Strange behavior but no code, should I worry?

[wawa]

I just receive my short shifter so I did a trip with my 2000 Boxster S to buy some lithium grease to install it. Well during the trip, the Boxster hesitate a couple of time when accelarating (not hard). I stop at the shop, bought the grease then drove back using the highway. While accelerating harder to enter the highway the Boxster nearly died but as soon as I let go the gas, it was good again. I was able to accelerate normally. I try again a little harder acceleration and it was ok. When exiting highway, put the clutch down and engine simply died. I stop on the side and restart it, no problem, idle fine and was again able to drive normally to home. This morning I took the Boxster for another trip to the shop to by a code scanner, some MAF cleaner and Throttle body cleaner. Everything look fine, idle and standard acceleration. Did not try hard acceleration. Not CEL no nothing. I have check for code, nothing pending. Everything looks fine. Should I be worrying? As you guess I will clean the MAF and the Throttle body in prevention. Never done it since I own the car about 1 1/2 year ago. Air filter is new, that its. Thanks Chris

[thstone]

Cleaning the MAF and TB is a good starting point. Then see what happens. If the problem persists, eventually you should get a code and can use that as a starting point to find the root cause.

[Spinnaker]

Might be a fuel delivery issue. When was the fuel filter last changed?

[jb92563]

Originally Posted by Spinnaker

Might be a fuel delivery issue. When was the fuel filter last changed?

Maybe water in the fuel or like the others suggested the fuel filter or maybe the fuel pump is cutting out.

I don't know that any of those things would throw any codes.

[Jager]

Fuel Pump... It will start failing like this and not trigger alarms.

[Bala]

MAF is what you should look at first. I had the same issue. If you drive like grandma it would be ok the moment you stepped on it it would joke like someone was strangling its throat. Let go of the gas and all is well. In my case I have had a poor maf for a while. Cleaning could only do so much. Bought the maf from JD suggested vendor on eBay. All is well now. Yours may just need a good cleaning though.

[trimer]

maybe the car knows you are going to put the short shifter on and it got mad...

[Homeboy981]

Could be "winter-blend" fuel but most likely is the intake needs cleaning…1 ½ years? I am cleaning it every other month! One of us is over the top. Having said that, I never had an acceleration problem and I HAVE to go DOWN DIRT ROADS. If you go too slow on dirt…the car kind of looks like "Pig Pen" or a helicopter landing - with all the dust kicking up!

When you changed to air filter last did you clean, wipe, touch, or "blow air" on the MAF? Stupid thing is darn sensitive! Can be a quick couple hundred dollar mistake to mess with it if you ARE NOT CAREFUL!

When you do get around to cleaning the throttle body, a good compliment to that "repair" is to run race gas (105+ octane) if you can find it! NOT AV GAS!!! Race gas! We have a station nearby that carries it. There are a number of MX and Race tracks in the North Texas area so they carry it….for $7 a gallon.

Don't fill the tank with it but DO up the octane rating of your Premo gas - especially if you are in some areas of the world where Premium gas is only 90 octane or less! I also add fuel injector cleaner in the tank prior to running the Race Gas. NOT in the same tank!

CAUTION: You will become ADDICTED to RACE GAS if/when you run it! The gas will launch your car like a rocket! So be warned….

[ProjectM96]

My car did that when the O2 sensor was bad. Shortly after that hesitation feeling, the Check engine light turned on telling me to replace the O2 sensor. After I replaced them, I never experienced that hesitation again.

[shadrach74]

Originally Posted by Homeboy981

Could be "winter-blend" fuel but most likely is the intake needs cleaning…1 ½ years? I am cleaning it every other month! One of us is over the top. Having said that, I never had an acceleration problem and I HAVE to go DOWN DIRT ROADS. If you go too slow on dirt…the car kind of looks like "Pig Pen" or a helicopter landing - with all the dust kicking up!

When you changed to air filter last did you clean, wipe, touch, or "blow air" on the MAF? Stupid thing is darn sensitive! Can be a quick couple hundred dollar mistake to mess with it if you ARE NOT CAREFUL!

When you do get around to cleaning the throttle body, a good compliment to that "repair" is to run race gas (105+ octane) if you can find it! NOT AV GAS!!! Race gas! We have a station nearby that carries it. There are a number of MX and Race tracks in the North Texas area so they carry it….for $7 a gallon.

Don't fill the tank with it but DO up the octane rating of your Premo gas - especially if you are in some areas of the world where Premium gas is only 90 octane or less! I also add fuel injector cleaner in the tank prior to running the Race Gas. NOT in the same tank!

CAUTION: You will become ADDICTED to RACE GAS if/when you run it! The gas will launch your car like a rocket! So be warned….

Homeboy,

Rant warning...

I'm not trying to be a dick, but your race gas comments make no sense at all. The difference between race gas and pump gas is octane rating, or more specifically the additive that reduces the fuels tendency to detonate (read uncontrollable ignition) under high pressure/temp situations. In an otherwise normal running normally aspirated engine the 2 factors that affect internal cylinder pressure(ICP) and temp most are the ignition timing and compression ratio. A stock Boxster is tuned from the factory to run on 93 octane pump gas. If your car has stock pistons and is operating within Porsche's ignition timing specs, race gas is a waste of time and money. In fact, high octane race gas actually has slightly less energy (BTUs) by volume than pump gas because of the addition octane increasing additives that displace the base stock.

Further more, "Race gas" does not burn cleaner than pump gas, it does nothing for your injection system or MAF (which never sees fuel anyway). Period. Any "Rocket" like launches that you feel on race gas are psychosomatic, unless of course you've remapped your car's timing program and/or have installed higher compression pistons, and even then, if you changed from pump gas to "race" gas, it would take several driving cycles for the ECU to realize that it could advance the timing to generate more power (this has to do peak ICP, crank angle and how they interact, but that's for another post).

Also, just an FYI. Anyone who runs a stock car at altitudes above say 5000ft on 93 oct pump gas is most likely wasting their money. Your manifold pressure at those altitudes is low enough to likely permit 89 and maybe even 87 oct without the ECU needing to retard the timing to prevent knocking/pinging. This means ZERO loss in performance by running lower octane...

I mean no disrespect, but I see so many people perpetuating the myth that race gas is some kind of highly potent "nitro" like substance... It's not, it is simply less volatile than pump gas thus enabling engines to be tuned to specs that would cause them to self destruct from detonation on pump gas. That is all. Anyone who tells you otherwise is full of it, pulling your leg, trying to sell you something or too uneducated on the subject to know what they don't know.

Rant off...

[wawa]

Well it happen again tonight but something new happen too. Idle start moving by itself. It goes slow from 1k to 2k than jump down to 1k. When I arrive at home entering the garage I realized that there is a belt or bearing noise coming from engine. Could it be a bad alternator?

No cel light again but I will look again for any pending code tonight

Later
Wawa

[Meir]

Originally Posted by wawa

Well it happen again tonight but something new happen too. Idle start moving by itself. It goes slow from 1k to 2k than jump down to 1k. When I arrive at home entering the garage I realized that there is a belt or bearing noise coming from engine. Could it be a bad alternator?

No cel light again but I will look again for any pending code tonight

Later
Wawa

Remove the belt and spin each element by hand.

[wawa]

Well no CEL but there is 2 pending code on my code reader.

P0507 - Idle Air Control - Idle Speed Too High (that match the idle going up to 2k than jump down at 1k)

P1126 - Oxygen Sensing Adaptation Area 1 (Cylinders 4 - 6) - Rich Threshold

What could cause that with all other symptoms?

Later
wawa

[wawa]

Well I losen the belt and all elements seam to turn freely without noise. I also start again the engin and no noise so I dont think the noise was releated to my problem. But when i started the car it did a good smoke clould kinda blue. I'm really starting to think about a fuel problem.

later
wawa

[thom4782]

My best guess now that you mentioned the 'hunting' idle is that you should clean the MAF and the throttle body. A dirty throttle body can cause the idle to vary up and down. I had these symptoms and never saw a code.

[wawa]

Throttle body was just a bit dirty and have been clean. MAF was looking like new. No dirt at all but I still spray it with MAF cleaning product, let dry and reinstall.

I had a very good Porsche specialist near and never had a problem. Now that I move 300km from him, problem start I dont know any mecanic around, no porsche stealer and shipping for parts take long or cost crazy for fast shipping.

well, now... do I shoot in the air hoping to get it right (like changing fuel filter, spark plug and other small stuff like this) or is there a better way to diagnose the problem, keeping in mind that I'm far from being talented in mecanic.

thanks
wawa

[Eric G]

Originally Posted by Jager

Fuel Pump... It will start failing like this and not trigger alarms.

Reread Jaber's statement, there is truth there you may have missed.

[Bala]

Originally Posted by wawa

Throttle body was just a bit dirty and have been clean. MAF was looking like new. No dirt at all but I still spray it with MAF cleaning product, let dry and reinstall.

I had a very good Porsche specialist near and never had a problem. Now that I move 300km from him, problem start I dont know any mecanic around, no porsche stealer and shipping for parts take long or cost crazy for fast shipping.

well, now... do I shoot in the air hoping to get it right (like changing fuel filter, spark plug and other small stuff like this) or is there a better way to diagnose the problem, keeping in mind that I'm far from being talented in mecanic.

thanks
wawa

Not sure if you ruled out the maf yet but, try disconnecting the maf and driving it short trip. If it still exists then maf is ruled out. I replaced my maf and all is well - had the same issue.

[wawa]

I will try the MAF disconnecting tonight

I had to drive it again this morning and everything look fine as long as I was driving like my grand-mother. I connect the code scanner when I arrive at home, P0507 is not there anymore (idle was good, so its normal) but P1126 was still pending, yet no CEL.

wawa