86Pontiac

First off it's not an f-body, buta g-body I was told to come here for help

Car
1986 Grand Prix LE 305 with the computer controlled carb.

Problem
It wants to stay running when you shut it off, probably 70% of the time. This forces me to shut it down in gear, which doesn't always do the trick right away. It's been doing for this off and on for the last month or so. Car idles/runs fine, until shutoff

It's not a timing issue. And the other day I noticed it seems to be, or is flooding itself when shut off, discharging a little fuel from what I believe is the choke valve(not the butterfly, but the front one)? I was told this a known issue and a rebuild and mod of some sort will resolve it.

What exactly causes this and would it be wise for me to dive in with a rebuild without any prior carb experience? I'm quite mechanically inclined when it comes to engines but never got my feet wet with carbs yet

My Questions
Does this sound like a carb issue you guys? Will just a rebuild do or will it need "modded? I can't afford a brand new carb nor to have it recuild by a shop at the moment. It's either I attempt it or just get a used one from the local yard

five7kid

iTrader: (14)

Welcome aboard thirdgen.org.

Generally, this is for discussion of 3rd gen f-bodies, but we'll allow discussions that can be considered "3rd gen related".

"Butterfly" is a generic term. There are 4 sets of "butterlies" on a q-jet - the primary throttle blades, the secondary throttle blades, the choke butterfly, and the secondary air valves. I'll assume you mean the choke butterfly.

When the engine is warm, the choke butterfly should be straight up & down. If it is at any kind of angle, something is wrong. If the choke thermostat (the round black plastic piece on the passenger side of the carb) is not operating properly, such as not getting the 12 volts it needs to warm up and release the choke, or has gotten weak over time (it happens with all the heat cycles), then not only will the choke butterfly not open completely, but the high idle cam will not disengage properly, which will lead to run-on. However, if this is the case, your engine is not idling fine - it's idling too fast.

Look at those things, and also let us know what your warmed-up idle RPMs are.

86Pontiac

I'll have to put the carb back on but that's no big deal. Once I get it on I'll answer your post in detail.

I had a few people tell me that it is indeed idling too fast/high but imo it seems like it's fine. Also, it has a clock instead of a rpm gauge. This thing is completely stock and still has all of the emission hookups


Like I said I'll post up here in a few

86Pontiac

Sorry it's been so long since I replied as I've been without internet.

Anyways. I went ahead and got a replacement carb, installed it and the problem went away. I have a new problem now:

The little filter that sits in the breather housing(part of the pcv system) managed to make it's way into the choke butterfly while it was open. Now it's stuck open and when you try to manually shut the butterfly it immediately opens back up. It seems to be under a spring load. I looked at it for a good hour trying to find the problem area with no luck. I did notice the choke linkage is down and when lifted up it just drops again with no resistance

86Pontiac

weird.

I just went out after it sat all night long and the choke is closed. It's not fully closed but it's not how it was last night

What could be wrong?

Zwrench

The choke was warm and the thermostatic spring was holding it open. When it cooled off overnight it closed the choke. If you tap the throttle it will probably close the rest of the way.
It sounds like it's normal to me.

86Pontiac

it seems to be fine now without doing anything

Now I need to look into adjusting the choke(the butterfly isn't closed completely and has play in it) and some other adjustments

edit-gonnastart it up and drive it around the block to see how it does. I'll recheck the butterfly when I get back to see if it's stuck back open or not

86Pontiac

I turned the key on, engaged the choke(worked perfectly) car started within 4 seconds.

Let it warm for 5 minutes then went for a ride to the car wash. It's bogging a bit under normal throttle but when kicked down it smooths right out. I'm certain this carb needs adjustments, just don't know how or what needs done

Anyhow. Shut the car off, checked the choke and it is wide open and does not close when restarted. Is this normal?

naf

iTrader: (7)

Normal for a hot engine. You may need to make slight adjustments to the Idle Air Bleed to get it optimized for your engine. This may be the cause of your slight hesitation under part throttle. This is with engine warm, right?

86Pontiac

I feel retarded since that's normal

Yes, the hesitation is when the engine is warm. Does it cold as well though.

Is that the only adjustment I should look into? Will I be able to get it right without a tach? This thing came with the clock

naf

iTrader: (7)

You'll need a dwell meter to properly set the IAB. The intent is to adjust the amount of air allowed into the idle mixture so that cycling of the mixture control solenoid (MCS) as measured by dwell is in the middle of the range, 50% or 30 degrees on the six cylinder scale.

The ECM changes the rate of cycling by looking at throttle position and vacuum sensor readings and rewrites these blocks based on O2 readings. Setting dwell correctly allows the ECM the most range so that it can respond to lean/rich conditions under operating conditions.

86Pontiac

yea this carb hasn't had the cover rivets drilled out yet. I noticed that the original carb cover from my first post has been removed.