Thread: Rough/hunting idle

I have a rough/ hunting idle. It all started right after I installed all the mods in my sig. I did them all at one time. At first the surging idle was do to not running a pcv valve and running a breather. I ran one night like that and dug into it because I was pushing so much oil out the breather under boost. So now I am running a welded shut pcv valve and a 3/8 hose out the top of my oil fill cap to vent the crank case. Even after I fixed the huge vac leak it still was surging. I know it isn't a vac leak because I searched with carb cleaner 3-4 times and my trims are as low as -10 at an idle. I have not and am not throwing any codes. I have replaced the maf, IAC, and O2 sensors. The thing is it doesn't always hunt. It is kind of random sometimes being worse than others. Sometimes it will hunt up to a 1000rpm difference and sometimes it is only a 400 rpm difference. It seems to get worse when it warms up. BTW I am running stock injectors because I wanted to eliminate the 65#'s. The car seems to run very good anywhere above 1000 rpm. If I think of anything else I will update this thread.

I have a similar problem, and my car is almost stock.... good luck, maybe a flaky CPS

Ok so I talked to the engine specialist at the local dealership. He looked at my car and couldn't find anything on the Tech II other than it was random missfireing on cylinders 1,2,and 3. He went back and listened to the exhaust and felt it and noticed it was sucking in sometimes. So his thought is maybe a stuck valve. The weird thing is that the other day I had the front valve cover off just checking things out and randomly decided to push on one of the valves. It didn't seem to snap back like it normally should but I didn't think too much of it. I thought maybe it was snapping and I just wasn't noticing it. Another thing is that it seems to get worse when the car warms up, which would support the sticking valve theory. So I am going to go home and pull the from valve cover off and recheck things more closely with the engine warmed up to operating temp. I will report back with the findings. The sad part is I really hope this is it, I just want my car to run right.

Well I pulled the front valve cover off and sure enough some of the exhaust valves were sticking, but not all the time. I called the guy that redid these heads the first time and he installed bronze guides. He also told me that if any coolant gets in the intake it will cause the guides to stick. Well when I put my engine back together last fall I used an easy performance rubber TB gasket (which are known to leak) and sure enough it leaked. So I guess I am pulling my heads of to have them reworked.

Got the front head off, with the help of Travis. I don't have a valve spring compressor so I couldn't pull the valves to see what they looked like so I guess I will have to wait till I drop them off at the machine shop.

Funny you say it sucks. I am very happy that this is the problem. I have been getting so sick of it not running right that I finally got the attitude that I don't care what is wrong I just want it fixed. I had to pull the heads sometime soon anyways because I am running SI intake valves with a turbo. Plus I can fix my double roller now. I talked to the machinist and he said that usually when this happens it only takes a little honing and the guides will be good again. Plus I love to tear into my car. I thought we did good tonight, had the front head off in 1.5hrs. could have had both off but I got lazy. I guess this should be a good lesson to anyone running bronze guides.