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Hi guys,

Changed battery in mums 03' Auto Nissan Pulsar (N16, QG18DE) sedan. After that, engine ran rough, low idle (600rpm +/-), and often would stall on startup (had to apply a bit of accelerator to not stall). When accelerating/decelerating (in park/neutral), RPM would go up as usually, but then drop right down to almost stall, then settle at low rpm.

Tried my OBD II scanner, but as it turns out, it's Nissan Consult (with an OBD port), so that was no luck.


A bit of Google I found it's very likely when battery disconnected, it wiped settings in the ECU, so now it would need to re-learn how to idle correctly. After driving for a few days, nothing changed. Found some learning procedures online, but not 100% sure if it's for this Nissan N16, as the re-learning section mentions "Disconnect Throttle Position Sensor (brown in colour) connector.", which the car doesn't have, only a single Green connector.

This is what the TB looks like and a procedure I tried (youtube search W1bsUedze5M) . Unfortunately doing that, the car went into some sort of limp mode, where accelerating did very very little to the RPM

A couple of people suggested cleaning the throttle body, as that can impact the idle speed. Upon inspection, I found the throttle body was filthy, so I got some throttle body cleaner and tried cleaning. Unfortunately it was in an awkward position, and the TB was pretty dirty, I removed the TB to clean it better. During so, I did remove the butterfly valve (not sure if that's OK or not), and cleaned the edge of it. Then reinstalled everything.
Gasket, thin metal sheet, looked physically fine, and many people just said to reuse if it's clean and not damaged.





Q: Is removing the butterfly valve to clean a bad idea? It has 2x screws so I figured it would just screw back into place, rather than being installed within a specific specification ? Would it be worth loosing the screws, wiggling the valve to try reseat, then tightening again ?

The Idle Air Control Valve was rivited to the TB (see youtube above link for pic), so I couldn't remove that to clean. Unless I drill out the rivets > clean > apply new rivets, but didn't want to risk it.

Once I had it all back together, I started the car and it start good, no low idle. The RPM did go up to 1k +/-, but slowly came back down and settled at about 800rpm (within spec). Let it idle for few minutes and though all was good. Started car again, just to make sure, but the RPM shot up to 1.5k rpm, then settled around 1.3k rpm. Couldn't get it to change. Tried the re-learning procedures mentioned above, no change.
Why would it start OK afterwards, idling at 800rpm, then mess up again when trying to restart?

Mum drove it to work, and said it kept feeling like you put your foot on the brake for a little bit then taking it off. When she got home, she said it wasn't running well, and thought it might break down.

I ended up disconnected the battery for several minutes, then starting, now it seems to idle around 1150rpm.

I tried checking for vac leaks by 1st using some gas from butane can, and moving it around the hoses, and where the TB bolts to. But not change in RPM. I tried using some TB cleaner on the hoses, and where the hoses connect to (but more dangerous, I know), but still couldn't hear any change in RPM. Can't really hear any hissing noises that might indicate a vac leak either.
I'm tempted to buy a little fog/smoke machine, and pump it through the air intake to see if anything comes out :/

Someone suggested running some Subaru upper engine cleaner, not sure what that would do though ?

I've been trying to find a Consult cable to maybe help diagnose issues, and run a re-learn via Nissan data Scan (I think you can?), but nothing I can afford (yet). There's the ECUTalk cable, but their software won't do re-learning procedures apparently.

I have yet to contact various Nissan dealers, and independent mechanics on costs to re-learn via their Consult tool, but until then, can anyone think of anything else I can try? This has become a PITA.. all I wanted to do was change the battery :/

Sorry for the long post, wanted to put as much info as possible.

EDIT: I noticed the oil residue on the side of the TB where the gasket sits against. Should I apply some sort of oil to that side to maybe create a better seal? Just wondering if the oil had anything to do with sealing it or not.

Thanks in advance,
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