Exhaust popping/spitting update (EDITED)

Some time ago I posted about the excessive (I felt) popping/splatting/spitting coming from the exhaust during one-two upshifts. A reminder: it didn't strike me as being the more pleasant burbling/crackle one hears in various demo videos. Also, it developed after maybe 10,000 miles or so. Starting in January, the car has had a few uncharacteristic stumbles and uneven fast-to-normal idle episodes EDIT: when cold, except one time a longer crank to start when warm.. Next week the car goes in for a final, pre-warranty expiration servicing and've asked the dealer to see if they can find something amiss. There hasn't been a CE light. Anyway, a couple weeks ago I figured I'd try some form of "dry gas" just in case the car got some bum fuel lately. I put in Heet, (yellow bottle) when the tank was maybe ⅓ full and ran it down. Those odd idle episodes were few and far between, so although there hasn't been a recurrence, perhaps it helped. I added another bottle with the next fill-up. What I have noticed is the popping/spitting business barely happens now. There's a product called Iso-Heet that also claims to clean injectors, etc., but as my dealer always adds some sort of stuff with each oil change, I figure it's best to leave it at that. After the servicing (next week) I'll add another yellow bottle with the next fill-up. Oh, I don't think it could be a change in summer/winter fuel formulations, as this has been going on irrespective of seasons.

By the way, Gold Eagle, the company that makes Heet, also makes STA-BIL, and I find that stuff works really well: my snow blower, a Honda 4-stroke, only has a pull start, yet at each first use kicks over after 3 pulls at most. At the end of the season I just add STA-BIL, run the machine for 10 minutes so the treated gas gets into the carb system, and top off the tank.



Edited 1 time(s). Last edit at 04/22/2016 03:53PM by Laz. (view changes)

HEET is just a fuel system anti-freeze/water remover. I seriously doubt water in the gas is a problem. Ethanol -- assuming you are not running ethanol free gasoline -- absorbs any water and ethanol along with the gasoline is burned in the engine. The small amount of water -- if any -- the ethanol picks up is not a problem.

What the car/engine probably needs is a treatment with Techron. What I found after I switched from Shell to Chevron was after a few tank fulls of Chevron gasoline my Boxster engine perked up some. And my usage of the Boxster didn't change, I drove it lots of highway miles almost every day in my 30 mile work commute with Shell gasoline and I continued this pattern of usage after I switched to Chevron gasoline.

The Boxster engine perked up like it used to after a longish -- ~50 mile -- highway high speed run. Primarily the Techron cleans deposits from the injector nozzle -- which consists of very tiny holes -- which improves the fuel spray pattern and this then results in better combustion. It also helps remove deposits from the back of intake valves which improves cylinder filling and fuel/air mixing and this also results in better combustion.

If you go with a bottle of Techron the recommendation is if you notice a benefit from the one bottle to do a second. It is also recommended that you schedule the Techron treatment prior to an oil/filter service so after tank with the Techron added is down enough to "fill up the tank" you can get the car in shortly thereafter for an oil/filter service.

I've been aware of the notion to have a treatment beforehand, but haven't been too concerned. Along with my other dealer service items, (they got an email with images,) I'll request not having the additive put it, unless they tell me what it is and give a reasonable explanation as to putting it in at the oil change. I figure it's convenient for them, and chargeable, rather than hoping for customers to come in just for that.

Speaking of Shell, for a couple years I've been splitting fill-ups at a local Shell vs. Mobil. What I like at the Mobil station, even with a recent change in ownership, is all I have to do is wave and smile, and the attendant activates the pump. I pay them after the fill. It's nice to be trusted like that. (They like seeing the car, too.) I started using Shell because of an associated Stop & Shop card where one gets 10¢ a gallon of Shell off per "100 points" accumulated at S&S. There was a problem about a year ago with the points not showing up. A manager at the supermarket gave me a Shell service number and it was corrected. However, recently there was another problem, and whomever I spoke with at Shell said the local station told them "everyone" gets the points discount due. I told the Shell rep, "So what you're telling me is that I'm nobody, and that I should never buy Shell gas ever again. The local Mobil is perfectly fine with me, and I won't be losing any sleep over this. Goodbye." End of conversation. I've got nothing against S&S, but there's another supermarket that's actually more convenient, so I've been grocery shopping mostly there again.

Quote
Laz

By the way, Gold Eagle, the company that makes Heet, also makes STA-BIL, and I find that stuff works really well: my snow blower, a Honda 4-stroke, only has a pull start, yet at each first use kicks over after 3 pulls at most. At the end of the season I just add STA-BIL, run the machine for 10 minutes so the treated gas gets into the carb system, and top off the tank.

I haven't experienced any excessive spitting, just the nice burble and pop. I've used STA-BIL before hibernating the Boxster. In Spring, it fires right up with the first turn of the key as if I'd just parked it the night before. It sure has a strange smell untill you burn up the first tankful, though.

Then again, maybe it'll stop the excessive exhaust noise!



Edited 1 time(s). Last edit at 04/23/2016 10:39AM by Laz. (view changes)

Did you try checking with a code reader? Transient or intermittent problems sometimes cause pending codes that go away before the CEL is activated.

The codes are really helpful for narrowing down the problem. I would check the ignition system since there are common issues there, specifically:

- Are the ignition coil plugs all snapped in tight?
- Are there any cracks the ignition coils?
- Do the spark plugs look good ("no" could be a symptom of a burn problem, not necessarily a cause)?
- How old are the plugs?

I've been aware that no CEL doesn't mean there's no code, and will have the dealer check. The car is going in tomorrow for "end of warranty" servicing (they already have my checklist) and to have the nose and front hood protective films changed.
Coils: I would think the coils would've been inspected and reinstalled properly by the dealer when the plugs were changed as part of the 40k service.
Maybe I just don't like the sound as heard from inside the car, and perhaps I could have somebody else drive it while I followed to see if it sounds like those online videos.

They should cover it after it expires. The coil cracks can be elusive and there is certainly no guarantee a tech would catch it, especially in a 40k service (because it's early for such a problem, unless someone previously took out the coil and didn't torque it properly when putting it back).