6 cylinder problem - Team Camaro Tech
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post #1 of 15 (permalink) Old Jul 17th, 03, 11:05 AM Thread Starter
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Will
 
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Alright what am I not doing right. I have a 68 with a 230 L6 that starts fine but as the car warms up it acts like it is missing. I've changed the distributor, points, plugs, fuel pump, carburetor (twice), intake exhaust manifold gasket and the problem persists. The car has 109,000 miles on the engine and the problem shows up the warmer the engine gets yet it runs fine when I get it up to speed. Hesitates and stumbles at low idle. (Vacuum? Timing?) At one point I thought I needed a timing gear but when I pulled the timing cover off it looked brand new.
I know a 230 is not as exciting as a BB or even a SB but can someone put me on a track where I can diagnose my problem and get me going again.
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post #2 of 15 (permalink) Old Jul 17th, 03, 11:26 AM
 
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Have you checked all of your vacuum hoses? Do you have power brakes? You could be losing vacuum through the booster. It also sounds like it could be your timing. Are you static timing it, and then setting the timing without vacuum advance? Heck I don't even remember if the L6 had vacuum advance. Are you getting any blue smoke? With that many miles on the engine, you could be getting some oil blow-by. Don't ever let anyone put down a 6 cylinder car. At least you have a car and the real plus is that it is a Camaro!
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post #3 of 15 (permalink) Old Jul 17th, 03, 01:01 PM Thread Starter
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No blue smoke, no power brakes, this is a bare boned car, 2 speed powerglide, column shift. (At least it's Matador Red) Could vacuum be affected with engine warm up? I don't hear any leaks, but then again, I used to listen to the Allman Brothers at full blast with my head between the speakers so my hearing could be suspect. It is aggravating and makes me want to sell the car before I'm ready to. (I'm building another 68 as we speak.)
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post #4 of 15 (permalink) Old Jul 17th, 03, 01:42 PM
 
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It sounds like to it the vacum advance to me.
this mite sound a little wear but pull off the
vacum hose and take off the cap , put a new hose on the vacum advance and suck it,if it dose not move its bad or dose not stay move hole whin you hole it with a vacum with your toung.. sorry but i sad its weard
Larry
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post #5 of 15 (permalink) Old Jul 17th, 03, 03:07 PM
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There is also a vacuum line that goes to the Powerglide. You might want to check that. Also the valve on the powerglide that the vacuum line goes to can fail and suck trans fluid into the engine.
Daniel

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67 RS/SS 350 auto (owned since 81.)
97 V6 5-speed Coupe (work car ordered new)
2012 1LS (V6 6-speed) Coupe (new work car)

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post #6 of 15 (permalink) Old Jul 17th, 03, 03:13 PM
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I bet the gas is boiling in the bowl. My old Nova is real bad about it. Use the insolator base gasket and the aircond. alum. plate if you can find one. I ended up putting a piece of insolation between the manifold and the carb bowl that finally fixed it.
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post #7 of 15 (permalink) Old Jul 17th, 03, 03:15 PM
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Definately sounds like a vacume leak.Check all hoses coming from the intake.

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post #8 of 15 (permalink) Old Jul 17th, 03, 05:22 PM Thread Starter
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I'll replace every foot of vacuum line on this thing tomorrow and I'll let you all know if I'm riding smooth, if not there might be a project car for someone that will hit the papers.
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post #9 of 15 (permalink) Old Jul 17th, 03, 05:45 PM
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I feel your pain. I been trying to diagnose the exact same problem w/ my '67 250 convertible 3spd manual. Mine idles poorly but runs fine at speed. I just had the engine/head rebuilt and have replaced all major components. I started pulling plug wires and traced it to cylinders 3 and 4. I have good compression so I suspect a vacuum leak at the middle port of the intake manifold. I had the manifolds milled flat but didn't think to do the same with the head. My next step is to pull the manifolds back off and check the flatness of the head. Hope this helps.

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post #10 of 15 (permalink) Old Jul 18th, 03, 04:22 AM
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Have you tried to replace the coil?
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post #11 of 15 (permalink) Old Jul 18th, 03, 05:51 AM
 
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If you do decide to sell her, let me know. I may be interested.
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post #12 of 15 (permalink) Old Jul 18th, 03, 06:51 AM
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Give the insolators a try. On a 6 the exhaust is right under the carb for cold weather heat. It works fine in the winter but when the weather gets hot there is too much heat. I was playing with mine one day when the idle kept going away. Like yours it ran fine at speed. You could watch the fuel boil out of the carb at idle but when you opened the throttle above idle there was enough airflow to cool the gas and it quit boiling. I started with the insolator gasket and ended up having to put a piece of insolation under the float bowl
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post #13 of 15 (permalink) Old Jul 18th, 03, 07:37 AM
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If you have an exhaust preheat valve, make sure it is opening after engine warms up. Mine stayed closed after warmup causing one side (V8) to miss. Opened the valve with a stick while it was running and that was the problem (that time [img]smile.gif[/img] , other problems since )

Luck, Kevin

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post #14 of 15 (permalink) Old Jul 18th, 03, 07:37 AM
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I am going to throw out one more suggestion. Try cleaning the choke mechanism! My car had the same symptoms as yours, it would run fine when cold, but as the engine got warmer, the choke was sticking, and the car would start to run like crap! It did this intermittenly so it was very difficult to figure out.. Finally, I sprayed my choke mechanism with carb cleaner, and the problem was solved immediately. Give it a try, it can't hurt.. You could also wire the choke open to make sure that this is not the culprit..

Let us know how it turns out..

-Kyle Baker

1969 383CI, T-56, 12 bolt-3.31 posi, 13" C5 Rotors, PBR Calipers, rear disc system..
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post #15 of 15 (permalink) Old Jul 18th, 03, 02:56 PM Thread Starter
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VACUUM WINS BY A LANDSLIDE!!!! About a 1/2 inch tear on the pcv line from the intake back to the valve. I feel like an idiot. I cut off the torn part and re-attached runs without missing. Now all I have to do is get it to idle without my foot on the gas. I guess I'll start playing with the distributor and my single screw adjustment carb. My car only has about 30 inches of small vacuum line, with the majority being around the air cleaner. There is no vacuum to the transmission unless I have to get under the car to find it.
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