EGR delete question...

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Ninja
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Joined: Tue Apr 23, 2019 5:56 am
Location: Tribune, Kansas
Isuzu vehicle(s): ‘86 Isuzu Pup w/ 1.9L g200

EGR delete question...

Postby Ninja » Wed May 29, 2019 5:55 am

My secondary throttle plate I believe? Is stuck open on the carburetor and I think its because I don’t have the EGR system hooked up... but I’m not sure. Can someone shine some light on this please? :?:

oldestisuzuist
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Location: N W Arkansas

Re: EGR delete question...

Postby oldestisuzuist » Wed May 29, 2019 7:34 am

EGR enters the intake plenum below the carb so I don't see how it could stick a throttle plate. Probably it's just in a bind, see if you can force it free, then clean all linkages & moving parts well with carb cleaner, lube lightly with something like WD-40. The carb secondary is vacuum operated, it won't open until the engine revs enough to produce the required vacuum to activate.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.

Ninja
Regular Member
Posts: 7
Joined: Tue Apr 23, 2019 5:56 am
Location: Tribune, Kansas
Isuzu vehicle(s): ‘86 Isuzu Pup w/ 1.9L g200

Re: EGR delete question...

Postby Ninja » Wed May 29, 2019 7:45 pm

That’s the thing. The vacuum from my understanding is the egr pipe going underneath the carb. The egr pipe is chopped off because I put a pacesetter header on and there was no place to put the factory egr pipe. I was reading in my Haynes manual and it says that the secondary opens once the egr has reached a certain temp. But if it’s not even connected it won’t reach any readable temperature. Also, the secondary throttle plate is not stuck or in a bind from what I can tell. It moves freely, but it shouldn’t...

oldestisuzuist
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Location: N W Arkansas

Re: EGR delete question...

Postby oldestisuzuist » Wed May 29, 2019 10:02 pm

The EGR does not supply vacuum, it consumes it: the exhaust gasses are pulled through the tube by the vacuum created by the pistons, the same vacuum that operates the distributor vacuum advance & carb secondary & sucks air/fuel into the cylinders. There are about three vacuum controlled emissions valves that control when & how much exhaust is drawn through the tube that also changes with temperature, but all this occurs below the carb. There is a vacuum controlled temperature dependent valve in the air cleaner snorkel that draws warm air off the exhaust manifold until engine temps reach a certain level. You may not have the warm air connector if you have a header. With the EGR inoperative you don't need any of the control valves that are part of the system, either disconnect or remove altogether, then cap each vacuum source at the intake. Same with the air injection rail & pump, it doesn't work correctly without the EGR functional.
All your engine needs to run is a vacuum to the distributor, PCV & fuel return charcoal cannister, and the air cleaner temp valve won't hurt. The rest is emissions, & you've deleted at least a part of that.
The carb secondary throttle plate is closed by a spring & held by a tab on the throttle linkage until the throttle is opened far enough to unlock the tab, then when engine vacuum is high enough & as more throttle is applied the vacuum will open the throttle plate & suck the secondary air/fuel mixture into the engine.
'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, body ROUGH, bought new 12/4/78. A pre-P'up?
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch.

Ninja
Regular Member
Posts: 7
Joined: Tue Apr 23, 2019 5:56 am
Location: Tribune, Kansas
Isuzu vehicle(s): ‘86 Isuzu Pup w/ 1.9L g200

Re: EGR delete question...

Postby Ninja » Thu May 30, 2019 9:40 pm

The secondary is completely open all the time. There is nothing holding it up or opening it when I give it throttle. It honestly doesn’t seem to be affecting the performance of the truck but It just caught me off guard when I seafoamed the head and seen the secondary just sitting wide open. I really appreciate your great information oldestisuzuist! You definitely know your way around this motor better than I do.
I think I’m just going to take a closer look at it and come back with more of an understanding with what you just told me. Thanks

JLEMOND
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Re: EGR delete question...

Postby JLEMOND » Thu Jun 06, 2019 9:35 am

Ninja wrote:The secondary is completely open all the time. There is nothing holding it up or opening it when I give it throttle. It honestly doesn’t seem to be affecting the performance of the truck but It just caught me off guard when I seafoamed the head and seen the secondary just sitting wide open. I really appreciate your great information oldestisuzuist! You definitely know your way around this motor better than I do.
I think I’m just going to take a closer look at it and come back with more of an understanding with what you just told me. Thanks


ARE YOU SURE THAT YOU ARE LOOKING AT THE SEC THROTTLE P[LATE , IT IS IN THE BOTTOM OF THE CARB AND WORKS WITH A LOSS OF MANIFOLD VACC , AS YOU STEP ON THE THROTTLE AND THE ENG SPEEDS UP LOSS OF MANIFOLD VAC WILL CAUSE THE SEC PLATE TO OPEN DEPENDING ON LOSS OF VACC . IF THE SEC THROTTLE WAS STUCK FULL OPEN THE ENG IS VERY DOUBTFUL IT WOULD EVEN RUN, I THINK THE PLATE YOU ARE LOOKING IN THE TOP OF YOUR CARB IS THE ELECTRIC CHOKE PLATE AND IT IS MOST LIKELY WORKING , SINCE IT IS STANDING STRAIGHT UP, IT IS IOPENED BY AN ELECTRIC COIL IN THE CHOKE CAP.