Hi;
My Daughter just gave me her 1984 Z-28 H.O 5 speed which she bought new. I flew to Wisconsin and drove it back to Florida 2 weeks ago.No problems.Went through 7 tanks of gas so tank should be clean. Now it has picked up a rough idle. It still runs great and don't miss going through the gears.Just the rough idle.
I went through some of the topics on this site and find they talk alot about vacuum leaks and fuel filters.Not being involed in cars that have carburetors for along time. I could sure use some help.Like where is the fuel filter located?? And where to look for the vacuum leaks?? Also there is a little motor which is located in front of the battery that blows cool air through some 2 inch tubing on the carburetor.To keep it from vapor locking and I haven't heard that run for a couple of days.Also the gas got a little low on this last fill so maybe it sucked something up. Any help would be greatly appreciated.

 

I have an 86 Z28. LG4. When i first bought it, it also had a rough idle. I have come to know that with these cars, it takes a little bit of fine tuning every few months to keep them in top notch shape. Anyway, I rebuilt the carb, and no more rough idle, but it will still do this at time. There are two adjustments on the left and right front of the carb, right by the plate on the bottm. They are the air inlet adjusters. I wouldn't tinker with them too much, but once in a while to do need to adjust this.

As for the fuel filter, if its the stock Qjet, then the filter should be right on the front of the carb, pass. side. Vacuum leaks are a big one, but surprisingly, all my hoses are original, except for a few that I replaced with the new air cleaner I got, an HO just like yours. But mine still draws in about 22 inches at idle and sometimes I have gotten 27 at freeway speeds cruising. SO I haven't had that problem yet. Could be running rich or lean though. Might wanna check that out. Anyway, I hope that helped some at least!

Will

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'86 Z-28 305 c.i. LG4
Rochester QuadraJet 4bbl
Flowmaster 80 series Chrome Tips
Dual Snorkel Air Cleaner
K&N Filter
Michellin P215/65/R15 X-Radial Plus
Lots of Mods on the way
Pioneer 4"x6" dash
Pioneer 6"x9" rear
Alpine 8" Type S in bandpass box
Alpine Amp 300x1 bridged
Sony 4000X- x-Plode Deck 50w x4

Soon to be sporting Hooker SuperComp Shorties, CompCam Xtreme 256H, Edelbrock Performer EGR, World Sr Torquer 305's, DynoMax Super Converter, and American Thunder 3" Cat-Back !!!

http://camaroz28.cardomain.com/id/stanghunter211

 

Thanks Will; I will look into your suggestions. Thats why my daughter gave me the car. She knows I like to tinker and it will give me something to do.Been retired for 7 years now. Other car is 99 Tourch Red corvette conv.Vortex Ram Air And Borla Exhaust. Thanks again Bob

 

The "motor" you are talking about is the AIR diverter valve for the AIR system - an emissions component. Injects air into exhaust manifolds and catalytic converter during for cleaner burnoff. Unless you have a vacuum leak to that valve (very possible), it will not affect idle. Check for vacuum leaks, timing, plug/wire/cap/rotor condition, and try throwing a new ignition module at it - they can cause strange problems and be almost impossible to diagnose.

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1985 Z28, Jasper Class 1 350, Edelbrock Performer intake, Dual snorkel air cleaner, K&N filter, Edelbrock headers, Catco cat, Hooker cat-back, built 700r4 w/ Darrell Young 2400 stall TC, Jet stage 2 chip, SSM subframes, Lakewood LCA's, Powertrax locker w/stock 3.23's, Centerline Auto Drag's

 

Ya, weird stuff has happened to me with this car before. Things I would never have thought of and things few mechanics I know have seen or heard of as well. Like one day, i was out cruising and when I pulled up to a stop, I noticed the car was idling a little high. Thinking the choke was somehow in cold start mode, I put it in park and goosed the throttle to kick it down. But nothing. Well, needless to say the problem only got worse as the night progressed. Got to where it was doing nearly 2K in park. Went to my grandads and myself, him and my dad all puzzled as to what was doing this. Well I knew I had a bad alternator because of the power spikes I was getting when I would give it gas. Switched the alt and there went my problem. Now of all the things to be affecting the choke?!!? Anyhow i hope everything goes well. I wish I could get my hands on an HO 305. But hopefully I will have a 350 built up pushing 400 horses for my Z by next year. Till then, gotta baby this block cuz I sure don't need it going out on me! Take care!

Will

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'86 Z-28 305 c.i. LG4
Rochester QuadraJet 4bbl
Flowmaster 80 series Chrome Tips
Dual Snorkel Air Cleaner
K&N Filter
Michellin P215/65/R15 X-Radial Plus
Lots of Mods on the way
Pioneer 4"x6" dash
Pioneer 6"x9" rear
Alpine 8" Type S in bandpass box
Alpine Amp 300x1 bridged
Sony 4000X- x-Plode Deck 50w x4

Soon to be sporting Hooker SuperComp Shorties, CompCam Xtreme 256H, Edelbrock Performer EGR, World Sr Torquer 305's, DynoMax Super Converter, and American Thunder 3" Cat-Back !!!

http://camaroz28.cardomain.com/id/stanghunter211

 

That is normal it is like how when you boost somone the engine slows. Well when you have extra power the engine speeds up. MY prob with my car is the needle vavles get stuck every once and a while and it revs at 3000 so I have to try not to spin the tires.