My engine will not idle when cold. It will start and idle rather well if head bolt heater is used to warm engine first. It seems to run real rich. Also loses power on hills. It runs rough at certain speeds on highway.
Sounds like the ECT – Engine Coolant Temperature Sensor may be giving you an issue. First I would pull any existing engine codes. Post any of the codes found below in the comments. This will help narrow down any issue related to the engine. The good news is, this can be done without a scan tool. Do to this I have added a link to explain how to go about doing just that.
Engine Will Not Idle
Idle Speed Adjustment
The engine utilizes sophisticated multi-port fuel injection systems in which an engine control computer utilizes information from various sensors to control idle speed and air fuel mixtures. No periodic adjustments are either necessary or possible on these systems.
Idle Air Control
The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows air, determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed. A vacuum leak will disrupt the ability to do its job cause it will be fighting itself.