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Discussion Starter · #1 ·
hey guys I changed out the IAC with a new one on my 3.0L Vulcan. Turns out the old one was a BWD model one that the PO's mechanic put in for them. Anyways, the new IAC helped but didnt solve the problem completely. When I shift into park it is still a little louder then i think it shoudl be with a new iac. I got out and watched the engine idle and it seems to slightly vibrate. like i can see the spark wires moving around alittle. Does this mean I have a vacum leak? I noticed the tube going to the oil filler, the rubber elbow, is loose like i can pull it off with out using pliers to remove the pretension clamp first. Is that normal or do you guys think I have a vacum leak some where else?

Thank you in advance, the stupid idle issue is almost fixed!
 

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Could be a vacuum leak. Checking fuel trims will help isolate the problem.

No engine, especially at idle runs "smooth as glass". They all shake / move around a little. Bad motor mounts, worn "dog bone" bushings can allow the engine to move around more.
 

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Discussion Starter · #3 ·
Could be a vacuum leak. Checking fuel trims will help isolate the problem.

No engine, especially at idle runs "smooth as glass". They all shake / move around a little. Bad motor mounts, worn "dog bone" bushings can allow the engine to move around more.
Thank ya i will check around for vacumm leaks. I put a new pcv valve in this summer and the gasket around the valve seemed to be loose. Like it seemed really easy for me to slip the new valve in. I didnt have to put oil on it or shimmy it in there. Could that be a source of my leak?

I will also inspect the other parts of the vacum system and let you know what I will find.

It seems if the biggest issue i have with it is that its a solid nice idle in drive mostly but once i shift it into park it seems the rpms pick up some ( not as much as before the new iac). I had my trans rebuilt this summer and he said the mounts looked ok still. Plus if the shop rebuilt my trans im hoping they would make sure its not a wiring issue from the vss etc. Even if its just a vacum leak, can this issue be hurting my newly rebuilt transmission?
 

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Your tranny will be fine. Only way a vac leak could possibly hurt the tranny is if the leak makes the idle speed so high, like 1800 RPM, that putting it in gear would "shock" the tranny.
 

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When you shif into PARK or NEUTRAL it WILL idle at a slightly higher speed than when in DRIVE or REVERSE, at least until the PCM senses this and takes measures to reduce the idle speed.
 

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Discussion Starter · #6 ·
When you shif into PARK or NEUTRAL it WILL idle at a slightly higher speed than when in DRIVE or REVERSE, at least until the PCM senses this and takes measures to reduce the idle speed.

Cool ok that makes sense. But what is weird is that alot of times when i drive and then shift it into park it will slightly raise idle like it should but then it stays there. Should it go back down if i leave it idle for 30 seconds or so? Is it bad that it stays at the higher idle?
 

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Discussion Starter · #7 ·
Cool ok that makes sense. But what is weird is that alot of times when i drive and then shift it into park it will slightly raise idle like it should but then it stays there. Should it go back down if i leave it idle for 30 seconds or so? Is it bad that it stays at the higher idle?
Hmm Do you guys think my throttle position sensor could be acting up? I heard it can cause issues kind of like i have been having at idle. Does the throttle position sensor ever wear out?
 

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Discussion Starter · #8 ·
Could be a vacuum leak. Checking fuel trims will help isolate the problem.

No engine, especially at idle runs "smooth as glass". They all shake / move around a little. Bad motor mounts, worn "dog bone" bushings can allow the engine to move around more.

Thank you. I checked and found out the pcv tube that runs by the thermostat and distributor had alot of visible cracks in it. I wrapped it in tape temporarily till i buy the replacement tubing. even with just the tape on the cracked tubing the engine seemed to idle better in park. Where can i find an exact replacement pcv for this?
 
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