It’s a filter for the Idle Air valve... on many diagrams appears as #46. Where does the hose connect on the end you’re holding? Sort of doubt that your “leak” is from this component. Just because you heard air flowing through it does not mean it’s leaking. A vacuum leak from a hose that large would make your engine rev up quite a bit due to a severe leaning of air/fuel mixture... probably be idling at around 1800-2000 rpm. Once plugged or “bypassed”??? the engine speed would drop back down to around 800 rpm... unless there was another leak somewhere.

 

Actually if you Were to plug the connector where this hose normally goes, you might not even be able to keep the engine running except by throttling up with the accelerator. Please provide a few more details about that “leak” and what symptoms other than ”hearing” a leak.

 

Hope these photos of diagrams help.... in diagram, the valve is called IAC (Idle air control)

 

 

Often called the idle speed solenoid (or ISC) on this forum.

 

Thanks folks. I don't think the IAC is my issue. I mainly have a fuel trim issue when in open loop at idle the fuel trim rises to 30, car almost dies and drops back to 0 on fuel trim then repeats. One mechanic suggested a bad intake manifold gasket but I can't find evidence of a leak there yet.

 

intake leaks will be evident whether in open or closed loop but will affect fuel trims differently.
if its fine when in closed loop, and idling normally, then whats affecting it in open loop as its warming up...oh, right, idle air circuit.....

 

Just curious as to how long you think your engine is in open loop....??

 

I should note, on cold start and when in closed loop the STFT was -6 at 71 degrees, 3.9 at 100 degrees, 11.7 at 123 degrees, 18.7 at 131 degrees and 32 at 134 degrees (same for the O2 sensor). Then it goes into closed loop. So the STFT is acting up in closed loop too.

 

Then you have a big air leak, possibly a split hose. At +30 the ecms well andtrypuly lost control 9f mixture,the sudden reversion to 0 is either the ecm resetting or the leak suddenly resolving.

Check the O2 sensor graph, is that actually doing what it should? If that's screwed up then that would also account for it.

Cold start and closed loop? How? Won't go closed loop until its warm.

What's ltft saying?

What are both like at 2000 rpms after 30 seconds?

 

once its in closed loop it should stay there as O2 sensor is hot enough to function properly. Usually there after a minute from cold start.
LTFT determines next start fuel level until it hits closed loop then STFT takes over.

If its going open loop you have a big air leak at idle or your IAC is losing control. Hows your exhaust system? any leaks?

I see the STFT and LTFT hit 0 in those graphs, was that at steady revs? if it was then thats as I would expect.
Somethings screwy at idle, start pinching off vac lines until you see things stabilise, even block off the brake booster hose to prove thats not the issue.

 

once its in closed loop it should stay there as O2 sensor is hot enough to function properly. Usually there after a minute from cold start.
LTFT determines next start fuel level until it hits closed loop then STFT takes over.

If its going open loop you have a big air leak at idle or your IAC is losing control. Hows your exhaust system? any leaks?

I see the STFT and LTFT hit 0 in those graphs, was that at steady revs? if it was then thats as I would expect.
Somethings screwy at idle, start pinching off vac lines until you see things stabilise, even block off the brake booster hose to prove thats not the issue.

Can't find an intake leak anywhere and replaced some hoses while checking them - no change. Brake booster hoses are fine, good whoosh of air when I pulled one. I think the IAC is 'probably' OK - pulled the line to it from the intake which killed the car - but haven't tried anything else yet. Took it for a short drive, runs OK as long as it's in closed loop but still on the lean side. Leaning toward an exhaust leak ahead of the upstream O2 sensor as you suggested - will have a mechanic check that out, I'm running out of time.

 

Did you actually block the brake booster line? If there's a leak in the booster that can be enough to upset idling and not be noticeable in brake performance

 

Interesting, I'll try that in the morning - thanks! That the hose released a lot of air pressure when I removed it made me assume the booster was fine.

 

Vacuum leaks are sneaky little buggers, you need to remove each hose and block it at the manifold. That then eliminates the hose and whatever its connected to. When you find the one that fixes the issue, start checking back from there,

If it is an exhaust leak you can test that by wadding up a rag and blocking the exhaust tailpipe with your hand. 3 things will happen, you will hear the leak,(bad, gotta find it and fix it) it will pressurise and lift the sprung loaded joint (if fitted) off its seat (good, no leaks) or it stalls (no leaks)

 

Vacuum leaks are sneaky little buggers, you need to remove each hose and block it at the manifold. That then eliminates the hose and whatever its connected to. When you find the one that fixes the issue, start checking back from there,

If it is an exhaust leak you can test that by wadding up a rag and blocking the exhaust tailpipe with your hand. 3 things will happen, you will hear the leak,(bad, gotta find it and fix it) it will pressurise and lift the sprung loaded joint (if fitted) off its seat (good, no leaks) or it stalls (no leaks)

Ah, still chasing windmills. Checked the brake booster, block the port on the manifold - no change. I already replaced all the little vacuum lines and a few others, but noticed that the vacuum port on the top of the throttle body that goes to the EGR VSV (photo) delivers no vacuum. Took the intake tube off to clean it and could blow through that port, but when everything is reinstalled and running still no vacuum at idle or 2500 rpm (and I can't blow through it with the intake reassembled). Hmmm.

 

A good way to check for leaks is to take a pliers and pinch a vacuum hose. You should have no change in idle in any hose, other than the vacuum hose going to the ISC. While hoses may look good, and whoosh, etc., pinhole leaks, bad connections, etc. can cause leaks as well...ones that you cannot see.

 

ahhh, what gasket doesn't have a hole in it perhaps?

 

Yeah, that takes me back to the intake manifold gasket question - ugh. Car only has 75K miles, but yeah, still 22 years old.

 

The actual orifice in the throttle.body casting is usually a lot smaller than the exterior elbow(where hose attaches).
2013GV has very valid observation... air passing through when separated, then no air when assembled back, obviously points to something blocking that orifice on the inside.

 

The actual orifice in the throttle.body casting is usually a lot smaller than the exterior elbow(where hose attaches).
2013GV has very valid observation... air passing through when separated, then no air when assembled back, obviously points to something blocking that orifice on the inside.

My bad, took it apart and cleaned again - then discovered I only get vacuum through that port at 2500 rpm or above. Not sure if that's right.

 

An update to close out this thread. After chasing non-existent vacuum leaks, cleaning and throwing a few parts in still no change. One mechanic said bad EGR VSV (not it), another wanted to do the intake manifold gasket (no) and finally the third traced it correctly to a MAF running out of spec. I had replaced that a year ago with a cheap one which later was the source of the pending lean codes, suspecting that I put in a $140 Delphi which also was not to spec. It took a $$$ Cardone to get everything back to normal. Lesson learned - don't buy a cheap MAF!

Before and after smog tests: