CIS mystery

Platiporsch · 05-23-2003, 07:24 PM

OK I have suspected a vac. leak for some time but cant pin point it, i was just outside messing around with the car and i decided to block of the air intake with some hard plastic with the engine at idle, the air filter housing is firmly in place and see what happened i suspect the engine would stall but it didnt phase it it just kept idleing normally. whats up with that? i must have a massive leak but how can that much air be supplied from a vac. leak.

cowtown · 05-24-2003, 08:34 AM

If your car still idles, then it's geting fuel as well as air, so the leak would be between the air intake (which you blocked) and the air meter plate (the arm by the fuel distributor that goes up to let in air and meters fuel). So I'd keep the intake covered, idle the car, then look in this area. Carb cleaner or wd40 can be sprayed around, and when the idle changes you're getting close.
Good luck.

Joe Bob · Joe Bob's Garage

Never used it...but they say propane is safer and cheaper to use....

RoninLB · 05-24-2003, 10:26 AM

Quote:

Originally posted by mikez

..but they say propane is safer and cheaper to use....

do what you gotta do.. most guys grab whatever is laying around.. if you want safe, there is a nice vacuum/exhaust leak detector available.. it beeps, and you can really pinpoint in questionable areas.. I have the Snap-On version, but it's a routine machine sold by various suppliers.. a good shopper could probably buy it for less than $75... Pelican Parts is worth a shot, IMO................Ron

Platiporsch · 05-24-2003, 12:37 PM

bump

cowtown · 05-25-2003, 04:51 PM

Have you tried anything that was recommended? A little more information would help us.

Platiporsch · 05-25-2003, 08:58 PM

If i spray carb cleaner around the left side of the air box it will raise the idle 300 to 400 rpm to about 950 and i can drive it for a while and it holds its idle. if i shut it off for 1+ hours it starts hard, low idle unless i spray the carb cleaner again in the same spot and its back to normal again i cant tell where the leak is, im going to get my hands on a oxygen tank and try that method.

gustaf · 05-27-2003, 11:52 AM

Do you have a pop-off valve? If not, you may have a cracked airbox unless you have already ruled that out.

-Dave

Ruben911 · Ruben911's Garage

You say that when you spray carb cleaner around the air box that the idle goes up 300-400 rpm up to 950 (this tells me your idle is at 500 to 600 rpm which I believe is way too low -should be around 950 rpm depending on your model). Have you tried to get your idle up to 950 with the idle adjustment screw behind the throttle body. Also, what makes you suspect that you have a vacumn leak? Is the car hesitating under load, is the idle surging, etc. I just need more info to help troubleshoot. Thanks

Platiporsch · 05-27-2003, 06:08 PM

Yes it has a pop off valve,it starts quikly goes to 950 then drops to rough idle then stalls unless i spray carb cleaner around the left side of the air box,the box looks fine the screws are down not raised.also if i dont spray carb cleaner and try to rev it it hesitates and backfires [way to lean] if i spray it it revs up fine without these simptons and once its warm seems to run ok,ive checked the duty cycle relating to the Lambda and its steady at 45% to 55% telling me the mixture is close to being correct, i just cant determine were that leak is is it possible to remove the CIS system with the engine in the car it doesnt look like fun.

ruf-porsche · ruf-porsche's Garage

Quote:

Originally posted by Platiporsch
is it possible to remove the CIS system with the engine in the car it doesnt look like fun.

Yes it possible to remove the CIS system with the engine still in the car and

yes it's a lot of work. Label or take digital picture (if you have a digital camera) so that you will know where all the hoses goes.

If you gonna remove the CIS replace the oil sending unit, it a lot easier with the CIS remove and you won't have to do a partial drop if it goes bad.

RoninLB · 05-27-2003, 08:52 PM

Quote:

Originally posted by Platiporsch

, i just cant determine were that leak is is it possible to remove the CIS system with the engine in the car it doesnt look like fun.

Hey Guy..
Before you start playing with the CIS.. if your sure about a vacuum leak, why not spend $75 for the electronic leak detector..
I mentioned it in my last reply on this.. I'm sure it's good bang for your bucks at this stage ................Ron