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Engine Running Rough

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Old 12-02-2009, 06:21 PM   #1
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Engine Running Rough

This one is a head scratcher, my 97' S10 4x4 5-speed has been acting very strangely. Upon startup it runs fine, idles smoothly, no issues. But from the 1000 to 2500 RPM range it jerks and misses. After warming up however, the problem goes away and it runs smoothly for the rest of the day. We took it to a mechanic who replaced the plugs, wires, cap, rotor, and coil. This seemed to take care of it. Here is where things get really strange, about a month later it started doing it again, almost imperceptibly missing and jerking for the first 20 minutes or so of running and then going away. The jerking and missing got a little worse each day until finally, one day while driving up a hill around 40 mph with my head smacking the back window, it gave a loud backfire and shut off. It would not start back up. We had it towed to a new mechanic who replaced the coil AGAIN as well as the crank position sensor and once again the problem went away. A month later the same thing happened and we took it back to the second mechanic who tried for 2 weeks to solve the issue and was unsuccessful. He replaced the coil a third time, put in a new computer, plugs, wires, cap, rotor, checked the timing, compression tested it (i assume), and even installed an octopuss to bypass some of the fuel valves. And after all of that it was still acting like a hungover college kid. Any insight to this matter would be greatly appreciated.
Old 12-02-2009, 10:31 PM   #2
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Re: Engine Running Rough

Dizzy gear
Dirty selinoid
vacuum leak
MAP sensor
EGR in need of cleanning
Ignition Mod


My advice: connect a vacuum gauge with about another 6' of line so you have it on the dash. Then you can at least see what is happenning when it starts to trailer hitch on you.

But that's just me. And I only believe in replacing parts because they need to be replaced or for preventive maintanance...
Yes I'm lazzy... but my vehicles start as soon as the starter turns.
Old 12-03-2009, 04:06 PM   #3
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Re: Engine Running Rough

I'll talk to my mechanic about that list, but I was just reading another thread and their issue sounds exactly like mine. Several people suggested that the distributor gear could be bad so I'll try that too. Thanks for the advice.
Old 12-03-2009, 06:28 PM   #4
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Re: Engine Running Rough

The list is endless, but after read about your issue I think that I'd start by looking at the coolant temp sensor ( not the engine temp sender that goes to the dash).
Old 12-04-2009, 03:08 PM   #5
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Re: Engine Running Rough

Yea I read that too about the coolant temp. sensor. I'm not sure if it's running rich or not, I'll ask my mechanic if the plugs are really dirty in the event that the dizzy gear isn't the problem.
Old 03-04-2010, 01:05 PM   #6
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Re: Engine Running Rough

did you fix this? mine does the same thing. please let me know thanks
Old 03-20-2010, 10:23 AM   #7
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Re: Engine Running Rough

Yeah this really gets to me. People posting problems and never coming back with a resolution. Im having an issue very similar...
Old 03-20-2010, 03:23 PM   #8
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Re: Engine Running Rough

I'm also curious as to what the fix is.

Send the guy a friendly message,no harm in that.
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