Do I need to tune anything following a dual-snorkel upgrade?

[Oddball]

True2Chevy saw this post on cx28.com and suggested I post it here.

This past fall I upgraded the intake on my 86 LG4 (4bbl carb) from a single to dual snorkel element air cleaner. Almost immediately since swapping out cleaner assemblies (including all of the vaccuum lines), my "Check Engine" light would go on during highway speeds (70+ MPH) and go off during "city" or "bumper to bumper" traffic. It always came up code 44 (lean).

I had asked if there was any retuning you had to do as the engine and carb were getting more air. The popular concensus was the primitave computers would compensate. The lean most likely is a weak O2 sensor. Since they only run $20 I can probably put the car on ramps (let it cool) and replace it.

Other than a leak in the engine, do you think the lean condition at highway speeds only could be caused by anything else? Do you know if I need to tweak anything after upgrading the air intake?

Thanks.

[Ian]

I don't know what you mean by "leak in the engine". Yeah, the O2 sensor going bad might cause that. Or maybe your carb is a little lean, but because you never got enough air in there with the old single snorkel air cleaner assembly, it never set a code. just a thought.

[NJSPEEDER]

the L69 carbs from the cars equiped stock with teh dual snorkel are set up slightly richer. since it is still a computer controled qjet you can prolly adjsut it mechanically or get a proper chip burned and fix it.

later
tim

[9secfirebird]

this guy is a real clown

[Ian]

Originally Posted by 9secfirebird

this guy is a real clown

[Oddball]

Originally Posted by Ian

I don't know what you mean by "leak in the engine". Yeah, the O2 sensor going bad might cause that. Or maybe your carb is a little lean, but because you never got enough air in there with the old single snorkel air cleaner assembly, it never set a code. just a thought.

Sorry, forgot the key word of vaccuum leak.

[ar0ck]

When I had the mighty LG4 in my old Trans Am, I removed the stock air-clearner assembly, and ditched it for a Edlebrock paper Open Element. I didnt have any problems with that. I dont see why changing to a duel snorkal set-up would be any different, compared to and open element.

I mean its allowing just as much air in as an open element, so why would it have to be leaned out.

I would think their is something else to blame.

[84HOtransam]

does it idle ok?

are you sure all the vaccum lines were hooked up the right way..

There is a ¼ inch or so vacuum line coming out of the front of the carb. (its larger than all the rest) this line should be maybe 8-10 inches long and connect to a plastic valve that has other lines going to it. im not sure what that plastic valve is called but when it goes bad it puts vaccum to that ¼in line. When the engine is running disconnect the line from the front of the carb and see if it has vacuum. If it does plug it up and take it for a test drive and see if the problem is fixed.

when I had my carb worked on the guy adjusted it once it was back on the car, and found that valve was bad… it was making the engine lean out a bit at high rpm..