_MIKE_P

iTrader: (1)

Hello,

I'm replacing my leaky and worn out E4ME with a re-manufactured unit from National Carburetors and have run into an issue with the gaskets.

When I took off the carburetor there were actually two gaskets underneath it, a thin one with the bore holes all "seperated" on top and a thicker 3-4mm gasket below it. The thicker one has just one big wide open hole. My replacement carb only came with a new "thick" gasket/spacer with the large port and not the thinner one.

Do I need to purchase the thinner one or was that a result of a previous owner not following correct instructions or trying to tune the carb or something? What would be the correct stock or preferred setup?

The car is a stock 1984 z28 5.0 L69 5 speed. with CCC E4ME Quadrajet and all emissions.

_MIKE_P

iTrader: (1)

Also, I just noticed the front of the new thick gasket/spacer is cut more open than the one off the car. Is this normal or is the new gasket for the wrong application/made to be generic?



(old on left, new on right)

sofakingdom

iTrader: (1)

There should only be one, and it should have 4 holes. The 1-holer will work but the 4-holer is better for this application.

No telling why somebody stuck 2 of em under there.

_MIKE_P

iTrader: (1)

I went ahead and bought a Felpro 60482
http://www.summitracing.com/parts/FEL-60482/

Every website and the computer at O'riellys list it as the correct gasket for the carb, lines up almost exactly like the old one.

I noticed there's a thin stainless steel heat shield also listed for this car, should mine have it? I didn't see one when I took off the carb.
http://www.summitracing.com/parts/FEL-60731/
http://www.amazon.com/Fel-Pro-60731-.../dp/B000C2CBZ8

sofakingdom

iTrader: (1)

Yeah that gasket is fine. The one you have would work OK too.

The thin shield isn't used in these cars, goes in ones from around 69-70; the exhaust crossover passage actually had apart that went up under the front of the carb, and the stainless thing went on against the manifold to seal the exhaust.

_MIKE_P

iTrader: (1)

Alright I installed the reman carb, hooked everything back up and its not running correctly. The engine is at full temp, the choke flap appears to be open fully. The engine wants to idle high and the idle fluctuates up and down

If I leave the little electric solenoid connected on the drivers side, when I blip the throttle, the little piston pops out and holds the assembly at about 1500rpm, if I unplug its wire and push the piston down then the idle settles down but still fluctuates between 500 to 1000rpm and the motor still feels like its on fast idle and not the smooth normal idle.

I noticed even with the solenoid disconnected, the throttle linkage on the drivers side still does not return to touching the idle screw. Theres a small, maybe 2mm gap between the idle screw and the throttle linkage. Would something in the choke or fast idle linkage hold it up?

sofakingdom

iTrader: (1)

It's supposed to work like that.

Set the screw to the curb idle spec on the emissions sticker. THen set the solenoid (the hex head of the pluger is the adjustment) so that when you take blip the throttle, it holds the idle at around 1300 RPM, then lets it come down.

Since you have a 5-speed car, that's how the factory made it pass emissions; it keeps it from blowing the giant puff of rich when the throttles slam closed in between gears.

_MIKE_P

iTrader: (1)

I tried turning the screw in further but it doesn't seem to help the car run any better. just raises the idle. The real issue is that the RPMs still wander up and down and the car doesn't want to settle down at a consistent speed.

I reconnected everything, put the aircleaner, etc on and went for a test drive to check out the driveability. It definitely seems to perform well, I can actually hear the secondaries open (never got that famous quadrajet moan with the old carb) and theres a noticeable improvment in power and torque.

However, as noted during my idle testing the solenoid will not let it idle down past 1200-1500 rpm and the idle still wavers back and forth.

Could my problem be some sort of sensor or electrical issue? I don't know when the o2 was last changed, the wire running to it across the motor is a little crispy looking. The plastic plug that connects to the mixture control solenoid on top of the carb is a little melted but it was working fine with the old carb. Perhaps all the movement may have finally broken or cracked a wire somewhere? However,I can hear the MCS clicking when it idles and as stated before the driving performance is good, so I dont think that plug is the culprit.

What else could cause an erratic idle and energize the solenoid on the drivers side of the carb? I know the a/c is one of the things that controls it, but its all off and the clutch isnt engaged. Bad ECM?

sofakingdom

iTrader: (1)

How responsive is the carb to adjustments to the idle air bleed valve?

84ws6ta

My car had this same engine when it was new. The thick gasket is supposed to be used, it helps keep heat from transfering to the carb. There are two set screws to adjust on the carb. The one on the passenger side is for cold temp starting. The one on the driver's side is for the curb idle. The solenoid on the side of the carb is for when the a/c or heater is on. When on they will drag down the idle so the solenoid will kick in and "adjust" the curb idle. Once the heater or a/c is off, the solenoid should release. You said you bought a rebuilt carb, what are the idle screws set at? For these carbs on a 305, you shouldn't need more than 3 turns out on each one.

_MIKE_P

iTrader: (1)

@sofakingdom
The IAB is the slotted bronze screw just foward of the primaries on the top of the carb correct? I'm hesitant to mess with it too much but what would the expected results be from turning it clockwise/counter clockwise?
@84ws6ta
Its a re manufactured E4ME from National Carburetors part#ND4477, I gave them all my specs and the tag included states it was dyno engine tested and "Fuel pressure tested @ 5 pounds, Engine vacuum 21 inches @900 rpms". However their engine could be anything and you never really know what you get. I'm hesitant to mess with the mixture screws before I give them a call. I don't have any of the adjustment tools, gauges or a dwell meter so I'd like to eliminate any other possible issues before going that route.

If I were to buy or loan a dwell meter would it tell me anything useful with the IAB or mixture screws?

sofakingdom

iTrader: (1)

Yes in fact it would... that's the "ideal" method of tuning it.

The mixture screws (the ones down in the throttle plate) have almost no authority at all; do virtually nothing. Set them somewhere convenient, anywhere from 5 to 7 turns out should do fine.

The IAB is indeed the huge screw looking thing down in the center of the front of the choke tower. Turning it clockwise richens the idle (and high-vacuum cruise, to some extent). I'd suggest trying that. Set the mixture screws as above, then try running the IAB CW in small increments like ¼ turn. Keep careful track of how far you've moved it so you can put it back. N.b., there are 2 O-rings on it; very easy to damage during installation; if they're wasted, they will let in excess air (essentially bypassing the valve) and make it run WAAAAAAAAAYYYYYYYYYYYY lean all the time except at WOT.

The lean and rich stops for the MCS might also need some tweeeeking, but those are harder to get at without the tool. I made my own about 25 or more years ago, looks kind of like about a 3/16" dia screw head with a real wide slot.

Putting one of these things back together to the "factory specs" is pretty much a crap shoot. Consider that as a reliable starting point for tuning, not the be-all end-all Holy Grail of complete carb perfection. Even if the rebuilder put it exactly there, that's no guarantee of "optimum" behavior. Then, consider the "dyno engine tested" thing: did they have a 84 L69 exactly like yours to test it on, ya think? Probably not; they more likely stuck it on whatever generic test mule they have, and made sure it at least worked... not that that's bad, actually that's more than most would do; just, there's NO WAY they could possibly have "dialed it in" that way. All that does is assure that there's no gross malfunction like total needle & seat failure and such as that.

As described, in the L69/5-spd setup, the solenoid does more than just hold the idle up for the A/C; it's actively involved in driving the car. Set it as described and let it be until the other issues are worked out. You will almost certainly find that it needs adjustment every time you change something else. You may also find that if it's totally inoperative (i.e. has no authority to hold up the idle speed at all) the car will die when letting off the gas between gears, especially when it's already not tuned right. I know my 83 L69 sure did that alot when I first got it way back when.

Try the IAB first and see what happens. Even if that's not "the answer", it'll tell you alot about what else is going on. If it has a HUGE effect, then the carb is idling way rich or lean (more likely you'll find, lean).

_MIKE_P

iTrader: (1)

Alright I went out and bought a dwell meter and tried experimenting with the IAB screw. Counting the turns down it was in the 4-5 range before bottoming out. At 4 turns out the dwell seems to stay around the 5-10 range (on the 6cyl scale) Clockwise down seems to make a marginal improvement and with the IAB bottomed out completely it tends to hover around 15 somtimes closer to 20. The idle rpm still rises up and down no matter where the IAB is. These readings were taken with rpm's in the 750-1000rpm range. Engine is at full temperature, to the point where the cooling fan comes on. Revving the motor makes the dwell meter sweep around, that means its in closed loop and the o2 is reading something, correct?

Any ideas?

sofakingdom

iTrader: (1)

Right; it's in closed loop.

The IAB should make a MASSIVE difference. Might want to pull it out and check the O-rings.

You may also have a vacuum leak somewhere else; check around the base of the carb, trace all the lines, etc.

Does your car have the baro sensor? Is there a vac line going to it? If so remove the line.

_MIKE_P

iTrader: (1)

To remove the IAB, I just unscrew it all the way and lift out? I've traced all the vac lines and they appear okay, no open connections or any holes that I can see, but I'll try looking closer and maybe capping some lines to be sure. One thing I noticed is that the new carb has an extra vacuum port on the front of the baseplate, to the right of the one I'm using for the pcv.

Not my carb, just a google search image, it would be the port with the red cap:

My old carb didnt have it at all, so I left it capped. Should it be used for something?

sofakingdom

iTrader: (1)

Yup, just unscrew and pull out. Smear a little oil or something on the O-rings before trying to put it back in if they're OK.



What letter is that port labelled? Should work fine if capped off though.

What about the baro sensor?

_MIKE_P

iTrader: (1)

There's a letter K stamped into the carb body above the extra port. I looked, but I couldn't find anything resembling a baro sensor, where would it be if I had one?

I pulled the IAB out and it looks ok, has two O rings, a rounded one up top and a smaller, more squared off looking one towards the bottom.



Put a little oil on the rings and put the IAB in 5 turns out from bottom and started the motor. At about 3.5 turns out, dwell begins to hover around 25. Turning it further down makes dwell decrease to as low as ten, then when lightly bottomed out it slowly rises back up to the 26-30 range. Idle is still high and wandering, around 750-1000 even with the curb idle screw backed out to the point where the throttle arm isn't even touching it. I've taken off the electric solenoid for now.

I bought the mixture screw tool at O'riellys, should I leave the IAB around 3.5 out and try backing out the two mixture screws at the front base of the carb and see how it reacts? Is there a particular method, ie both at once or adjust one then the other?

five7kid

iTrader: (14)

On the cowl lip by the AC housing. It should have an electrical connector on it but no vacuum line.

_MIKE_P

iTrader: (1)

Didn't have time to play with the fuel mixture today but I checked again for the baro sensor, no sign of it near the a/c. Upon closer examination I found a teal looking 3 prong connector zip tied to the main harness. Is this the baro sensor harness? If so, what would running without one do? I've been driving without one since I got the car a little over a year ago, didn't seem to notice any particularly strange behavior.

naf

iTrader: (7)

That's certainly the baro sensor connector. I'm not certain how it will act without it.

If the curb idle lever is not resting on the set screw, it's likely that the fast idle cam on the opposite side is holding it up. Make sure all of the choke linkage is clear and allowing the throttle to rest on the curb idle set screw before trying to set the idle.

If you're getting a wavering dwell around 25-30 DEGREES, you're where you want to be. This sets the dwell within the midpoint and allows the most control over mixture lean/rich for the ECM.

I would double check the mixture screws if you haven't already. Make sure they're around 4 turns out EACH. I've chased problems before that turned out to be uneven settings here.

Don't just visually inspect for vacuum leaks. I like to plug each port, then with the dwell meter hooked up, re-connect each to see if the dwell changes (or just test each with the mityvac).

The extra port on the baseplate was used in later models for the charcoal canister line. Earlier ones just tee'd this line into the PCV hose. You can just plug it.

_MIKE_P

iTrader: (1)

Both mixture screws were 2.5 out, I put them to 4 turns out. Iab at about 4 turns as well. The dwell appears to be in its correct location, fluctuating around 25-32 with the current settings, but idle is still high and fluctuating at around 1000. Curb idle screw is backed out and the choke cam appears off

Started hunting for vac leaks but ran out of time before work, I capped the nipple screwed into rear of the intake manifold in front of the distributor as the lines to the cruise control were dry rotted. Didn't make too much of a difference but I'll keep hunting.

The missing baro sensor is making me curious. Did all L69's come with it? Could someone in the past have removed it and tweaked the carb to run without it and now my new carb is bringing the issue to light? I'm gonna try junkyard hunting for a good one just to see what it does, were they all the same for LG4 and L69 models?

sofakingdom

iTrader: (1)

Not all L69s had it (mine didn't for example) but the presence of the connector makes it seem likely that yours did.

Definitely sounds like a vac leak somewhere. Take em all loose except for the MAP sensor one (port N in the diagram) and the PCV (hook up JUST the PCV valve with an unbroken piece of hose) and cap the ports; see if it works right; if it does, start hooking em back up one at a time. Could even be the PCV valve itself.

_MIKE_P

iTrader: (1)

I pulled and capped all the vacuum hoses, except for the PCV and Vac sensor. Still the same high and wandering idle around 1100 rpm or so. Dwell is in the 30 range. Pulled the PCV out of the valve cover and capped the large port at the base of the carb, still the same result. I checked for trouble codes, light just flashes 12 over and over (no codes?)

What else could it be? I'm going to try swapping the original carb back on tomorrow and see how the car reacts because I'm running out of ideas. Could the o2 have gone bad at a coincidental time?

Can someone with a baro sensor E4ME car try unplugging it to see what behavior it creates?

naf

iTrader: (7)

Another possible cause of the high idle on q-jets are worn throttle bushings. The bushings can allow unmetered air in and/or get slightly hung up and not close completely. Check them by removing the throttle linkage and spring and check for play WITH the throttle open (otherwise the butterfly valves will eliminate the play).

Check your timing? Should be 4-6 BTC with the ESC wire removed and should look to be around 20 or so with it reconnected and increase when the engine is revved. Observe it with a light while it's idling, make sure it's not doing crazy weird stuff.

Have you eliminated the idle speed solenoid as an issue? You can disconnect it and let the plunger stay seated so you know it's not affecting anything for now.

O2 shouldn't have that much affect.

_MIKE_P

iTrader: (1)

The ISC is currently off the carb, I'll check for throttle shaft play.

_MIKE_P

iTrader: (1)

Don't seem to have any real play in the throttle, even spraying carb cleaner near the shaft areas results it no measurable change in engine rpm. Tried unplugging the the TPS and MCS then disconnecting the battery for a few minutes to try and clear any previous settings. Still the same high wavering idle behavior when running, even with no TPS and MCS connected.

I don't have a timing gun to check timing. I'll see if I can borrow one.

Any other things I can check?

naf

iTrader: (7)

Did this thing run right before the carb swap? or did you swap the carb because of a problem?

If unplugging the TPS or MCS did not change the idle quality it's probably not fuel ratio related, although a vac leak could still be present. Unplugging either of these would cause the carb to go rich with fuel.

84ws6ta

Naf has a good point here, how was this engine running before you decided to replace the carb? How many miles are on the engine as well? Last time a tune up was done? Condition of the engine is important if you're going to tune the carb to run properly.

84ws6ta

Also reading another point by Naf about the timing, good call by the way. I remember now having a similar issue where the engine idle ping ponged back and forth. Turns out that the nylon coating GM puts on the upper timing chain gear came off and allowed the timing to advance and retard. Replaced the timing chain and gears and the issue was corrected. This could be your issue, something worth looking at anyway.

_MIKE_P

iTrader: (1)

The engine seemed to run fine before I replaced the carb. It has about 177,000 miles on it, not sure what kind of work has been done to it over the years, as I bought it about a year ago with 174k. I've replaced the spark plugs, plug wires, PCV, air filter, and fuel filter shorty after I got it. The only things I haven't changed are the cap and rotor (both looked fine when I looked inside) and the o2 sensor (Car ran fine). So its only been about 3 to 4 thousand for a majority of tuneup components.

I replaced the carb because I believed the choke coil to be malfunctioning on the old unit (manually pushing the fast idle tab on the pass. side of the carb would make it idle normally, then pulling the throttle would click it back up one notch and fast idle. Turning the coil clockwise cured the issue but made cold starts difficult. I also was not certain the secondary air flaps were working correctly, as I could never hear the carb make the "moan" that a full throttle quad should. Also, the accelerator plunger was leaking fuel out the top onto the carb. So I figured with all the issues, a remanned unit would be the more economical choice.

Unplugging the 4 terminal ESC connector to the base of the distributor results in a lower idle, closer to 750ish, but it still wanders up and downa bit. I need to get a hold of a timing light to see if its timing that's changing. Should it stay around 0-6 degrees regardless of rpm with the computer disconnected?

84ws6ta

The timing is supposed to be set at 6 degrees with the ESC 4 terminal plug disconnected. But whatever the timing was set at it should be steady. Unplugging will cause the engine to run at a lower rpm because you no longer have any advance input from the computer. One of the posts claim that the idle mixture screws at the base of the carb do nothing. That's not true, you're basically running off those at idle. Normally to adjust them, you turn them out and then turn them in until the engine runs rough and then back them out until the engine runs smooth again and then about half a turn after that. For me I've found that 3 1/2 turns out seems to be about right. You shouldn't have to go more than 5 turns out for that carb/engine setup. If you can turn the screws in with no change in the engine while running, then the primaries are not closing properly at idle.

_MIKE_P

iTrader: (1)

Just to see what happens, I put the old carburetor back on, only the PCV and VAC sensor connected and...it idles perfectly. Once warm the idle stays nice and steady around 650 ( or whatever that hash mark between 500 and 1000 is). Dwell is nice and steady around 30 as well. I suppose I need to give the folks at National Carburetor a call.

One difference I noticed between the two carbs is when I unplug the vacuum line for the air cleaner housing on the old carb, the choke pull off always loses vac and releases. Capping it will make the choke pull off contract again.

On the new carb, leaving the port for the air cleaner open makes no difference to he choke pull off, it stays pulled in. Unplugging the tiny 3 inch line does make it let go. Which behavior is "normal"? Could this indicate some sort of internal problem?

naf

iTrader: (7)

The choke pull-off should be connected to vacuum thru a bronze metal tee, the other end of which is connected to the air cleaner flap. If the line to the flap is released, this port looses vacuum.

At this point I would be opening the carburetor up to see what's what, but since it's likely still under warranty, I'd give them a call. Odd that it would go open loop, give good dwell and still not allow a steady idle. What did the dwell do as the idle went up and down? Anyway let us know how it goes with your next one.