CIS Airbox Questions

[lespaul]

1. My car will not cold start if the air filter is in the airbox. It just turns over and over but does not fire and I smell fuel. I am using the proper starting procedures set forth in the manual.

If I take the filter out, the engine will fire and start up. Once started, I can install the air filter and it runs perfectly. The air filter is brand new (I replaced it thinking I was not getting enough oxygen because the old one was dirty). Any ideas?

2. On a related topic - once the car was running, out of curiousity, I placed my hand over the intake nozzell for the airbox thinking that if I starved the engine of oxygen, it would stall or run rough. However, even when I completely seal the intake, there is absolutely no difference in engine speed or operation. This is true at high or low revs. This makes no sense to me. Is there some other way that oxygen gets to the engine? Shouldn't the engine stop if starved for oxygen? Is this normal? If not normal, is this issue related to my starting problems?

Any sound advice will be well appreciated.

[lespaul]

Bump -- especially question 2?

[patkeefe]

Any sound advice will be well appreciated.

Well, I don't know how sound this is, but no, a car will not run without air and fuel. So, you must be getting air into the system somehow when you choke off the airbox inlet. Possibly leakage past the airbox cover, combined with a few other things, perhaps sucking air back in through the oil tank breather system, maybe other air leaks. Does your car run OK? Is it rich? I would further guess that if you were to choke off the airbox inlet and try and drive the car, you would not get far, as it would starve with the load on it. Do you have a popoff valve in the airbox? Did this starting issue happen suddenly?

[lespaul]

Thanks Pat. Starting problem did come on suddenly. And your right, perhaps the air that the car is running on is coming in through the oil breather hose - from the oil tank. I did install a pop off valve about 4000 miles ago. I think I have a good seal on it.

Based on some other threads, I am going to take off the "popes hat" and clean my sensor plate.

[tcar]

Did it happen when you change the filter?

Open popoff valve?

Cracked airbox?

Bump or pull off a vac hose when you changed air filter.