[Aero97x252]

I just did a head gasket and timing cover replacement on my 02 9-3 SE. I replaced the head gasket because of a major oil leak, not because it blew. I finally got everything back together and I'm having issues with the engine idling roughly. If I open the throttle slightly to speed the engine up, the engine stalls when I let off the throttle. I've checked all of the vacuum hoses and everything seems fine. I even tried a different ignition cassette, just in case the other one got knocked over and damaged. I also noticed that if I disconnect the positive terminal of the battery after the car is running, it idles even more roughly. I've never known an alternator to effect the way an engine runs, but I think it's important to note that the oil leak resulted in the alternator getting thoroughly covered in oil. While I had it off the car, I cleaned it in a parts washer to get the oil out of it and then sprayed it out with an entire can of contact cleaner. It let it sit for a week before I reinstalled it. I'm sure it was dry. Could the alternator cause rough idling? If not, what could cause this? I wasn't having an issue with this before I did all of this work to the engine.

 

[Aero97x252]

I also wanted to mention that the computer isn't generating any error codes when I let it sit and idle. I did get P0300 a few times when I was disconnecting and reconnecting vacuum hoses, and electrical connectors, but I chalked it up to that.

 

[jvanabra]

I also noticed that if I disconnect the positive terminal of the battery after the car is running, it idles even more roughly.

You really don't want to do that. The battery shorts spikes and transients to ground, and disconnecting it allows those irregularities to travel the electrical system. They can permanently damage sensitive electronics in the car. In some situations it can also result in current spikes which damages or kills the alternator.


Are you 100% sure you got the cam timing correct? Did you crank the engine over by hand multiple times to check to be sure cam timing was retained as the tensioner took up slack?

 

[Aero97x252]

You really don't want to do that. The battery shorts spikes and transients to ground, and disconnecting it allows those irregularities to travel the electrical system. They can permanently damage sensitive electronics in the car. In some situations it can also result in current spikes which damages or kills the alternator.


Are you 100% sure you got the cam timing correct? Did you crank the engine over by hand multiple times to check to be sure cam timing was retained as the tensioner took up slack?

Thanks for the heads up. I never knew that could be so bad for a car.

I set the timing, and I cranked it over by hand, but only twice. I'm not 100% sure about the timing. I thought about this earlier, and now that you've asked, it really makes me wonder. I'm almost certain that everything is reconnected the right way. The timing is really the only thing that could have changed.

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[jvanabra]

Setting timing can be tricky, especially the first time. It might be worth doing a cylinder balance test too, especially if you didn't get the head checked and/or reused bolts. Just IMHO.

 

[Aero97x252]

Setting timing can be tricky, especially the first time. It might be worth doing a cylinder balance test too, especially if you didn't get the head checked and/or reused bolts. Just IMHO.

The problem turned out to be the timing. The first time I set the timing this past time, I asked someone to assist me by holding a wrench on the camshafts. They weren't much help, and they acted like I was majorly inconveniencing them and rushed me. Additionally, I was using the outside mark on the crankshaft pulley to line up the pulley with the timing cover mark. I completely forgot that there is a mark on the inside of the crankshaft pulley, so I don't think the marks were lined up exactly. I did it again myself and the engine runs smoothly now. I wasn't able to get the marks for the intake cam to line up exactly, but they are extremely close. I have to replace the valve cover gasket, and when I do, I'm going to set the timing again, and try to get all of the marks lined up as dead on.

 

[Jeremy R.]

You'll never get the camshaft marks to line up perfectly. If you search this board for timing information, you should find posts that tell you how many links should be in between the two camshaft sprockets. That's a better indication that it's timed properly. When it's timed correctly, with the notch in the crankshaft pulley right over the line on the timing cover, one camshaft marking should be right on the mark on the bearing cap, but the other camshaft marking will be very slightly off. That's when counting the links will tell you if everything's correct.