed a connection at the ECU that got the tachometer working (the car is indeed sitting at just below 5000RPM) and ensured everything is solidly connected. Learned the code for the LED-flashing and through some trail-and-error, have ended up with just one code at this time. Slow/slow/slow/pause/fast-fast-fast = "33 - Heated Oxygen Sensor". The o2 sensor condition indicates it is definitely running rich.

However, another interesting note is that while I was choking the throttle body with a rag, the intake hose and MAF were not attached to the throttle body, they were just sitting in the engine bay. So even though the MAF wasn't "part" of the intake system, the car still floors itself. It seems likely that the MAF may be defective after all, but still within "proper" parameters so it isn't throwing a code. Anybody have an opinion on that? Should I be looking at the MAF or the oxygen sensor first?

It's not the o2 sensor. The car will start, idle, and even run fine without the o2 sensor hooked up. In fact, it takes the o2 sensor some time to warm up before it even starts sending a signal to the ecu (hence the term, 'heated o2 sensor').

I'll caution you to not choke the engine with a rag, if it gets sucked into the engine, you won't be a happy camper. Just use the palm of your hand next time.

Check the maf signal voltage with the key on, engine off. Then blow air through the maf, and you should see the voltage increase.

C

Thanks, you are absolutely right in regards to the rag issue. I only chose to it this time since I know the throttle plate is staying closed. I did it in lieu of my hand since I want someone to be at the key and I'm currently working solo.

I assume I need to set up a way to backprobe the connector for the MAF sensor since I need to test for voltage with it connected? I will start researching information now.

Have you checked or tried blocking off the Auxilary Air Regulator? It's under the intake manifold, towards the passenger side.


Auxilary Air Regulator for the SR20 motors. This is the piece on the underside of the intake manifold.

C

I have not tried anything with that unit as of yet. I will check it out, I just need to know where on the unit I should be blocking it.

If the hoses are still flexible enough, you can pinch them off. If not, you could remove the assembly, and cap the ports on the engine.

C

I just remembered that one of the hoses on that unit was "beyond repair" so I replaced it. It is the one that goes from the intake manifold to what is the "black side" in the above picture. I looked underneath and noticed that even with the clamps on, my new one does not quite seat properly - the opening is very slightly too large. I am going to go replace that hose with a better fitting one right now.

I pinched off the hose with vise-grips, the one that goes from the intake manifold to that AAR unit and it dropped the RPM from a smooth 5000 to a slightly-hesitating 4000rpm. Not too sure what to make of that.

Edit: I removed the entire unit and pinched off both hoses and it didn't make a difference. I'd like to figure out how to test the voltage the MAF sensor is getting, but that involves it being plugged in and I'm not sure if it is safe to backprobe the connector.

I installed a new MAF since the price was reasonable, and I wanted to rule out the component itself as a cause. Still no change. Checked the voltage at the MAF sensor and the reading is matching what is considered normal in the service manual (under 1V key on, engine off).

The only thing I have found that has made any change at all was pinching off the hose at the auxiliary air control valve, which reduced a smooth 5000RPM to a hesitant 4000RPM. Any idea where I should be looking next?

If you have access to an air compressor, pressure test the intake tract/intake manifold etc.

C