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Ron
Ron, ASE Certified Technician
Category: GMC
Satisfied Customers: 35515
Experience:  35 years in the Automotive repair business.
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Have a 97 sonoma 2.2 blowing black smoke had talked to

Customer Question

Have a 97 sonoma 2.2 blowing black smoke had talked to another mechanic on here but he hasn't answered back in a while have changed all new injectors timing chain all new vacuum lines no vacuum leaks but each cylinder was wet with fuel when I removed plugs when it was running after the work I did blew black smoke very rich smell idle was very rough but would not stall had no power sounded like it was missing I have spark on all cylinder and and noid tested the injectors are getting power as should and ohmed out in spec. Also checked coolant temp sensor is good all sensors have the 5v reference .any hope is appreciated
Thank you
Jeremy
Submitted: 1 year ago.
Category: GMC
Customer: replied 1 year ago.
Also only code I have gotten has been for map sensor tested ground tested signal and tested old sensor it was bad replaced it still getting that code
Expert:  Ron replied 1 year ago.

Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

If you fuel fouling all the spark plugs and running rich I would also install a fuel pressure gauge and monitor the fuel pressure. Normal pressure needs to be right at 41 to 47 PSI. Check this for me and post back with the results and we can work from there. Also if you can, give me all the actual fault code and or codes your getting and we can work from there.

Customer: replied 1 year ago.
Ok sir, so ran my little blue tooth scanner only code shown is p0107 for map sensor I have test all aspects to the best of my knowledge good ground has 5v reference and and hooked my vacuum machine I have signal and is working as should at least test out that way fuel pressure key on went to 43psi then planned down to 39 after 10 or so seconds cranking fuel psi was 43 and when it would slightly fire would got to about 41psi have inspected all fuel lines wouldn't hurt to replace but no leaks I can see or smell
Expert:  Ron replied 1 year ago.

Fuel pressure looks okay . The code P0107 usually means you have a low voltage concern to the MAP but if your getting 5 volts reference it should be fine. I have to wonder if you fuel fouling the spar plugs anyways that perhaps your PCM has failed. Injector pulse is controlled by the PCM.

Customer: replied 1 year ago.
I used my noid lights on the injector harnesses and they seemed to all be flashing correctly to see for the pcm had put them on full rich due to failure also checked coolant temp sensor cause I read they can do same when they fail will make motor think it is still.cold am I correct
Expert:  Ron replied 1 year ago.

A bad ETC can cause a rich condition but it will in most cases set a fault code. If you sure the MAP is oaky then this dose point towards a failing PCM.

Customer: replied 1 year ago.
That's kind of what I've been leaning towards guess with how much I've spent so far a $40 pcm out of the junkyard can't hurt I have one I know of that is exactly the same anday happen to know how's truck it was and why it's there so with everything I've tried and tested would you recommend me trying this .thanks
Customer: replied 1 year ago.
My scanner also shows throttle position and it seems to be working and showing correct position
Customer: replied 1 year ago.
Well it's a nice day in indiana so I'm ganna run to the yard and yank a computer out worth a trying
Expert:  Ron replied 1 year ago.

Anytime you install a PCM new or used it will require programming.

Customer: replied 1 year ago.
I would either have to take it to a dealership or order a pre programed one ?
Expert:  Ron replied 1 year ago.

Either one would work, you may want to start with a used one first as it would be more cost effective.

Customer: replied 1 year ago.
Can I get my hands on a used pre programed pcm ? I would like to try and go about this in the least expensive way I only bought this for a gas saver to haul my dirtbike to races. Thanks
Customer: replied 1 year ago.
If I were to find a used one the dealership must also have the vehicle and pcm to complete the process correct? And what's your views on a pre programed one off line looks like 150 to $200
Expert:  Ron replied 1 year ago.

Im not aware of any place that sells them this way. You may want to check with your salve yard to see if by chance they have the ability to do so.

Customer: replied 1 year ago.
besides probably hooking truck to a oscilloscope there's no easy way to trouble shoot the pcm
Expert:  Ron replied 1 year ago.

Unfortunately no there is not. The only other way is to remove it and send it in to a company that build them and have it professionally checked.

Customer: replied 1 year ago.
if I have another truck exactly the same down to the colors that pcm is worthless unless it is reprogrammed even know the motor should have colse to the same perimeters set on it just curious its hard to find gooder information on theses kinds of issues , thanks again I will be ordering a pcm today
Expert:  Ron replied 1 year ago.

The problem is going to be with the Pass-lock system , there is different programming from truck to truck.

Customer: replied 1 year ago.
Have new ecm on the way should be there within a day or 2
Expert:  Ron replied 1 year ago.

Okay hopefully that resolves you problem.

Customer: replied 1 year ago.
Ok I helped a buddy pull some parts at a junkyard and in exchange he bought a ecm there just to give it a try installed truck took a bit due to fouling plugs but started I help the throttle at about 2k for a few mins and you could tell the motor was learning cause one by one the cylinders started firing in the proper order now I believe the slight roughness is from bad plugs now from getting drenched with fuel
Expert:  Ron replied 1 year ago.

Well that would sure make since. Clean you fouled plugs and see if it clears.