If you decide to change new plugs, run a bottle of Berryman 2611 first.

 

Update: Installed new belt and tensioner. Cleaned and tightened battery terminals. Engine did start but same as before. Ran rough like it was missing. After a couple of minutes it smoothed out and ran great. No missing. Hooked up scanner and no codes showed up. Still running on original plugs and coils (165k) miles. (Plan on changing them soon ). Confused with the cold start, rough idle issues for a just a few minutes ..After that it runs good for the rest of the day.

Thinking about the ECT sensor. How soon after starting could it affect the running of the engine. Could a wonky ECT only make it run badly for the first minute or two ?

 

Yes !

 

 

Replaced the coolant temp sensor thinking rough starting and idle when engine is cool as in morning or late in day. In between when I’ve been using the car, it’s fine. Replacint the CTS made sense. But no luck. Any thoughts on the fuel pressure sensor on the fuel rail as a possible solution.?? Again after it does finally start and runs roughly for a couple of minutes, then smoothes out, it’s good for the rest of the day..

 

What's your definition of rough idle? If your rpm is fluctuating between 500 to 2000 for a couple of minutes then YES.
if it's high, but steady around 1200 to 1500, only on cold start, for a minute or two that is NORMAL and you are overthinking, as long as it settles to around 750 afterward.
And don't throw random parts to your car. If you just want to spend some money on it, run Berryman 2611 yearly, 2616 twice a year and 0116 every 2 or 3 fill ups.

 

It’s more than a rough idle. When it does start it sounds like it’s running on 3 cylinders, makes weird puffing sounds from inside the engine. It’s running so irregular that the new tensioner is slightly oscillating back and forth with the irregular running of the engine. Does this for a minute or two and then smooths out and runs great
But it does crank over very slowly when I’m doing this first startup. Battery is new and cable connections are tight. After this initial startup problem, battery and engine crank over just fine.

 

Has your fuel consumption increased recently ?

 

Not that I’m aware of but I haven’t driven it much since this problem had arisen.

 

Battery connections can look good and be tight,,,but if there is corrosion between the cable end and the battery post that is not visible and causes a lot of problems.

The only way to verify the connections are good is to do voltage drop tests OR JUST REMOVE THEM AND CLEAN THEM with sandpaper or wire brush.

A little FYI, don't be fooled by stuff called battery terminal protector. You spray it on and the terminal looks fine, but the moisture comes up under the uncoated connection and gets corroded and you can't see it.