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Old 07-17-2013, 09:13 AM   #15
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It's a 1990 fuel injected 460. That means that it has oxygen sensors, electronic ignition, and the fuel air mixture is controlled by the computer. With that information an intake manifold leak (IML) will introduce extra air into the system that is not accounted for by the MAF (mass air flow) sensor. You would probably set the check engine light on with a lean code. I doubt you have an intake manifold leak without setting some codes.

I'm also somewhat against adding any means to increase your coil output. There is sufficient voltage available on these electronic ignition systems to jump any spark plug gap you have. That's why today you can go for 100,000 miles without changing plugs. Save your $$$$ for some good plug wires.

Bad plug wires are one of the reasons the auto industry went to coil over plugs or COP. It eliminates one area where the older systems failed and that is plug wire breakdown causing misfires.

TeJay
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Old 07-17-2013, 09:26 AM   #16
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Quote:
Originally Posted by TeJay View Post
It's a 1990 fuel injected 460. That means that it has oxygen sensors, electronic ignition, and the fuel air mixture is controlled by the computer. With that information an intake manifold leak (IML) will introduce extra air into the system that is not accounted for by the MAF (mass air flow) sensor. You would probably set the check engine light on with a lean code. I doubt you have an intake manifold leak without setting some codes.

TeJay
And it is definitely not a sticking float!
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Old 07-17-2013, 12:55 PM   #17
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Ok so I replaced the wires and it ran perfect for about 3 miles and once again same symptoms, now I am totally confused I checked all my wires at the cap and everything was tight it was way to hot to check the wires at the plug my geuss is a loose boot? Any other suggestions
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Old 07-17-2013, 02:08 PM   #18
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Did you change the cap?
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Old 07-17-2013, 02:46 PM   #19
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If you have a timing light you can easily check the operation of the distributer advance. If the weights are sticking, you should see it as the timing mark fails to advance in the strobe light. Putting a vacuum gauge on it will show if a change in vacuum coincides with the misfire. Have you hooked it up to a scanner? If you don't have one, here's a YouTube video on how to use a jumper to read them:
How To Run A Self-Check On Fords 1987-1995 - YouTube
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Old 07-17-2013, 08:36 PM   #20
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Mitchyb,
Make sure the plug wires are separated and in a set of wire separators and also that the wires are not laying on the exhaust or the valve covers, this could cause a spark leak. Also check that you don't have an exhaust leak that is blowing the hot exhaust on one of the wires or plugs.
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Old 07-18-2013, 09:23 AM   #21
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I've been retired from teaching automotive for 8 years but if memory serves me right all spark control is taken care of either by the ignition control module or the on board computer. I also don't believe that spark control not working will cause a misfire of any sorts. Spark control if not working correctly will effect power but not a misfire.

Troubleshooting any problem requires a systematic approach. Just throwing parts at something without testing is not the best method. Those ignition parts that were changed probably needed it anyway so you're out nothing. NEVER assume that just because a part was changed that it is good. I've done that before.

If it is still misfiring then one can assume that we are dealing with an electronic issue. You've changed all parts(plugs, wires,cap, rotor related to the secondary (high voltage) side of the ignition system. What created that voltage??? The control module. On a Ford, again if memory serves me right, is the sandwich sized aluminum looking sealed module that plugs into the distributor. That's where the spark is controlled. Here are two things you can do to maybe simulate or created the misfire condition. While the engine is running push on the module. If no results then heat it up with a hair dryer. Sometimes those little parts react to heat, expand and create a misfire. Maybe that's why it took three miles to happen because it or some other electronic part got hot.

Be careful what you read on these and other forums. Sometimes the information is good and sometimes not so good. Just remember this fact. Everything on mechanical/electrical devices can be tested to see if they can or are operating correctly. Don't change a part just because somebody else did it and it fixed their problem. Use this information as a method to understand, and direct or guide you in a direction so you know what to test or have tested.

TeJay
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Old 07-18-2013, 10:00 AM   #22
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Thanks Teejay that's great info. I worked on it all day yesterday and have realized that I do have a skill set for this type of thing this problem is just above my skill level as well as patients level, as we are leaving tomorrow and I do have to work I have bitten the bullet and decided to take it in, ill keep you posted to what it is
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Old 07-18-2013, 03:23 PM   #23
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Well the worst case has happened I think it turns out there is a burnt or sticky valve :( and even at a deal it looks like its gonna be a couple thousand to fix! So any chance of a long trip has gone to the wayside now. I know there is no cure in a bottle but does anyone know of an additive that I could add to the oil to help the problem ?
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Old 07-18-2013, 03:41 PM   #24
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No additive is going to fix a burnt or sticky valve. At best it would allow you to get far from home, to some remote place where there are no mechanics, then the valve would break off and ruin the whole block. Fixing it now is removing and machining heads, if it fails, it's a new engine.
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Old 07-18-2013, 03:42 PM   #25
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How did you determine that it is likely a burnt or sticky valve? Did you do a compression check? I admit that the symptoms do fit a bad valve condition.
If it actually is a burnt valve then there is no quick or EZ fix. If it is a sticky valve, then Seafoam in the oil and drive it around MIGHT free it up eventually but no guarantees.
What a bummer, especially with a trip planned.
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Old 07-18-2013, 03:48 PM   #26
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A burnt or sticking valve will not come and go with rpm. It either works or it doesn't!!
Sounds like a lean misfire to me. You can get some gm fuel treatment plus from any gm dealer that will clean injectors and decarbon the engine.
There are other brands that people use that work also but all i use is the gm stuff.
Good luck
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Old 07-18-2013, 06:37 PM   #27
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A burnt or sticking valve will not come and go with rpm. It either works or it doesn't!!
Sounds like a lean misfire to me. You can get some gm fuel treatment plus from any gm dealer that will clean injectors and decarbon the engine.
There are other brands that people use that work also but all i use is the gm stuff.
Good luck
Actually that is not accurate at all. They valve can stick at a given RPM. The early Focus 2.0L engines had an issue with valves sticking causing the same exact symptoms. The test was to warm up the engine to full operating temps and then hold the RPMs at 2500 for a few minutes. After that time return it to idle. If there was a misfire at that time, the valve was sticking.
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Old 07-18-2013, 06:49 PM   #28
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Well the worst case has happened I think it turns out there is a burnt or sticky valve :( and even at a deal it looks like its gonna be a couple thousand to fix! So any chance of a long trip has gone to the wayside now. I know there is no cure in a bottle but does anyone know of an additive that I could add to the oil to help the problem ?
Reading your symptoms did sound like a valve issue but I waited until you changed the plug wires to chime is as the wires seemed most likely. However, It may be a damaged valve but it may also be excessive carbon build up on the valve causing the issues. At low throttle there is little air flow and if there is enough carbon build up, the fuel can soak and get caught up in the soot and cause a low RPM misfire. Ran into it a few years ago. Don't bother with any oil additives at it would not likely fix it. Ford does have an upper cylinder combustion chamber cleaner. I don't know if seafoam or other additive would work or not. I did not have good success with seafoam on carbon build up in my 2 stroke tuned pipes so I don't have much faith in this job. But what you do is get the engine really hot and use one of the small vacuum lines and dip it into the combustion chamber cleaner can. Use the whole can and hopefully the engine stalls. Allow it to sit for a while and do it again. The oil will need to be changed after this. You want to make sure there is no cleaner in the oil as it may cause bearing damage.

To check for a damaged valve, the valve covers need to be removed. In a class A, it is pretty easy. loosen up the rocker arms and remove the spark plugs. There is a leakage tester that uses 100 PSI air pressure and it screws into the spark plug hole. If there is excessive leakage, it will be heard in either the intake manifold, exhaust, or if it is a ring issue, the crank case.
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