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How hard to change engine temp sensor?


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2000 2.7 boxster

75% of the time I start the car after about 4-5seconds the rpms drop really low, car starts shaking like going to die if I give a little gas to keep rpms above 1000 after about 10seconds it idles out fine, was told it is not recognizing the right temp and probably needs new sensor anybody change one of these or have any other suggestions?

thanx

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My 98 Boxster 5 speed is having similar symptoms, except I do not need to touch the throttle when the rpms drop below 1000 because my engine recovers quickly after it starts shaking after start up. It almost seems like the engine is seeing how slow it can go before dying! Also, blackboxster, my engine only does this after it has already been started up and driven recently. So, it doesn't do this when the car is cold, but if I run errands and have the car off for a few minutes and then return to drive it, it does what your car is doing. I don't know if it makes a difference, but on your car, is this problem happening when cold or warm, like mine?

Another factor could be outside temperature. I've noticed in my car, that there's a higher probability for this when the temperature is colder outside (say below 75 F as opposed to the normal 90+ in Houston). While I obviously don't know what is really wrong, I suspect it may be MAF (mass air flow) sensor related. Maybe someone can advise us on this.

James

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Idle Control Valve and/or carbon build up on the throttle butterfly?
Loren, is this carbon build up/ idle control valve part common causes of problems on the Boxster? Also, how does one go about fixing these two potential problem causers? Should I just remove the throttle body and blow compressed air on it? How about the idle control valve? Where is it located? Can I clean it or replace it? Thank you for the tip Loren.

James

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Idle Control Valve and/or carbon build up on the throttle butterfly?

Loren, is this carbon build up/ idle control valve part common causes of problems on the Boxster? Also, how does one go about fixing these two potential problem causers? Should I just remove the throttle body and blow compressed air on it? How about the idle control valve? Where is it located? Can I clean it or replace it? Thank you for the tip Loren.

James

What year is your car (so I know whether it is egas or not)?
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Loren,

Mine is a 98, non egas, 5 speed Boxster. Thanks.

James

You will want to get some carburetor cleaner and a lint free rag to clean the throttle body and butterfly (1). You will likely want to remove and clean the idle control valve (3) too. If the (insides) of the valve does not turn freely then it may need to be replaced. To remove the Idle Control Valve just disconnect the electrical connector, then remove the two (allen head - I think) screws. Be careful to not lose or damage the paper gasket (16) that fits between the valve and the throttle body.

post-2-1138600530.png

This is an egas throttle body that we cleaned at a work on cars day - your's won't look quite the same but the carbon build up on this one made the car idle erratically. I should of held the butterfly open so you could see how badly carbon'ed up the inside of the throttle body was.

1-15016.jpg

(Tool Pant's image)

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Loren, I think mine is egas 2000 2.7 5speed is the instructions that much different or since it does it only on first start of the day when cold could it be something different like the engine temp sensor? would like the instructions to clean throttle body anyway, thanx
If your car is egas then it should look just like the pic above.

On egas cars there is nothing to disassenble. Just open the butteryfly and clean it throughly with carb cleaner.

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if a dirty throttle body was the problem it should have a rough idle each time I start the car right? (Instead of just on cold starts)
Not necessarily, if there is enough carbon then it will absorb gas and make the mixture too rich on warm starts. Bottom line is that if it's dirty clean it - it can only help.
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  • 4 weeks later...

I will clean out the throttle body and IACV this weekend, but have a few questions.

1) Are tightening torques for the screws important?

2) Is it safe to spray carb cleaner inside the IACV?

3) Is it safe to push around the flap inside the IACV? I'm worried that the flap or whatever that the IACV contains is not meant to be pushed around. Also, is cleaning the IACV the only maintenance for it or should I lubricate it too? I just don't know what to expect with the IACV, thanks.

James

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Not necessarily, if there is enough carbon then it will absorb gas and make the mixture too rich on warm starts. Bottom line is that if it's dirty clean it - it can only help.

The carbon can't absorb gas, as the injectors squirt directly into the chamber directly behind the inlet valves. However, the 'if its dirty, clean it' is true, as the ring of carbon filth causes problems as follows:

When the engine is idling, the DME controls the idle speed by small movements of the main throttle butterfly. When the butterfly is completely closed, if held to the light you can see there is a small gap between the butterfly and venturi walls. This is enough to still allow some air to pass. So you start the engine and the DME tries to settle at idle. As it closes the butterfly, instead of air passing the small gap as above, the butterfly closes on to the carbon ring and suffocates the engine, causing a rapid drop in revs. The DME notices the engine is about to stall, and rapidly opens the throttle again. And so it oscillates, until the DME realises it needs to hold the throttle further open to idle (fairly) smoothly.

When the throttle body carries out the 'learning' or 'adaptation' procedure, the DME checks it can move the butterfly to predetermined positions and notes the feedback positional values. However, when it moves it to the closed position, there is no way of knowing that it is completely closed off, until the engine is (trying to) idling, as described above.

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  • 6 months later...

Regarding the idle air control valve. When you have it out for cleaning, how exactly is the flap supposed to sit? The flap can easily open and close completely with my finger, but rests with a 1/8" air gap. That seems a little odd to me for a normal resting state. Don't tell me after all this cleaning I'll still have an idle problem with the AC on and need to try again with a new IACV?

post-6418-1157789960_thumb.jpg

Thanks!

PS: here are some before-cleaning pictures of my throttle body. This is a 98 Boxster with 73k miles. I suspect the throttle had never been cleaned.

post-6418-1157790610_thumb.jpgpost-6418-1157790625_thumb.jpg

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