Roadking_

Hey everyone!
My wife's Jeep started missing one day. I started by replacing the spark plugs,cap & rotor, and new spark plug wires. (turns out they were orig).

Still running rough, so after reading several posts in these forums I checked for voltage at the injectors. Key on engine NOT running I get 7.25v at each of the 6 plugs. Engine running I get 14.2v at every location. After doing the remove each plug while running, I discovered the #4 injector plug is the culprit. I switched #5 and the #4 and it followed the plug. So #4 injector is okay. (plugged #5 in to #4 and it worked fine).

The service manual says to connect a 12v light across both terminals to check for flashes. Is this whats called a Noid light? I've also heard to connect the neg lead from multimeter to the positive post, and the positive probe to the opposite wire (other than the 14.2v ) but dont know what I should read.

My plan is to take the cover off the big harness and to unwrap the #4 splice and have a look to make sure no corrosion and the solder is in good shape.
I also have a wiring diagram that shows what wire goes to what PCM plug terminal. I can check to make sure I have continuity from the PCM to the harness is that correct?

I didnt see an injector relay described in the discription or diagnostic areas in the service manual or in the wiring diagram/schematic. Just the Auto shutdown relay in the underhood box. I believe the ASD relay only sends a signal to the PCM for start/run, not the injectors individually?

Current DTC code is 27 injectors not responding to commanded position.
supposed to be individual ie. injector #1-6,ect but the OBDI too vauge I guess. I am doing the key on off 3X and counting flashes.

Does this method sound like I'm on the right track? I hope you guys/gals can help me shed a little more light on this subject. Thanks for reading my "Book" :-)

BillyBoy

Yes on the "noid light." The rest. I don't know.

LACK

Sounds like you're on the right track. Inspect the wiring, plug itself and trace it back. Sounds to me like damaged wiring or plug, check with a multimeter for continuity as well as checking your power wire to ground for any shorts. Make sure you disconnect the battery when you check the power to ground, don't want to ground out a hot wire.

I do know that O'riley auto sells new pig tails with the connector for injectors if you do wind up needing to splice in a new plug.

If you're trying to use a digital multimeter to check for pulses in the injector circuit you're not going to get an accurate reading, the digital gauge doesn't react fast enough to keep up. A noid light is basically a test light designed to read (light up during) injector pulses. There are different sizes/prong configurations for different model injectors. They can be had at harbor freight for relatively cheap.

http://www.harborfreight.com/11-piec...set-97959.html

The plugs as well as terminals on the injectors on my 94 were heavily corroded, so much so that I couldn't get a proper reading with my multimeter before I cleaned them.

Roadking_

Okay!
Thanks for the fast responses! I will definitely get one of the noid lights. I do have an older D'arsonval meter with a needle. (am I dating myself?) Anyway, I hope I can trace the wire to the PCM. If I'm not getting the flashes, then I'm thinking its new PCM time.


How available are they for a 94? Aftermarket I'm guessing. I would really like to buy it from a dealer and have it flashed for my Vin all in one shot. (If I need one).


Thanks again,
RK

Roadking_

Problem Solved!!!!!
Began very carefully unwrapping harness following the #4 injector pigtail. Got all the way to the firewall and found the pcm wire broken, barely connected with only the insulation holding it. I stripped wire back found dirt collected around the ends indicating it had been broke/worn thru for a while. I slid a section of shrink wrap down the wire, got out my old weller soldering gun, in line twisted wires together, soldered them together, slid the shrink wrap down over the splice and heated it ,spiral wrapped those wires separate with electrical tape. then re spiral taped the harness back together.


Started Jeep and wow! What a difference! Went ahead and pulled the #4 injector plug just to check and it tested correct! So, Horray!


Test drove and it seemed like it had more power! No telling how long my wife drove it like that before she noticed it??


Anyway Thanks for the input and all the answered questions on other threads that lead me to check my problem! This has been bugging me since before Christmas last year!!!


When I return home from work today I wont know what to do with myself now that I don't have to work on the Jeep :-)

LACK

Glad you got it all fixed, definitely a sense of accomplishment when you figure it out and get it running properly.

BillyBoy

GJ. And thanks lock.

LACK

No problem, I'm sure you'll find something else to fix/upgrade before too long. Its the nature of jeeps. ha