Quadrajet fast idle issue.

[86Peter454]

hello guys.
been a while since i posted on here. i havnt been driving my truck much but i decided to get it out and drive it some and i have an annoying issue with this quadrajet carb on my 454.

it has an electric choke on it and at a time it worked fine but some time ago it seemed to stop kicking down the idle speed. in fact it would seem i can manually move the fast idle cam down and it will idle down but once i push on the gas it will go back to the fast idle. seems backwards to what i feel should be happening.

here are some pics and videos of the operation and whats going on.

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video is at this link.

carb issue

New item · Album by Matt Wagner

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im not sure if choke needs adjusted or what might be causing this. let me know of any other info you might need. any help is much appreciated.

thanks,
Matt

 

[fast 99]

Check for power at the choke thermostat. If it has power OHM the stat.

 

[Paladin]

i have an annoying issue with this quadrajet carb on my 454.

Hmmmmmm.........seems to be a common denominator with so many carb problems herabouts as of late. And that problem is spelled Quadrajet!!!! LMFAO Get a HOLLEY!!!!!

 

[Bextreme04]

The electric choke is not heating up to pull the choke off. Like Fast 99 said, check for voltage at the choke wire(it should have voltage at all times when engine is running). If it is getting voltage, you need a new choke. If no voltage, check the fuse, then check the oil pressure switch above the oil filter.

 

[fast 99]

Hmmmmmm.........seems to be a common denominator with so many carb problems herabouts as of late. And that problem is spelled Quadrajet!!!! LMFAO Get a HOLLEY!!!!!

Many replacement Holleys have the same type of electrically heated choke. Have seen them either heat too fast or too slow for the application.

 

[86Peter454]

thanks guys for the suggestions. i actually do plan to get a holley eventually but not till i do the rest of the engine work. so just trying to get this working for now.

@Bextreme04 i know when i first got the truck i bypassed the oil pressure switch as it was not supplying voltage. i ran the choke to a wire that was hot when the engine is running. it also happened to just be hot with the key on so i have just had to keep that in mind not to leave the key on long allowing it to warm the choke without the engine running.

i will check the voltage at the choke for sure would make sense that maybe its not heating up. or maybe just completely out of adjustment maybe?
ill post back what i find out.

 

[86Peter454]

well good call boys.
here is what the wire that runs to my choke looks like. (sorry out of focus but you can see it lol)

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id say there is no voltage lol.
i did go ahead and test that i was getting voltage before the break in the wire and i am so just fix this and should be set.

thanks for the help sorry to waste anyone's time with this.

 

[Vbb199]

So I randomly came across you'd introduction thread.

I saw the truck has a nv4500 mated to a 454.

How's that been treating you?

 

[86Peter454]

So I randomly came across you'd introduction thread.

I saw the truck has a nv4500 mated to a 454.

How's that been treating you?

lol well if you happened to check out some of my other threads you would know the nv4500 didnt work out. lol.

yea like 5 days after i got the truck i lost 5th gear. pretty common on those trans though mine didnt walk off it blew apart the 5th gear synchro. so i drove it as a 4 speed for a few more months then i put it in reverse one day and it wouldnt come out lol.
so i pulled it and put in a full manual th400. i fixed t he issues with the nv4500 and sold it.

th400 has been working well for me though so far so thats good lol.

worst part of this truck is this carb. it needs rebuilt bad. cant full throttle or it stumbles all over itself no matter how much i ease in on it. its just a pain. thats why i plan to just go holley. i feel it will be easier for me to figure out how to tune than finding all the little tricks for these quadrajets.

 

[Vbb199]

lol well if you happened to check out some of my other threads you would know the nv4500 didnt work out. lol.

yea like 5 days after i got the truck i lost 5th gear. pretty common on those trans though mine didnt walk off it blew apart the 5th gear synchro. so i drove it as a 4 speed for a few more months then i put it in reverse one day and it wouldnt come out lol.
so i pulled it and put in a full manual th400. i fixed t he issues with the nv4500 and sold it.

th400 has been working well for me though so far so thats good lol.

worst part of this truck is this carb. it needs rebuilt bad. cant full throttle or it stumbles all over itself no matter how much i ease in on it. its just a pain. thats why i plan to just go holley. i feel it will be easier for me to figure out how to tune than finding all the little tricks for these quadrajets.

To some guys, the q jets are second nature, and no doubt, if you're well versed in a particular area, by all means indulge.

I have messed with 1, it wasn't for me, I have messed with some eldebrocks, and while I *** a little younger and dumb then, I still found them a little more difficult than just a plain ol holley.

Always have liked a holley, because I like WOT action. I don't like putting around.


As far as that 5th gear flying apart and the th400 swap, I guess I overlooked that one.

Thats cool tho.

I'm running a th400 behind my big block c10 myself.

 

[86Peter454]

To some guys, the q jets are second nature, and no doubt, if you're well versed in a particular area, by all means indulge.

I have messed with 1, it wasn't for me, I have messed with some eldebrocks, and while I *** a little younger and dumb then, I still found them a little more difficult than just a plain ol holley.

Always have liked a holley, because I like WOT action. I don't like putting around.


As far as that 5th gear flying apart and the th400 swap, I guess I overlooked that one.

Thats cool tho.

I'm running a th400 behind my big block c10 myself.

yea ive seen some qjets that have been set up well and really i think they are a great carb i just feel like you have to know them well to get them to run well.
as a guy who knows next to nothing about carb tuning there is a lot more readily available info on holleys than there is on the qjets so i feel thats the easiest route to go so i can learn.

yea the trans was a bummer but its all good and i learned a lot through rebuilding the th400.

 

[Matt69olds]

well good call boys.
here is what the wire that runs to my choke looks like. (sorry out of focus but you can see it lol)

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id say there is no voltage lol.

Well, obviously a Holley would have fixed that problem. .
i did go ahead and test that i was getting voltage before the break in the wire and i am so just fix this and should be set.

thanks for the help sorry to waste anyone's time with this.

 

[fast 99]

A q jet stumbling at full throttle? On the top housing there is a vent hole. Using a small screwdriver insert it in the hole. There is a metering rod in there. You should be able to detect the rod holder going up and down. It has a small spring underneath. If no movement the rods are stuck, usually in a lean condition.

If the secondary air valve isn't adjusted properly that will also cause a stumble. Have seen quite a few with the spring tension on the sec valve set too light. It causes the air to move before the fuel has a chance to flow in the venturis, thus a lean stumble.

 

[86Peter454]

A q jet stumbling at full throttle? On the top housing there is a vent hole. Using a small screwdriver insert it in the hole. There is a metering rod in there. You should be able to detect the rod holder going up and down. It has a small spring underneath. If no movement the rods are stuck, usually in a lean condition.

If the secondary air valve isn't adjusted properly that will also cause a stumble. Have seen quite a few with the spring tension on the sec valve set too light. It causes the air to move before the fuel has a chance to flow in the venturis, thus a lean stumble.

thanks for the info ill check on the movement of the rod you described.

i have played with the secondary air valve quite a bit assuming that was my issue but i couldnt ever get it any better with it. i always assumed its the power valve leaking or not functioning properly but i guess thats not likely the case thinking about it as it will stumble even when slowly working up to full throttle.

 

[fast 99]

It's rather common for the primary rods to get stuck lean/down. Without the specs in front of me the secondary air valve spring wind up is about 3/4 to 1 turn.