2.6 4ze1 idle (solved)

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2.6 4ze1 idle (solved)

Postby TroopDawg » Sat May 01, 2021 9:24 pm

The underlying idle seems to be fine...
No check engine light


If i squeeze the idle air control valve hose,, it smoothens out.

If i unplug the IDle air control blave, nothing changes.

No AC or high idle control valve... So thats not it.

Its timed on 12 degrees and has a strong throttle response.

Has anyone experienced idle like this? If so, why?

Btw, wich way does the fuel filter point? Would it cause this if the wrong way?

Fuel filter is new, fuel pressure regulator is new, new mass air flow sensor.

Throttle position sensor has to be adjusted but it drives and has a nice underlying idle...

https://youtube.com/shorts/CDZdj8LYCJ4?feature=share
Last edited by TroopDawg on Tue May 04, 2021 6:04 pm, edited 1 time in total.
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Re: 2.6 4ze1 idle

Postby TroopDawg » Sat May 01, 2021 10:27 pm

I got it to idle nice but its a little high at 1500.. it fully warmed up and it will only dtay happy at 0 degrees in the crank. If i set the timing to 12 devrees, the idle goes up and down
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Re: 2.6 4ze1 idle

Postby mudoilngears » Sun May 02, 2021 5:36 pm

Perhaps you would get more help if you keep one post updated on this issue. Currently you have at least three on this.
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Re: 2.6 4ze1 idle

Postby TroopDawg » Sun May 02, 2021 6:42 pm

Well as the rabbit hole goes deeper, the problem changes.. my bad.

The auxillary air valve has two wires... one yellow and the other is green. I onow for sure the green ine i a ground. Is the yellow one supposed to be ground as well? Wehn i hook my ohm meter uo to the yellow wire, it ohms out with ground, i traced it all the way to the blu plug under the dash! I goes from yellow to black with an orange stripe.

Is this a ground?

Where does the 12 volts com from for the Auxilary Ifle Valve to operate?
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Re: 2.6 4ze1 idle

Postby Ed Mc. » Sun May 02, 2021 7:34 pm

The Air Regulator valve is powered off the same circuit that feeds power to the fuel pump when the fuel pump relay is closed. So there is power to the little heater in the air reg. valve all the time when the key is "ON".

I attached a diagram which shows the wiring colors and connections. With the engine running, you should have 12VDC to ground at the yellow/green wire in the valve's connector plug.

Pretty basic, no timer, no input from ECM, no nothin', just a heater that warms the bi-metallic element in the valve, to make it move and shut off the extra "cold-start" air.

BTW the EGR solenoid is powered off the same circuit, and controlled by the ECM.

HTH........ed

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Re: 2.6 4ze1 idle

Postby TroopDawg » Sun May 02, 2021 7:44 pm

Awesom info! Thank you! Could a bad fuel relay mess with the aux air valve?

And is it normal to get an ohm/closed loop reading when i test between the two pins on the engine harness?

(green wire and yellow wire), with the battery disconnected?

Im just getting into diagrams because of this trooper lol, forgive me
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Re: 2.6 4ze1 idle

Postby TroopDawg » Sun May 02, 2021 9:24 pm

So the air aux valve gets a constant 12 volts just like the fuel pump?
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Re: 2.6 4ze1 idle

Postby TroopDawg » Sun May 02, 2021 10:50 pm

Well, i spliced the yellow wire into the black and yellow fuel pump wire.

Hope this goes well. Ill have it started tomoro. Hopefully.

If someone know weather or not this is doable before i do it... let me know lol
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Re: 2.6 4ze1 idle

Postby Ed Mc. » Sun May 02, 2021 10:57 pm

Well, that's what the diagram sez! If the fuel pump is powered-up, then there is supposed to be power available to the air valve and the EGR.

With the engine running, measure voltage across the terminals of the air regulator valve connector. If you don't get battery voltage there, something's wrong.

If the fuel pump relay were bad, where the fuel pump wouldn't run, you won't have power at the air reg. valve or the EGR.

If you do have power at the air reg valve connector, then either its heater is burnt out, or the thermostatic element is stuck/shot.

It certainly would be possible to bench-test the thing, just put power across its terminals. I don't expect it would be polarity-sensitive, either.

I found a section in the shop manual with resistance value for the heater element; supposed to be 38-42 ohms. So if you find the heater doesn't pass resistance checks, then it's shot. If the heater seems OK, then it's a mechanical issue with the "guts".

If you're going to start putting raw power to electrical devices, I'd recommend adding a 20-amp fuse inline to the testing rig. Unless you have a DC power supply with fused output, then you'd be OK.
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Re: 2.6 4ze1 idle

Postby TroopDawg » Sun May 02, 2021 11:08 pm

Ok then i should be good. I dont want to short anything out... but i keep remembering... thats what a heat element is. Pretty much a “controlled short” between hor and ground right?

My main concern is this...

If i test the engine side conmecror of the air refulator plug... is it supposed to ohm out? Mine does. And both side have a closed loop to ground.


Im mechanical... but electrical is a totally different ball game that i have serious respect for and i try to be as safe as i can while attempting things alone.

I seriously appreciate the help, and sorry to the mods for my duplicate post. My phone will mess with me sometimes.
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Re: 2.6 4ze1 idle

Postby TroopDawg » Sun May 02, 2021 11:13 pm

Oh and i did an ambient bench test on the regulator. I used a small torch from about a foot beneath it!! It closed in about 2 min. Ohmed out to 48. I havent tested it with voltage yet because polarity was my next question... but you answered that.


Also, the john 5tech mod is NOT cali sensor friendly. Everything goes haywire!! DO NOT mount the aux idle valve on the front of your intake plenum lol! The regulator is half reliant on ambient heat. Thats why it is crammed between the intake and block! Yes it has a heat element, but if that fails, at least you have block heat to close the valve. If you put it on the front of the plenum... it takes FOREVER to close, if not at all. This is do to the open air and circulation near the fan, as well as the intake being colder than usual in california due to all the emissions. The regulator needs all the heat it can get.

I plan to write up a “super post” about this body swapped p.o.s. and what ive learned once its running and well. I owe it to you guys lol
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Re: 2.6 4ze1 idle

Postby DSUZU » Mon May 03, 2021 6:10 am

Polarity doesn't matter. It is a resistance heater. The ECM has nothing to do with this receiving power. Dennis
1991 LS Trooper 2.8 V6 5 speed conversion (Sold)
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Previously owned: 1987 Trooper II LS, 1989 Trooper (parts only), 1994 Trooper 3.2 Auto, 1997 Rodeo 2.6 5 speed, 1993 shortbed pickup 2.3 (project - sold) 1992 Rodeo 4x4 LS (parts car, devoured by Spacecab needs) plus some 70 plus other non Isuzu vehicles over the years. 1994 Amigo devoured to provide head and EFI system.
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Re: 2.6 4ze1 idle

Postby TroopDawg » Mon May 03, 2021 11:14 am

I trust the diagram and you guys... im just confused on how its possible to send 12 volts to the regulator if both wires are ohming out to ground. The green wire is directly attached to ground on the intake, That makes sense... but the yellow wire also ohms out to ground somehow...

if i test between yellow and green, the loop is closed. If i test green to ground, the loop is closed. If i test yellow to ground, the loops is closed.

Is this normal?
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Re: 2.6 4ze1 idle

Postby TroopDawg » Mon May 03, 2021 1:06 pm

This is with the battery removed btw
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Re: 2.6 4ze1 idle

Postby Ed Mc. » Mon May 03, 2021 1:09 pm

TroopDawg wrote:I trust the diagram and you guys... im just confused on how its possible to send 12 volts to the regulator if both wires are ohming out to ground. The green wire is directly attached to ground on the intake, That makes sense... but the yellow wire also ohms out to ground somehow...

if i test between yellow and green, the loop is closed. If i test green to ground, the loop is closed. If i test yellow to ground, the loops is closed.

Is this normal?


You're measuring the resistance of the fuel pump to ground, since it's also in that circuit.
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Re: 2.6 4ze1 idle

Postby TroopDawg » Mon May 03, 2021 1:17 pm

Ahhhhhh, ok ok! So with the battery connected and the key in the ON position... the yellow and green wire leading to the regulator should be passing 12 volts. My pump runs strong(its new) so im sure the black and yellow wire are getting 12v. Since ive directly spliced the regulator wire into the pump wire... i should be good :thumbright:
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Re: 2.6 4ze1 idle

Postby islandscrub » Mon May 03, 2021 2:10 pm

If you squeeze shut the iac valve and it idles better, wouldn't that mean the IAC has a leak internally?
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Re: 2.6 4ze1 idle

Postby TroopDawg » Mon May 03, 2021 2:17 pm

That would be true if it WAS closing all the way. Im not even sure if it was getting power yet. Ill check when i get home today. I know for sure it wasnt getting enough ambient heat from the engine to work right. The connector was really greasy/gunked up as well. I cleaned that.

It idles better and lower when i clamp it, so it must be staying open from no power or no heat. Its not stuck, i bench tested it and it works fine, i still have to bench test it with 12 volts though. It ohms out ok as well so im guessing it is fine. Hiw do i leak test the valve?

Just cap one end and pull a vac on it?
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Re: 2.6 4ze1 idle

Postby islandscrub » Mon May 03, 2021 2:55 pm

Are the hoses leading to it in good shape?

Yeah, I'd let the valve heat up and suck/blow on something connected to it and see if air goes through.

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Re: 2.6 4ze1 idle

Postby TroopDawg » Mon May 03, 2021 3:27 pm

The hoses to it are brand new and clamped well. How often do these things leak? I picked ip some jb weld to wipe around the seem of the regulator. It is a pain to reach!!!

Luckily when i rebuilt the motor and intake, i removed it to relocate it somewhere else. So right now its out of the vehicle and easy to test. Im going to apply 12 volts to it when i get home and leak test it befor i jb weld it.

As for relocating the refulator... find a hot spot on the engine so it can soak uo heat and work properly. I believe this was at least 20% of my problem.
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Re: 2.6 4ze1 idle

Postby gwana66 » Mon May 03, 2021 4:20 pm

Just to answer your general electrical question - a resistive heater is just a coil of wire, as is any solenoid, or even a light bulb. It will always read continuity to ground on either side unless the coil has a break. There should be some resistance in the coil itself, usually less than 100 ohms on automotive circuits.
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Re: 2.6 4ze1 idle

Postby DSUZU » Mon May 03, 2021 4:22 pm

It doesn't need a hot spot on the engine. It has the internal heater that if the ignition is on, the heater is on. This same unit is / was used on other vehicles (including the Datsun 280Z and it wasn't bolted to a "hot spot". Based on that, when I did a "5-Tech" (similar) conversion on my Spacecab, I bolted mine to the firewall. It worked fine. Dennis
1991 LS Trooper 2.8 V6 5 speed conversion (Sold)
1989 LS Spacecab 2.6 5 speed 4x4 manual hubs, Rodeo torsion bars, extended shackles, 2" lift, K&N air filter (drop in), dump bed conversion, burgundy interior change, warn brush bar. Engine is bored .020 oversize and upgraded to 1994 pistons, head and EFI system.
Previously owned: 1987 Trooper II LS, 1989 Trooper (parts only), 1994 Trooper 3.2 Auto, 1997 Rodeo 2.6 5 speed, 1993 shortbed pickup 2.3 (project - sold) 1992 Rodeo 4x4 LS (parts car, devoured by Spacecab needs) plus some 70 plus other non Isuzu vehicles over the years. 1994 Amigo devoured to provide head and EFI system.
Heavily damaged by engine compartment fire while driving on March 24th 2018, condemned by insurance company and taken on March 30th 2018 :cry:.

https://forum.planetisuzoo.com/viewtopic.php?f=15&t=64060
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Re: 2.6 4ze1 idle

Postby TroopDawg » Mon May 03, 2021 4:48 pm

I plan to relocated mine to the firewall as well after i bench test it with voltage...
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Re: 2.6 4ze1 idle

Postby islandscrub » Tue May 04, 2021 12:11 am

TroopDawg wrote:I plan to relocated mine to the firewall as well after i bench test it with voltage...


Yup, blow into it and see if air passes through, then hook it up to 12v, wait a few mins, 10 I guess to be sure, then try blowing into it again, air shouldn't pass through.
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Re: 2.6 4ze1 idle

Postby giusedtobe » Tue May 04, 2021 6:52 am

TroopDawg wrote:I plan to relocated mine to the firewall as well after i bench test it with voltage...


I stuck mine on the right fender well.

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