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QG16DE Idle Problems + IACV Location?

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Kevinzz
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Joined: June 24th, 2020, 9:47 pm

QG16DE Idle Problems + IACV Location?

Postby Kevinzz » June 24th, 2020, 11:19 pm

What's up tuners, first timer here on the forums and loving the community so far. I'm having an issue with my Singapore Almera and hoping at least one of you guys can help me out. Engine is a QG16DE (automatic) and is E-Throttle. Car has been going strong for 9+ years with regular maintenance.

The problem I'm getting is a sudden and consistent drop in rpm (rpms drop for a split second then rise back up) when the engine is at 1500rpm or less (idling). Any higher rpm and the problem is not there or at least not noticable. Note this only happens after the engine has warmed up for more than 1-2 minutes. It feels similar to the sputtering and jerking up a bad coil pack would cause but it isn't the packs. Tested with 2 sets of confirmed working coil packs and the problem was still there. Where the problem really shines is when I put it in gear. The car immediately drops the idle, which is normal. But the idle randomly dips below the regular rpm causing the car to rock back and forth as though I now learning to drive a manual. As a result, when I stop at a red light, if I don't put it in neutral, it eventually stalls.

Today I cleaned the throttle body and mass airflow sensor thoroughly using CRC products MAF sensor cleaner and throttle body and air intake cleaner. Both worked great and throttle body come out looking fresh. However all of this was in vein as upon putting it all back together an giving it a start, the problem persisted.

At this point I called two of my mechanics and after explaining all of the above, they both told me it could be a dirty Idle Air Control Valve (or failed one). The problem is, they told me that for my engine, the IACV is built-in to the throttle body (which I find hard to believe).

That's why I turned to you guys. Does anyone out there know about the location of the IACV on a QG16DE E-Throttle? Likewise have you experienced the same problem with this engine? I tried looking all around the intake manifold, throttle body and EGR valve but couldn't find a single thing. So this leaves me wondering.. Is it really built in to the throttle body and does that mean I need to replace the entire throttle body? Any help would be greatly appreciated!!!

P.S. thanks for taking the time to read this mess of a post

Sundar
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Re: QG16DE Idle Problems + IACV Location?

Postby Sundar » June 26th, 2020, 12:16 pm

hey dude, before you proceed, check the Air Flow Sensor Harness/Jack for a short. my cousin had a similar issue and it turned out to be that.

kbhajan868
Riding on 13's
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Joined: January 25th, 2021, 2:49 pm

Re: QG16DE Idle Problems + IACV Location?

Postby kbhajan868 » January 25th, 2021, 2:51 pm

Hey man, just started getting the same issue with my Singapore model. Did you find the issue? I've heard its the Intake air control valve but I'm not sure.

make meh care
Trinituner Peong
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Re: QG16DE Idle Problems + IACV Location?

Postby make meh care » February 11th, 2021, 12:42 pm

the iacv is the throttle body . the ecu controls the butterfly valve on the throttle to adjust the idle.

GreenMilitant784
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Re: QG16DE Idle Problems + IACV Location?

Postby GreenMilitant784 » April 2nd, 2021, 8:41 am

Any luck? Having the same issue

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Kevinzz
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Re: QG16DE Idle Problems + IACV Location?

Postby Kevinzz » May 8th, 2021, 3:41 am

Good day 2ners, sorry I know this post overdue for an update and a few people have sent me DMs concerning my solution. Apologies for the delay and well long story short, I ended up doing a Singapore to Japanese conversion on the engine side.

I did this because my ECU ended up frying itself along with some Chinese coil packs I unfortunately got roped into buying.. The cause of the problem is still unknown but the two strongest possibilities may have been either the Chinese coil packs, or a bad ECU ground connection.

Since the QG 15,16 and 18 family of engines are nearly identical with only minor differences like throttle body (cable type/E-throttle), bore/stroke and displacement, it makes sense that the ECU's would also be pretty much the same. And for the most part that's true (slightly different fuel and compression ratios). However, you also need to look at the wiring harness and it's pins/jacks when looking to do a conversion.

There are certain pins that require inputs from speed sensors and other auxiliaries like the tranny ECU. My auto electrician was well versed in these conversions so it didn't take long for him to finish the conversion. But we did have some trouble sourcing the right ECU and harness. An important thing to pay attention to is the previous engine the ECU and harness comes off of. If you have an E-throttle engine, a Cable-Type ECU WON'T work and vice versa (don't ask me how I know this). All in all, consult with your auto electrician on what to look for if you plan on searching yourself. Or, drag him along with you to help you look hahah. Either way, you don't want to buy the wrong parts and cause yourself a headache.

Currently, I'm running an ECU and harness that came off of a 4wd Japanese Almera (Bluebird Sylphy QNG10). It's been over 6 months now with it and there have been zero issues (The Code on the ECU is YU for those wondering). I also haven't noticed any changes in fuel economy but the engine does idle a bit lower than it used to when up to temp (not by much and it makes the car almost silent from 15ft away). As for HP? I'm not convinced it went up but with that being said, the car certain became much more snappy on acceleration. Maybe it's a placebo effect?

So to recap this mess of a post, I ended up doing a Singapore to Japanese conversion because the price some places call for the V3 ECU alone is a joke and to import it would be just as costly, remember to do your research or ask your auto electrician about the pins and jacks you need to look for on the new harness, and lastly, this conversion was done to avoid any headaches related to Singapore ECUs in the future. The Japanese versions are more widely available and way more budget friendly.

Also, feel free to correct anything I may have gotten wrong. I'm not a professional when it comes to cars, just sharing what I learnt!

Hope this at least helps a person or two!!

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