drwhosc

So last question for the day, and I think this one is an important one for me.

I let my car sit at idle for about 10 mins today to test the functionality of my cooling system, As usual, the idle was very rough at first, but things got much better as the engine warmed. In fact it sounded and seems to run just fine.

Then I moved the throttle pretty aggressively, and things are not right. I think this will lead me to my issues.

In short, when I hit the gas, I heard a sucking sound, and a big time hesitation. Very very poor throttle response. It only happens when I hit the throttle hard. This is now making me believe that I have a big time vacuum leak somewhere.

Here is a video. I hit the throttle heard at about 20 secs into it. the last three are the issue.....

hwyengr

Have you tried the old hose-in-the-ear trick to see where the noise is coming from?

Manifold vacuum decreases when you open the throttle, though, so it would be odd for a leak to be more apparent when you hit the throttle and open up an easy pathway to the atmosphere. With your airbox and tubes off, that just might be the sound of air rushing into the MAF.

drwhosc

yes on the air rushing in, but also has a poor throttle response. it takes about 1/2 second or so for the engine to respond...

bronto

I had a BMW that did that. I had been using cheap gas for a very long time and the combustion chambers had carboned up. I ran a Techron treatment through it and it solved the problem. The hesitation results from the amount of time it takes for the gas to saturate the carbon.

SMTCapeCod

You are on the right track wrt vacuum leak. Just have to hunt it down, not always fun, unless you are into cigars.

Speedtoys

??

Continue.....saturate the carbon?

safulop

Poor throttle response is often traced to ignition electricals, I thought.

jpitman2

Vacuum leaks can easily be found by spraying something lightly flammable on any hoses or manifold joints and listening for a change in idle.
jp 83 Euro S AT 56k

Koenig-Specials 928

If you are looking for a vacuum leak then I would suggest you use this rig that was made up by Dwayne in one of his epic DIY writeups. He used air pressure to test for leaks BUT I took my car and his set-up to a mechanic that had a smoke machine and it identified 2 hoses that were cracked at a bend and a not so good hose connection.

P.S. For the smoke test you do not need the gauge.