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Thread: Good circumstances but what path to take to rid nervousness from a sr20 while having another running one that isn't nervous.

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2019-10-02 15:49:32
Good circumstances but what path to take to rid nervousness from a sr20 while having another running one that isn't nervous.
Finding some good answers I can work with for this question is important to me. A good while ago I posted about this but I know I wasn't very clear. I also didn't have another Nx2000 donor car that runs proper as a daily driver.

So this description is my main Nx2000, I bought it nine years ago and this problem was there already. The car is nervous when cold and I ask for daily traffic acceleration.

It also happens when the engine is warm, I ask for daily traffic power and it acts nervous, like three or four times and it is good again.

It sure does happen in rpms just above 1000 and below 1500. I just used Datascan and put my car after warming, in timing mode. Only there is nothing to adjust, nice 850 rpm, proper ignition timing.

From all the knowledge and understanding I have for sensors on a sr20, I can't think of anything I should check. Please tell my how you would diagnose my problem and I'll follow up. There is a running donor car that absolutely does not have this nervousness. I would like to learn what steps to take and swap out parts to transfer the nervousness to rust-egg before I sell it.
2019-10-04 07:53:02
It sounds like you mean the engine is sputtering and not providing smooth power delivery between 1,000 - 1,500 RPM. (Nervousness in English typically describes darty behavior in steering and handling.)

If this were high RPM, I'd say maybe a clogged fuel filter, or misbehaving fuel pressure regulator. Possibly some other things...

Low RPM stuttering though could be the oxygen sensor failing, but almost everything is going to be suspect at this point. The MAF maybe, the ignition components, the fueling components, the ECU...

Again, I think you should start by confirming proper firing order and strong spark. Stop fuel to the engine by pulling the fuel pump fuse and crank it will all plugs out of the engine (but grounded) and record with video to see proper firing order and strong spark on all while you crank the engine.

Then do the same thing for the fuel injectors. Reinstall the fuel pump fuse (but keep the spark plugs out so the engine turns over easily) and crank the engine while the fuel rail is removed from the intake manifold with injectors still installed. Watch for proper firing order and high quality spray pattern from each injector. Use rags to contain the fuel.

If both of those check out, you should suspect the oxygen sensor, MAF, and ECU next (in that order).

Who knows? It could be the EGR system acting up? Maybe a bad cam angle sensor somehow? It's tough without more info...
2019-10-13 15:40:05
I've made a little progress.

Swapped parts
Fuel pump
Power Transistor

Fuel pump, a lot easier to maintain cruise speed
TPS, my old TPS always raised 0,06 volts before closed TPS signal went to open
Power Transistor, nothing noticeable but also no means of testing
Coil, old one had 10,5 kOhm secondary and the one I put in was just at 10kOhm and that is the specification

For the FPR, one screw was already messed with and of course the one just below the fuel line. I've ordered some tools but closest pickup date next saturday.

I considered swapping the whole fuel rail but time and weather wouldn't allow that yet. I'm aiming to change the injectors since the fuel rail from rust-egg looks bad

Distributor and cap, below 30k miles. Orginal rotor. Hitachi cap.

I did not check the spark plugs, those are indexed. I do have strong spark.


But here is a problem description I'm hoping I will get answers for

When I drive around with Datascan I can tell when TPS closed signal is red (closed), the car sputters about three times. It does this in low rpm range. What should I consider checking?
2019-10-14 01:55:45
Originally Posted by richardwbb

When I drive around with Datascan I can tell when TPS closed signal is red (closed), the car sputters about three times. It does this in low rpm range. What should I consider checking?

When the TPS is closed, your engine will rely on the three parallel idle systems.
-The idle stepper motor (IACV)
-The idle bleed-by screw
-The air assist solenoid (forgot the name, it's for sudden events such as sudden power steering at idle)

I'd start by checking all these.
Remove the IACV and clean it out. Check that resistance is according to spec. Also check that it's being actuated, I had one ECU with a burnt out idle PWM channel! Check with it connected and off the car that it moves once the engine is started. You will need to block off the hole in the manifold while checking this, otherwise it will over-rev

The idle bleed screw is most likely OK, seeing that you get 850rpm when setting timing.

The air-assist solenoid could also be faulty, but easy to check. With the car ON, does the RPMs rise when you suddenly turn the steering wheel (or start the AC)?
2019-10-20 13:53:25
I have swapped the AAC and FICD, which gives a smoother ride. Besides I learned about good and bad parts and have some nice pictures made, rust-egg now sputters and my Nx benefits from being able to maintain speed because of the fuel pump and engine sounds a lot smoother warming up and driving it just sounds like new.

I have a hard time explaining what is going on now but rust-egg has inherited a lot of sputtering and my Nx lost most of it.

Still my Nx sputters three times now and this is very recognizable and then when I ask for very low throttle, the problem is a lot smaller but it is still there. It is just so it is annoying but no longer everything is shaking so I'd say a 90% successful AAC plus FICD swap.

But the problem isn't gone yet. I imagine I should swap the air regulator on the underside of the engine block but I'm lost at rising engine rpm when I use my power steering.

It still won't rise idle and Datascan shows a working power steering switch. Also all other loads make my engine lower rpm, just for 25 rpm or so but it is noticable and visible within Datascan.

This means my FICD is bad right? Both FICD show this problem which rust-egg doesn't have.

I believe I miss something. Is it correct FICD is responsible for rising engine rpm? If not, what parts should make my engine rpm rise under load? It is doing the opposite.
2019-10-21 17:02:42
What part on a Sr20 makes the actually engine speed rise? Datascan sees my powersteering switch but idle lowers about 25 rpm. Please?
2019-10-22 09:11:50
From The Manifesto:
The ins and outs of the stock idle control system.

The IACV/FIDC is responsible for maintaining idle when the power steering pump is under high load (or when the A/C is turned on).
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