"Swooshing" sound when engine is on - culprit of high idle?

86 911 · 86 911's Garage

Yesterday I found that all the sudden my car idles at 2000 RPM, which is very weird since it usually idles at 950-1000 RPM. Today I took the airbox off and started the car. I'm hearing a swooshing sound when the engine is running and especially when the engine is shutting off. It seems like the sound is coming from the center to right side of the engine compartment. Where/What should I look at? Would this be coming from the AAR valve? If I take the AAR valve apart to clean it, do I need a gasket for it?

86 911 · 86 911's Garage

Anyone?

Paulporsche · 05-14-2006, 12:43 PM

Sounds like it might be air being sucked into a vaccum line. Check all the hoses and your decel valve, AAR, and AAV. Also check your popoff valve. I don't think you need any gasket for the AAR or AAV.

86 911 · 86 911's Garage

Is the AAR the part on the right side of the engine under the right side of the airbox? Vacuum lines seem to be ok as well as the pop off valve, but the lines are hard to check since the engine is not out.

86 911 · 86 911's Garage

I think my problem is my AAR (the cylinder shaped thing near the blower and air sensor with 2 vacuum lines coming off it). My dad did a little experiment and took the vacuum line off it, which lowered the idle a litte. When he put the vacuum line back on, the car idled high again. Do I need to replace the AAR in this case?

Paulporsche · 05-14-2006, 04:05 PM

If the car is warmed up and you pinch off the AAR hose, the revs should not change if the AAR is OK. Your revs change, so I think you should check the regulator and the lines.

Also, see what happens if you close off the line on the top of the decel valve. If the revs go back to normal , then probably the decel is faulty. Many guys just leave it closed off.

You may have other vacuum leaks, or maybe a faulty distributor, or your sensor plate may be incorrectly set, or your mixture too lean.

Your throttle linkage could also be binding and hanging up on something.

Your 02 sensor may also be faulty, although someone else will have to advise you on that. I don't have one.

You should get a Bentley manual for the car. Also search the archives here for lots of info.

86 911 · 86 911's Garage

Thanks for the wealth of info Paul. Acutally, I thought the decel was the AAR in the previous post, so disregard that. When we took the line off the top of the decel valve, the revs lowered, but only went down about 100 RPMs. This morning when I first started the car, I pressed the gas which was really hesitant and I heard a muffled low backfire everytime I stepped on the gas pedal. This only occured for about 30 seconds though. What do you think is going on? I've got half of my CIS system on the garage floor in pieces.

BTW, I don't have an 02 sensor, just a poorly running CIS system

.

Scott R · Scott R's Garage

It sounds more like a large vacuum leak then cmponent failure. Has this CIS system ever run correctly? Also please post your system control pressures so we can make sure the warm up cycle is working, you could be stuck at the cold control pressure level and have this issue.

86 911 · 86 911's Garage

Before yesterday, the CIS system ran like a champ -- I've never had any problems with it before. It was like all the sudden something happened. I'll post pressures in a few days when I can borrow some tools to test the system.