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98 Silverado running rough
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1998 chevy 1500
New User
Jul 23, 2011, 10:32 AM
Post #1 of 6
(4626 views)
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98 Silverado running rough
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Hi all,
I have a 1998 Chevy Silverado 5.0 with 85000 miles that is giving me problems. I have owned this truck since new and have done most maintenance and repairs myself. It has always ran like a top. However, in the last few months the truck has started running a little rough and it seems like it is loosing power. It seems I have to give it a lot more throttle to maintain speed then I did in the past, the truck is constantly downshifting back and forth. Subsequently, it seems to be using quite a bit more gas then in the past. I drove it to the lake last weekend and it barely made it up the hill to the cabin. Even on a flat road, once the truck kicks into overdrive, it seems as if it starts missing just slightly and will eventually have to downshift back to 3rd.
Well, I changing out the plugs, no difference. I replaced the MAP sensor at someones recommendation, no difference. replaced the fuel filter for the hell of it, no difference. I decided to take it to a local auto shop, they ran a diagnostics and found nothing wrong. They charged me $98.00 to tell me that.
I am going to replace the plug wires this afternoon but after that I have no idea where to start. I thought at first this was a sensor failure (like an 02 sensor) but the diagnostics didn't pick it up. Any ideas??
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Kasper
User
Jul 23, 2011, 1:37 PM
Post #2 of 6
(4614 views)
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Re: 98 Silverado running rough
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How long has it been since you changed the transmission filter and fluid?
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Kasper
User
Jul 23, 2011, 4:26 PM
Post #4 of 6
(4597 views)
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Re: 98 Silverado running rough
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Sorry was just trying to help I thought about the converter too. But thaought I'd ask that first my bad.
Hope 1 or the other helps good luck
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Hammer Time
Ultimate Carjunky
/ Moderator
Jul 23, 2011, 4:29 PM
Post #5 of 6
(4595 views)
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Re: 98 Silverado running rough
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Even if it was a transmission problem, changing the fluid would not be advised at that stage so it really doesn't matter if it's been changed or not.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Sidom
Veteran
/ Moderator
Jul 23, 2011, 5:41 PM
Post #6 of 6
(4585 views)
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Re: 98 Silverado running rough
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The same thought popped into my head to after reading that post.....
If he doesn't have access to a BP gauge, he could look at vacuum under load.....A vacuum reading dropping very low at high rpms would also point towards a restricted exhaust system....
But back pressure is the best way to go....
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