usapadyra
Active Member
- Joined
- November 23, 2022
- Messages
- 80
- Reaction score
- 57
- City, State
- Ukiah, CA
- Year, Model & Trim Level
- 98 Ex XLT 4.0 SOHC 2WD
1998 Explorer 4.0 SOHC RWD
Back in Jan 2022, while trying to figure out a lean condition, I bought a Duralast IAC and noticed straight away that the engine started flaring up quite high on startup.
At the time I didn't think much of it, wrongly assuming that the new part was doing something correctly that the old part wasn't, when in actuality I can now say with some certainty that the old part (OEM) was not faulty at all.
This winter I'm up in Tahoe, and the cold start flare was particularly bad and sustained. Perhaps it's the greater density of the frigid air? It even flares to 2k when restarted hot, even if only 5 mins have passed. I do the 'poor man's pre-oil' (WOT to crank and release after a few seconds) so I'm not super worried about the engine spinning so fast straight away. That said, I didn't love how it started aggresively in the morning when the oil is so thick from overnight temps well below freezing.
I did some reading and decided to try and find an OEM (Hitachi) brand IAC. This is supposed to use a proper solonoid, and not a stepper motor.
When I got the part I compared it to the Duralast one and found something very interesting. Check out the pictures attached.
Between the OEM and Duralast IACs, there is a huge difference in the 'resting' position of the valve. The Duralast valve is open much further and would thus allow for much more air to flow through. I don't know for sure if the valve sits in this exact position when the engine is first started, or whether the ECM in fact closes it upon engaging ignition. But based on my experience I would have to say this was the cause of my high startup flare.
Maybe it's an out of box failure, but I don't think so. A few months ago I bought another Duralast IAC and swapped it out to see if it had any effect. It didn't - same high startup flare (returned it after a couple of days).
The Hitachi one gives me a super soft startup now. It's great. On a cold start it reaches maybe 1200 / 1300. Warm restarts barely go above 1k. Throttle feels more responsive as well. If I blip the throttle from the engine bay, I get a quick kind of 'chirp' as the IAC instantly closes, then the RPMs settle quickly after letting go. Before they would kind of hang and gradually come down.
The part was hard to find. I got it from autoplicity:
autoplicity.com
$100 but worth it, imo. Maybe this is the cause of the lean CEL, since I've done almost everything else. After all, I could drive 500 miles on a hot engine and not get a code. But multiple cold starts would quickly bring it back. We'll see. Even if there's still an air leak somewhere (likely) I'm sure this part will help.
Back in Jan 2022, while trying to figure out a lean condition, I bought a Duralast IAC and noticed straight away that the engine started flaring up quite high on startup.
At the time I didn't think much of it, wrongly assuming that the new part was doing something correctly that the old part wasn't, when in actuality I can now say with some certainty that the old part (OEM) was not faulty at all.
This winter I'm up in Tahoe, and the cold start flare was particularly bad and sustained. Perhaps it's the greater density of the frigid air? It even flares to 2k when restarted hot, even if only 5 mins have passed. I do the 'poor man's pre-oil' (WOT to crank and release after a few seconds) so I'm not super worried about the engine spinning so fast straight away. That said, I didn't love how it started aggresively in the morning when the oil is so thick from overnight temps well below freezing.
I did some reading and decided to try and find an OEM (Hitachi) brand IAC. This is supposed to use a proper solonoid, and not a stepper motor.
When I got the part I compared it to the Duralast one and found something very interesting. Check out the pictures attached.
Between the OEM and Duralast IACs, there is a huge difference in the 'resting' position of the valve. The Duralast valve is open much further and would thus allow for much more air to flow through. I don't know for sure if the valve sits in this exact position when the engine is first started, or whether the ECM in fact closes it upon engaging ignition. But based on my experience I would have to say this was the cause of my high startup flare.
Maybe it's an out of box failure, but I don't think so. A few months ago I bought another Duralast IAC and swapped it out to see if it had any effect. It didn't - same high startup flare (returned it after a couple of days).
The Hitachi one gives me a super soft startup now. It's great. On a cold start it reaches maybe 1200 / 1300. Warm restarts barely go above 1k. Throttle feels more responsive as well. If I blip the throttle from the engine bay, I get a quick kind of 'chirp' as the IAC instantly closes, then the RPMs settle quickly after letting go. Before they would kind of hang and gradually come down.
The part was hard to find. I got it from autoplicity:
Hitachi Auto Products ABV0052 HITACHI Air Bypass Valve
HITACHI ABV0052 Air Bypass Valv
autoplicity.com
$100 but worth it, imo. Maybe this is the cause of the lean CEL, since I've done almost everything else. After all, I could drive 500 miles on a hot engine and not get a code. But multiple cold starts would quickly bring it back. We'll see. Even if there's still an air leak somewhere (likely) I'm sure this part will help.
