Burntz

Ok I replaced the cap and rotor on my 84 Camaro Z28. I posted a carb topic awhile back. Its all stock w/ the electronic quad. Iv been trying to get it to run right, and a carb rebuild was on the list. The cap and rotor were pretty bad so i replaced them, and i have 2/8 wires replaced with borg warner premiums. It quit missing but its idle is horrible with the mixture control solenoid plugged in, but if I unplug it, it idles "decent". Does that mean the mcs is fryed? Or what else could it be? Also I hear a rattling and it sounds like its coming from I think cyl 4? not sure, its left side when standing in front of car, sounds like the 2nd cyl away. What would that be? The higher the rev the faster the rattling, i know that.

Angelis83LT

Mine does that as well as far as the rattle goes.. I removed the Computer controlled stuff.. You probably looking at a full rebuild on the stock carn more than likely.. the rattle from the passenger side is something I am styill looking to find out what it is... I had one block that did it before hand. also a 305... turned out it was cyl 6 coming apart... the final straw was when it broke the dish ring on the face of the piston and broke a chunk out of the piston skirt... But it rattled for a good year before it did that...

naf

iTrader: (7)

Unplugging the MCS (top pass side front of carb) will stop the solenoid from pulling the rods into the primaries allowing gobs of fuel into the mixture. Idling better unplugged indicates the carb needs some adjustment. Have you rebuilt it yet? You may also want to check for vaccuum leaks. I would recommend pulling all the vaccuum lines off and plugging each port with a cap during the adjustment/troubleshooting procedure. Get the carb running right then reconnect each one to ensure there are no leaks.

Is the rattling like a ticking noise? Does it change or go away as the engine warms up?

Burntz

I know I need to rebuild the carb and tune it, so I cant say much until I do that.

The rattle is thier at idle, and while the rpms are dropping. When it accelerates, it isnt thier, but when it goes up, and I let off, while coming down it makes the noise.

Burntz

thats prolly why it idles ****tier when i put a new cap and plug in, the spark was weak before, so it was easier to combust w/ the lean mixture, now the spark is strong, so its better for the rich mixture with teh mcs unplugged, am i right?

naf

iTrader: (7)

Hard to diagnose a rattle second hand, but you may want to pull your valve cover off and check all your rocker arms. Could be loose heat sheild around the manifold,etc.

Did you replace the plugs? If so did you gap them correctly? 0.035 is a safe gap. If the new cap and rotor improved a miss, it shouldn't affect idle.

You selling this car? That's just wrong.

Burntz

I've been considering it, because the car is frusterating me, but I HAVE A SECOND CARB IDENTICAL TO MINE TO REBUILD NOW woo, my moms b/f just randomly says he has 1 up in his storage.

Yes I replaced all the plugs except cyl 8 which I cant seem to get to. Champion racings gapped at .045 I believe, thats what the book told me. I have all the new wires on except the 2 farthest and hardest ones to get to on the passenger side, and the new cap and rotor. It idles like **** with the mixture control solenoid plugged in, but good until completely warm w/o it in.

My air pump/smog pump doesnt work and doesnt have a belt on it, I was told this is whats screwing my car up, besides needing a rebuilt carb and being tuned, is this true?

And as for the noise, I was told its prolly a lifter or a loose rocker by a couple co-workers, also is this possible? lol

Thanks for any advice.

Oh and as for the rattling noise, it only seems to be thier when completely warm.

Randy82WS7

all the smog pump does is inject fresh air into the exhaust manifolds to burn any raw fuel that didnt burn in the cylinders

it isnt going to affect how it runs, connected or not, no


you should pull the valve cover at check for rocker nut that may have loosened up, maye need a new nut, this happens on old chevy engines commonly

i have had them get so loose that the rocker breaks

the nut just isnt doing its job anymore, old, needs replaced

also a real small exhaust leak at the manifold gasket or at a smog pump injection tube can cause a ticking noise

happens all the time also, common

Burntz

prolly the noise, either that or a lifter

and my moms b/f swears UP and DOWN that the smog pump is making it run ****ty, which the only reason that would make sense is because its throwing the o2 sensor off.

also, a quadrajet off an 85 350 pickup... looks the same as the one on my car, almost identical to me, but it has an electric choke i think? Are they the same?

edit: looks completely identical except for the mixture control solenoid on mine looks greenish and the one on this 1 is blue, could the green just be worn blue and look green?

naf

iTrader: (7)

Don't worry about the smog pump, it's not affecting your engine idle by not being connected. The 85 q-jet is probably essentially the same as yours, they should both have electric chokes. The primaries (jets) may be different sizes and the secondary rods/hangers are likely different, but it would probably work on your car. M/C's can be anywhere from green to blue or in between.

Replace that last spark plug-you may have to get it from underneath. Replace the rest of your wires and your O2 sensor. Make sure the single wire is connected to your choke and it's slowly opening as the motor warms.

Rebuild your carb and use the spare as a guide.

five7kid

iTrader: (14)

The A.I.R. flow goes to the manifold when the system is in open loop - i.e., the O2 sensor input is ignored. It is diverted to the cat when in closed loop so it doesn't cause false O2 readings.

If for some reason the A.I.R. flow is going to the manifolds in closed loop, it would cause the O2 sensor to indicate a lean condition, and the ECM would richen up the mixture. As already stated, unplugging the MCS gives it full rich, and if that makes it run better, that indicates it is running too lean when the MCS is plugged in - and A.I.R. flow getting to the O2 sensor can't make it run too lean.

naf

iTrader: (7)

"...also, a quadrajet off an 85 350 pickup... looks the same as the one on my car, almost identical to me, but it has an electric choke i think? "

Or the choke is missing/fubar and unplugging the MCS is compensating.

Burntz

i have like 10 pictures of my carb and they both have electric chokes, everything. the little canister thing on the right on the 1 i have is messed up and id have to take it off mine in the car.

the carb i have looks in good shape, the gaskets look ok, could i get by with cleaning it with carb and brake cleaner and put it on? do you have to rebuild it to change the rods and hangers? how big would the difference be?

edit: this is the carb on the car, the 1 i have is considerably cleaner

naf

iTrader: (7)

Certainly wouldn't hurt anything to try the swap. Just be careful with the fuel line connection-hold the big nut in place while loosening the smaller-don't let the line kink. Your replacement may not have the same vaccuum ports but just plug them all (on the carb) and don't reconnect any (except maybe pcv) until after you know if it'll run fine.

You'll probably need a dwell meter to set the IAB and you may need to adjust the idle mixture screws. Are they exposed on the carb you got? Pull the secondary rod and hangers off. Check the letters on the hanger and rods. They don't matter now but may be good ones to hang on to.

You've got to pull the original off anyway and it takes like 5 minutes to hook one up and see if it will run.

Secondary rods hangers held in place with real small screw in between the two larger secondary air flaps center rear. Take the screw out (use pliers to turn it) lift out hanger, rods will be attached.

Burntz

the carb i have is off a 350 truck tho, and mines a 305 camaro.. i was told id def have to rejet it

five7kid

iTrader: (14)

If it is a computer controlled carb, you don't have to rejet it. But, you might need to put different rods and/or hanger in the secondaries.

Burntz

i was told that a flattened cam lobe could be alot of my problem, is that true? my dad told me that it could be causing my rough idle and rattling. how likely is that? god i hope not lol

naf

iTrader: (7)

Possible, yes. Likely, no.

five7kid

iTrader: (14)

A flat lobe could certainly cause a tapping noise and rough idle. However, unplugging the MCS would not make a rough idle due to a flat lobe go away.

I've tried to read more carefully though this whole thread unstead of just the last few posts. I didn't realize when I made my A.I.R. comments that yours isn't operating. That will not cause your problems - I know this for a fact because my A.I.R. has been inoperative for more of the 7 years I've had my car than it has operated, something on the order of 5 years inop to 2 years operating, and I do not have any such problems.

You have not made any reference to an SES light or having pulled trouble codes from the computer. Does the SES light come on? Does it work? Have you checked for codes?

Burntz

the ses light has never came on. im not sure if it works but the choke light comes on sometimes while starting it.

i think what im going to do is have some1 try to tune it and go from their? what would my best bets be? If i have some1 do diagnostics and stuff its easily 100-200... and im poor atm.

Burntz

and i have another carb, identical to mine, except that it came off a 85 350 truck, and iv been told its jetted differently and putting it on my car would/could blow it, but some1 else said the jets dont matter cuz its comp controlled? im so confused

five7kid

iTrader: (14)

When you turn the ignition to "on" without starting the car, the SES light should come on. If it doesn't, either the bulb is burnt out or the ECM is kaput.

If you work at a parts store, you should be able to use a store scanner to pull trouble codes. Auto Xray is nice, because it doesn't rely on the SES light to get the codes. It will also tell you if the ECM is not responding.

You'll probably learn more about what's going on from that exercise than anything else you could do right now.

Burntz

well our store scanner isnt their atm, at least the 1 we lend out, and they wont let me use the other ones