diff --git a/consensus/clique/clique.go b/consensus/clique/clique.go
index 4f637c3aa5..3b89e71560 100644
--- a/consensus/clique/clique.go
+++ b/consensus/clique/clique.go
@@ -680,11 +680,13 @@ func CalcDifficulty(snap *Snapshot, signer common.Address) *big.Int {
 
 // Start implements consensus.Engine, starting the clique consensus engine.
 func (c *Clique) Start() {
+	log.Info("Start clique consensus engine")
 	atomic.StoreInt32(&c.running, 1)
 }
 
 // Stop implements consensus.Engine, stopping the clique consensus engine.
 func (c *Clique) Stop() {
+	log.Info("Stop clique consensus engine")
 	atomic.StoreInt32(&c.running, 0)
 }
 
diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
index 094085aa8c..2cb72676e9 100644
--- a/consensus/ethash/consensus.go
+++ b/consensus/ethash/consensus.go
@@ -32,6 +32,7 @@ import (
 	"github.com/ethereum/go-ethereum/consensus/misc"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/log"
 	"github.com/ethereum/go-ethereum/params"
 )
 
@@ -556,11 +557,13 @@ func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header
 
 // Start implements consensus.Engine, starting the ethash engine.
 func (ethash *Ethash) Start() {
+	log.Info("Start ethash consensus engine")
 	atomic.StoreInt32(&ethash.running, 1)
 }
 
 // Stop implements consensus.Engine, stopping the ethash engine.
 func (ethash *Ethash) Stop() {
+	log.Info("Stop ethash consensus engine")
 	atomic.StoreInt32(&ethash.running, 0)
 }
 
diff --git a/core/tx_pool.go b/core/tx_pool.go
index 7007f85ddf..0fb5ca52b2 100644
--- a/core/tx_pool.go
+++ b/core/tx_pool.go
@@ -465,6 +465,9 @@ func (pool *TxPool) SetGasPrice(price *big.Int) {
 	pool.mu.Lock()
 	defer pool.mu.Unlock()
 
+	if pool.gasPrice == price {
+		return
+	}
 	pool.gasPrice = price
 	for _, tx := range pool.priced.Cap(price, pool.locals) {
 		pool.removeTx(tx.Hash(), false)
diff --git a/eth/api.go b/eth/api.go
index ef66e99cbf..a6b4319872 100644
--- a/eth/api.go
+++ b/eth/api.go
@@ -96,7 +96,8 @@ func NewPrivateMinerAPI(e *Ethereum) *PrivateMinerAPI {
 // Start the miner with the given number of threads. If threads is nil the number
 // of workers started is equal to the number of logical CPUs that are usable by
 // this process. If mining is already running, this method adjust the number of
-// threads allowed to use.
+// threads allowed to use and updates the minimum price required by the transaction
+// pool.
 func (api *PrivateMinerAPI) Start(threads *int) error {
 	// Set the number of threads if the seal engine supports it
 	if threads == nil {
@@ -111,17 +112,14 @@ func (api *PrivateMinerAPI) Start(threads *int) error {
 		log.Info("Updated mining threads", "threads", *threads)
 		th.SetThreads(*threads)
 	}
-	// Start the miner and return
-	if !api.e.IsMining() {
-		// Propagate the initial price point to the transaction pool
-		api.e.lock.RLock()
-		price := api.e.gasPrice
-		api.e.lock.RUnlock()
+	// Propagate the initial price point to the transaction pool
+	api.e.lock.RLock()
+	price := api.e.gasPrice
+	api.e.lock.RUnlock()
+	api.e.txPool.SetGasPrice(price)
 
-		api.e.txPool.SetGasPrice(price)
-		return api.e.StartMining(true)
-	}
-	return nil
+	// Start the miner and return
+	return api.e.StartMining(true)
 }
 
 // Stop the miner
@@ -162,7 +160,7 @@ func (api *PrivateMinerAPI) SetEtherbase(etherbase common.Address) bool {
 
 // GetHashrate returns the current hashrate of the miner.
 func (api *PrivateMinerAPI) GetHashrate() uint64 {
-	return uint64(api.e.miner.HashRate())
+	return api.e.miner.HashRate()
 }
 
 // PrivateAdminAPI is the collection of Ethereum full node-related APIs
diff --git a/eth/backend.go b/eth/backend.go
index 62a85f3fcb..a41adebcfd 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -166,7 +166,13 @@ func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
 	if eth.protocolManager, err = NewProtocolManager(eth.chainConfig, config.SyncMode, config.NetworkId, eth.eventMux, eth.txPool, eth.engine, eth.blockchain, chainDb); err != nil {
 		return nil, err
 	}
-	eth.miner = miner.New(eth, eth.chainConfig, eth.EventMux(), eth.engine)
+
+	// Specify etherbase explicitly.
+	var etherbase common.Address
+	if addr, err := eth.Etherbase(); err == nil {
+		etherbase = addr
+	}
+	eth.miner = miner.New(eth, eth.chainConfig, eth.EventMux(), eth.engine, etherbase)
 	eth.miner.SetExtra(makeExtraData(config.ExtraData))
 
 	eth.APIBackend = &EthAPIBackend{eth, nil}
@@ -338,7 +344,7 @@ func (s *Ethereum) StartMining(local bool) error {
 		log.Error("Cannot start mining without etherbase", "err", err)
 		return fmt.Errorf("etherbase missing: %v", err)
 	}
-	if clique, ok := s.engine.(*clique.Clique); ok {
+	if clique, ok := s.engine.(*clique.Clique); ok && !clique.IsRunning() {
 		wallet, err := s.accountManager.Find(accounts.Account{Address: eb})
 		if wallet == nil || err != nil {
 			log.Error("Etherbase account unavailable locally", "err", err)
diff --git a/miner/miner.go b/miner/miner.go
index 9cfc8fd64f..0da233dd74 100644
--- a/miner/miner.go
+++ b/miner/miner.go
@@ -54,12 +54,13 @@ type Miner struct {
 	shouldStart int32 // should start indicates whether we should start after sync
 }
 
-func New(eth Backend, config *params.ChainConfig, mux *event.TypeMux, engine consensus.Engine) *Miner {
+func New(eth Backend, config *params.ChainConfig, mux *event.TypeMux, engine consensus.Engine, coinbase common.Address) *Miner {
 	miner := &Miner{
 		eth:      eth,
 		mux:      mux,
 		engine:   engine,
-		worker:   newWorker(config, engine, common.Address{}, eth, mux),
+		coinbase: coinbase,
+		worker:   newWorker(config, engine, coinbase, eth, mux),
 		canStart: 1,
 	}
 	miner.Register(NewCpuAgent(eth.BlockChain(), engine))
@@ -108,15 +109,22 @@ func (self *Miner) Start(coinbase common.Address) {
 		log.Info("Network syncing, will start miner afterwards")
 		return
 	}
-	log.Info("Starting mining operation")
-	self.engine.Start()
-	self.worker.start()
-	self.worker.commitNewWork()
+	if !self.engine.IsRunning() {
+		self.engine.Start()
+	}
+	if !self.worker.isRunning() {
+		self.worker.start()
+		self.worker.commitNewWork()
+	}
 }
 
 func (self *Miner) Stop() {
-	self.engine.Stop()
-	self.worker.stop()
+	if self.engine.IsRunning() {
+		self.engine.Stop()
+	}
+	if self.worker.isRunning() {
+		self.worker.stop()
+	}
 	atomic.StoreInt32(&self.shouldStart, 0)
 }
 
@@ -132,9 +140,9 @@ func (self *Miner) Mining() bool {
 	return self.engine.IsRunning()
 }
 
-func (self *Miner) HashRate() (tot int64) {
+func (self *Miner) HashRate() (tot uint64) {
 	if pow, ok := self.engine.(consensus.PoW); ok {
-		tot += int64(pow.Hashrate())
+		tot += uint64(pow.Hashrate())
 	}
 	return
 }
diff --git a/miner/worker.go b/miner/worker.go
index 3d2a99a5be..1dcf2c9b1e 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -127,8 +127,8 @@ type worker struct {
 	unconfirmed *unconfirmedBlocks // set of locally mined blocks pending canonicalness confirmations
 
 	// atomic status counters
-	mining int32
-	atWork int32
+	running int32
+	atWork  int32
 }
 
 func newWorker(config *params.ChainConfig, engine consensus.Engine, coinbase common.Address, eth Backend, mux *event.TypeMux) *worker {
@@ -175,7 +175,7 @@ func (self *worker) setExtra(extra []byte) {
 }
 
 func (self *worker) pending() (*types.Block, *state.StateDB) {
-	if atomic.LoadInt32(&self.mining) == 0 {
+	if atomic.LoadInt32(&self.running) == 0 {
 		// return a snapshot to avoid contention on currentMu mutex
 		self.snapshotMu.RLock()
 		defer self.snapshotMu.RUnlock()
@@ -188,7 +188,7 @@ func (self *worker) pending() (*types.Block, *state.StateDB) {
 }
 
 func (self *worker) pendingBlock() *types.Block {
-	if atomic.LoadInt32(&self.mining) == 0 {
+	if atomic.LoadInt32(&self.running) == 0 {
 		// return a snapshot to avoid contention on currentMu mutex
 		self.snapshotMu.RLock()
 		defer self.snapshotMu.RUnlock()
@@ -204,7 +204,7 @@ func (self *worker) start() {
 	self.mu.Lock()
 	defer self.mu.Unlock()
 
-	atomic.StoreInt32(&self.mining, 1)
+	atomic.StoreInt32(&self.running, 1)
 
 	// spin up agents
 	for agent := range self.agents {
@@ -217,15 +217,20 @@ func (self *worker) stop() {
 
 	self.mu.Lock()
 	defer self.mu.Unlock()
-	if atomic.LoadInt32(&self.mining) == 1 {
+	if atomic.LoadInt32(&self.running) == 1 {
 		for agent := range self.agents {
 			agent.Stop()
 		}
 	}
-	atomic.StoreInt32(&self.mining, 0)
+	atomic.StoreInt32(&self.running, 0)
 	atomic.StoreInt32(&self.atWork, 0)
 }
 
+// isRunning returns an indicator whether worker is currently running or not.
+func (self *worker) isRunning() bool {
+	return atomic.LoadInt32(&self.running) > 0
+}
+
 func (self *worker) register(agent Agent) {
 	self.mu.Lock()
 	defer self.mu.Unlock()
@@ -266,7 +271,7 @@ func (self *worker) update() {
 			// Note all transactions received may not be continuous with transactions
 			// already included in the current mining block. These transactions will
 			// be automatically eliminated.
-			if atomic.LoadInt32(&self.mining) == 0 {
+			if atomic.LoadInt32(&self.running) == 0 {
 				self.currentMu.Lock()
 				txs := make(map[common.Address]types.Transactions)
 				for _, tx := range ev.Txs {