How to check possibly bad pcm?
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From: Longview,TX & Tricitys,WA
How to check possibly bad pcm? I've narrowed down the problem to my pcm or wireing harness in the engine bay. When random problems come up i hit both around and bit, restart the car and it works.
What i'm wondering is what the best way would be to narrow down the culprit. Here's a few things i've done:
I might have tightened down the pcm too much or too little, don't have a torque wrench, its says tighten no more than 5 +- 1 lbs. I tried really tight, really loose, and what i believe is normal and none seem to keep it constant.
I've had the engine running while its running poor and shaked around the wire harness some around the bay and it didn't change really, noticeable that is.
I've heard some wierd electric buzzing sounds coming from the glove box location (where the pcm is) occasionaly while driving.
Cleaned up the grounds really well, inspected fuses and such.
Visually inspected each pin and socket for the pcm and the wire harness around the bay (except behind the intake).
I have notice wierd higher sounding frequencies coming through the speakers (never had this happen before).
Radar detector has randomly thrown a couple LASER readings while this has gone on, no where near any cops or city influence.
The car doesn't throw codes and have random "no starts" ect, just occasionally starts running more poor than it should, then i do the usual: turn it off, smack everything around, turn it back on. Sometimes i can tell it runs alot better sometimes not. Dealer charges $80 to inspect a pcm.
Edit: I've also been wanting to get a frost tune, i'm not sure if he sells pcm's with tunes?
What i'm wondering is what the best way would be to narrow down the culprit. Here's a few things i've done:
I might have tightened down the pcm too much or too little, don't have a torque wrench, its says tighten no more than 5 +- 1 lbs. I tried really tight, really loose, and what i believe is normal and none seem to keep it constant.
I've had the engine running while its running poor and shaked around the wire harness some around the bay and it didn't change really, noticeable that is.
I've heard some wierd electric buzzing sounds coming from the glove box location (where the pcm is) occasionaly while driving.
Cleaned up the grounds really well, inspected fuses and such.
Visually inspected each pin and socket for the pcm and the wire harness around the bay (except behind the intake).
I have notice wierd higher sounding frequencies coming through the speakers (never had this happen before).
Radar detector has randomly thrown a couple LASER readings while this has gone on, no where near any cops or city influence.
The car doesn't throw codes and have random "no starts" ect, just occasionally starts running more poor than it should, then i do the usual: turn it off, smack everything around, turn it back on. Sometimes i can tell it runs alot better sometimes not. Dealer charges $80 to inspect a pcm.
Edit: I've also been wanting to get a frost tune, i'm not sure if he sells pcm's with tunes?
Last edited by The Mighty Texan; May 27, 2011 at 12:04 PM.
Thread Starter
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From: Longview,TX & Tricitys,WA
While it is running or when it's turned off? I'll prob try both anyways sounds like something else at least to check thanks! Did yours turn out to be bad and need replacing?
Thread Starter
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From: Longview,TX & Tricitys,WA
I tried that and didn't notice much or any change, is there anything more thorough i can do? Or, is there any way of checking the wire harness or will that be too hard to check each individual wire?
Remember we established that you have a definite fuel pressure issue since it bleeds back so fast when shut off. It could be coincidence about tapping on the pcm or the harness. From how much trouble you are having diagnosing it I would seriously recommend to save yourself the headache of guessing. Don't be scared of the dealership they can only charge you your original estimate for diagnosis which industry standard is 1.0 labor hour. For most dealers that is 80-120 dollars. When they tell you whats wrong with it and how much they want to fix it then you can either have them do it or decline the work and just pay the diagnosis fee and fix it yourself. Some things are just best left to people who do it every day.
When you bring your car in you don't want to give them a long winded explanation of what you have done or make statements like just inspect the pcm because that is all they will do. Technicians hate being told by a customer what they think is wrong with it just bring it in with the complaint that the car has an intermittent misfire and they will inspect everything to find what is wrong. The more you mess with it the more psyched out your making yourself. Without lots of knowledge you can easily become confused and over analyze everything.
