OK, I've got an 84, L69 which I have just finished a cam swap in. The cam is a Comp Cams 12-238-2, I also installed a Weiand 8004 intake and am running an HEI Vac Advance distributor. The carb that is presently on is the stock cc carb (it gets poor gas mileage this way, but know it works, where as the new one is unknown). During the cam swap, I replaced plugs and wires, but left the original cap, rotor and coil since they are fine.

I broke the cam in, but had the rockers too tight. Fixed that and now it starts up fine.

I've got the idle set at about 800 rpm (it's a standard-a little high but more on that in a minute)when warm and the timing at 10*. The timing is correct, no doubt about it, I checked it 3 times and torqued the clamp down good and rechecked again.

I had it set at 8* and 750, but it was worse at those settings.

Here's the deal, the car starts fine, especially cold. The car will take a load, and is drivable, but definately not right.
The problem comes in when the car is warm, and it still gets very warm, has probably 4 miles on the new cam. When warm, if you are at the correct idle speed and you step on the gas, it dies. If you flutter it to get the RPMs up just to about 1200, it has a carb back fire (minor) and then accelerates, but not as quickly as desired.

Now the wierd part: When the engine is decelerating, it'll either slow its decent at about 1500, or just stick and idle at 1500 rpm.

Setting the timing below 8* when warm is impossible, it dies, and the idle screw is in much further than with the stock set up.

Please help.
Also, when warm, it doesn't like to take a light load. Even turning the steering wheel in neutral at idle when warm will kill the engine.

Just a side note, I don't think it should affect this, but I do hear a little noise (very little) from the rocker arms. I figured I'd give them a 1/4 turn extra instead of 1/2 for now since I over did it last time. Just mentioned in case it was relevant.

 

Pull your plugs and see what they look like. Also, how is your fuel pump and filter? Any kinks in the fuel lines? How is your vacuum readings? Also did you degree the cam?

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"Pray to God, but at the same time use your hands"

-Greek Proverb

 

No, I did not degree the cam, shame shame!!

Fuel pump is fine, plenty of fuel, and the filter is new also.

I had trouble getting fuel at the very beginning, but opened the fitting at the carb and cranked it over, and something blew out, because where there was no fuel, there suddenly was some!!!

I do notice that the exhaust manifold is super hot, glowing almost!!! I don't know if I'm not igniting all of the fuel, but I'll go pull the plugs and see what I see.

Any other suggestions please?

 

If you've got glowing manifolds, I think your first problem is that you're running too lean. Backfiring through the intake is also a sign of running lean as is also a hesitation and dying. Get some more fuel in there.

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88 firebird formula
350 Vortec TBI
214int/224exh, .471int/.491exh
Edelbrock headers
SIX-speed
open 3.73's
2 1/4 stock catback
I love pissing those LS1's off
My Formula

All your base are belong to us.

 

Birmass,

That's what I was thinking...

I'll try pulling the plugs first, and see what I see, then try the new carb.

The only thing about being too lean is that when the computer is unhooked from the CC carb, isn't it supposed to run at the richest setting?

 

A CO/HC monitor would be helpful, and also a thermal gun, but oh well... I would play with the timing and try slowly advancing it a tad, you may read 8º, but may in reality still be retarded. Firing the plug too late will also cause high temps and glowing headers.

------------------
"Pray to God, but at the same time use your hands"

-Greek Proverb

 

Let's see if this works



If the picks don't work, try this link:

http://www.angelfire.com/az2/bdsc/plugs3_15_01.htm

Carbon deposits on the plugs. They were clean after the initial break in, but the timing was much higher.

I don't think the cause is weak ignition, although it could be. What do you think?

 

Try the link anyhow, it's got a cool pic that's not in the reply.

 

I don't see any pics of plugs, but how big (or little) is that air filter?

 

You didnt degree the cam? Shame on you!

Actually I do it anyway but even if it is off at all with MY tools, chances are its probably not or so small it doesnt matter. I would guess that isnt the problem.

If the accelerator pump is working (you know how to check that?) then you have some sort of timing problem. Probably something to do with the vacuum advance. Change where its ported to, or make sure it works, or both.

 

Madmax,

The vac port seems to work just fine. I'll try another just in case.

I played with the timing a little more, and same problem. I just realized that I don't have the fast idle cam hooked up......maybe? It's too hot to fish it out of there right now. It's not touching the exhaust, but I would be if I tried to get it.

I can hear the accelerator pump working. I have a feeling it might be a combination of carb and ignition, but am stumped. When I rev the car up, it doesn't do so very quickly.

When it sticks at 1500 rpm, if I quickly close the choke, it brings it back down and it stays where it should. But even the idle isn't steady.

The air cleaner is 15" x 2". I don't have hood clearance for any taller. I'm having these problems with the cleaner off sitting in the garage however, so I doubt that's it.

Here's an quick over view of the trouble again:

Inconsistent idle
Carbon fouled plugs
Slow engine acceleration
Back fire through carb
After running higher rpm, idle only drops to 1500
At least 1, but only a few rockers "tapping".

I know it's not lack of fuel.
Spark seems to be good.
Air is plentiful.
Timing is set at 8*, now at 1000 rpm. It's the lowest I can go and keep it running.

 

Vac. leak??

It will run fine in choke mode but not after the choke comes off.
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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

R.I.P. #3
My favorite quote about D.E. "He can see air"

[This message has been edited by Engineboy (edited March 15, 2001).]

 

No vac leak that I can detect. It's all pretty sound, but I'll double check.

 

You keep describing similar symptoms in like three different posts, all on the first page...so I'll answer this one again...

Are you absolutely sure your distributor is not off a tooth? How are your posts oriented on the distributor cap? Is the cap excessively rotated? You describe a classic case of timing that is excessively retarded. You had to crank your distributor a lot to just get 8º or 10º, you headers/manifolds are extremely hot and you have idling problems with normal advance and idle settings. You keep repeating the fact that you are sure of the timing, however you have carbon fouling on all your plugs, so I'll go through a roundabout way of this...
The typical reasons for carbon fouling an entire set of plugs:
1) Incorrect heat range spark plug
2) An over-rich air/fuel mixture (caused by a clogged air cleaner filter element, too small an element, a sticking heat riser valve, or a faulty choke)
3) Weak ignition system voltage
4) An inoperative preheating system
5) Poor cylinder compression
6) Heavily retarded timing

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"HEY laser lips... Your mamma was a snowblower!"

-#5

 

Overly retarded timing. That would cause your manifolds to glow, inconsistant idle, lack of power, and carbon fouled plugs (not lean)

Maybe your advance weights are stuck or something with the vac adv can.


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'88 Camaro RS 2.8L
'88 Formula 350 (Too many mods to list...)

 

Red Devil,

The timing is perfect. Distributor points directly forward. Car starts instantly when cold, no problem. Timing is now at a steady 8* at about 800 rpm. It definately is NOT the timing. I've gone over it time and time again, just incase I missed something. I even undid everything, removed the distributor, turned cylinder 1 to TDC, dropped it in so that it was lined up, and timed it again. Removed all plug wires and made sure they all went to the appropriate cylinder. IT IS NOT TIMING.

RB suggested that maybe I've got a hidden vac leak somewhere. I'm going to check with a new can of carb cleaner this morning.

It is not the carb, had the same problem with 2 carbs. It is not lack of fuel either. It has to be either a problem in the valve train or a vacuum leak I'm sure....I hope it's the vac leak, and am pretty sure it is. Now I just have to find it.

 

Whipped out a can of carb cleaner. Test one, found nothing, car got too warm and consistent idle disappeared. Waited for 2 hours and tried again.

I found 2 very small leaks, one on each side of the intake manifold, in the center. When I spray the carb cleaner there, the engine bogs down......spray it near the other bolt, nothing. No variance any place else.

So, it's off with the manifold and replacing the gasket. I tried retorquing the bolts, but no luck. I did have them torqued according to the manual, but they had loosened up. Guess I should've used a little loc-tite. I will this time. I hope this is my problem.