Hey everyone.

I've got an unusual electrical problem where the engine idles rough when I step on the brake during a cold start. The RPM seems consistent according to the tachometer, but you can feel the engine shuttering when the brake pedal is pressed and returns to normal when the brake is released. This started around the time I tried installing LED bulbs which I later read could cause a back current, so I removed them, but the rough idling persists. This rough idle seems to dissipate at FOT.

Another, possibly unrelated, issue is that the engine power occasionally drops which always coincides with the temperature gauge dropping. No other dash instruments fluctuate, only the temperature gauge. During last Winter, the power would sometimes drop sharply, creating jolts right when I'm accelerating. I've changed the CKP and coolant temperature sensors, but the problem persists. Haven't changed the TPS sensor yet, but I do have a new one on standby. I just have a feeling it's not the TPS because of the temperature gauge's involvement. Could a faulty PCM or its relay cause power disruptions that also couples the temperature gauge fluctuations?

Any input or suggestion is greatly appreciated. Thanks in advance.

 

I would start by watching your voltages and see if something is going on. A cheap cigar lighter style gauge could give you indications if your alternator is fluttering. (This could cause one gage to go wonky but not the rest.) This might not be the cause of everything or your brake issue but its something easy to try first.