Vacuum line out

Hi I have discovered that one of my vacuum lines in behind the resonance flap seems to have come out. There is no vacuum coming to the solenoid valve next to the alternator, so I traced the line back and noticed that it joins a three way connector behind the resonance flap pipe. The line from the solenoid valve is plugged in fine. The second connector seems to go to the vacuum cannister. The third connector seems to have plugged nothing in it. Its very difficult to see clearly in there as to whether there is a loose line hanging around there that should be plugged into the connector. So I have two questions: 1. What impact will having no vacuum coming through this line (and the vacuum cannister being unable to create a vacuum due to the open connector) on the running of the engine? 2. Is there an easy way to get in there to access the connector without removing the throttle and the two pipes? I've done this before to install my PSE (which is probably when I knocked the line out!!) and it was a very hard job to get the two pipes back on. Cheers Greg

I would have thought that a vacuum leak would cause a slight increase in idle speed and a lean mixture. What does it idle at? Should be 700rpm. As for access, I don't think there is any easy access on a 996 engine!! Sorry I'm not much help.

Thanks Richard. It idles between about 775rpm i'd say so it probably is a bit high then. So you don't think there is any risk of harm or is there no problem leaving it until I have the time to dig my way to the back of the engine again? Also, I've always struggled to get a decent mpg in it. I assume as it would be running lean then this wouldn't be causing this? thanks Greg

No, it shouldn't do any harm. The MAF is measuring the air flow into the throttle body and adjusting the fuelling accordingly. I think that once the engine is running at reasonable revs then it won't make a signifcant difference to the mixture, as the volume through on open throttle will be considerably more than the leak. On yours (with mechanical throttle) at idle, the butterfly is closed, and the idle air intake is regulated by the idle control valve. In this situation, the air leak will have a bigger effect - as you have found by a 10% increase in idle speed. As for a decent mpg - don't we all struggle? [ ]

Bit the bullet this morning and removed the throttle and the first of the two intake tubes behind the throttle. Took me a while to work out where the empty connector was meant to connect to. Couldn't see any loose pipse to plug into it. Ended up burying my arm in well past the elbow into well behind the vacuum cannister and found that the solenoid that controls the vacuum valve on the cooling system under and just in front of the engine had only one vacuum line connected onto it. There was no pipe on one side of it at all (just like on the three way connector). Had some spare pipe so connected it up, put it all back together again and it seems to have solved the problem. Idle speed is back to bang on 700 rpm and it seems to be holding a vacuum now. So it appears that this vacuum line has probably been missing since before I got the car and the problem has probably been there the whole time that I've had the car. It will be interesting to see if it runs any better now. Presumably this will be the first time that the resonance flap has worked since I got the car, as there previously was no vacuum supply to it. I don't know if it makes much difference but I guess I'll find out! One follow up question though. I noticed there was a fairly heavy lining of oil inside the intake tube that the throttle connects onto. It seems to be coming from the black tube that goes onto the left side of the throttle. Is this normal or is it a sign of another problem? Cheers Greg Edited to add that it was overfilled with oil slightly for a week or so late last year after its annual oil change. I ended up draining out about 500ml of surplus oil. I wonder if this might be related to the oil in the intake?

Well done Greg! I think that might be the tube from the air/oil separator, so may have been due to overfilling. If the throttle body was dry and oil-free inside I wouldn't worry. It will be interesting to see how it runs now, and if there is an improvement in mpg. Keep us posted.

Great. Throttle itself was fairly spotless so hopefully thats all it was. Thanks Richard. Cheers Greg

By the way Richard - ignore my double post on renntech. I know you post there from time to time. It seems my problems have been solved here before renntech could help me.