Author Topic: Rough idle (Read 3186 times)

Zcomm17 · « **on:** January 18, 2013, 05:22:10 PM »

Hello, I am new here and have a problem.

I just recently bought a 91 318i with 150k miles on it. After driving for a week I let it sit for a couple days. coming back to start it, is just kept turning over finally after starting it it spews an endless cloud of water vapor out the tail pipe. I changed the head gasket and water pump and start it up, it idles rough with a put put sort of attitude and the check engine light is on but once I rev the engine the CEL turns off. I did the turn key to on and tap accelerator 5 times giving the code 1222. I am stumped because I put all the vacuum lines back when I put the car back together (I had taken pictures of the process of removal and worked backwards)

If anyone could give me some advice on where to start that would be appreciated. I don't have the money to take it in to a shop and have them look it through, and it is my daily driver.

Nelson_40 · « **Reply #1 on:** January 18, 2013, 10:57:26 PM »

It can be a large number of issues from AFM to vac leaks to O2 sensor failure to plug wire/coil trouble. Read here for M42 Club coverage, and just search with terms M42 and code 1222 or just 1222 on M42 Club.

bmwman91 · « **Reply #2 on:** January 19, 2013, 12:11:56 AM »

There's a vacuum leak that gets people sometimes, and it is very hard to figure out. The upper intake manifold may not be bolted to the lower one perfectly, and this is due to the front steel bracket that holds it. When installing the upper intake manifold onto the lower one, always do it with both steel brackets loosened up. Once all of the 11mm nuts are fully secured, then you should tighten the steel brackets down. If you don't, there is a chance that the upper manifold will be cocked at a funny angle and have a big gap between the two manifolds! That got me once.

Also, the vacuum lines are prone to cracking, especially the nasty mess of ones under the throttle body.

bmwman91 · « **Reply #3 on:** January 19, 2013, 12:11:58 AM »

There's a vacuum leak that gets people sometimes, and it is very hard to figure out. The upper intake manifold may not be bolted to the lower one perfectly, and this is due to the front steel bracket that holds it. When installing the upper intake manifold onto the lower one, always do it with both steel brackets loosened up. Once all of the 11mm nuts are fully secured, then you should tighten the steel brackets down. If you don't, there is a chance that the upper manifold will be cocked at a funny angle and have a big gap between the two manifolds! That got me once.

Also, the vacuum lines are prone to cracking, especially the nasty mess of ones under the throttle body.

Zcomm17 · « **Reply #4 on:** January 19, 2013, 04:44:27 AM »

Quote from: bmwman91;119377

There's a vacuum leak that gets people sometimes, and it is very hard to figure out. The upper intake manifold may not be bolted to the lower one perfectly, and this is due to the front steel bracket that holds it. When installing the upper intake manifold onto the lower one, always do it with both steel brackets loosened up. Once all of the 11mm nuts are fully secured, then you should tighten the steel brackets down. If you don't, there is a chance that the upper manifold will be cocked at a funny angle and have a big gap between the two manifolds! That got me once.

Also, the vacuum lines are prone to cracking, especially the nasty mess of ones under the throttle body.

Thanks I'll try that first, I don't remember the order I tightened those few things in. When I first bought the car it ran fine and when I took my intake off I noticed a lot of cracked hoses, but I figured since the car ran smooth before it hadn't effected the performance. I guess buying new hoses wouldn't hurt and/or, doing the "mess under the intake" mod that I just recently found out about.

I also read about the code troubleshooting but just wanted to double check if anyone had any preference as to where to start or had a similar issue and found a simpler solution rather than checking all the individual things listed.

bmwman91 · « **Reply #5 on:** January 19, 2013, 05:06:13 AM »

Unfortunately, code troubleshooting is sometimes useless with these cars. Code 1222 is supposed to mean that the O2 sensor is bad, but it really means "Have fun checking for vacuum leaks and bad sensors, it could be anything that messes with the mixture!"

If you saw that lots of hoses were cracked and you did not replace them, then I would bet that they are your problem. Forget replacing the stock stuff...all that stuff under the throttle body is a pain and the OE suppliers now sell cheap junk from China that cracks after 2 months. Get some PCV hose from the local parts store and do 2 things.

1. Connect the valve cover outlet directly to the hose barb under the throttle body. You can re-use the 90 degree plastic elbow and just trim the hose pieces you buy to fit.

2. Connect the idle control valve inlet directly to the intake boot. You can do this using the existing hoses, assuming that they are not cracked. Just take a hose coupler from the stupid thing under the TB and join the existing 90-degree ICV hose to the hose that connects to the bottom of the intake boot. You may nee to trim one of them. This makes the hoses MUCH easier to access for maintenance and eliminates the need for the funky rubber air/coolant thingies under the TB.

Zcomm17 · « **Reply #6 on:** January 19, 2013, 05:16:10 AM »

Quote from: bmwman91;119381

Unfortunately, code troubleshooting is sometimes useless with these cars. Code 1222 is supposed to mean that the O2 sensor is bad, but it really means "Have fun checking for vacuum leaks and bad sensors, it could be anything that messes with the mixture!"

If you saw that lots of hoses were cracked and you did not replace them, then I would bet that they are your problem. Forget replacing the stock stuff...all that stuff under the throttle body is a pain and the OE suppliers now sell cheap junk from China that cracks after 2 months. Get some PCV hose from the local parts store and do 2 things.

1. Connect the valve cover outlet directly to the hose barb under the throttle body. You can re-use the 90 degree plastic elbow and just trim the hose pieces you buy to fit.

2. Connect the idle control valve inlet directly to the intake boot. You can do this using the existing hoses, assuming that they are not cracked. Just take a hose coupler from the stupid thing under the TB and join the existing 90-degree ICV hose to the hose that connects to the bottom of the intake boot. You may nee to trim one of them. This makes the hoses MUCH easier to access for maintenance and eliminates the need for the funky rubber air/coolant thingies under the TB.

I'm a little confused, do you mean the hose barb that conveniently fits through the horse shoe thing that is secured to the underside of the throttle body?

bmwman91 · « **Reply #7 on:** January 19, 2013, 06:18:00 AM »

For (1) I mean the hose barb that is connected to the TB. It should be a 90-degree elbow one.

For (2) I mean any of the straight barb / coupler thingies.

Zcomm17 · « **Reply #8 on:** January 19, 2013, 05:03:39 PM »

So I went out today and started the car, it ran fine till it got warm then started to bob and idle rough. I noticed that if I move the throttle a bit it would react but the rpm would slowly fall to barely above idle all while I held the throttle in the same position. I haven't started taking anything apart because as of right now it is 10 degrees, but I sprayed wd40 around the upper to lower intake junction and there was no reaction, I also sprayed where the injectors are and no change. I think I will check the IACV and TPS next since they don't require to much work to get.