89 sidekick electrical problems

[bruski]

The kick runs good, however the dash eng light and fuel gauge goes off, then comes back on on dirt roads. Check eng light always comes on when shifting gears and I let off the gas. This is how I know the gauges arn't working when check eng light doesn't come on. Gauges effected are temperure, gas and check eng light. Some times they work sometimes they don't.