Vacuum leak, suggestions as to where to look...
03-07-2005, 05:26 PM
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Vacuum leak, suggestions as to where to look... On the way home from the Sat gathering I started showing around -10 to -8 on my boost gauge when normally it is -20 at idle which is causing my motor to run rough at idle\low rpms. It seems like it is running lean. No wierd smoke from the exhaust, no SES light. Car runs rough as the vacuum starts lessening.
Now the last time this happened was when I put my new intake on, it ran smooth but surged and idled fast, did not run rough, if this matters. It seems like a sizable leak but I do not see anything wrong, even the thingy on the back of the intake seems in tact.
I am hoping it is not my intake or maybe I am, it just is a PITA to seat properly if a gaske is blown.
Any suggestions besides my intake? How can I test and see where the leak is from?
Thank you as always for your input.
Now the last time this happened was when I put my new intake on, it ran smooth but surged and idled fast, did not run rough, if this matters. It seems like a sizable leak but I do not see anything wrong, even the thingy on the back of the intake seems in tact.
I am hoping it is not my intake or maybe I am, it just is a PITA to seat properly if a gaske is blown.
Any suggestions besides my intake? How can I test and see where the leak is from?
Thank you as always for your input.
03-07-2005, 05:41 PM
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Check your intercooler tubing and connections and check the catch can, did you do anything near the brake booster?
Easiest way to find a vac leak is carb cleaner... trust me... did it all the time on my 94 Thunderbird SC when ever I had to take the intercooler off because one of the connections would never seal right and it was a pain tracking it down. Problem with boosted cars is the slightest vac leak can cause the biggest headache.
Even had some in the car and when I tried picking it up from the shop and it wouldn't idle once I got it started I checked the intercooler tubes and there was a huge leak in the bottom connection... I just left it there, took my loaner back and left them a voicemail telling them I wasn't picking it up and to fix it. (was warranty work on the motor)
Easiest way to find a vac leak is carb cleaner... trust me... did it all the time on my 94 Thunderbird SC when ever I had to take the intercooler off because one of the connections would never seal right and it was a pain tracking it down. Problem with boosted cars is the slightest vac leak can cause the biggest headache.
Even had some in the car and when I tried picking it up from the shop and it wouldn't idle once I got it started I checked the intercooler tubes and there was a huge leak in the bottom connection... I just left it there, took my loaner back and left them a voicemail telling them I wasn't picking it up and to fix it. (was warranty work on the motor)
03-07-2005, 05:52 PM
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Originally Posted by rookiels1
Check your intercooler tubing and connections and check the catch can, did you do anything near the brake booster?
Easiest way to find a vac leak is carb cleaner... trust me... did it all the time on my 94 Thunderbird SC when ever I had to take the intercooler off because one of the connections would never seal right and it was a pain tracking it down. Problem with boosted cars is the slightest vac leak can cause the biggest headache.
Even had some in the car and when I tried picking it up from the shop and it wouldn't idle once I got it started I checked the intercooler tubes and there was a huge leak in the bottom connection... I just left it there, took my loaner back and left them a voicemail telling them I wasn't picking it up and to fix it. (was warranty work on the motor)
Easiest way to find a vac leak is carb cleaner... trust me... did it all the time on my 94 Thunderbird SC when ever I had to take the intercooler off because one of the connections would never seal right and it was a pain tracking it down. Problem with boosted cars is the slightest vac leak can cause the biggest headache.
Even had some in the car and when I tried picking it up from the shop and it wouldn't idle once I got it started I checked the intercooler tubes and there was a huge leak in the bottom connection... I just left it there, took my loaner back and left them a voicemail telling them I wasn't picking it up and to fix it. (was warranty work on the motor)
Good suggestion.
03-07-2005, 06:32 PM
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Your intercooler piping cannot be the source, as you have a blow through setup, so the leak is after the throttle body. Rookie's suggestion of carb cleaner will work, but might get a bit messy for you. (Spray small shots around areas where you suspect a leak and see if the idle changes, find the change, find the leak) You may be able to hear the leak, and track it down by listening at the end of a piece of garden hose as you move the other end around the area that you suspect the leak. I would check around the brake booster, and its related plumbing, as possible sources, also look to where your boost gauge picks up its signal. along with the usual suspects of IM gasket, TB gasket, etc.
Hope this helps.
Hope this helps.
03-07-2005, 07:14 PM
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Originally Posted by burbman
Your intercooler piping cannot be the source, as you have a blow through setup, so the leak is after the throttle body. Rookie's suggestion of carb cleaner will work, but might get a bit messy for you. (Spray small shots around areas where you suspect a leak and see if the idle changes, find the change, find the leak) You may be able to hear the leak, and track it down by listening at the end of a piece of garden hose as you move the other end around the area that you suspect the leak. I would check around the brake booster, and its related plumbing, as possible sources, also look to where your boost gauge picks up its signal. along with the usual suspects of IM gasket, TB gasket, etc.
Hope this helps.
Hope this helps.
Can any of those check valves be broke\worn out, should I replace all of them?
Thank you for your suggestions.
It this does not work I am going to perfectly polish everything and take it all apart.
03-07-2005, 09:25 PM
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The EGR block-off plate is a prime suspect. Carb cleaner or starting fluid should find it. Either will change how it runs. Starter fluid isn't as nasty on parts. Spray it around the EGR & intake to head surface. Also try wiggling the MAP (the thingy on the back of the intake) while the engine is running.
Want me to come over?
Want me to come over?
03-07-2005, 10:23 PM
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Originally Posted by Todd2001SS
It has to be unmetered air getting in. If the plumbing is loose there is lost boost. I am looking for a vacuum leak possibly from the MAF into the motor. It could be the MAP sensor, just can not see the darn thing. I can dis connect the supercharger and it idles fine-when running correctly.
Good suggestion.
Good suggestion.
