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Hey guys I have a major issue, back in November I got a mail order tune from Jeremy @ limeswap which works great. At the beginning of December I started getting a intermittant p0303/p0203(injector circuit cyl 3) at that time I ohmed out all wiring from main connection at rear of valve cover for all inectors to pcm which ohmed out at .08 (normal). I moved coils around (no change) moved spark plugs (no change) compression test (normal) leak down test ( less than 5% loss). I even hooked up a noid light on cylinder 3 injector harness and during misfire light was pulsing(so pcm is commanding injector) I decided my issue might've been due to bad/cheap gas so I went to Wal-Mart and grabbed 2 quarts pf denatured alcohol and dumped them in a half tank of gas. Once that tank showed low fuel the misfire was completely gone and has never come back on that pcm.

Fast forward....I told Jeremy of this issue and that id like some alterations to save more gas since my daily commute has extended to an hour each way. He offered to send out another pcm and when I got it I plugged it up and immediately got a dead miss on cylinder 3. Codes that set are p0203/p0303 & crank relearn code. I rechecked my harness connections at pcm/injector/coil all ok nothing found. I contacted Jeremy and told him my issue...he offered to set up another pcm and send it out. ...when I got it same thing. Now when that happens I can plug back up the original pcm that is also tuned and it runs great and smooth.

I decided to contact another member that is local to me and has same year same motor truck and I put the new pcm(misfiring in mine) into his truck and it ran great and smooth no codes other than the crank relearn. So by this I assume it is something specific to my truck. Only thing I haven't changed was the injector since it is a big deal to get to. So I ordered a new injector and installed it today along with new intake gaskets. This time I ohmed out all wiring from pcm to injector which came out fine on both wires on cylinder 3. I replaced injector #3. Reassembled and on old pcm it runs great as it did. I put in new pcm and dead miss cylinder 3 again with same codes again. At this point im lost at what it could be. Jeremy asked if I could try performing case relearn which I attempted but it will not complete or accept my snap of the throttle and yes I tried it quite a few times.


Any help? Anyone seen this?


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Mmmm, pins look ok on the PCM cable connection? I had a loose socket once that caused me grief. Used a welder tip cleaner to gauge if all were the same size and found one very loose which made an intermittent connection...

Frank
 

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Discussion Starter #5
I did not and since I'm getting an injector code I didn't think it were necessary. I can take a test light and touch each cylinder injector wire and when I do so you can feel the engine stumble on all cylinders except number 3. Granted if it's not getting fire it will do the same.

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I did not and since I'm getting an injector code I didn't think it were necessary. I can take a test light and touch each cylinder injector wire and when I do so you can feel the engine stumble on all cylinders except number 3. Granted if it's not getting fire it will do the same.

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Did you check the PCM signal right at the coil packs?
Oscilloscope or a DMM?
Don't use a test light. Use a tester with a higher impedance.
 

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Mmmm, pins look ok on the PCM cable connection? I had a loose socket once that caused me grief. Used a welder tip cleaner to gauge if all were the same size and found one very loose which made an intermittent connection...

Frank
I think I might have this problem. What did you do to fix it?
 
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