papapayne

Ok, got an issue that i am pretty sure i have narrowed down to either carb/fuel issue. (I think) Breakdown is, 84 z28 HO with the 4 barrel carb. I bought the car a few months back (4th 3rd gen) first carbed one though. In the car was a new OEM carb the original owner bought but never put on. Car sat for 4 years, I bought and have been tinkering with. Changed Every fluid so far except differential. The old carb was majorly gummed up so I put the new one on. (only drove 1-2 times before new carb) Heres where the fun begins.....

when you start the car, unless you keep your foot on the gas pumping it and keeping it over approx 2.5 rpm car dies
rough idle even when hot
if, even after hot, turn car off then restart car then still have to pump gas to keep car running
after like 10 minutes of idling sometimes you can leave pedal alone
several times at red lights/middle of u turns etc car dies off


List of things i have tried....

Redone vacuum lines to makesure no vacuum leams
done my best to adjust fast idle screw
messed with choke screw to see if it helps
I am not all that experienced in Carbs so any help would be great

naf

iTrader: (7)

Welcome to TGO.

A new, or reman, carb may still require some adjustment once installed, although this sounds like a timing issue, maybe combined with a maladjusted carb.

First step in adjusting the carb is ensuring the ignition system is good. Have you replaced the cap, rotor and plugs? Verified the timing is set per the under hood sticker (I think 4 degrees BTC for your 84?)? WITH the ESC wire (four pin connector) disconnected at the dist?

The sticky at the top can help with carb adjustments, but check that ignition system first.

When you swapped carbs did you check the secondary rods and hangers to verify they were the same? The HO came with a sweeter set than the LG4s. The LG4 was much more common though and the new carb may have come with the fatter (less fuel at WOT) rods. They can be swapped over if different, no problem.

papapayne

Timing is dead on, new plugs, and yes same rods as old carb. My buddy seemed to think it was problem with choke but i don't agree since it occurs long after the car is heated.

naf

iTrader: (7)

When the car is at operating temp are the choke blades completely open, 90 degrees straight up? Once it's open completely it should no longer affect the motor, but choke blades not opening completely will cause trouble. It should take a couple minutes once the engine's running for it to slowly open completely.

Is the check engine light on? have you pulled any codes?

Do you have access to a dwell meter or scanner? This will allow you tell whether the ecm is going into open (feedback) loop and can be used to adjust the carb.

Have you verified that the ignition timing is advancing with throttle? Running around 18-22 degrees advanced at idle with ESC wire connected to dist?

Does manually opening the EGR valve while the engine's running cause a difference?

Mixture Control Solenoid in the carb clicking properly when the ignition is turned on? It should click while the engine is running too but is harder to hear.

Most of the above assumes a ccc-qjet although some export models, particularly to Canada, came with a mechanical q-jet.

papapayne

lot to answer....

after warming up, choke fully open, no check engine light, just rechecked timing...with the 4 plug still on is at 15 degrees, dwell meter? carb clicks but cant tell for sure if its carb clicking or if its the starter relay. How would i manually open EGR? have considered trying to tune carb but....have never done it and dont know anyone that would know how to do it well with out paying a fortune.

papapayne

just another piece of the puzzle perhaps. On the front passenger side under choke vacuum mechanism there is a female metal clip that looks like it needs a female clip to attach to it. There are 2 other wiring harnesses plugged into the carb. I searched around the male clip and found a wire that looks like it had at some point a female attachment....went to junkyard to see if i would get lucky and see a carbed 3rd gen to compare wiring....no such luck. Any ideas as to what clip is, and if needs reattachment how to do it?

five7kid

iTrader: (14)

The timing with the 4-wire plug still connected is irrelevant. You need to disconnect that plug and set it to 4 degrees (or whatever the under-hood sticker says - a couple of degrees more usually helps). 15 degrees with the 4-wire still connected sounds like too little, for what that's worth.

You need that to adjust the idle air bleed. Connect it to the green plug by the heater box that doesn't connect to anything. You're looking for 30 degrees on the 6-cyl scale with the engine warmed up and idling. If you have a scan tool but not a dwell meter, look for 50% duty cycle on the mixture control solenoid.

The clicking while running is the mixture control solenoid. The starter relay will only "click" when you turn the ignition to "start".

Either reach under it and push open the diaphragm, or hook a vacuum pump like a MityVac directly to the valve.

It can be done with some relatively simple special tools and test equipment. You don't need a fully equipped shop to do it.

naf

iTrader: (7)

For me it can be a good indication that the original poster set the timing correctly in the first place and/or that the advance is working correctly after ESC is re-connected. Seen bad harness to dist cause lack of advance even after timing was set properly. Does seem a little low..I'd recheck the base timing.

Should be three wire connections at the carb. Three-wire connection at TPS, front, driver's side; Two-wire connection at MCS, top pass side and single-wire connection to choke heater coil. A fourth single wire connector will plug into the idle bump solenoid that is attached in front of the driver's side idle speed screw-but it can be argued that this is not 'technically' attached to the carb (solenoid is).

papapayne

carb heater wire connection clip is AWOL and will have my buddy bring his timing gun back over and set timing. Its been pouring here so I haven't had motivation to dig into testing EGR suggestion yet. Hopefully can day after X-mas. If that is the problem, how would i go about solving it?
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Asked around at a shop and he suggested removing and plugging all unnessary vacuum lines (car is smog exempt in my county in california) think that would help and where would i begin? I have always hated the spaghetti of vacuum lines under these carbed third gens.

five7kid

iTrader: (14)

Pretty stupid, actually. Did he tell you what was "unnecessary"?

naf

iTrader: (7)

When I'm setting up a carb (after ensuring ignition is proper) I like to plug every vacuum port on the carb with a cap. Then after carb is adjusted properly, reconnect each one with motor running and meter hooked up. If one of them is leaking it will show itself fairly quickly.

If your choke heater wire is missing, the choke should not have been opening. It should spring shut when cold, open slightly when the motor starts (and vacuum pulls the choke pull off in) then open slowly as 12volts is applied to the little 'heater' coil inside the housing.

Pics of my 87. Different manifold (it's on vortec heads) but all the carb connections are there except for the plugged port to the thermac that's not used. That dust everywhere is remnants of paint I've DA'd off recently. I might wipe the bay down later today.

papapayne

so if choke not opening, would that be the problem with it dying off on start up and when stopping?
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Naf,

I noticed on your pictures of the carb, you have deleted some of the vacuum lines the one that stuck out is capped by the yellow cap right on the front of carb. Did this improve your perfomance? my vacuum lines are a mess and really want to figure out what can be removed. My third gen is smog excempt too if that changes anything.

five7kid

iTrader: (14)

The only thing I see capped (the yellow cap) is the line that goes to the air cleaner thermovac system.

papapayne

looks like there are others missing from front carb, or maybe my car just has more spaghetti lol

naf

iTrader: (7)

Don't use my pic as an example of vacuum line routing. You can't see but the lines to the smog pump (headers w/out AIR), the EGR (vortec heads don't have the provision) and the EFE valve (exhaust recirc valve on pass side manifold) are all missing.

I should have taken a photo of my LG4 85, which I drive everyday (219K so far). Although I pulled the smog system off it last Summer. Some of the tubes had rusted through from the inside and it got to the point that it wasn't worth fixing any more. No real performance gains from removing any of that stuff though.

If your choke is not working properly your engine will never run right.

papapayne

so that heater coil wire being gone will cause those symptons?

naf

iTrader: (7)

If it's not the lone culprit, it's certainly contributing to your issues. Find the choke heater wire and reconnect it.

Choke should never be fully open if the wire is missing unless something has been tinkered with. It should spring shut when the engine is cold then slowly open as the choke coil warms up from the 12 volt applied to it as the motor is running.

If yours is stuck open, cold starts are going to be a problem. If it's stuck shut it won't run right hot.

papapayne

found the actaul wire but the clip is missing. tried local junk yard no luck...any know where a guy can possiably get new clip?

chevy89camaro

pull a plug and see if you burning the fuel good. if its black turn the fuel down. carbon fouled not oil. if its burning clean stick a timing gun on it. if timing appear to be good the watch for the timing to jump back and forth. if it does the pull the distributor and change the gear my friend. its worn badly. if none of that is working for you fire it up an run it a couple min...kill it and pull all plugs and first look to see if the plugs are bad... if you havent put new ones in id go ahead and do that to begin with. Look for a wet plugs...watch for water just in case theres a blown head gasket. you dont know how the previous owner drove the car before it was parked for 4 years. if any plugs look like there burning themselves then double check for vacuum leak. maybe intake gaskets are shot. watch for water in the oil. if you have doubts chage the intake gaskets anyway. there cheap and if you get busy you can have it done in less than a couple hours and have plenty of time to drink beer while doing it. best of luck to you

naf

iTrader: (7)

I checked a few sites and didn't find anything. You may have to fashion a spade connector or maybe try a small alligator clip (at least temporarily). I'll be hunting something to replace that clip myself soon for an '87Z I'm putting the motor back into.

papapayne

ok, I got sick of the way it was running so took into shop...Took a lot....I hate having people work on my car but anyways.

Base timing was 19 degrees. He put to stock. EGR is leaking, vacuum lines routed wrong but the real problem is the carb. He said the rods are bad, float is bad etc. New either to rebuild carb or get new one. I have to get car to pass smog to finish transfer then never again so need to figure out wat best course it. He would rebuild for 450....don't want to really do that. Anyone know a good rebuild place that is cheaper? Or would it be best to just buy new one?

summit has remans http://store.summitracing.com/partde...5&autoview=sku


or was thinking http://store.summitracing.com/partde...8&autoview=sku or maybe

http://store.summitracing.com/partde...9&autoview=sku

but i cant find on their whether those will be smog allowed or not.

How would i go about replacing EGR and both the thermvac systems?

thanks!!!

NoTransistors

I have read these posts a few times, and no one has said a word about old gas. Even if it was drained out, there is still major residue in the tank, and we do not know if the new carb was installed before the gas change.

I speak from experience. Bad gas ruined two snow blowers, and more recently, the 2bbl carb on my GF's '70 302 Mustang. Car sat for three years with a full tank of gas that was already 1 years old. Even with fresh gas, and an attempted carb rebuild, the thing craps out at every light. Pull any plug, and it shows a too-lean condition. Funny though that idle, both cold or hot, is silky-smooth. A leaking manifold gasket should severly mess up idle.
Carb is totally trashed, and a full tank of fresh gas didn't help.
I plan to empty the tank and have it steamed out, if I cannot do it myself.
Then a new Holley 2bbl with auto-choke kit goes on. So will a new fuel pump.

Seth

papapayne

Yeah, I want to drop gas tank and clean it the problem is the exhaust will need to be cut to get it down. As far as the carb...I think what I may just do is scan junkyard for one, get a rebuild kit and try to rebuild it myself and see how that goes. I've got the chilton manual that has step by step.

naf

iTrader: (7)

Can you try to rebuild the original one? A rebuild kit with a can of carb dip (gallon can from the parts store) should run around $40. It's not too difficult and we can walk you through it. You just want to make sure you count turns out on the lean and rich stop adjustment screw and the two idle mixture screws before removing them so they can be set back to original settings.

You'll probably want a dwell meter too so the carb can be properly adjusted when it is re-installed. Worst case could be replacement of the TPS (maybe $30?).

Which rods were bad, primary or secondary? I would guess that he found a problem with the primary metering circuit controlled by the Mixture Control Solenoid (MCS). This little puppy clicks the rods up and down and varies the amount of time they spend in the primary jets to meter the fuel per ECM command.

Your base timing was set at 19 and staying at 19 with the four wire EST connected? If so, it indicates something, or some sensor somewhere, is not working. The ECM should increase timing, adding around 18 or so degrees to base timing, even at idle. This should definitely throw a trouble code. I'd pull your codes from the ECM before going much further. Walk thru on codes is here: https://www.thirdgen.org/service-eng...ht-error-codes

Pull them and post. The only one you should see (other than the 12) is the EST error code, either 41 or 42. It's triggered by setting base timing, running the motor with the ESC wire disconnected at the distributor. If you don't see anything at first, check your lamp. It's common for prior owners to pull them.

naf

iTrader: (7)

Found the choke connection pigtail on Rockauto for around $3.50.

papapayne

Thanks for that Naf, I will have to pick one up. I can rebuild original one, but this is my daily driver/only driver. I work at pick n pull so i think it would be better to find one and rebuild it on on my own time then when ready put it on.

The guy at the shop adjusted the timing to specs, and increased idle speed and enriched mixture. He said it was running way to lean and thats why it dies and has no power and is sluggish at times.

papapayne

so any suggestions on which area of the carb is the culprit. Symptons categorized are

Lean
When driving any speeds, cruising/freeway/city at times car boggs out and takes flooring it and a ton of hesitation before it finally surges

what area should i look at

naf

iTrader: (7)

Did you check for codes?

To adjust and troubleshoot the computer controlled carb:

Get a dwell meter, set on six cylinder scale and connect it to the green diagnostic lead near the blower motor. With the engine running and warm it will show the percentage of time that the ECM is commanding the primary rods to be in the primary jets. (They click up and down at a constant rate but the ECM commands them to 'dwell' in the jets at a different rate depending on sensor input-more dwell = less fuel). A scan tool works well too, but they're kinda expensive.

Your goal is to make small adjustments to the idle mixture screws and IAB until you get a dwell that varies (needle wavers /- 10% or so as the ECM corrects of O2 readings) and will respond to the air horn being choked with a rag by leaning the mixture (dwell increase). Once you get it to behave properly make small adjustments to the IAB to get near 50% at idle.

I like to do this initially with every vacuum port plugged, dial in the carb then reconnect each one while watching the meter. A vacuum leak will be evident immediately.

There's more info in the sticky on rebuilding the E4ME at the top of the carb forum. I can also provide more detail if you need.

papapayne

I wanted to ask something. So if its really the carb thats bad...wouldn't the problem exist every time i drive the car? The reason I am asking is the last few days I haven't had any problems, the car has been responsive, powerful, and no problems. I am starting to think that maybe the carb aint the problem it seems to me that if its a mechanical problem with the rods or floats or something it would always affect the car. Am I thinking correct?

naf

iTrader: (7)

Did it fix itself or has it been good since the mechanic looked at it?

papapayne

fixed itself. Idling was fixed by mechanic, it doesnt die at lights. But it was still bogging out at speed. It just stopped for like a week today it did a bit of bogging out today and the check engine light popped on for a few miles then fixed and light turned off

naf

iTrader: (7)

Check the trouble codes on the light and post back.

papapayne

pulled following codes:

23, 24, 41, 44

five7kid

iTrader: (14)

https://www.thirdgen.org/service-eng...ht-error-codes

Code 23: Throttle position sensor error

Code 24: Circuit fault in vehicle speed sensor

Code 41: Cam sensor fault (means the ECM isn't seeing the distributor input - this code is set when you unplug the distributor to set the timing)

Code 44: Oxygen sensor lean (typically a weak O2 sensor)

papapayne

i looked at the haynes and it said 23 is mixture solenoid. and 21/22 is the tps.

what can i do about all these codes? I figured 41 was from setting timing. how hard is putting in new 02 sensor. Where can I get the best price on euther tps or the M/C S?

naf

iTrader: (7)

Let's check the TPS first. It's a common fail item. You'll need a voltmeter. You want to check the voltage with engine in 'run' (doesn't need to be running though) at the three wire connection to the TPS, front drivers side of carb. You have to check the voltage at the plug WHILE it's connected so you'll have to backprobe the the wires into the connector with a thin piece of wire/needle, etc. The bottom wire is the ground, the top wire is the 5.0 volt source from the ECM-make sure it's good, the middle wire voltage should vary between 0.40 at idle and 4.0 volt at WOT. You can open the throttle while checking with engine not running, but key in 'run'.

If the readings are close, within 0.25-.50 volt or so, it's probably fine, but may need adjustment. If the readings are erratic or staying at high voltage, the TPS is bad.

O2 sensor can be replaced fairly easily depending on whether anti-seize was used when it was installed. A tool can be 'borrowed' from AZ or one of the others.

papapayne

if the O2 sensor was bad, or dirty, could it be sending signals to lean out the carb?

naf

iTrader: (7)

O2 failure typically results in a rich condition.

five7kid

iTrader: (14)

But a lean error code. The ECM thinks the mixture is lean and richens the mixture.

naf

iTrader: (7)

Exactly.

You posted earlier that the symptoms were categorized as 'lean' (among other things). Both O2 and TPS failure typically result in a rich condition. O2 for the reason above and TPS because it generally fails and sends a high voltage signal to the ecm commanding 'full rich'.

Your mechanic could have compensated for this, though, by leaning the mixture, maybe getting it near right at a certain rpm/load. The bad TPS would still prevent the ecm from adjusting the mixture correctly at other rpms/loads. It would be lean in spots and rich in other spots.

The TPS should be tested before replacing, along with the wiring and voltage signal from the ECM. The O2 is a wear item, routinely replaced at a regular service interval that is probably long since expired.

papapayne

ok. This whole carb/car thing is really been a pain. Some days the car runs like a charm then for a few days it will run like crap, die off have no power and bog down.
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those are symptoms of running lean correct?

papapayne

yea, the car was sitting since 2002 when I bought it. I have been doing some catch up on stuff. I need to get 120k mileage done (sitting at 119k) i will guess i need to ad the O2 sensor to the list.

naf

iTrader: (7)

Not necessarily. Come and go carb problems may be result of choke linkage, gummed up, getting stuck, mal-adjusted, etc.

Get the TPS checked and replaced if necessary.

NoTransistors

NAF had a point that needs to be taken seriously- vacuum leaks.
Every problem that my car has had, supposedly with the carb or computer [none as severe as yours] has been ultimately traced to a hidden vacuum leak.
The reservoir for the heater control, then a few hoses and two plastic tees, then a valve cover gasket, then the four-nipple vapor purge valve, then the cannister purge valve, then the actual vacuum valve on the heater control assembly. All of these leaked at one time or other, causing the computer to freak out. Not knowing better, I blamed both the computer and/or the carb. You or your mechanic cannot make adjustments to compensate, as the car cannot possibly run properly under most situations.
BTW, an out-of-adjustment TPS does do a wonderful job of making things worse. It really does need to be set close to specs.

Seth

papapayne

ok, i going to take it back into the shop on pay day and have tps replaced. I have tons of spare vacuum lines so I just going to have to go through them on at a time and replace every dang one.

NoTransistors

The point that I was trying to make was that these control valves and switches and sensors usually have a rubber diaphram that goes south, creating major leaks. Most of these things use one common vacuum source, which is a bunch of tees off the line that runs fron the pvc valve to the base of the carb. The more outside air that leaks in, the less likely the computer can create or maintain closed-loop. That engine should idle silky-smooth, especially in closed-loop.
Also, when not in closed-loop, the leak simply leans out the mixture.
When everything gets ironed out, you will be exhuberant as to how well that little engine runs.

Seth

naf

iTrader: (7)

If you want to try this yourself I think we can walk you through it. You'll need a volt meter and a dwell meter.

papapayne

i dont have either of those

naf

iTrader: (7)

Dwell meter ~ $30
Volt meter ~ $10-15
Carb rebuild kit ~$30
New TPS $25?
Carb Cleaner $5

Compare to the cost the mechanic would charge you.

NoTransistors

You need to add one thing to that list.

Warm California climate ~ Priceless.

It is all of 20 degrees here. Doesn't include the proverbial 'wind chill factor'.

Seth