Troubleshooting bad fuel injector

[ISHOU]

Have been slowly trying to track a miss in my 94 ATX. Misses at idle and at all driving speeds but is intermittent. I have done the following.

1) put in 3 new spark plugs in front bank, and it still missed. Moved front bank plugs to rear bank and it still misses

2)Replaced fuel filter.

3)Tested fuel pump with gauge and it tested out ok.

4)Cleaned MAF sensor

5)Swapped out DIS with a known good one. Still misses.

Motorcraft plugs wires(and plugs) have only 12,000 miles on them. No oil in plug wells. No codes and cylinder balance test came back good.Only thing left to try is the coil.(Do they go bad at 100,000 miles?)Thought the coil on these engines rarely fail.

Anyway, how can I test for a bad fuel injector. Shouldn't a bad injector show up on the cylinder balance test?

Any help is appreciated.

 

[olympic]

The problem you describe should show up on the balance test IF the miss is happening during the test. But it may not since you said it was intermittant.

Coil packs are known to go bad occasionally, so the next logical step to swap it out.

 

[Mr Anonymous]

Any other KOEO codes that might not seem related?

If there aren't any ignition system related codes, I'd suspect either the plugs or wires, a ground path problem, or a vacuum leak. I recommend going all the way with another 3 new plugs, and checking the wires. Then move on to looking for a vacuum leak.

The DIS and coil pack are pretty reliable at generating DTC's, so I'd leave the coil pack alone unless all else fails. You could also pull the coil pack and take it to AutoZone for a free test if that would give you more peace of mind.

FWIW, injector failures are extremely rare, and while not out of the question, I'd examine the more common causes before even thinking an injector might have failed.

<small>[ August 11, 2003, 12:22 AM: Message edited by: SHOooo ]</small>