Mechanics

GMC SUBURBAN EGR VALVE PROBLEM

1994 GMC Suburban • 160,000 miles

My truck (K2500 7.4L V8 OHV 16V) has been having some engine trouble. It feels like it is "hesitating" with a low idle, like it is not getting enough fuel. It seems to go back and forth from normal driving to problem driving (it never dies and will provide enough power to drive under most circumstances, not on a steep uphill grade or sustained high speeds). I had a mechanic replace the fuel pump but that did not fix the issue.
Lately I figured out that hitting the dashboard in front of the steering wheel will get it to "fix" the problem. I have also noticed that going over a bump in the road will also jolt it back to normal.
I have not run any diagnostics to get any engine codes. Most of the advice I have seen says to remove the vacuum hose from the EGR valve and plug it to check, etc. I have no idea where the EGR valve is to check it though.
Any help is greatly appreciated.
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October 29, 2012.



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