Thread: 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.

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...

I've made a little progress.

Swapped parts
Fuel pump
TPS
Power Transistor
Coil

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.

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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?

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)?

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.

What part on a Sr20 makes the actually engine speed rise? Datascan sees my powersteering switch but idle lowers about 25 rpm. Please?

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).

After reading EF & EC fsm page by page, reading my topics on this forum and this great link of The Manifesto, I'm only able to suspect my CAS.

This is because I have swapped, fuel pump, coil, TPS, AAC stepper motor, FICD solenoid, Air regulator bi metal thing on the underside of the block.

I did also swap power transistor and here is a placeholder for a nice story with pictures on how bad a power transistor can be, so I swapped this one back. The AAC can also be bad I learned.

My FICD wiring is messed up by the former owner with excessive force but the swapped FICD clicks fiercly or not by connector fiddling. My sputtering is a lot easier to control by foot but very low rpm, below rpm when cold which is 1350, is still crap.

Of course my timing light went out because of storing it for a couple of years and the new ebay timing light is under its way so I will swap CAS or the whole ignition housing.

My fuel pressure and fuel rail has not been swapped because of time constraint and weather considerations as a street mechanic and I will swap the iginition thing you can move to advance or retard timing. Honestly this should do the trick I believe but if there are more options please tell me.

After swapping the CAS I'll rewrite my initial topic question.

And my plan went to the gutter.

I broke off one of my igintion housing bolts. I'm evaluating my options right now and one of them is to swap anyway. Would that be unwise to do?

After three fuel pump swaps I found out that the new fuel pump aftermarket is a crappy version and made rust-egg run well and quite lean I suppose since my Nx with lambda (rust-egg has no lambda), stuck in open loop which gave bad fuel economy.

I have a fuel pump that most probably won't send my ecu to open loop mode but I haven't confirmed. This is because this fuel pump gives a hard to stay at cruise speed issue. Now I use a fuel pump that is original but has been sitting dry for eight years the least. It gives no noise, started working right away and while I believe I can tell just below 60 mph it is not in open loop but just above it I still can hear it a bit being in open loop but after running one tank of gas I will be able to tell if this pump gives similar fuel economy to what I used to. My question is that the way it should go? I have been told dry fuel pumps go bad. This one has been running for a hundred miles or so. Is it unwise to stay using this fuel pump for risk of loss of function?

I have a cold idle issue introduced before I acquired rust-egg and it was minor but annoying enough. Just before that, I accidentally dropped my custom air intake and it broke to four pieces. I was aware before dropping it had been leaking air in to the throttle chamber but this was before the MAF and the cracks where minor so I reasoned it was able to take some unfiltered air but again, before the MAF. After using a tube of super glue on it, I made sure all cracks are airtite and guess what, cold idle issue, stalls about three to five times when cold, depending on how cold it is and revving a bit makes sure it runs. What part is responsible for cold start airintake and that if it's bad, it makes my engine stall?

I'm sorry because I think my question isn't very clear but let me start with the usual suspects while having rust-egg around for parts swapping. I hope you can help me because this is beyond me already. I've marked my questions bold.

I wish I could help more but I never had fuel issues on my prior cars. But my new car has been giving me 23-24 MPG consistently, and the car feels under-powered and sluggish. It is all stock. I have changed the fuel injectors, fuel filter, O2 sensor, spark plugs, spark plug leads, new K&N air panel filter, changed the transmission fluid, new PCV, new FPR.... typical tune-up stuff and I still have the same results. If this thread progresses further, maybe I can learn more about why I am seeing this poor mileage pattern in my new-to-me vehicle.