Rough Idle at Start Up

[0356kid]

So. California car (so it is not cold outside) and have an 08C2S w/37,000 miles, major service completed 6 months ago. Past two days in a.m. when starting the car in the morning that for about 15-20 seconds the idle seems a little rough. Back out of drive and take off for work and all is fine. Possible rough idle issue might be?

Thanks in advance.

[White987S]

What was done at the major service 6 months ago?

Plugs?

Do you ever use Chevron Fuel System Cleaner with Techron? May want to run a couple tanks worth. Dirty injectors?

When did you last get gas? Did the problem start after that? Maybe bad fuel? Keep topping up your tank with fresh fuel, see if it improves.

[Mijostyn]

White is right. I vote for bad gas. I have seen this numerous times over the years even from such vaunted suppliers as Mobile and Sunnoco. Usually it is one of the privates and I religiously stay away from them. I had one instance that was so bad I had to change my fuel filter. When I took it off it was full of dirt and water!!

Techron comes up quite a bit. I have never used it but some swear by it. JFP, is this stuff safe to use in our cars? Does it work?

The Porsche guys say not to use any additives but they also tell you that you have to stick to N rated tires.

[0356kid]

Plugs were replaced during the major service. As for fuel, I only run Chevron 91 octane and have since new. Refueling happened this past weekend and I refuel at the same Chevron station by my house all the time (or at least 90% but still buy Chevron). And it is possible the problem started just after the last fill up. I'm down to 1/2 tank so I will buy more gas this weekend and keep an eye on it. Thx...

[White987S]

Techron comes up quite a bit. I have never used it but some swear by it. JFP, is this stuff safe to use in our cars? Does it work?

The Porsche guys say not to use any additives but they also tell you that you have to stick to N rated tires.

I use the Chevron/Techron product before every oil change in all my Porsches.

[JFP in PA]

White is right. I vote for bad gas. I have seen this numerous times over the years even from such vaunted suppliers as Mobile and Sunnoco. Usually it is one of the privates and I religiously stay away from them. I had one instance that was so bad I had to change my fuel filter. When I took it off it was full of dirt and water!!

Techron comes up quite a bit. I have never used it but some swear by it. JFP, is this stuff safe to use in our cars? Does it work?

The Porsche guys say not to use any additives but they also tell you that you have to stick to N rated tires.

Techron is an excellent product, often used by the dealerships as well as most "indies". We recommend using it at least once a year, in the last tank of gas just before an oil/filter service (it often causes the oil to collect some carbon and other crud during the cleaning process), particularly for cars being prepped for winter "hibernation". Techron often cures niggling idle problems as well as off idle stumbling issues related to varnished injectors.

[0356kid]

While I know Chevron has Techron in their gas, what exactly are you using before every oil change and where do you get it?

Thx,

[Loren]

I buy it in the 4 pack at Costco...

[JFP in PA]

While I know Chevron has Techron in their gas, what exactly are you using before every oil change and where do you get it?

Thx,

Sold by most auto parts outlets as well as online (Amazon and other). Get the 20 gallon size as most Porsche tanks are over 18 gallons in capacity.

[0356kid]

Thanks gentlemen! My wife lives at Costco and me on Amazon so I'll check it out.

[JFP in PA]

Thanks gentlemen! My wife lives at Costco and me on Amazon so I'll check it out.

Check out your local AutoZone as well, they were recently offering a buy one, get one free for Techron products.

[0356kid]

Thanks again to all!!

[Jvc300]

I had a rough idle on startup one day and didn't think much about it. A week later it ran rough again and the 'check engine' light came on later that day. I couldn't figure it out..

So, I opened the engine compartment and my hand swiped the oil cap.. Yes, the oil cap was loose.... Which causes the engine to lose vacuum (rough idle) . A month before I did an oil change and apparently didn't tighten the cap enough.

I tightened the oil cap (AND Double checked that it was as tight again... ), reset the Check engine light (Disconnect the battery)...... It never ran rough and the CEL never came on again!!!!

Check the oil cap....

[JFP in PA]

I had a rough idle on startup one day and didn't think much about it. A week later it ran rough again and the 'check engine' light came on later that day. I couldn't figure it out..

So, I opened the engine compartment and my hand swiped the oil cap.. Yes, the oil cap was loose.... Which causes the engine to lose vacuum (rough idle) . A month before I did an oil change and apparently didn't tighten the cap enough.

I tightened the oil cap (AND Double checked that it was as tight again... ), reset the Check engine light (Disconnect the battery)...... It never ran rough and the CEL never came on again!!!!

Check the oil cap....

Small suggestion here: Never clear check engine lights before reading and noting the codes. Far too often, when people pull the battery cable and clear what they think is a single code problem, they actually clear multiple codes that could have proven critical in quickly and correctly diagnosing and permanently fixing the problem(s). And when the light comes back on and they take the car to a shop, the tech now has very limited data to work from, which then ends up costing the owner more money (and aggravation) then it should. When the check engine (or other MIL's) light up, your car is trying to tell you what is actually going on, and may have stored multiple codes that took some time to trigger the light; by disconnecting the battery, you have permanently thrown all that data away............... We see this happen far too often, and it ends up costing you more money.

[Jvc300]

I had a rough idle on startup one day and didn't think much about it. A week later it ran rough again and the 'check engine' light came on later that day. I couldn't figure it out..

So, I opened the engine compartment and my hand swiped the oil cap.. Yes, the oil cap was loose.... Which causes the engine to lose vacuum (rough idle) . A month before I did an oil change and apparently didn't tighten the cap enough.

I tightened the oil cap (AND Double checked that it was as tight again... ), reset the Check engine light (Disconnect the battery)...... It never ran rough and the CEL never came on again!!!!

Check the oil cap....

Small suggestion here: Never clear check engine lights before reading and noting the codes. Far too often, when people pull the battery cable and clear what they think is a single code problem, they actually clear multiple codes that could have proven critical in quickly and correctly diagnosing and permanently fixing the problem(s). And when the light comes back on and they take the car to a shop, the tech now has very limited data to work from, which then ends up costing the owner more money (and aggravation) then it should. When the check engine (or other MIL's) light up, your car is trying to tell you what is actually going on, and may have stored multiple codes that took some time to trigger the light; by disconnecting the battery, you have permanently thrown all that data away............... We see this happen far too often, and it ends up costing you more money.

Thanks! I was under the impression that the current error was cleared.