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97 S10 pickup runs rough with misfire codes

 
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mescottyboy mescottyboy
New User | Posts: 5 | Joined: 08/06
Posted: 07/31/06
09:14 PM

97 4.3 V6 X engine 150K miles, runs rough with random misfire codes. Runs great with MAP sensor disconnected (open loop). Have changed MAP sensor, plugs, wires, rotor, VCM computer, EGR, catlytic converter 02 sensors. Local mechanic checked fuel pressure and fuel injector assy, both OK.

Anyone have any thoughts?
Thanks,
Scott  

Gary_602Z Gary_602Z
Enthusiast | Posts: 423 | Joined: 06/06
Posted: 08/01/06
11:24 AM

Did you do distrubtor cap also? I presume you did.

Gary  

mescottyboy mescottyboy
New User | Posts: 5 | Joined: 08/06
Posted: 08/01/06
06:56 PM

yup, cap & rotor. Thanks  

automotivejtm-#001 automotivejtm-#001
Guru | Posts: 1019 | Joined: 03/06
Posted: 08/02/06
02:32 AM

how often does it misfire? Or how often does your check engine light come on?  

mescottyboy mescottyboy
New User | Posts: 5 | Joined: 08/06
Posted: 08/02/06
08:29 AM

The check engine light is on all the time. When the code is cleared manually with the scan tool it comes back immediately.  
When the truck is cold, it misfires consistantly when accelerating from a complete stop. The misfire can be felt and the code comes up shortly therefter. After it warms up, the misfires can not be felt when accelerating, but the code does not clear by itself. It also misfires consistantly and can can really be felt going down a hill after running at constant speed.  
IF the MAP sensor is disconnected no PO300 codes are raised and I can not feel any misfiring.   Thanks for your help.  

automotivejtm-#001 automotivejtm-#001
Guru | Posts: 1019 | Joined: 03/06
Posted: 08/02/06
10:43 AM

if your positive it runs good in open loop that would suggest a bad senor, have you checked your cam position sensor?  

mescottyboy mescottyboy
New User | Posts: 5 | Joined: 08/06
Posted: 08/02/06
08:54 PM

No, have not checked CAM sensor yet. I will check on Sat. busy marching in parades tonight and fri night - local bagpiper.  

mescottyboy mescottyboy
New User | Posts: 5 | Joined: 08/06
Posted: 08/05/06
02:16 AM

Hey Automotivejtm, you da man!!

I opened the distributor cap and found one of the torx screws I installed to fasten the rotor to the distribuor was too long and it wore away part of the CAM sensor. Replaced the CAM sensor and it runs like a top.

If you are ever in Rochester NY email me and I'll buy a couple pints of ale.

Cheers, Scott  

Gary_602Z Gary_602Z
Enthusiast | Posts: 423 | Joined: 06/06
Posted: 08/06/06
10:37 AM

Thanks for posting back with the solution to your problem! So many people don't. This way we can all learn a little bit more!

Gary  

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