Hi, I ve got a 87 z28, she wont run from cold, once started unless you keep you foot on the gas she'll cut out. I found the choke stat firstly being disconected and faulty. I replaced it and rewired it hoping it would cure it.but no joy. As anyone got any ideas or Iam I missing something simple ? Thanks

 

Yeah, you'll need to fix it. Choke linkage problems on the QJet are pretty common. Here's how it's SUPPOSED TO work- make yours work like this and you should be good to go:

When overnight cold the choke plate should SNAP shut when you open the throttle a little to unlad the linkage. When you fire up the motor the little vacuum canister on the pass. side of the carb will retract, move the choke linkage slightly, and pop the choke open slightly (such that you could just slide a ~1/8" drill bit vertically between the back of the choke plate and the inside of the choke tower). The vacuum canister must retract like I describe or the motor will flood out quickly. Make sure the canister is working properly (holds vacuum, retracting fully as soon as the engine starts). As the choke warms up the choke will eventually retact on it's own, but the little vacuum can does all the work for the first minute or two. There is an adjustement (phillips head screw) on the arm of the vacuum canister that adjusts how much it initially opens the choke plate. Better to have it open a little too far than not far enough.

ALSO...... any time the choke is on, even a little, it engages a "fast idle cam" built into the choke linkage. It's purpose is to open the throttle a little and speed up the idle speed on a cold engine to help keep it running smoothly. The adjustment for this "fast idle" is a little screw (could be Slotted or Torx head) underneath the choke linkage on the pass. side of the carb, with the head of the screw pointing straight forward. It's easiest to see with the choke set closed. It affects the idle speed ONLY when the choke is on. Once the choke opens up idle speed is no longer affected by it's adjustment.

I have found the best method of adjustment is "trial and error." Set the vacuum pull-off as I describe and then play around with the fast idle speed setting. Over the course of several moringings where the motor is overnight-cold play with them a little until you get it to idle well on initial fire-up. You only get a couple shots at it every morning before the settings become almost meaningless to the next overnight-cold startup.

Good luck!

 

thanks for the info I'll give it a go and see hows she goes

 

Dear Damon, had ago with your tips still no joy tried to move her off my drive gave up after cutting out six times with my neighbours shouting at me. In england they dont like the sound of a roaring V8, they much prefer the sound of clanking noise of their Rover diesels. Have you (or anyone else got any ideas ) PS any Camaro owner get together's in Orlando ?Thanks for any advice

 

Is this a computer controlled carb? Does it only have the one wire going to the choke on the passenger... oh wait, on the right side of the car, or does it also have two other electrical connectors going to it?

Is the choke pulloff (vacuum can), pulling itself off?

What is the hot idle speed?

Any engine modifications?

When you start the car cold, you should press the gas once to the floor completely, then start it up, you shouldn't have to touch the gas aside from the first press, which is to make the choke "snap" shut.... at least it's that way for me, if I keep pumping the gas as I start it it'll flood.



Anyway, the previous part there is just questions, here's the suggestion:

Your cold idle is controlled by the fast idle cam, as well as the choke pulloff, but also by the thermostat. You know how there are 3 screws (or rivets), holding the black "cap" into place? Where the one wire goes into right? Ok, that can be turned clockwise or CCW to suit. When the engine is dead cold, before you start it in the morning, pop your hood and turn the throttle cable by hand, make sure the choke blade snaps shut completely, if it doesn't ,you can loosen those three screws and turn the cap until it is shut. That's your rich/lean adjustment for cold startup, most likely what's causing your problems. You'll notice as you turn it you're pushing against spring force (if it's setup right, if not take off the cap and make sure the "tang" is in the loop.... well, you'll see)....
If there is no spring force, you may need a new thermostat.




Rover diesels? wow, what a different country, V-8 sound for me thanks.

 

i tried the stat thats working, if anything I feel its not getting enough fuel. any ideas anyone?

 

Hi Billy Bob,
Simple question. Will she idle when hot? If that's too low then she may not idle when cold. Just a guess - my 'Bird has a good old Holley carb with mechanical choke.
Not enough fuel? Or does she sound like she's "choking" on too much?

How can the neighbours not love a V8? Don't tell me, you live in a quiet cul-de-sac full of 4x4s which only do the school run, or the local branch of the Women's Institute (Mothers Against Guns & V8s chapter) have their knitting classes there?

Tossers! Come and move oop north and terrorise Lancashire

Mark.

 

no she idles fine and starts fine once hot enough, and yep i do live in a cu de sac !!

 

hi to everyone, i tried all the suggestions no luck she doesnt appear to ecm controlled and the diagnostic port seems to have only a six pin connector. thers's fuel there's spark no run HELLLLLP !!!!

 

Your problem seems to be changing, if it has fuel and spark, it should run, and you mention is does, just idles poor, and runs fine hot. Does it run now or not?

You said you have tried our suggestions, but you have given zero feedback, meaning we have no idea HOW you tried our suggestions and what they did. I think myself and Damon asked a few questions that you haven't replied to either...


The only reasonable problem would have been solved by Damons and my answers, if you can give us details on what you did to eliminate those problems and the results (worked better, worked worse, no change etc.) then we can give further suggestions.

 

sorry, I quickly explain whats occurring from the start and what Ive done. When i bought the car she was in a sorry state after 11 owners. Anyway, when i tried to start it to drive home she would run only with my foot on the gas pedal. this was the case for about five minutes or so when she was warm she idled fine, i then drove back up the M1 to Solihull. I done several jobs on her over the winter. in an attempt to solve the running problem i found firstly the choke stat disconected and upon rewiring it to be faulty. I then replced it to find the same problem she'll start but only keeping my foot on the gas. I have set it up as Damon instructed and ensured the vac unit etc was working ( they appear to be ) and I have also checked what Sonix advised. But the same problem persists I have thrown around my other thoughts of possible reasons of the fault in the hope it my trigger a responce from someone who has had the same problem. Thanks

 

k, then, again:

What is the hot idle speed?

Any engine modifications?

When you start the car cold, you should press the gas once to the floor completely, then start it up, you shouldn't have to touch the gas aside from the first press, which is to make the choke "snap" shut.... at least it's that way for me, if I keep pumping the gas as I start it it'll flood.

You'll need a friend to start the car this way for you, then watch what the carb does, as it starts (before you'd have a chance to run to the engine), the choke pulloff should go. And on the first press of the gas, before starting, you should be able to watch the choke blades snapping shut.

Also, make sure the fast idle cam is "up" on a cold start, that'll happen with the choke blade snapping shut. I can show a pic of that if desired. Then on a cold start, have someone hold the throttle down to keep it running for a few seconds, then let off the gas, and let it, presumably, die, while you would be watching the throttle tang, it should NOT try to rest on the hot idle screw, it should only go to within 1/8" of it, but not touch it, that means it IS on fast idle. That's something to check.


What kind of mileage do you get? very bad? Perhaps the mixture screws aren't setup right... With that many owners you probably have a plethora of problems, best to eliminate the easiest ones first.



Check on as many of those as you can, and let me know, if you need some detailed pictures of where to look for what, I can attach, i've had this problem a few months ago, and took high quality digital pictures to show my problems