Throttle Body leak?
Thread Starter
Pro
Joined: Aug 2002
Posts: 715
Likes: 0
From: Warner Robins GA
Throttle Body leak?
Hey guys,
I'm trying to figure out a possible vacuum leak I may be having around my throttle body area on my 88. I noticed sort of a hissing sound coming from near the TB. I removed the accordian duct that goes between the MAF and the TB and started the car to see if it changed the sound, and it didn't. So next I put my hand over the opening to the TB to prevent as much air from going in as possible and the hissing sound got noticably louder, so I believe I have some sort of vacuum leak.
Is this abnormal or is it possibly caused by my IAC? I tried feeling around for any opening points around the TB, and even sprayed starting fluid around the IAC, TB gaskets, etc and it didn't change my idle.
My original problem was that when I start the car and it's cold, it idles way low (around 500) and almost dies until I feather the gas a couple of times. Also if I rev it up, it'll fall too much and almost die. Once it's warm it's fine.
Could this vacuum leak even be the cause of my problem, or is this sucking I'm hearing normal (which I highly doubt)?
I'm going to tear it all out this weekend and reseal everything, but I'd at least like some reassurance that it's going to help something in the end. Then again, I've always heard that vacuum leaks cause a higher idle rather than a normal.
Thanks.
I'm trying to figure out a possible vacuum leak I may be having around my throttle body area on my 88. I noticed sort of a hissing sound coming from near the TB. I removed the accordian duct that goes between the MAF and the TB and started the car to see if it changed the sound, and it didn't. So next I put my hand over the opening to the TB to prevent as much air from going in as possible and the hissing sound got noticably louder, so I believe I have some sort of vacuum leak.
Is this abnormal or is it possibly caused by my IAC? I tried feeling around for any opening points around the TB, and even sprayed starting fluid around the IAC, TB gaskets, etc and it didn't change my idle.
My original problem was that when I start the car and it's cold, it idles way low (around 500) and almost dies until I feather the gas a couple of times. Also if I rev it up, it'll fall too much and almost die. Once it's warm it's fine.
Could this vacuum leak even be the cause of my problem, or is this sucking I'm hearing normal (which I highly doubt)?
I'm going to tear it all out this weekend and reseal everything, but I'd at least like some reassurance that it's going to help something in the end. Then again, I've always heard that vacuum leaks cause a higher idle rather than a normal.
Thanks.
Team Owner
Joined: Jan 2003
Posts: 20,324
Likes: 250
From: Summerland B.C. Canada
Re: Throttle Body leak? (Tourney3p0)
On my 86 there is a small vacuum line under the mouth of the throttle body. Could be the one?
It sounds like you have an iac problem. Your base idle will be set around 450 and the iac adjusts it from there. Maybe the plug into iac is off or faulty. :cheers:
[Modified by AGENT 86, 7:39 PM 5/27/2003]
It sounds like you have an iac problem. Your base idle will be set around 450 and the iac adjusts it from there. Maybe the plug into iac is off or faulty. :cheers:
[Modified by AGENT 86, 7:39 PM 5/27/2003]
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Throttle Body leak? (Tourney3p0)
The throttle blades, when "closed" are actually a controlled vacuum leak, set by the idle set screw. When you cover the TB opening with your hand, you choke off this flow, and the computer adjusts by opening up the IAC.
Have you tried calibrating the IAC and TPS? Check 65Z01's website for the how to. I did this last week and it helped out considerably. I still think I have a leak though, because idle hovers around 1200 under certain conditions.
Have you tried calibrating the IAC and TPS? Check 65Z01's website for the how to. I did this last week and it helped out considerably. I still think I have a leak though, because idle hovers around 1200 under certain conditions.
Thread Starter
Pro
Joined: Aug 2002
Posts: 715
Likes: 0
From: Warner Robins GA
Re: Throttle Body leak? (CentralCoaster)
Thanks for the tip.
I thought about the IAC but not the throttle body blades themselves. I suppose it would make sense though, since you can't have a running engine without at least SOME air.
I replaced and calibrated the IAC last weekend but I plan to do the TPS next. Replacing the IAC didn't fix my low idle on cold startup, but it fixed my "600 idle even though I calibrated it for 750 whether warm or cold".
I also noticed it only makes this sucking sound when it's cold, so that lends to the idea that maybe it's not a leak but the TB blades and IAC. In any case, I'll continue investigating.
I thought about the IAC but not the throttle body blades themselves. I suppose it would make sense though, since you can't have a running engine without at least SOME air.
I replaced and calibrated the IAC last weekend but I plan to do the TPS next. Replacing the IAC didn't fix my low idle on cold startup, but it fixed my "600 idle even though I calibrated it for 750 whether warm or cold".
I also noticed it only makes this sucking sound when it's cold, so that lends to the idea that maybe it's not a leak but the TB blades and IAC. In any case, I'll continue investigating.
