Troubleshooting an SC CIS problem
 

I am having a lurching problem with my car. It's been going on for a while. It seems like it started right after I installed the popoff valve. The car will lurch or hesitate when I start off from an idle. If I slip the clutch from about 2k rpms, it's fine. but if I take off real slow from an idle, it will lurch uncontrolably. I will have to disengague the clutch and then rev to about 2k and slip it to get it smoothed out again. I thought it might be from the popoff valve leaking around where I drilled the box so I slapped on a lot of epoxy around the area, and it didn't change the situation. Also, I took the air cleaner cover off right after I stopped the car, and flipped open the popoff valve, and there was a bit of smoke comming out of it. Is that a sign of anything, or is that normal? I checked the oring and it looks fine. I'm not sure where else to start looking to find the problem. Please help.

Could it be a worn throttle linkage or bad motor mounts. Does it happen when it is warm or cold? You can check the pop off for vacume leaks with carb cleaner while idleing. My car does that a little when it is cold. But I figure, hey it is running. I have CIS also, but not for long

get a mirror and a flashlight and check all around the valve to be sure the epoxy stayed put, and didn't leave a gap that would cause a vacuum leak.

I smeared a bunch of high temp silicone around the valve, let it sit over night, and still no change. there is no way that there is a gap anywhere between the valve and the airbox now. Only happens when warm. It seems like the valve is popping at low RPMs, but there is no dent in the air filter from it. Could this be another issue that was present before the popoff valve was installed? Such as lean/rich mixture causing the valve to pop, but not enough to have blown up the airbox before the popoff valve was installed? Getting frustrated here.

I guess it could be a lot of things. Check your fuel pressures and check the mixture. Check your timing also

Make sure you bleed fuel system after disconnecting fuel handling components...Sounds like a fuel filter to me....

Uhhhh..... Disconnecting fuel system components? I didn't disconnect anything, was I supposed to? The fuel filter has not been replaced to my knowledge, and I have a spare one so I will do that over the holiday. I didn't suspect the filter because it is fine at high rpms. I thought if there was a fuel starvation issue, it would get worse at higher rpms.

My car also likes to get into the rhythmic lurching thing when crawling through parking lots. John, are you saying that a vacuum leak might cause this?

Noah,

That sounds like good advice to me. I have the same feeling about the valve. Given our 30 deg weather, I will probably spend the holliday tearing it appart. Now, I need to know what the best epoxy is to use. I need something fairly firm since I know my hole is not very straight.

Are you sure this happened just after the popoff valve installation?

You might check the baseline on the car: How's the CO? Timing? The valves adjusted as well? Fuel filter for certain! Are you possibly still on the same tank of gas under which you put on the valve?

John

Casey, I think you can very easily check the pop off with carb cleaner while idleing. I don't think that is it. I would think you would have a high idle if the pop off was leaking.

Casey, squirt some carb cleaner on the popoff at idle. That should tell you all you need to know.


Joe

Is the 02 sensor still connected?

My popoff valve montra: check the O ring! When I got mine new, the O ring wasn't seated properly. If you push the ring down with your fingers, you won't get a sealing surface that mates directly with the door. Pull the O ring out and gently put it back in the seating ring. Then use the door to push it into position and seat. This way you are guaranteed a proper seal all the way around. You can also put silicone lube on it for even better sealing.

What you're describing has to be related to your newly-instlled valve. It screams vacuum leak and with this being the new component it's likely the source.

Casey, you didnt pull off the air box to drill it?

Been out of town so I'm just reading these. No, I didn't pull off the airbox to drill it. I have read many instructions that said it was not necessary. I was able to vacuum out all of the plastic from drilling. I am a little relieved to hear that it is indeed a vacuume leak issue as I though it was. Since it started right after I installed the valve, I am almost positive that it is the culprit. I will first inspect the o-ring. What about putting a lubricant on it to help it seal, such as silicone (greese, not sealant). If that doesn't fix it, I'm going to remove it, clean it well, and reinstall. I will report back with my findings. Thank you for the advice.

Careful with the silicone grease or RTV, it can play heck with your O2 sensor.

81 RoW = No O2 sensor.

Just thought I would report back with what I have discovered. My problem is the popoff valve not sealing. I re-epoxyed the valve, and checked for airbox leaks. No leaks around the valve, or from the airbox. I smeared some silicone greese on the oring and the problem went away for a while. The silicone eventually wore off, and the problem creeped up again. So now I'm thinking of putting a stronger spring on the valve. Anyone have any idea what the best way to do this would be?

Sound like the popoff valve you have is defective.

Maybe an o-ring that is a little thicker will provide the additional sealing.