Questions and Answers
Surging Mustang
Q. My son and I are restoring a 1982 Mustang GT with a 5.0 Liter HO engine, Autolite 2150 carburetor, manual transmission, PS, PB, 90K miles. Our problem is that the engine does not run very smooth at any speed. There is about a 50 rpm fluctuation (surging) at idle with a vacuum change ( no flutter) of about one inch (19 - 20).
As the engine speed is increased, the fluctuation becomes less noticeable but does not go away. It can even be felt under acceleration. At first, we thought it was the carburetor, but that didn't seem reasonable since the surging occurs under a wide variety of conditions. However, we rebuilt the carburetor anyway. We also replaced the plugs, wires, and distributor cap. What should we look for next ? Does the fact that this is an HO engine have any significance?
Richard
A. Usually a surging such as you describe is caused by a bad O2 sensor. I would check that it is working correctly. If it is, then the problem could be in the EGR system. Perhaps a mis-routed vacuum line or a bad EGR valve or EGR solenoid.
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