Another misfire issue

[Divorce Court Dan]

97 Lumina 3.1 POLICE PACKAGE misfire cyl 1. Here is what I have done so far.

1. New wires
2. New plugs (started getting the misfire after changing the plugs)
3. New coil pack
4. Checked compression 180PSI
5. All new injectors (should have tested electrical system first)
6. Checked cylinder 1 wire harness to injector, getting a steady light (not pulsing) Would that be a PCM issue? I'm assuming if the LED test light lights up on that circuit than I should not have an open in the wire right? Thanks in advance

[maxwedge]

Get a noid lite and see if that connector for the injector pulses when running, I assume this is a constant miss? Scan says p0301? Did you recheck that plug is not cracked?

[Blue Bowtie]

If you are using an injector test lamp connected to the harness, and the lamp remains lit constantly while the engine is idling, either the driver transistor for that injector circuit in the PCM is shorted, or the wiring between the injector and PCM is grounded. Remember that the PCM completes the ground side of the circuit to operate the injector.

[Divorce Court Dan]

Ok, thanks so far guys. I picked up a Haynes manual and looked at the wiring diagram, and realized I probed the pink wire to the injector (which is B+ from the underhood fuse panel) instead of the solid black wire to #1 injector. I probed that wire with a LED test light and I do have a pulse. Maybe a problem with the injector connector? I would hate to have to take everything apart again just to test that one connector. Gonna double check the spark plug now.

[jeffcoslacker]

Gotta go where logic takes you...if you picked up a misfire after changing the plugs, you cracked a plug insulator or broke a wire end.

[richtazz]

I agree with Jeff, it sounds like the plug or wire on that cylinder is the problem. Since the #1 cylinder is in the back, and that plug is probably the hardest to change, you may have damaged that plug during install, or not gotten the wire firmly in place.

[tblake]

i've also seen where brand new plugs were ordered from the parts house, and they come and it appears that one was dropped at the store. I agree, check the plugs and wires again.

[Divorce Court Dan]

WOW!!!! YOU GUYS HIT THE NAIL ON THE HEAD ON THIS ONE!! The insulator on plug #1 was chipped, cracked and even loose!! A $2 dollar fix using platinum. Too bad I decided to change all the fuel injectors before I found the problem. Thanks guys!!! Great help! I would have never thought to check a brand new plug. I'm sure while wiggling the spark plug socket around trying to get the plug threaded, thats when i damaged it.

[jeffcoslacker]

Originally Posted by Divorce Court Dan

WOW!!!! YOU GUYS HIT THE NAIL ON THE HEAD ON THIS ONE!! .

That's because we've all done it at some point...

I was working on a car once with hard to reach plugs and picked up a misfire after installing new, even took them back out to re-examine and inspect the plugs, wires....then I realized since I couldn't see back there, somehow I'd stuck one plug wire on an exhaust manifold stud, thinking it was the plug..

[wrightz28]

Originally Posted by jeffcoslacker

somehow I'd stuck one plug wire on an exhaust manifold stud, thinking it was the plug..

I'll fess up to the embaressment of that one too. Man was I shocked, leterally, when I found I did it :

[gw84]

Would a misfire trigger a SES light (every time). Also, how do you know if you've got a misfire??? I was curious if this could be the same problem a few of us have with '99 luminas/montes jerking. Any thoughts???