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Old 05-18-2013, 10:53 PM   #1
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Engine surging

Hey y'all I have a 87 4.2L and it surges every once in awhile when I'm driving after awhile, I replaced the fuel filter a thousand miles back, and I was told by a friend that it could be vac lines, what do y'all think?

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Old 05-18-2013, 11:45 PM   #2
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is it all stock under the hood, carb etc?

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Old 05-19-2013, 12:28 AM   #3
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is it all stock under the hood, carb etc?
Yea nothing modified
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Old 05-19-2013, 05:36 PM   #4
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It could be fuel (carb) or spark/electrical (Ignition Control Module). It's always good to check for vac. leaks but I don't think a vac leak would cause that symptom since it happens only once in awhile.
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Old 05-19-2013, 07:26 PM   #5
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It could be fuel (carb) or spark/electrical (Ignition Control Module). It's always good to check for vac. leaks but I don't think a vac leak would cause that symptom since it happens only once in awhile.
How would I be able to test or fix if it is fuel or spark/ electrical?
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Old 05-19-2013, 08:21 PM   #6
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How would I be able to test or fix if it is fuel or spark/ electrical?
The ICM really can't be tested. A big box auto store might say that they can but if the problem is intermittent their "test" won't work. If you still have the original it's way overdue for replacement. You could also have a bad coil. I swapped out both on my 89 at the same time. If your carb is original there could be an issue there also. You can try cleaning it and also add Seafoam to the tank to see if that helps. I hate to throw parts at a problem but sometimes you have to eliminate the most likely causes based upon the symptoms. Unfortunately, a worn distributor can cause similar issues. I like to go from the least expensive and work my way back.
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Old 05-19-2013, 10:45 PM   #7
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The ICM really can't be tested. A big box auto store might say that they can but if the problem is intermittent their "test" won't work. If you still have the original it's way overdue for replacement. You could also have a bad coil. I swapped out both on my 89 at the same time. If your carb is original there could be an issue there also. You can try cleaning it and also add Seafoam to the tank to see if that helps. I hate to throw parts at a problem but sometimes you have to eliminate the most likely causes based upon the symptoms. Unfortunately, a worn distributor can cause similar issues. I like to go from the least expensive and work my way back.
The previous owner said that the engine had been rebuilt by the guy before him, so I'm not sure on how old the stuff is, but if I replace it then itl make me feel better lol I will try the sea foam thing first, If not then the icm would be the second choice, would it be better to go ahead and upgrade it?
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Old 05-20-2013, 10:42 PM   #8
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It was doing it really bad tonight for some reason, can't figure out whyvyet

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