Question for anyone with the definitive answer: if Chevron isn't available...

2000 Boxster S.

When I do a mild or heavy acceleration in 2nd or 3rd, I get a light pause before the motor winds out. Have not had that previously. I do not have a check engine light. Idle fine, performance fine except for that.

Any thoughts on what I should check on? 3- 1/2 years, ~9K on the air filter.

I am thinking that the throttle body needs a cleaning.

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Tony in Whittier
2000 Boxster S.

When I do a mild or heavy acceleration in 2nd or 3rd, I get a light pause before the motor winds out. Have not had that previously. I do not have a check engine light. Idle fine, performance fine except for that.

Any thoughts on what I should check on? 3- 1/2 years, ~9K on the air filter.

I am thinking that the throttle body needs a cleaning.

With a healthy AOS and a properly installed and functioning stock air filter and air intake the throttle body doesn't need cleaning. I have driven over 200K miles since the 1st and last time I cleaned the throttle body and it was dirty/oily but this was due to a failing AOS.

Couple of things...

How are the plugs?

How many miles on the car/engine? Do you drive year 'round in all kinds of weather? The answers to these could point a finger at the coils, maybe even the O2 sensors.

So far I have not to replace the coils in my Boxster -- this with nearly 300K miles on the originals -- but they do misfire once in a great while. Next service -- at 300K miles -- they will be replaced. Might add so too will the coils in my 996 Turbo. The engine misfires a bit upon cold start every 2 or 3 weeks but at no other times. This car is due to go in for its 140K mile service and this service will include new coils.

I've replaced the O2 sensors in the Boxster but except eliminating the CEL and error I have not noticed any change in how the engine runs. Now I have not replaced all 4 at once, like I recently did with my 996 Turbo (at 132K miles). After replacing all 4 the 996 Turbo engine was running a bit better. Not much but it was noticable.

How do you drive the car? Does it get some extended use on the highway? My experience is even if it does the engine could use some fuel system/engine deposit removal treatment.

You can switch to Chevron with Techron. A few tanks of this had my 2002 Boxster engine noticably peppier. Honestly the transformation was noticable and welcome.

Or you can accelerate this by using a bottle of Techron as per instructions on the bottle. The general rule is if this first bottle helps to do this again with a 2nd bottle. After the last bit of fuel with Techron added is nearly gone I like to do an oil/filter service.

What else?

You can try an E-Gas calibration. With the key off and your foot off the gas pedal turn the key to the on position. Leave on for 60 seconds. Turn the key off for 10 seconds. The next time the engine is started the calibration is complete.

Tell us more about the circumstances - how often do you drive it? How warmed up was it? Ambient? What RPM? What load, WOT?

Blah, blah, blah - it might all be important.

G

Grant

gee-lenahan-at-gee-mail-dot-com

I have multiple cars, so I drive it about every 2 weeks for about a week or two. During that week or two, I drive it every few days. Most of my driving is city driving and when I can I drive on the freeway, at higher speeds I do. The city driving I do always gets the engine to operating temperature. I do not push the engine until it is warmed up.

The hesitation occurs when I accelerate from about 1500 rpm to 2000 rpm on the way up to 4000 or 4500 rpm. It only happens for a split second. I would bet that it occurs at 50 % to 70% of WOT. I drive assertively, but do not drive it hard that much anymore.

The plugs have about 30K on them. Original coils.

I tried Marc's e gas reset. It appears to have worked. For the past week or so, when the engine returned to idle when stopping for a light, the idle would stay at ~1200 before settling down to 800 or 900 after ~15 to 30 seconds. That appears to be gone since the reset.

I will check it out further this week. Don't know if it makes any difference, but I just changed the serpentine belt about 500 miles ago.

Thanks guys.

If its above and beyond that, its mysterious. Certainly mixture issues (O2 sensor, Marc) can be a culprit.
It also sounds like the car does not get enough frisky exercise. Deposits certainly can form. I wouldnt know, mine
typically have the opposite problem. :-)

Coils are normally a problem at hgih rpm. You're not there.

Coils are also often worse on occasionally sued cars and those that never truly warm up. If there are any micro cracks that allow moisture in, they misbehave until the moisture is boiled off by heat. for me this has meant as much as 20 minutes on the track - 6k and WOT pretty much all the time. So road driving might NEVER do the trick.

Thnks for the info. Incidentally, the first sentence has me perplexed, but i dont think its material to the discussion anyway.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com



Edited 1 time(s). Last edit at 01/18/2016 12:28PM by grant. (view changes)

1500 RPM seems pretty low engine speeds even with a cold engine. As Grant said, deposits will form. There's were an "Italian tuneup" comes in. Once the engine is warmed up, run it up into the 6000 - 7000 RPM range in second and third. That's also when the "whole orchestra" starts roaring into full song. Even if you hit the rev limiter when accelerating, it won't hurt the engine. Pedro has even said that when he does a PPI, he worries if the engine has never hit the rev limiter, suggesting the engine might have been lugged too much.

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Tony in Whittier
I have multiple cars, so I drive it about every 2 weeks for about a week or two. During that week or two, I drive it every few days. Most of my driving is city driving and when I can I drive on the freeway, at higher speeds I do. The city driving I do always gets the engine to operating temperature. I do not push the engine until it is warmed up.

The hesitation occurs when I accelerate from about 1500 rpm to 2000 rpm on the way up to 4000 or 4500 rpm. It only happens for a split second. I would bet that it occurs at 50 % to 70% of WOT. I drive assertively, but do not drive it hard that much anymore.

The plugs have about 30K on them. Original coils.

I tried Marc's e gas reset. It appears to have worked. For the past week or so, when the engine returned to idle when stopping for a light, the idle would stay at ~1200 before settling down to 800 or 900 after ~15 to 30 seconds. That appears to be gone since the reset.

I will check it out further this week. Don't know if it makes any difference, but I just changed the serpentine belt about 500 miles ago.

Thanks guys.

from a Techron treatment or two.

My experience is just a bit of highway driving is not sufficient to do whatever a longer (~40+ miles) drive at a nearly constant highway speed does. Even though my work commute is 30 miles mostly highway miles in the past I have found a longer drive of in one case (over and over again) a drive of 40 or 53 miles had my Boxster engine running noticably better.

However, I managed to get the same improvement to the engine -- and honestly a bit more -- when I switched from Shell to Chevron gasoline. After a few tankfulls of Chevron gasoline (I get around 300 miles of driving per tank) the engine perked up considerably.

Low end response was better and once underway the engine pulled a bit better at higher RPMs. The change was rather remarkable and frankly I would have not thought it possible had I not experienced it. I have gone back to Shell for a tank or two and have felt no drop off in the engine's performance but I see no reason to make Shell the standard fuel for my Boxster after having experienced the benefit of I guess the Techron in Chevron gasoline. That Chevron gasoline is still often a bit less expensive than the Shell gasoline at the station I have to pass to get to the Chevron station just makes staying with Chevron a win win decision.

how much Techron ought to be added to how much non-Chevron gasoline to mimic Chevron's?

Minus 40 degrees... Is that Fahrenheit or Celsius?

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Laz
how much Techron ought to be added to how much non-Chevron gasoline to mimic Chevron's?

If gasoline with Techron is not available -- doesn't Texaco gasoline also have Techron? -- I wouldn't try to duplicate the blend of Chevon. Who knows what the percentage of Techron to fuel is?

My recommendation would be to use a bottle of Techron mixed according to directions on the bottle every so often. How often you ask? Well, that's a good question and I have a good answer. I don't know.

Taking a stab at some kind of answer my opinion would be once a year.

If you drive a lot the engine derives some benefit from this so maybe once a year - just before an oil/filter change -- could be just the thing.

If you drive so little as to need the oil changed based on time -- annually -- instead of miles, again once a year could be sufficient. And again just before the oil change.

Try a bottle. If there is an improvement run another bottle through the engine. If there no improvement in the engine's performance after one bottle then maybe a year's plenty of time between treatments. Or maybe no treatment is called for.

While my Boxster engine perked up after switching to Chevon gasoline the 996 Turbo engine did not. Perhaps the Turbo engine is just a cleaner running engine, or because it is boosted it is more efficient at burning away engine deposits that do accumulate, or because the Boxster engine has so many miles it develops deposits as a result of this while the relatively low miles Turbo engine does not.

I would not go overboard with this Techron even if the engine showed an improvement. My info is the stuff out of the bottle is pretty strong even though it gets diluted in IIRC 10 gallons of fuel.

Maybe half an ounce per tankful would be ok. Or perhaps it could be calculated more precisely based on how many tank refills are done between oil changes, a common(?) benchmark for adding a bottle.

It is good stuff. Also BG makes a very effective cleaner.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

but I'm inclined to think adding a teensy bit (<.5 oz) from the bottle with each tank fill of say, 10 gallons or so, ought to be ok, too, and not too much of a bother.
I'm aware it's been said to add a bottle one fill before an oil change, to get rid of what might get into the oil. Then again, my dealer adds some sort of fuel treatment at each oil change, so whatever it is, it's perhaps getting into the new oil. Then again, so can unburned and combustion products all the time.

Minus 40 degrees... Is that Fahrenheit or Celsius?

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Laz
but I'm inclined to think adding a teensy bit (<.5 oz) from the bottle with each tank fill of say, 10 gallons or so, ought to be ok, too, and not too much of a bother.
I'm aware it's been said to add a bottle one fill before an oil change, to get rid of what might get into the oil. Then again, my dealer adds some sort of fuel treatment at each oil change, so whatever it is, it's perhaps getting into the new oil. Then again, so can unburned and combustion products all the time.

Fuel treatments -- I guess the good ones at any rate -- have a vapor and liquid deposition phase. There are or can be components of this additive that do not burn -- so they can then transistion from a liquid to a vapor then back from a vapor to a liquid and in doing so deliver their detergent benefits -- and as a result this can result in the oil getting a larger amount of combustion "by-products" than it would normally. This is the reason behind doiing an oil change after using something like Techron.

BTW, I've asked my dealer techs to stop adding a fuel treatment to the fuel tank at service time. Now that I'm using Chevron I feel the fuel system is getting all the treatment it needs.

Because you don't know if Techron is going to help your engine as I stated previosly my recommendation would be to use a bottle as per directions. If it helps use another bottle. Then afterwards if you want to add a small amount at every fill up that's up to you.

If running a bottle through the tank doesn't help perhaps your car's engine runs cleaner naturally and adding even a small amount every fill up is just a waste of time and fuel additive. As I mentioned in an earlier post while the Boxster engine clearly benefitted from the Chevron gasoline (and I assume the Techron contained in it) the Turbo engine didn't show any benefit. Both cars get driven the same way so my thinking is the Turbo engine just runs cleaner naturally.

Minus 40 degrees... Is that Fahrenheit or Celsius?

At ~2000 to 3000 rpm. Yesterday, I treated the engine more aggressively (Left in 2nd at 4000 instead of upshifting while cruising, shifted at higher rpms, etc.).

Idle still stays at 1050 to 1100 for about 3 to 5 sec. before dropping to 600 or 700 when I lift to stop for a stop light.

Filled it up at Chevron too. Will test more.

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Tony in Whittier
At ~2000 to 3000 rpm. Yesterday, I treated the engine more aggressively (Left in 2nd at 4000 instead of upshifting while cruising, shifted at higher rpms, etc.).

Idle still stays at 1050 to 1100 for about 3 to 5 sec. before dropping to 600 or 700 when I lift to stop for a stop light.

Filled it up at Chevron too. Will test more.

Wtih the extra info you provided the elevated idle could be an intake air leak.

A high idle could be a vacuum leak.

You are sure the AOS is not acting up?

Check the oil filler tube cap is not leaking. If it leaks it is has more effect at low engine speeds. At higher engine speeds the amount of unmetered air the cap lets into the intake represents just a small fraction of the engine's total air consumption as to not really matter.

I take it the CEL is off? If so I'd still advise you to use a code reader and check for any pending error codes.

The cap was tight, But when I pushed down on the plastic funnel to check it's return travel, I noticed it was not very "springy". Then when I gently pulled up on the funnel and noticed that it comes out. The spring below the funnel also is easily removable. Are you supposed to be able to lift these out? Is the spring supposed to be connected to the funnel? Mine are separate.

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

It's quite easy to clean. If you haven't done it I would do that.

Grant

gee-lenahan-at-gee-mail-dot-com

Hesitation on acceleration many times can be cause by a faulty or dirty MAF (Mass Air Flow sensor).
In order to determine if it is the MAF or not. disconnect the MAF and see if the hesitation persists.
If the hesitation goes away, most likely the problem is the MAF.
Be aware that running with the MAF disconnect will trigger the CEL.
You can reset it after the MAF is reconnected with any Code reader or by disconnecting the negative side of the battery for more than 30 secs.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna