Willbanks

Well , I had this big long topic typed out but it looks like i deleted it. I just bought a Z28 w/ 305 in it, this IS my first project car ever and i'm not to good under the hood. My first question is about the idle of the car, when it starts up it idles @ around 2k rpm, rocks from 2k to 1750 and back. I took the carb cover off and it droped down low and shut off. I drove around with the carb cover off a mile or two and it seems like it was running better, after i parked the car it idled better but was still too high. Under the hood it says idle @ 650 rpms but it idles @ 2k w/ carb cover and 1k w/o carb cover. I understand this could be something with the vaccume but I would like to know where to start. Also how can I tell what carb I have installed ?

Willbanks

Also, what would be the main cause of the car not turning off when you turn the switch off. It idles around for about 5 seconds then dies.

85cmroz28

Welcome to TGO.
Just a thought, the reason you idle drops when you have the air cleaner off could be that the THERMAC is causing a vaccum leak when disconnected. Vaccum leaks can be tricky to pinpoint. Inspect all your vaccum hoses and connections. You can also have vaccum leaks around the base of the carb and manifold. Remember that your idle will be higher during your initial startup due to the choke, but once the car warms up, give the gas a quick tap and it should idle down.

As for the deiseling(car still running when turned off) problem, there are usually 2 causes:
1. timing not set correctly
2. idle speed too high***

If you track down and fix any vaccum leaks, it should run better.

Willbanks

Thanks alot 85cmroz28, Like a kid on christmas i'm going to wake up tomorrow morning ready to tool around on my new project car. I don't exactly know what a vaccume hose looks like but i'll figure it out. I'll post the results tomorrow and see what I could get fixed.

Sonix

iTrader: (1)

you have a quadrajet, if it's the stock carb.
if you can get a picture that would help.


You're in richmond as in canada, or some other richmond in usa? it actually effects what carb/dist would be on the car stock...

running after you turn the key off is usually from too high timing, from what i've seen.


err, you said miles, I guess that answers my question...

Willbanks

Well it is a 4 barrel, i didn't get a chance to do alot to it today because of the rain. I live in richmond VA, usa

85cmroz28

yeah, i'm in lynchburg,va right now and it's not good weather to work on your car

Willbanks

Well, i got to work on it a bit today. It turns out some of the funky noise and loss of power was coming from the alternator. The barings were rusted and it just wasnt working right. I put new plugs and wires and now it seems to have alot more power but still have problems with the carburator.

When i start it it won't idle by itself, i have to hold the gas down a little bit. I found out it's a quadra jet carb from the guy i got the car from. I guess i need to learn how to tune the carb, and what exactly i need to do to make it crank/idle without me having to use the gas pedal.

85cmroz28

The carb should not need to be tuned. The stock quadrajet was computer controlled. Perhaps your O2 sesnor needs to be replaced. As for the hard starting, adjust the choke. If you don't know how to adjust the choke, take it to a mechanic- they usually adjust it for pretty cheap.

naf

iTrader: (7)

Your choke could be causing most of your problems. If it's not opening all the way (90 degrees) when the car is warm it can cause dieseling after the ignition is turned off (as can a vaccuum leak). Clean your choke linkage with some carb cleaner and make sure your choke is all the way open when the engine is warmed up. Let us know what you find.

The computer controlled q-jet shouldn't need to be tuned (unless rebuilt or different/modded engine) but you may want to check it for proper operation and make sure all of the sensors (MAP, TPS, CTS, baro, etc.) are good. A manual can help with this too.

Willbanks

thanks, i'll do timorrow if the freakin raid goes away. I'll let you know what happens.

F-BIRD'88

On your Qjet carb should be a anti-desieling solenoid.
it acts on the throttle linkage. When the cars key is on, (Running) the solenoid extends and opens the carbs throttle linkage a little. When you shut the car off, the solenoid retracts and closes the throttle off, stalling the motor. ( removes all airflow at idle) A hot motor using low octane fuel will tend to "run on" even thou the ignition key is off.

By haveing the antidesieling solenoid open the throttle when running and close it off completely when the motor is turned off , desieling or "run on' is prevented.

Check the solenoid's operation. If it is missing replace it.

Willbanks

Excelent F-BIRD'88, I added that to my list. So far I have:

Check vacume hoses
Check to see if choke is sticking
Adjust timing
And now I have your comment

Tomorrow i'm going to focus on trying to get it to crank without having to use the gas pedal, fixing it to where it idles right, and fixing the "diesle" effect.

Should be an interesting day.

naf

iTrader: (7)

Not sure about Canadian models but our ccc-qjets don't have a solenoid that works as F-Bird88 describes. We have a throttle kicker that is similar. It bumps the idle speed up when the A/C is energized. It shouldn't be causing your problems.

Willbanks

Ok, here is what I got so far.

I tested the vac and it pulls pretty good.
I replaced the carb fuel filter.
I cleaned the choke/4 barrel breather ( i guess thats what it is )

Now I think I have a better understanding of whats wrong.

Cold start: It cranks, revs , then bogs down and dies. After about 5 times of doing this and gassing it, it finaly revs without bogging but if i let my foot off the gas it dies. The choke never opens fully, and when i open it myself it dies. The car will idle @ around 2k rpm by its self if i open up the 4 barrel 100%. The diesle effects is gone now, i'm not sure how I fixed it, maybe it was just sitting so long and after running it a few times fixed it. So what could be the problem now?

Willbanks

Oh and I did check this, if it was i seen my solenoid is broken. Also there looks like a plug on it but nothing is pluged into it. It realy looks like it's in bad shape, can i just take it off?

F-BIRD'88

You can take it off and reset the required curb idle speed using the curb idle screw, but the motor will run on when you shut it off hot. The antidiesieling solenoids function is to avoid this problem. you can get a new one from most autoparts counters or a GM dealer. Bring the old one with you. It need 12volts power that switches on when you turn the key on.
All that stuff under the hood of your car is there for a reason.
It all works together to make the car driveable under most conditions you'll typically encounter. When you start butchering it, disconnecting this and that, that when things get all messed up and you get driveability problems like the
choke not functioning properly and the run on problem etc.

naf

iTrader: (7)

Does your choke have a single wire connected to it providing 12 volts?

What do you mean by opening the four barrel 100%? I'm not really following. Once it warms up is it idling at 2000rpm with the choke blade closed? Did you try to manually open the choke blade with the engine warmed up?

Does your mixture control solenoid (in the carb under the two wire connector pass side front) make a clicking sound when the ignition is first turned on? Is everything hooked up? Check engine light on?

Do you have A/C? If it's been removed you can lose the throttle kicker, but it shouldn't be causing any trouble.

Willbanks

I don't know what it is, I have 2 slots the one in the front is the choke i guess and the one in the back ( the larger one ) what is that ?

naf

iTrader: (7)

Willbanks-see if you can pick up a manual, I'm not really sure we're always talking about the same thing. The choke is on the pass side of the carb. It has a bimetalic spring inside connected to a 12 volt wire. The wire expands when heated and slowly opens the choke blades. It's all under a round black plastic cover. Make sure the wire is connected.

F-Bird 88- You may be confusing the function of the idle speed solenoid on US q-jets. The solenoid should engage when the A/C is on and provide a higher idle speed. Basic idle speed is still set with the idle speed screw. Similar to the older vaccuum operated idle speed compensator. Some q-jets also have an idle speed control motor that actually adjusts idle speed by the ecm but not our models.

Willbanks

I can order a manual from this site right?

naf

iTrader: (7)

Grab one at the parts store(autozone, etc) about 15$ well spent. It can help you with adjusting the choke and carburetor.

I suspect you have choke adjustment problems and/or the choke wire may not be connected or providing the correct voltage. If I were nearby and could have a look at it... read up a little then get back on here with any specific questions.

Willbanks

Ok will do, I place an order online for the books so it will be a few days.

I got

Chevrolet Camaro Repair CH7317 1 12.96
Manual 1982-1992

How to Tune & Modify Your MB-0436X 1 15.16
Camaro 1982-1998

Sonix

iTrader: (1)

Here, you can use the colored arrows to describe parts.

This is a non-cc carb, but the parts you're having trouble with are the same.


and yea, I concur that i've heard of the A/C idle kicker, i've never heard of an anti-dieseling solenoid... something else, or another word for the same part??

pennylessz28

Oh no, that doesn't sound good at all.

Willbanks

Excelent, thats what I need is a picture, but where is they key?

When I said "Rookie needs help" I meant just that. I wont be offended one bit if you type/talk to me like I was a small child.

I just don't know what the arrow color stands for.

EDIT: Oh ok , I see , you posted that for me to tell you what i'm talking about when i post my problems. Great thanks alot.

I did find something today though, the guy i bought it from had a gold T stuck inside a vac hose. Its right below the vac line the carb filter cover plugs into.

Willbanks

This picture has a chop stick sticking out of a hose. There was a golf T stuck in it but i took it out and lost it, then realized it may have been there for a reason.

naf

iTrader: (7)

That vaccuum port off the tee goes to the vaccuum hose attached to the air cleaner. It provides vaccuum to open the thermac switch on the snorkle and provides air warmed by the exhaust when the engine is cold. You should have a heat stove on the drivers side exhaust manifold connected to the snorkle by some metal flex hose.

If you don't have it connected just plug the tee at the carb. You can make a plug out of a small piece of vaccuum hose with a golf tee or screw in the end or buy a kit at the parts store that has several different sizes of vaccuum plugs. Leaving this port open will cause a slightly higher idle.

Willbanks

This is site is great.

Thanks naf, when i get my books i'll start posting real problems.

naf

iTrader: (7)

Sonix-is that an iron manifold under your q-jet? Or just dirty?

Sonix

iTrader: (1)

hahah, extremly dirty... (that's when I first got the car, i've replaced the manifold gasket since then, and now it's relatively clean-er... then again, new motor soon so...)

Forgot to mention, I used this pic with the two red arrows on it, before, so those aren't much help now....


so for example:

-purple arrow refers to the choke air horn
-orange arrow is the general vicinity of your curb idle screw
....
aww heck, why not use your picture? it's more accurate since it's a cc-carb...

naf

iTrader: (7)

I can't say anything, my 85 is real ugly. Right now the only things clean are the valve covers that I painted while swapping leaking gaskets. There's always more work than time.

Willbanks

I got my books today, trying to do the "tune your carb" section.

It is telling me to find my selonoid to adjust the idle but i cant find the damn thing. All i could find is this, and i dont even know what it is. It was not pluged into anything juts bolted on.

MorbidHobo

That looks like your I.L.C or Idle load compensator assist. It should have bolted to the drivers side of the carb. It kicks up your rpms when you turn your a/c on so your ideling rpms dont drastically drop. Dont quote me though b/c the pictures fuzzy.

naf

iTrader: (7)

The manual should have told you to disconnect the solenoid when setting the base idle speed. Then it should follow up with a section telling you to disconnect the a/c compressor plug, turn on the a/c and set a second adjustment (higher idle) with the solenoid. As MorbidHobo said, the solenoid provides a higher idle to compensate for the load of the a/c compressor. If that's the solenoid that was above the idle set screw on the driver's side of the carb it's the load compensator, picture's kind of fuzzy.

Some q-jets used a idle speed control motor that allows the ecm to set idle speed. Make sure your manual is not referring to one of these. Also some of the load compensators were vaccuum operated. Yours should have a one wire electrical connection.

Willbanks

the thing in the picture was not even hooked up to anything, and it looks broken. Should i replace it ? there was an unpluged wire ( i think it goes to it ) but it was melted , if i traced that wire back to where it comes from will you be able to tell me more ?

And yes the the book said to do that, but the picture it shows of the selonoind looks like nothing i have on my carb

MorbidHobo

yes we will. i have also attached this picture of how a functioning I.L.C. (Idle Load Compensator Assist) should look. this is my carb at the time when it was actually working. As you can see the green wire is supposed to provide the power to energize the solenoid. Tell me if this helps or if you need more information. (negate the top most arrow as its accidently pointing at the linkage) I may have missed the suggestion earlier but has anyone thought about the choke pull off being bad? If we havent mentioned it already i could highlight a picture of it too.

naf

iTrader: (7)

If it's the piece MorbidHobo shows, don't worry about it now. You can replace it later after you get the base idle set, if you need it for a/c load. The load compensator is also called the throttle kicker that we talked about earlier.

MorbidHobo

it wouldent be his choke pull off would it naf?

Willbanks

Yep thats it Morbid, thanks.
So I don't need to bother with this then seeing how I'm going to take my compressor off anyway. Why have AC when you got T-tops? Nevermind I just realized on a hot rainy day that AC may look real nice.


My base idle screw setting is not going good. I think there is just many variables. My idle jumps around so much it's hard for me to adjust it.

-When I put my filter cover back on it ups the idle
-When I gas it above 4k RPMS it ups the idle
-Every time I crank it, it has a new idle

Should I let the car run for 20 minutes or so, then adjust the idle ?

It just pisses me off because when I do that it's all good until I rev the engine up, then it's like something gets stuck and it just idles real high.

And another thing that gets me is if I set the curb idle screw to a good spot then crank it back up when it cools down it wont idle by its self.

I just got my books today so I didnt have a good chance to read and follow the instructions. Tomorrow I'm going to follow the book to the "T" and see what I can come up with. I'll let you know what happens.

EDIT: Also the diesle effect is not gone like I thought, it only stutters off when the idle is high (over 2.5k)

MorbidHobo

good luck on searching, talk to you then.

naf

iTrader: (7)

It's most likely your choke and the choke's fast idle that is causing your problems. Follow your manual and make sure you're setting the idle with the engine warmed up and the choke off.

When you rev it up, your fast idle choke may be catching, which could cause it to stick at a high idle.

What are you doing when you put the filter cover back on? This should, if anything, cause a slightly lower idle due to restricting flow.

naf

iTrader: (7)

1. Make sure you do adjustments with all the open vaccuum sources plugged. Plug the tee on the front of the carb that normally provides vaccuum to the thermac. The other side of the tee goes to the choke pulloff.
2. Check your choke pulloff by disconnecting the short vaccuum line connected to this tee, pushing the plunger in, holding your finger over the vaccuum line (or nipple on the pull off) and releasing the plunger. The plunger should not move back out until you release your finger.