Hi all,

In trying to diagnose a P0303 (cylinder 2 misfire detected) and P2096 (post catalyst fuel trim system too lean bank 1) on my 2005 R53, manual gearbox with 180K on it, I decided to do a compression test. I removed the fuel pump fuse, removed the spark plugs and wires, but did inadvertently did not remove the low voltage wire connection going into the ignition coil.

Cylinder compression came out to be much better than expected at:

1 – 170 psi
2 – 170 psi
3 – 175 psi
4 – 175 psi

After plugs, wires and fuel pump fuse back, I started the engine. The engine was misfiring badly, so I shut it down, cleared whatever codes were generated with a cheap code reader. Restarted the engine again but it still misfired just as badly. I drove the car about 10 miles to see if the ECU would reset its self. While driving the engine continued to misfire, at higher RPMs the engine seemed to have close to normal power, but less than 2500 RMP the engine did have much power.

I let the car sit for a couple of days, started it back up, still misfired, let the engine warm up enough to do another compression check, this time with the low voltage wire connections removed from the ignition coil and found similar cylinder compression. Thankfully it seems I haven’t ruined the cylinders/head/head gasket yet, but there was a bit of carbon build up on the spark plugs.

The codes after the ~10 mile drive are:
P2096 – post catalyst fuel trim system too lean bank 1
P0302 – cylinder 2 misfire detected
P1689 – Electronic Throttle Control Monitor Level 2/3 Torque Calculation Error.
P1109 – Manifold Air Pressure too High in Deceleration
P1242 – Secondary Upstream Manifold Air Pressure Sensor Too High in Deceleration
P2300 – ignition coil "A" primary control circuit low
P2303 – ignition coil "B" primary control circuit low
P0341 – camshaft position sensor "A" circuit range/performance bank 1 or single sensor


Interestingly P0303 seen before the compression test has gone away, possibly being replaced with the P0302.

So, does it sound like the ECU needs to be replaced?

Other troubleshooting/diagnostic things I’ve done prior to the compression test:

- Replaced oxygen sensor after the catalytic converter with genuine mini O2 sensor.
- Replaced fuel filter
- I have checked for a vacuum leak around the supercharger inlet green gasket by spraying propane, but didn’t see a change in the oxygen sensor values, but I did see a slight increase in the O2 voltage when using propane around the vacuum lines leading down the passenger side fire wall (EVAP system?), so that may be responsible for the P2096. Anyway there isn’t much in the way of tracking down that vacuum leak with the engine misfiring the way it is.

Thank you in advance for any thoughts/ideas/suggestions.

 

Couple of thoughts. First, have you tried to reset the ECU? Would think if you can reset it, then the chances are it is not fried. Below is thread on resetting. Secondly, there are ways to test for vacuum leaks without the engine running by doing a pressure test or a smoke test. On the pressure test, the second thread has some information on how to make a tester, allot of pictures are gone via photobucket but the last posting does have a picture on what the thing looks like ( I made one of these). The vid below is how to test for leaks with a cigar. The guy is pretty good, has an excellent video on AC issues.

ECU Reset https://www.northamericanmotoring.co...set-ecu-430947

DIY Tester https://www.northamericanmotoring.co...ak-tester.html

 

As an update:

I performed the ECU reset procedure yesterday, but didn’t see any change in engine misfire. Today, I replaced the ignition coil with a genuine mini coil with no improvement either.

As an additional data note, after replacing the fuel filter but before the compression test I had checked the fuel pressure with an AutoZone fuel pressure kit with the following measurements:

Engine not running – 60 PSI
Engine idling – 42 PSI
Engine at 2500 RPM – 38 PSI

For some reason I thought fuel pressure was suppose to increase with RPM. Is a lower pressure at higher RPM normal? I guess it makes sense, since the engine would be consuming more fuel per minute.

I haven’t had a chance to perform the suggested vacuum leak check by pressurizing the system as I need come up with a way to connect my compressor to the air intake. The cigar idea is clever and will likely try it if I can't come up with a way to put low enough pressure in intake from my compressor - I'm not much of a smoker.

 

you sure you hooked those spark plug wires up right? if I have a misfire I remove one plug wire at a time testing to make sure all 4 cylinders are firing.

post cat is an efficiency on the cat error, now if it was a pre-cat sensor I would be looking at a injector or airleak, but it's post cat probably just a worn out o2 sensor

 

Since you were able to reset the ECU I would think it is not fried.

Occam's razor?????

 

Mega72,

To test the cylinder firing, should I start the engine then remove a spark plug wire and listen for a change in the way the engine is running. If it runs the same without the wire then that cylinder is an issue? If there is a change in the engine noise, then reinstall the spark plug wire and try the next cylinder?

Here is a picture of my ignition wires. Cylinder 1 is on the passenger side and cylinder numbers are sequential with cylinder 4 on the drives side right? Wiring seems correct to me, but I wish it was something that simple.




R53Scoop,

I'll plan to check for vacuum leaks over the weekend.

Thank you all again!

 

Hi All again,

So my Mini is still not running with the same issue from over the summer. The engine will not start after doing a compression check - possibly related to not removing the low voltage ignition wire feeding the ignition coil pack.

I have done vacuum leak test as suggested but did not find any leaks. Recently I got K+Dcan OBDII reader and installed INPA diagnostic software. The only code that is currently showing is the post catalyst fuel trim being too lean. However when looking at the history, it appears the ignition timing is being advanced by 26 degrees on all four cylinders.

Any ideas on what may cause this? My understanding is the ECU calculates ignition timing based on the knock senor, crank sensor, and camshaft position sensor. Could a compression test caused one of these sensors to go bad?

Thank you in advance for any ideas

 

Wondering whether one of the sensors noted above is bad. Need the NAM Brain Trust to chime in. Either some very advanced members or the Way Motors and Detroit tuned guys that also have full service shops.

 

I'm new here. What is the issue with not removing the low voltage ignition wire feeding the ignition coil pack?

What is the "fix"? New coils? Or?

I ask because maybe the source of the misbehavior is related to not removing the low voltage ignition wire and this has possibly damaged the coils? If so then new coils might be the solution. But of course unless the new coils are rather inexpensive you would want some confidence their replacement was warranted.

It is unlikely the compression tested caused a sensor to go bad. 'course, a sensor could go bad any time but I think it unlikely.

What is more likely to have happened is when performing the compression you disturbed something. You need to review your engine compression testing to try to determine if you possibly dislodged a connector or damaged a vacuum hose or broke a vacuum hose fitting.

Or you failed to properly connect the coils or plugs.

Also, I note you last worked on the car back in August. Here is it January and you have to be aware of the possibility of stale gasoline. Some engines are more sensitive to stale gasoline that others. I don't think all the symptoms can be blamed on stale gasoline but if the engine is sensitive to it it is possible it can add to the misbehavior and confuse things.

 

Hi RockC, My understanding the low voltage wire is directly connected between the ECU and the ignition coil pack. My hypothesis is the ignition coil produced some stray high voltage that has corrupted the ECU or a sensor by not having spark plugs connected.

One of my troubleshooting steps after the compression test was to replace the both the ignition coil and the spark plugs, but that did not help.

I do like the compression test review idea, and will take a look at the engine bay tomorrow to see if I inadvertently messed with a connection.

The misfiring / engine not starting issue has existed since August so the car has sat in my driveway for a while. I am starting to be concerned with additional issues that may arise due to old gas, and possible issues with my brake disks rusting from being exposed to the elements.

Thank you for the dialogue.

 

I doubled checked the wiring and hoses that may have been affected by doing a compression test but didn’t find anything abnormal.

I wasn’t comfortable with the INPA diagnostic results as the software seems clunky and wasn’t sure I was using the software correctly / found all the fault codes. I installed a different diagnostic software (ISTA-D) and found fault codes listed in the attachments.

After clearing the codes, I tried to start the engine (still didn’t start) and got the following 3 codes that were also present before the clear:

• 000341 DME: Camshaft sensor (bank 1) –measuring –range or power-output problem and
• 005E19, 002096 DME: Oxygen sensor (bank 1, after catalyst) – exhaust-gas composition indicates oxygen-sensor fault (bank 1, catalyst)(mixture too lean)
• 005E19 ABS-DSC: CAN data error from DME/DDE (DSC lamp on as long as error is present)

Based on the 000341 fault I have order a camshaft position sensor – hopefully that will resolve all 3 codes.

I’m open any other ideas

 

Couple of things...
The above mentioned ECU reset procedure really doesn't "reset" the ECU, you need to find someone (dealer or euro shop) with the correct software to do the job.
Also, have you tried a different coil, maybe you simply damaged this one, and your getting weird voltage spikes causing these errors.

Just a thought.