A little carb cleaner probably won't hurt.

yep, im going to go and buy some of that asap.
thanks for the advice

just started my car up after having putting some plastic glue/seal on the leak. it idled at about 1800 rpms, i sprayed some carb cleaner on the leak, adn i was able to have it idle at ~1100 rpms for about 5 minutes, and then it slowly started to creap back up to about 11400 rpms. so im going to put some more sealant on that seam and see how that goes. also, there were no backfires when revved (big change from how it was) and the decel was slow as a freigh train. when i revved it to 3k rpms, it would fall at normal speed to 2k, and then take another two seconds to slowly get back down to 1500 rpms, where it held. also, it seemed that revving it (i reved it a couple times at about 3k) made the idle raise

Some very good advise was offered here with 9 pages and no success?

When there is a vac leak in a CIS, spraying carb cleaner on it will raise the RPM, not lower it.

Until the leaks in a CIS are eliminated, all other adjustments are meaningless and going all over the place doesn't help. :).

Trouble-shooting is a process of step-by-step elimination, find the components that work and then you'll find the one that fails.

CIS is very reliable when maintained properly; dirt and leaks are the enemy.

Best. SmileWavy

Yep, ive been through all the tests that have been listed here. And carb cleaner would lower rpms, not raise them. heres why, when you have an air leak that is letting unmetered/"false" air into your motor, your idle can be at 1k rpms when your speed screw is all the way closed. if you were to spray carb cleaner on the leak, it would temporarily partially seal it closed letting in less air casing the idle to drop.

the problem that im having right now is that i have an air leak letting in false air, and with the speed screw all the way closed, its idling where it should be 1k rpms. but that means its running really lean because unmetered air from a leak doesnt lift the flapped plate, so its not letting in a lot of fuel.

Listen to people who knows CIS.........
 

Scott,

It has been 10 long months since you started this post and you are not even close to fixing it!!!!!!! Listen to Gunter. Your problem is a very basic CIS problem and yet, you are making it into a research work!!!!! The problem is very simple to fix. It is so simple that I will offer you a special service.

Put the complete engine in shipping crate and have it delivered to me. I'll make it run like my cars!!!!! And I'll pay for the shipping back to you if I can not deliver my promise. Think about this before I change my mind. I got two (2) CIS engines sitting in my garage awaiting some TLC. I just wanted to help a fellow 911 enthusiast like you who is in need of some assistance.

Tony

How about this deal? I will buy a round trip cheap-o airfare to your place. You pick me up Friday afternoon and I will return Sunday or Monday morning. If I fix it, you pay for the ticket. If I don't fix it, you don't pay for the tickets and we bond and cry together. (You buy pizza in either case and put me up)

What's a ticket cost - couple of, maybe a few hundred bucks? That's about two hours shop time at a Porsche garage.

You've got to ask yourself one question: "Do I feel lucky?" Well, do you, Scott?

Offer is as serious as esophageal cancer. We would have a blast. Plus, you could put this behind you and start enjoying your car.

I had two big air leaks two years ago. One was the number 4 intake runner base and the other was an injector that pulled out of number 5 intake runner. Starting fluid into the pulled injector hole caused the RPM to lower and starting fluid onto the number four intake runner base caused it to increase. The starting fluid changes the idle RPM. That is all that is needed. There is a reason why one went up and one went down but is is of no consequence.

I really would like you to get some carb cleaner and spray it on the number 6 intake runner base and report back what you found. Also, the mechanic said the airbox was sucking air. Did he show you where? If he did, confirm that with the carb cleaner and then get some form of sealer and goop it up. I would use JB Weld or JB Weld Quik (5 minute stuff) and do a temporary fix. I think silicone can mess with the O2 sensor so pass on that. Cripes, use latex caulk for around your windows before painting or chewing gum. Just get the darned hole plugged and skip the carb thinking for now.

CIS air-box pressure test.......
 

This is how I test my air-boxes. Pressurize and submerge it underwater for several minutes and observe very closely for air bubbles. A leak-free air box will not have any bubbles coming out.

http://forums.pelicanparts.com/uploa...1318384221.jpg

Tony

Alright, alright, i get it.
I bought carb cleaner this morning and have been spraying with it
Ive been looking for holes, finding them and sealing them. i sealed the seam on the left hand side of the irbox today and i will continue looking tomorrow for others.

I think I might end up taking the airbox out and sealing teh holes then to make sure i find them all. I know this is a common problem, but there were other tests that people have been telling me to do, in fact, from what I remember, I only got the advice to spray with carb cleaner just yesterday or the day before, cant remember, from bob.

Ill forget the carbs for now, and ill work to get this thing fixed. tony, to be honest, thanks a ton for the offer but I probably wont end up dropping the motor again. someone posted a while back a picture of someone with thier airbox being dipped into a washer machiene. i think i will try that and that should find me all of the leaks.

carb cleaner will find teh leaks that i can easily spray/ reach but i think it will be hard to find them all without submerging the box.

sorry for making everyone angry, i have, for the most part, been following people's advice/ suggestions, in my opinion

you were right, carb cleaner on #6 speeds up the idle for a second. im guessing this means that it is not bolted down tight enough?
when i took my car in i told the guy that i couldnt get the inner nut on #6 tight enough i was assuming that he would tighten it

yeah, thats what I was talking about, i might have to give my airbox a test like this to make sure it is leak-free,
thanks

Maybe it was my picture.......
 

Scott,

Maybe you have seen the picture of the air box sitting on top of the washing machine but the washer was used only as prop for picture taking. I never used the washing machine for test. This is a very good example of how people looked at the problem. How on earth could a washing machine help you find the leak!!!!

I think I'm one step ahead of you and posted the picture of the air box for test. To be honest with you, I've never used a starting fluid for finding air leaks. I used it for my lawn mower and pressure washer when they failed to start.

Wish you well and good luck.

Tony

a washer machine is a large object that can be filled with water and then can be used to dunk the airbox? just a thought though, but maybe that wouldnt work, like you said
thanks for the help though

Need to nail that down.

Nice washer, Tony. (Scott, he does wash his car parts in there but will ever admit it)

haha, yeah, it seem like a good idea to me

Regarding number 6 - I installed a fuel pump on a '68 2000 Datsun Roadster recently. My pal had a 13mm wrench that had been "torched" and bent to allow for some unusual access angles. You have a vice? The nuts are 10MM? Bend a cheap box end wrench the way you want it. Propane can do it - just slower than oxy-acetelyne.

Plastic tub..........
 

Scott,

A residential washer will not be large enough to accommodate the CIS air box for complete submersion. I use a large plastic tub or container for the test. If you have a pop-off valve, you need to compress it down during the test. Otherwise, it (pop-off valve) would leak at pressure close to 5 psi.

Eliminate the air leak/s in the system first. If you could not eliminate the air leaks in your system, it would be a very difficult task to make the engine run good. Do you realize how difficult it is to install the CIS unit correctly with the engine installed in the car?

Tony

Of course it will increase idle.
That's what a competent mechanic would do.
A 13 mm swivel socket with a LONG extension will tighten the nuts for the intake runner #6.

Scott, you're NOT following advise and keep stumbling and bumbling along plus you're working against yourself. I get the impression that you try to make band-aid fixes which don't solve the problems.

It's painful to follow and a real waste of time. :rolleyes:

Why even ask for help if you don't take it. :confused:
After 9 pages, this engine should hum by now.

boyt911sc has gone out of his way to help you and one should be so lucky. :cool:

LOL. I've been following this saga as well, and you've said everything I wanted to. It's like two people talking on the phone who can't hear one another. Kudos to boyt and Bob for staying on the line this long. I would have given up.

To Scott, You don't appear to be coming from a good comprehension of the CIS system. (There are good books available.) And, it's for that very reason that you need to become more thorough and more methodical rather than less so and more haphazard. You need to work harder and probably go to greater lengths to make sure there is confidence in your tests. Exhibit 1... you claim to have performed a pressurized leak test that confirmed no leaks, and then you say a professional mechanic subsequently found leaks in your air box. Exhibit 2... ignoring the known loose #6 intake runner bolt. Exhibit 3... unwillingness to pull the engine to allow full access to the CIS system. I guarantee you could tighten that #6 bolt just fine with the engine out. If you're not willing to be more thorough and more careful, you should turn the whole job over to a professional. All the long distance advice from boyt and bob won't help.

Good luck,
Brett