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I have a 95 GMC c1500 with the 5.0 that when you let the…

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I have a 95 GMC...
I have a 95 GMC c1500 with the 5.0 that when you let the clutch out it stumbles and bucks. After you get rolling and the higher RPMs it runs just fine. Replaced the IAC and MAP sensor. EGR appears to work also.
Submitted: 3 years ago.Category: GMC
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Answered in 6 minutes by:
6/13/2015
GMC Mechanic: Jerry, Master Mechanic replied 3 years ago
Jerry
Jerry, Master Mechanic
Category: GMC
Satisfied Customers: 17,221
Experience: ASE Master, 30+ years exp. former shop owner/ manager
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What is the fuel pressure?
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Are there any trouble codes stored?
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Customer reply replied 3 years ago
NO trouble codes and no port to check pressure. High RPM runs just fine though, no stumble at all.
GMC Mechanic: Jerry, Master Mechanic replied 3 years ago
I see, thanks. I know they are a lot of work to hook up a pressure gauge to. The problem with an off idle stumble can be hard to pinpoint. However the best way to determine if it is a lean running problem, (off idle) is to unplug the EGR valve and see if the problem goes away, JUST AS A TEST, YOU won't want to drive it that way for an extended period of time.
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One of the things that I have seen cause that also way the trigger wheel inside the distributor. The only way to check that is to take the center shaft out to see if any of the trigger points have lost their magnetism. That is sort of rare though and sometimes a last resort.
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Of course you will want to make sure that the ignition system, (plugs, wires and cap/rotor) are in good working order as well.
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Please don’t forget to rate the answer, **** THAT IS THE ONLY WAY I GET PAID **** if you need any more on it, I will be here.
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Thanks and come again, anytime.
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Customer reply replied 3 years ago
Just to clarify, when starting in first gear, the truck bucks almost wildly, then when you get rolling, it accelerates fine and has no issues at higher rpm. Will look at egr and let you know what I find.
Customer reply replied 3 years ago
unplugged egr and made no difference.
GMC Mechanic: Jerry, Master Mechanic replied 3 years ago
Does it idle on all cylinders?
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Customer reply replied 3 years ago
Yes. Nice smooth idle. injector spray looks nice and even.
GMC Mechanic: Jerry, Master Mechanic replied 3 years ago
That could be just the TPS also, if it is loosing contacts inside. You can normally check with a scan tool to see how does or do a sweep test with an ohm meter.
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Customer reply replied 3 years ago
TPS is .69 to 4.63 WOT
GMC Mechanic: Jerry, Master Mechanic replied 3 years ago
Can you monitor the fuel trim/pulse width while driving it with a scan tool hooked up?
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Customer reply replied 3 years ago
No. Only have a gensys for OBD 1
GMC Mechanic: Jerry, Master Mechanic replied 3 years ago
That is all that I could think of on it, but wait there may be another expert who has more. I will opt out and open it back up. Please DON’T REPLY to this post as that will lock the question back to me, also DON’T RATE THE ANSWER yet, someone should be along shortly, I’m sure, thanks and sorry I wasn’t able to help with it.
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*******YOU CAN ALWAYS GET A REFUND WITHOUT RATING THE ANSWER AS BAD OR THE SERVICE AS POOR ********
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Customer reply replied 3 years ago
I replaced the throttle body assembly from a running truck and it had no effect on the problem
Customer reply replied 3 years ago
Anyone there?
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