3 out 4 cylinders working :(

[sweenrace]

I've got a 1993 US 318is that isnt firing on cylinder #2. I've swapped plugs and leads around and tried new coils and still cant get #2 to fire. I've got 12V going to the primary side of the coil itself. There is fuel going to the cylinder cos the plug is wet when i take it out and the car smells like it is running rich.

All of this started when i came off the freeway one day and the motor was running terribly. I managed to get it home and checked the codes with the peake tool and the pedal trick. Both suggested knock sensors (actually knock regulation). I changed the sensors and the codes were replaced with ignition coil codes. This led me to check the ignition and #2 not firing.

Any thoughts? Could it be the DME or is there anything else that would only effect one cylinder?

[Jeron]

Try swapping #2 injector with another.

[sweenrace]

mmm, so you think that even though the plug is wet, the injector might still be bad?

[Jeron]

I do.

I'm not an expert in this area, or any other for that matter, but fuel needs a certain fuel/air mixture to ignite, too much or too little wont burn. Also if the injector isn't misting the fuel properly that could cause no ignition as well.

Swapping injectors is little tougher than what you've done so far but I think its the next step.

[sweenrace]

i'll try it out then.

[Dave at Pelican Parts]

How's the compression? How does the starter sound--does it crank unevenly?

--DD

[sweenrace]

I havent checked the compression but i'd be surprised if it was bad. The car doesnt smoke in anyway. The car cranks really well and fires consistently. It will even start and run on 2 cylinders ( i found this out while trying to find the sparkless cylinder). Using a timing light confirmed no spark on cylinder #2

[Jeron]

So you have verified that there is actually no spark on #2. I thought you surmised that #2 wasn't firing based on the wet plug etc.

You've already swapped coils so I would look for damaged wiring all the way back to the ECU then check the ECU for cracked solder.

[sweenrace]

This turned out to be the DME. Here's how I finally worked it out.

I pulled the plug out of another cylinder and turned the engine over. With the plug grounded and with the plug wire still on, i could see a spark. I then did the same for cylinder 2 plug and saw no spark. This confirmed that there wasnt a fuel injection (flooding) problem causing the lack of spark.

I put a multimeter on the pins in the connector to the coil and checked for continuity back to the pins going to the dme. No problems there.

My Dad (old school car guy) pointed out that if there's nothing wrong with the wiring to that cylinder, the plug wire, coil or plug then it must be a DME issue. Otherwise at least one other cylinder would be affected because the DME responds to sensors that monitor either all 4 cylinders or pairs. If only one cylinder is affected then it cant be a sensor problem.

I got a tested DME off Ebay for $200, popped it in and the car fired up smoothly straight away - relief!

There was still a pedal code - 1444. It turns out that means there are no fault codes!

thanks all for the help
Ian

[Jeron]

DME = ECU

Glad you got it fixed. It could be cracked solder issue I mentioned above. Don't throw away your old one.