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Bad throttle body?

 
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Old 23 Nov 2013, 02:17 pm
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Default Bad throttle body?

2005 PT Cruiser GT turbo 112,000 miles

In the past year and a half we have replaced the MAP sensor, throttle position sensor, idle air controller, PCV valve and hose, spark plugs (gapped to 0.40), plug wires, crankshaft position sensor, camshaft position sensor, camshaft target magnet, upstream O2 sensor, timing belt, water pump, top and bottom front engine mounts, oil sending unit, power steeling pressure sensor, and intake and throttle body gaskets. Some of these repairs were just normal maintenance but we included it so you would know everything that has been done.

We think the car has a vacuum leak. We can hear a whistling sound when you bump the throttle. When we blow smoke into the intake manifold it comes out where the throttle cables attach, under the spring, which seems like a strange place for a leak... or is this a leak? normal? We own a live data scanner and when you bump the throttle, there is a spike in the manifold pressure and STFT comes up to about 16% and slowly comes back down. At 3,000 RPM STFT stays within 5%. LTFT stays at 11% through most RPM ranges. What started all of this was a rough idle and terrible gas mileage, 15mpg with conservative driving. The rough idle is worse in reverse and drive but seems ok in park and neutral. The cooling fan works properly.

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Old 23 Nov 2013, 02:44 pm
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Default Re: Bad throttle body?

that is a fairly common place for a vacuum leak. i had an Accufab that was leaking at the shaft. usually it isn't enough to effect anything though.

assuming you don't have a high or hunting idle from it, i'd consider that normal.
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Old 23 Nov 2013, 02:51 pm
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Default Re: Bad throttle body?

The idle seems normal until you put the car into reverse or drive and then it vibrates a lot. Is it possible it's a transmission problem? We bought a new transmission filter and fluid but haven't installed it or changed the fluid because as far as we know it's never been done.
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Old 23 Nov 2013, 09:12 pm
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Default Re: Bad throttle body?

Check the intake manifold gasket where it connects to the head.
I checked everything under the sun, even changed a injector but still had a miss fire and running rough until I took the intake off at the head and found it needed replaced. A whole piece of the gasket was gone but you couldn't see it was missing until I took the intake manifold off.
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Last edited by VegasPTGT; 24 Nov 2013 at 11:06 am.
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Old 24 Nov 2013, 11:28 am
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Default Re: Bad throttle body?

It sounds like the bushing for the throttle plate shaft is worn out of spec. If you can get your fingers on it to jiggle it and notice any play at all that's not good. Make a roll of paper or cardboard (like a paper towel core) and hold it to your ear with the open end at that area of the throttlebody to see if you can pin point the whistle noise. A length of 3/4" or larger hose works well, too. You can also try spraying a small dose of WD-40 or similar on the throttle shaft where it goes into the throttlebody. See if that knocks down the whistle noise at all. A while back a lot of us owners were on a kick to install slightly bored out throttlebodies and the going rate we would pay for an unmolested one was about $50. I hate to have you throw more parts at your problem, but it may take doing that this time around.

The smoke test is a good one but sometimes there isn't enough pressure to find those intermittent leaks that only happen at high vacuum and/or high boost. If the whistle noise isn't at the TB, use that long tube trick to probe around other places for it.
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Old 24 Nov 2013, 01:25 pm
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Default Re: Bad throttle body?

Get ready to fork out some more moola, you didn't mention timing belt, water pump etc
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Old 24 Nov 2013, 03:34 pm
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Default Re: Bad throttle body?

Quote:
Originally Posted by Busa_Powered View Post
Get ready to fork out some more moola, you didn't mention timing belt, water pump etc
lol, did you read the entire post? Timing belt and water pump were both listed as done within the past year, ie...3 weeks ago.


Intake manifold gasket was replaced a few weeks ago as well. We did spray carb cleaner around any and every suspended leak but didn't get any noticeable response. I didn't think about using a paper towel roll to help pinpoint the sound, definitely gonna be giving that a try. Thanks 2step.
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