Car rough idle problems need help.

1993 Nissan Altima GXE
Car rough idle problem need help.
I know I asked this before. I am going to be a little bit more detailed.
When in park, neutral it shakes When in reverse it shakes worse. When in drive it shakes under 30 mph. When going above 30 it shakes a lot less or does not shake at all. Shakes at stops.
From Reading Spark plugs & wires seem to be the most cause even if they look new. Wouldn't a compression test tell if it is bad spark plugs?
Next is a fuel filter. Which I am tempted to try.
The other is a fuel injector.
Greg Rozelle
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new.
Compression test will only show worn Piston rings or bad valve/valve seats.
Test your plug wires with an ohm meter doesn't really matter what reading you get just as long as all the wires are close I can't remember what resistance plug wires have per foot, but like I said if one is bad you will see a very large difference. Also look at the plugs and see if any are fouled (oil) or are also burnt white (which could indicate a lean running condition). like the wires all the plugs should look like each other of one is differnet then you know you have an issue in that cylnder which is causing the rough idle.
Take the time and mark you plug wires before you take them off.
Good practice to change your fuel/air filters when ever you do a tune up. You should be able to blow through the fuel filter fairly easely (be carefull of gas) If it is acting like your trying to blow up a balloon your filter is plugged.
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Dave Cox wrote:

When measuring with an ohm meter, the total from the coil to the plug, on any lead, should not be more than about 15,000 ohms. If over, replace them all.
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run some injector cleaner for a couple of tank-fulls.

could be bad plug wires(insulation breakdown),worn distributor cap/rotor. could be old,worn plugs;have to pull them and inspect.
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Jim Yanik
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My son's 91 240SX .. the cause was a fuel injector and old spark plugs and spark plug wires. One of the fuel injectors just stopped all together.
Plugs and wires were the originals so of course over the span of 16 years, they needed to be changed out. This even with just over 40,000 miles.

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What about plug WIRES? They get old and degrade.And cause misfiring.

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Jim Yanik
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Check intake manifold and injectors for vacuum leaks.(Had the same problem with 1999 Altima)
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