Ok, this is on my dads truck, it's a 98 has 4k gov springs #8 plate, head studs and 60 lb valve springs, timing is stock, injectors are stock. He pulls a 35' fifth wheel grossing about 21k. When pulling hills It starts to surge around 18-2000rpm and only in 4th gear. He can power through it but looking for a fix. Has a new lift pump and fuel filter. Any ideas at this point would be great!
Surging under load at 1800-2000rpm
- Thread starter jmoritz
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