Re: a comment....

Hi all,

I was quite worried this am when my Boxster (56k miles) bucked a bit on startup. Motor started normally and then
seemed to hickup/buck for probably 10 seconds. Seemed to clear up when I rev'ed the motor.

Since this has never happened before, I'm wondering if anyone has an idea what this might be?

I've got the AOS slated for replacement in the next two-three weeks - could that be the problem?

She has new plugs and plug tubes as of a couple of months ago. Battery is an Optoma in new condition.

thanks in advance,
Stefan in Seattle

Did you buy gas recently? Maybe either some bad gas or some water in the gas. Older underground tanks can rust and leak - water gets in and you pump it into your tank.

Mine does this when it is very cold. I was told they all do it.

is needing replacement I'd suggest you avoid driving the car.

If the symptom reappears *after* the AOS is replaced then there are other possible causes.

For instance, if the gas in the tank is 'old' (stale) and still holds say 'summer' blend gasoline a cold snap and a cold start can produce the symptoms you report.

Another possibility is the MAF (its intake air temp component) is mis-reporting intake air temp (reporting it warmer than it really is) so the DME does not provide a rich enough mixture at cold start.

Or the coolant temp is doing the same thing.

Or a fuel injector is leaking.

There was I take it no check engine light which (might) eliminate the coils. (The two times I've experienced something similar to what you report was due to misfires but the CEL came on immediately and may have even flashed in one instance. I pulled the error codes and general and specific misfire codes were present.)

Sincerely,

MarcW.

In general the AOS drips occasionally, then builds. Unless its so sever that its fowling, i cannot see any connection.

I'd suspect fuel delivery - moisture; fuel pump, anti-backflow check valve,

...

or something that is related to the first few minutes of cold operation - which is both rich, with cold lamda sensors, and with a feedback loop that has yet to stabilize. (yes, i dont have a suggestion yet, maybe other can follow this line of reasoning...)

Grant

Grant

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

represents an intake air leak that affects fueling. Even if the engine is being fueled correctly, all other things are working just fine, a leaking AOS can affect this fueling and cause the symptoms the OP reported.

Since the AOS is scheduled for replacement (which I guess means the AOS has been diagnosed as bad and needing replacement) I'd get this done pronto then see if the symptom reappears.

Sincerely,

MarcW.

or, absent the loop, what base setting might be off ( too lean, too rich)?

Grant

Grant

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

That is, unless it is really far off. My guess would be either ignition or fuel delivery. Given the admission of recent work on the plugs I would guess that one of the ignition coil plugs is not properly seated. My second guess is that the coil bolts were overtightened and one of them is cracked, though the first option is more likely.

In general the AOS drips occasionally, then builds. Unless its so severe that its fowling, i cannot see any connection.

I'd suspect fuel delivery - moisture; fuel pump, anti-backflow check valve,

...

or something that is related to the first few minutes of cold operation - which is both rich, with cold lamda sensors, and with a feedback loop that has yet to stabilize. (yes, i dont have a suggestion yet, maybe other can follow this line of reasoning...)

Grant

Grant

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

If you have not done the following in it's 56k history, you might consider the following:
-change out the AOS(new style)
-replace upper and lower injector o-rings
-clean out throttle body
-replace fuel filter
If you want a hand, and your around Bellingham sometime, drop me an email. They are not too bad to do, except the one side of the injector o-rings which is slightly tight. This really helps to improve metering, leakage , and detonation quality. The drive line mounts help to reduce vibrations, but that is another level of smoothing things out. I found afterwards, the engine runs so smoothly, you can barely notice the "cold running mode" which is nice.
regards

Por911 - thanks very much. I may take you up on that. Over Christmas, the fuel filter was in the list as well as the throttle body.

Hadn't thought about the injector o-rings at all. Are they easy to get at?

I have access to a hoist (for things like my forthcoming clutch replacement).


NB: have driven the car a couple of more times today and had no issues.

cheers,
S.

One side of the fuel rails is a pain to DIY, but do-able(you might do those on a separate day). It takes a bit, due to the fact you need to pull the rear access panel as well as the top engine panel(ie service position). There is a bit of plumbing that needs to be pulled out of the way for access. It is amazing though, the difference $70 worth of seals/clips makes. If you do a clutch, I've got the factory clutch alignment tool as well as an engine support bar(OTC stinger, and factory rms tool, ouch!).
Having done all that work, one other aspect that we've found on the car(which one could expect), the mpg has been fantastic(city21/22 and hwy 32) and very reliable.
regards

I had this before, ESP in cold winter morning, then my cel went on, replaced Maf sensor; its all good now now

I had this before, ESP in cold winter morning, then my cel went on, replaced Maf sensor; its all good now now