CCV and DISA replaced- Car undriveable (revs drop)
 

Hi,

Firstly, this was my first mechanical task. What I did:

1. I changed my oil, and this *may or may not* have been the last straw of my DISA valve. It broke, and I thought I may have heard the PIN fall out.

2. I removed the intake to look for the PIN. The CCV was brittle, so I replaced it.

3. I removed all the spark plugs to check for the PIN. I used an inspection camera. I did not find the PIN.

4. I replaced the DISA with an OEM BMW DISA.

5. The car was idle for ~60 days whilst I waited for parts/got the intake off. Battery was disconnected for ~40 days.

6. I put the spark plugs back in, and put the intake back in.

7. I followed a video (about the intake) and noticed that my engine doesn't have a solenoid he mentioned.
Also, I cannot find where to plug in the plug that is meant to go to the solenoid. (see photo here)

8. I used some jumper cables, and left the helper car running for about 10 minutes before I started the X5.

9. Car starts strong (for a few seconds), then the revs drop down and the car stalls within a few more seconds. I can hear a hissing sound in the engine. It's extremely unstable. I tried keeping the revs up to keep the engine on- but it is extremely choppy.

What could be the cause of this? Is this all related to my battery being flat? Could I have left something unplugged?


FYI: ODB codes are the same as before I did any of the above:
Powertrain Faults P1349, P1351, and P1354 (Misfire Cylinder 4/5/6 with fuel cut-off), MAF low input, O2 Sensor Heat Circuit and Random/multiple cylinder misfire detected

Later M54 engines do not have the solenoid and the black/white check valve, so that's ok. You have a plug where the hose would be.

Sounds like you have a large air leak. Double check all of the intake fittings, especially the boots to the idle control valve (small silver can) and the throttle body. Also ensure you plugged everything in/double check the connections.

Use a scanner and check the short term fuel trim. If you have a "Large" vacuum leak the computer will be adding fuel to compensate for a lean mixture. Engine has to be in closed loop for this to happen.

If the pin was not in the DISA valve that you removed I wouldn't run the engine until I found it.

Does sound like a vacuum leak. If you don't have a scanner it would be a great time to make the purchase. But, If you can hear hissing and the engine will run if the RPMs are up some you might be able to find the vacuum leak by sound or by spraying carb cleaner around the top of the engine. I sometime use propane or starting fluid. Engine will change rpms when cleaner is sprayed on the vacuum leak. Doesn't always work but might. Smoke test will find a vacuum leak quite easily.

Is it a constant hissing sound? Or an intermittent? (like to the beat of the engine)

If the engine runs really rough, regardless of the RPM, has the misfire codes, and you lost the Disa pin.... It sounds like the engine munched it. :dunno: I would stick a bore scope down cyl. 4-5-6 and see which valve is burnt. This sounds exactly like when I lost my Disa pin........ :(

What happens when that pin goes into the engine is: It bounces around in the cyl. and breaks a part of the valve off. The engine detects that it can't hold compression so it will cut fuel to that particular cylinder. Turning it into a 5 cylinder 3.0. It will run for the first couple seconds on all 6 cylinders if you clear the code, but no longer.

Kinda doubt in a pin can go down three cylinders. Best to do a compression test of all the cylinders. The one with the low compression reading (Variation greater than 10% of the rest of the cylinders) is the reason you engine is not operating correctly.

Yep, a constant hissing sound from the second the engine has started.


I've stuck an inspection camera down all cylinders, but and didn't find the PIN. What would a "burnt" cyclinder look like?


Once I get the revs stable (hopefully it's just this air leak) then check the cyclinders by swapping them (I don't own a compression kit)


This hissing is significant, so a large air leak makes sense.

With connections, I can't find anywhere this plug belongs. It is at the rear of the intake, with has little length. I thoroughly looking. Any ideas what it is for?

The plug:
http://i.imgur.com/ZnNa6rO.jpg

You're correct. But the code that he received was for a bank 2 (4-5-6) fuel trim cut off. Any off the shelf OBDII Scanner will give a generic P-Code, These codes give enough information to get the idea across. If mcfee03 were to use INPA, he would be able to see which specific cylinder is shut down.

Besides the massive air leak, this sounds exactly like the 2 Disa pin failures that I've whitnessed.

A burnt valve is one that does not seal properly.

We couldn't find the pin in the cylinder either with the last one, but the valve was definitely burnt. I've got a thread with pictures, but I'll post some here anyway. You're going to need an inspection camera with either a side camera or a mirror in order to see the valve.

All of the Disa pin failure engines that I've seen had a bad misfire but never failed/struggled to idle. I do agree with upallnight and do a compression test if you are uncertain as to how many cylinders are misfiring if any.

Ok Skeletor, doesn't sound good.


But firstly I need to fix the idle. The hissing sound starts immediately when the car starts, and comes from right inbetween the intake and the engine. Where the fuel injectors are.

Does this mean I need to take the intake off again? What could it be?

That plug doesn't look right to me.

It should be separated at the silver spring clip in the middle, not the way it is. Almost looks like the entire sensor end has pulled out of something. Intake air temp sensor maybe? Check the intake manifold at the rear and see if it looks like something is missing.

Or read the connector number on the plug (Xnnn) and we can look it up in the Bentley manual.