305 TPI Surges at Highway Speeds
08-16-2015, 11:05 AM
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Car: 1986 Z28
Engine: 305 TPI
Transmission: 700r4
Axle/Gears: 3.42
305 TPI Surges at Highway Speeds
Hi Guys - '86 Z, 305TPI auto all stock w/ 50k miles.
At highway speeds of 65mph+, I'm getting 500rpm rhythmic power surges under load, like climbing a steady upgrade or passing. Also, around 40mph I get constant 4th to 3rd to 4th gear changes. (not sure if this is the same issue but it has that surging feeling, too). No problem with acceleration from a standstill. It does have a tendency to run rough at start up after it has sat for a week but idles fine after a minute or 2. I run 89 octane consistently. No overheating issues. Plugs and wires changed about 3 years ago and the car maybe gets 1000 miles put on annually.
Any advice on where to start troubleshooting?
At highway speeds of 65mph+, I'm getting 500rpm rhythmic power surges under load, like climbing a steady upgrade or passing. Also, around 40mph I get constant 4th to 3rd to 4th gear changes. (not sure if this is the same issue but it has that surging feeling, too). No problem with acceleration from a standstill. It does have a tendency to run rough at start up after it has sat for a week but idles fine after a minute or 2. I run 89 octane consistently. No overheating issues. Plugs and wires changed about 3 years ago and the car maybe gets 1000 miles put on annually.
Any advice on where to start troubleshooting?
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