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Discussion Starter #1
I am an inch away from getting rid of this car! Nothing but problems since i bought it. Most recent one now is a no fire situation on cylinders 1,7,8. Last weekend I replaced the intake and carb on my 289 and everything ran great the car had more and power then it ever has with the timing set at 10 deg advance. Fast fwd acouple day. Car starts to mis at low rpm and at times doesnt start just cranks. Replaced coil everything runs well. Next day engine starts running rough while idling and low rpm and back fires through the carb. Ive replaced the cap,rotor,wires,plugs and coil. Reset the distributor at TDC and set advance at 10deg. Still runs like crap. Started this morning really rough idle Went to check timing and got nothing out of my light. Started pulling plug wires off while running and 1,7,8 dont change anything when pulled. Help!!!!
 

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Shouldn't be gaskets if 1,7,8 are not firing.... Have you checked to ensure your timing chain hasn't allowed the cam to jump a tooth or two?
(pull the valve cover over #1 side and rotate engine to what the valves show to be TDC on the compression stroke and compare to timing mark on crank pulley. Also pull the dist cap and see if the rotor points to the #1 wire at TDC)**at 10 degrees advance, the rotor might be a little off from TDC, but I could not tell you how much.
I doubt that 3 plugs or 3 plug wires would just go bad simultaniously so I think you can almost rule that scenereo out.
 

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Maybe you have an INTAKE or CARB gasket leak. I always look at what I just did when something like this pops up. Just maybe.

Dale in Indy
I had the almost the same issue, except it was 7,8. My vac line off the rear of the intake to the rest of the system was disconnected at the check valve, which was under the shock tower brace. Couldn't see it and barely could hear it.
 

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Intake and carb gaskets are a safe bet.
Just out of curiosity, where are you buying your parts and what brand name is on the boxes? A bunch of cheap Advance Auto ignition parts will do what your describing.
 

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Discussion Starter #6
The first thing that i will do today is plug off all unneeded vaccum lines and start looking for aleak i just didnt think that a vaccum leak good cause a no spark in multiple cylinders. I know that autozone parts arent exactly know for durability but they are cheap and right down the street with that im still having a hard time figuring out why im getting spark to some but, not all wires and plugs.
 

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You've not tested for spark. You've pulled plug wires and noticed no discernible change in the idle.
Testing for spark is not the same as pulling a plug wire and listening.

Started pulling plug wires off while running and 1,7,8 dont change anything when pulled.
Pull your plugs and make sure they aren't fouled from a weak or intermittent spark due to the ignition parts. They'll also help you diagnose it a bit better.

What kind of intake did you fit? Dual or single plane? Carb new or used?
 

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Discussion Starter #8
Well, found out why 7,8 arent firing is do to a cracked vaccum tree at the back of the intake so, now 7,8 are firing. Number 1 isnt firing at idle but, at about 2000 rpm it is. I checked for spark by taking the spark plug wire off while running placing a screw driver up the boot and then tried to get a spark from the screw driver to a wrench and got nothing. I bought one of those Summitt racing carb and intake combos. I have moved plugs around and tried different wires and have had no change. Im getting about 18in of vaccum at idle and its pretty steady.
 

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Discussion Starter #10
So, i pulled the distributor back out, reset number 1 TDC reinstalled the distributor, put on a new cap and rotor, double checked the plug wires. Now it is running on all cylinders at idle, set advance at 10 degree base with the advance unplugged. At this point it would idle and rev great really smooth and idled at about 650rpm. I hooked up the vacuum advance and now it wont rev up and the engine shakes horribly when trying to rev this happens under load or in park. Thanks for all the help guys.
 

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Check the ground wire inside the distributor (it connects the points plate to the base). They sometimes are loose or broken so that as the plate is pulled by the vacuum advance the connection is lost.

Are you sure the vacuum advance is hooked to the correct vacuum source? That could also be the problem.
 

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Any luck? Be sure you are using ported vacumm to the dizzy - not just any constant vacuum port or it will not run very well. Hang in there you will have her purring soon enough.
 

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Discussion Starter #13
This engine is just perplexing. Idles great the choke is working awesome im hitting on all cylinders and it drives just fine. All of this without the vacuum advance hooked up. I just dont understand. I can work on multimillion dollar aircraft all day long but, i cant figure out a 43 year old engine. The port that i have the advance hooked to gets no vacuum at idle as i should but, when should it start pulling vacuum. according to my gauge as soon as i crack the throttle im getting full manifold vacuum.
 

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The vacuum signal to the distributor should be gradual, not on/off like you describe. Either you have the wrong port or there is something wrong with your carburetor. What make/model carb are you using?
 

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The return spring inside the vacuum advance diaphragm is probably toast.
You can test this by simply off the distributor cap and sucking on the line connected to the advance unit. (Just be sure no one sees you doing this as it looks wierd) You should see the points plate move in proportion to the amount of suction you create. Some people suck more than others. The plate should snap back to its original position once you stop sucking. LOL If it doesn't snap back (or doesn't move at all) then the advance unit is probably shot-- although there's a chance it's an adjustable one and is simply adjusted all the way open or closed. Get a bunch of small allen wrenches and stick them into the nipple on the advance unit where the vacuum line attaches. If you feel one "fit" try turning it bit by bit and see if you get any change on the sucking test.
 

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Discussion Starter #17
Im using a Summit version of a holley 4100. Im sure that i have the advance hooked to the proper port. Anyway everything is working great with the advance unhooked. I advance the base timing to 12 deg. and the engine is running great. Thanks for all the help.
 
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