Idle Problem - Team Camaro Tech
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post #1 of 37 (permalink) Old May 4th, 15, 04:20 PM Thread Starter
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Bobby
 
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Idle Problem

Team Camaro, Need Help:

76 Camaro, bought it a year ago, slowly done minor work to it up to now (put heater in it, shortened choke line, put new tranny in, guages, etc. but no engine work). Recently put a 4 speed Muncie in over the Saginaw that was in it. Before I put tranny in car ran just fine although when I shortened the choke line, it dropped from 1000 RPM idle to 700 which I was OK with. Wanted to run her down the road last week when I put tranny in but now, the car will now not hold an idle. I've set the idle speed screw (have an Edelbrock carb) to about 1200-1300 RPMs so it won't die at idle but she's still 'rough'. Before I did this, I would start the car and it would hold at about the above 1200 RPM. Took my foot of pedal, and she died. This is what I have done:

A. Replaced distr cap, rotor button, plugs-no change in problem.
B. Took carb off my Chevelle and put on Camaro-no change in problem.
C. Sprayed Carb cleaner in all the areas to test for vaccum leak- no leaks (jumps in RPM) that I could see.
D. Ran compression on cylinders- All hit 110 PSI-So i doubt I have a rod, lifter, or valve problem.
E. I doubt Timing is off because I've not done anything to engine to throw it off.

Need some help team
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post #2 of 37 (permalink) Old May 4th, 15, 05:33 PM
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Doug
 
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Re: Idle Problem

First of all is the engine a 350 cid and is it stock? Take the carb off and turn it upside down. Look at the throttle plates on the primary and secondary. You will see what looks like a line in the bores. Adjust both throttle plates at .020 or until the line looks like a little square. (see attachment). Adjust the idle mixture screws all the way closed and then adjust them to 1 1/2 turns open. Install the carb and hook up all vacuum lines and linkage. Start the engine to see if it will idle.Once you get it to idle check the timing. If you have a timing light with advance set the knob to 36* and rev the engine to around 3000+ then adjust distributor until the balancer line is lined up with zero on the scale of the timing chain cover. Here is an article to help setup your distributor, adjust your transfer slot, and set your timing. http://www.crankshaftcoalition.com/w...butor#Overview

Last edited by Cdminter55; Oct 24th, 15 at 04:51 PM.
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post #3 of 37 (permalink) Old May 4th, 15, 07:47 PM Thread Starter
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Bobby
 
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Re: Idle Problem

Thanks for the input. Engine is a stock 350. I'll be honest, I've never fooled around much with carberators other than installing them or adjusting idle speed. I'll take a look at the article but it did not say how to adjust the throttle plates unless I missed it which I could have. Couple of quick questions:

a. Adjust idle mixture screws--so I need to turn them clockwise all the way until they stop and then turn them counter clockwise 2 1/2 turns, correct?

b. How do I adjust the throttle plates?

Thanks
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post #4 of 37 (permalink) Old May 4th, 15, 07:47 PM
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mike
 
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Re: Idle Problem

How old is the gas?
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post #5 of 37 (permalink) Old May 4th, 15, 07:49 PM Thread Starter
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Re: Idle Problem

Quote:
Originally Posted by bigblockragtop View Post
How old is the gas?
Gas is good and new.
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post #6 of 37 (permalink) Old May 4th, 15, 08:18 PM
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Keith
 
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Re: Idle Problem

the transition slot info noted above is for a Holley--I am unfamiliar if it is the same setup with edelbrock carbs...

The throttle (curb idle) screw control how far open the throttle blades are...

I just wanted to point out the above info--I iwll leave the tunig of the carb to the edelbrock experts...I've done only Holley carbs...

Keith
1967 Camaro
406, 10:1, comp xr282HR, Dart Iron Eagle 200cc, Holley Contender dual plane, Holley 750 DP
Muncie M-20
GM 8.5, 3.73 posi
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post #7 of 37 (permalink) Old May 4th, 15, 08:43 PM Thread Starter
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Bobby
 
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Re: Idle Problem

I believe the article said the plates need to be at 'that sweet spot' regardless of what carb you have. I've got an Edelbrock. What I don't get is if the carb is my issue, I don't know how it got out of whack, plus the edelbrock carb off my chevelle performed same as camaro carb when i put it on camaro. Only difference in the two, is one is elec choke and the other manual.

So are you saying the idle speed screw is what I need to work with to get the throttle plates looking like in the picture? Thanks team,
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post #8 of 37 (permalink) Old May 4th, 15, 08:47 PM
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Tom
 
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Are you sure that the distributor is clamped down good ? It sounds like it was turned or bumped and now your timing is off.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #9 of 37 (permalink) Old May 4th, 15, 10:47 PM
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Joe
 
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Re: Idle Problem

Edelbrock is a good carb, but you need to tune it correctly, and it has to be tuned properly for each engine. Just because it runs well on one 350 engine, does not mean it will run on a different one without tuning it for that particular engine.

If you simply have the mixture screws arbitrarily turned out 2.5 turns, just guessing or hoping that its right, I'll bet you that is where at least part of your problem is. The mixture is likely too rich, and therefore you had to turn up the idle speed just to get it to run at all.

download the PDF owner's manual for your carb. Take the time to read it and understand it, then you can learn how to correctly adjust the idle mixture, and also tune all other aspects of your carb. Just follow the instructions step by step. http://www.edelbrock.com/automotive/...ers-manual.pdf

"IDLE MIXTURE
The Edelbrock Performer Series carburetor has conventional Idle Mixture Screws (IMS) that provide a leaner A/F when turned clockwise and richer A/F when turned counter clockwise. The idle air flow is controlled by a conventional screw that opens the Primary Throttles. The following procedure should be used to set the idle mixture and speeds.
1. Fully warm engine and ensure choke is fully open.
2. Air cleaner in place.
3. Set desired speed with the air screw.
4. Adjust the IMS on ONE side to get the maximum possible RPM. Do not go rich beyond the maximum speed point.
5. If the above changed the idle speed more than 40RPM, then readjust the speed.
6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.
7. Reset the speed.
8. Carefully trim each IMS to again get the maximum idle RPM.
9. Go leaner just enough to get a 20 RPM drop in speed.
10. Reset the speed to the desired RPM.
11. This is a Lean-Best Idle Set. Setting richer than this will not improve idle quality or performance, but could tend to foul plugs."

For example, I just swapped on a 600 cfm edelbrock carb onto my 350 this last weekend. I set the idle mixture and it only required about 1&1/4 turns out. Every engine will be different.

Note the mention of fouled plugs if the idle was too rich. Pull your plugs and clean them, then put them back.

Another thing to look for is VACUUM LEAKS!!

If you have vacuum leaks anywhere, that can mess up all kinds of things, including making idle idle roughly, or not at all.

Then get yourself a quality timing light, and make sure your timing is correct, including checking your vacuum advance to make sure that is working properly and hooked up to the correct port on the carb.

The important thing here is that you ask me what kind of car I've got. "I've got a BITCHIN' CAMARO"
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'68 350 4 speed
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post #10 of 37 (permalink) Old May 5th, 15, 05:25 AM
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Kevin
 
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Re: Idle Problem

Change the coil too! I always had a rough idle and misses, changed the coil, now smooth! I also tried a old mexican coil I had laying around before I put the new flamethrower coil on, it would start and run, but die when engine come down to idle like you had happen.

Kevin


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post #11 of 37 (permalink) Old May 8th, 15, 10:18 PM Thread Starter
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Bobby
 
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Re: Idle Problem

Quote:
Originally Posted by kookykrispy View Post
Edelbrock is a good carb, but you need to tune it correctly, and it has to be tuned properly for each engine. Just because it runs well on one 350 engine, does not mean it will run on a different one without tuning it for that particular engine.

If you simply have the mixture screws arbitrarily turned out 2.5 turns, just guessing or hoping that its right, I'll bet you that is where at least part of your problem is. The mixture is likely too rich, and therefore you had to turn up the idle speed just to get it to run at all.

download the PDF owner's manual for your carb. Take the time to read it and understand it, then you can learn how to correctly adjust the idle mixture, and also tune all other aspects of your carb. Just follow the instructions step by step. http://www.edelbrock.com/automotive/...ers-manual.pdf

"IDLE MIXTURE
The Edelbrock Performer Series carburetor has conventional Idle Mixture Screws (IMS) that provide a leaner A/F when turned clockwise and richer A/F when turned counter clockwise. The idle air flow is controlled by a conventional screw that opens the Primary Throttles. The following procedure should be used to set the idle mixture and speeds.
1. Fully warm engine and ensure choke is fully open.
2. Air cleaner in place.
3. Set desired speed with the air screw.
4. Adjust the IMS on ONE side to get the maximum possible RPM. Do not go rich beyond the maximum speed point.
5. If the above changed the idle speed more than 40RPM, then readjust the speed.
6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.
7. Reset the speed.
8. Carefully trim each IMS to again get the maximum idle RPM.
9. Go leaner just enough to get a 20 RPM drop in speed.
10. Reset the speed to the desired RPM.
11. This is a Lean-Best Idle Set. Setting richer than this will not improve idle quality or performance, but could tend to foul plugs."

For example, I just swapped on a 600 cfm edelbrock carb onto my 350 this last weekend. I set the idle mixture and it only required about 1&1/4 turns out. Every engine will be different.

Note the mention of fouled plugs if the idle was too rich. Pull your plugs and clean them, then put them back.

Another thing to look for is VACUUM LEAKS!!

If you have vacuum leaks anywhere, that can mess up all kinds of things, including making idle idle roughly, or not at all.

Then get yourself a quality timing light, and make sure your timing is correct, including checking your vacuum advance to make sure that is working properly and hooked up to the correct port on the carb.
Thanks for the suggestions. I do not have a vaccum leak. I tinkered with the carb and still no better off. Carb has always been fine. Tomorrow I am going to put new plug wires on but don't think that will fix. I did notice the coil had scorch marks from top to bottom on opposite sides of the coil. To describe, it Looks like someone did a cut weld at 1/16 or 1/32 inch. I've got an extra coil and will put that in. I will check timing with timing light but am reasonably confident my timing will be good. I'll get this figured out one way or another. I'll take more suggestions too!!
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post #12 of 37 (permalink) Old May 9th, 15, 08:57 AM
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jerry
 
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Re: Idle Problem

First thing I would do is loosen carbs 4 mounting bolts, open throttle
Blades all way, centering carb so blades don't hit manifold, then retighten
Bolts. Oh, did you put new carb gasket on first? Then adjust low speed
Jets 1 1/2 turns out from closed position. Remember, turning jets out
Richens mixture and turning in leans it out. Next, make sure choke blade is
Fully open when engine is warmed up. Also , ck point gap and plug wires.
Did you hook up vac line to distributor? If coil is ok, start car and set idle
Speed.
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post #13 of 37 (permalink) Old May 9th, 15, 03:03 PM Thread Starter
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Bobby
 
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Re: Idle Problem

update: Had a spark plug wire that was bad, so the 'missing' has been corrected. Timing light showed timing is spot on. The idle is still off. I worked with idle mix screws and still have problem. Ran the car up and down road and did like it does when stationary, it surged and I had to keep my foot on pedal to keep it from dying. The car will surge a few hundred RPMS then drop a a few hundred RPMS and that is its idle! It's like it gets fuel then does not get fuel. I observed how gas was coming into my clear fuel filter and noticed it would just be a 'spurt' of gas going in. Is this normal? Could it possibly be my fuel pump (even though I'm used to 'when they go out they go out' type of thing).
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post #14 of 37 (permalink) Old May 9th, 15, 07:31 PM
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Bobby
 
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Re: Idle Problem

Are both your idle mixture screws responsive?

67 Camaro 350
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post #15 of 37 (permalink) Old May 9th, 15, 09:43 PM
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Doug
 
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Re: Idle Problem

rdobbs1977, What type fuel pump do you have? Do you have an old fuel pressure regulator laying around that you can add to your fuel system? Eddy carbs require no more than 5 lbs of fuel pressure. Check your accelerator pump squirting fuel into primaries. How long has it been since the fuel filter was changed. When first setting up the carburetor I said to adjust transfer slots, turn idle mixture screws closed then turn them open 1 1/2 turns. When you start the engine to get it to idle then you hook up a vacuum gauge to a port that has vacuum all the time. Adjust the idle mixture screws until you get the highest reading on the gauge. You said the timing was spot on. Make sure that it is at least 12* BTDC. If your engine has not been rebuilt and has the stock cam try setting the idle in drive to about 650-700 rpms. After checking the timing be sure to reconnect the vacuum hose to the distributor. Your timing should read something like this: with the vacuum line disconnected from the distributor and plugged off the initial should read 12* BTDC, total timing revved to 4000 rpms 34-36 rpms, and with the vacuum line reconnected to the distributor and revved past 3500 no more than 48*-50*.
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