M60 rough Idle/misfire-Long

[bimmer2u]

I have a 94 740iL but you 5er guys have lots of knowledge of the M60 engine.:D My problem is a very rough idle and what appears to be a misfire. I have searched this forum and the my normal forums (BB and RF) for this info and nothing has helped.

I had a new tranny installed and the guys screwed up a coolant hose from the resevior to the coolant manifold. They replaced the hose but when I picked the car up...there was a terrible misfire and no power on take off. Idle is very rough. :( When I have it in sport mode (thus higher rpm) it seems to help. I just replaced both O2 sensors prior to this and I have not code faults on the stomp test. I had my shop, which works on bimmers, jags, volvos, porsch, etc, look at it. There was coolant down in the wells of the spark plugs so everyone thought fouled plugs.

They ran a Diag and also got no faults. They checked each plug coil pack and also replace the plugs...didn't fix it. They checked for coolant or fuel smell out the exhaust...nothing. They lubed the butterfly and checked the MAF...nothing. They checked for vaccum leaks....none found. I even sprayed with carb cleaner...nothing either. Ran Techron with only a qtr of a tank of gas in it...nothing. Filled up with new gas (premium of course)...still nothing. I did a computer reset procedure but still nothing has changed. The shop wanted to send the fuel injectors out for cleaning/blueprinting (a $500 job) but I decided to install new ones myself from Five0motorsports, which I am waiting for now.

So this is where I am at right now....waiting for my new injectors. I would WELCOME any suggestions since I have the injectors out and waiting.

Thanks guys.

[bimmer2u]

Thanks again

[Bill R.]

pull the transmission the engine can tilt back if not supported and hit the firewall. On your car the fuel pressure regulator along with vacum lines is right there and all the stuff on the pcv plate is also right there..I'd look at the back of the intake manifold right there to see if anything got crushed or disconnected, I'd start with the fuel pressure regulator vacum line on the passenger side of the manifold at the back.




I have a 94 740iL but you 5er guys have lots of knowledge of the M60 engine.:D My problem is a very rough idle and what appears to be a misfire. I have searched this forum and the my normal forums (BB and RF) for this info and nothing has helped.

I had a new tranny installed and the guys screwed up a coolant hose from the resevior to the coolant manifold. They replaced the hose but when I picked the car up...there was a terrible misfire and no power on take off. Idle is very rough. :( When I have it in sport mode (thus higher rpm) it seems to help. I just replaced both O2 sensors prior to this and I have not code faults on the stomp test. I had my shop, which works on bimmers, jags, volvos, porsch, etc, look at it. There was coolant down in the wells of the spark plugs so everyone thought fouled plugs.

They ran a Diag and also got no faults. They checked each plug coil pack and also replace the plugs...didn't fix it. They checked for coolant or fuel smell out the exhaust...nothing. They lubed the butterfly and checked the MAF...nothing. They checked for vaccum leaks....none found. I even sprayed with carb cleaner...nothing either. Ran Techron with only a qtr of a tank of gas in it...nothing. Filled up with new gas (premium of course)...still nothing. I did a computer reset procedure but still nothing has changed. The shop wanted to send the fuel injectors out for cleaning/blueprinting (a $500 job) but I decided to install new ones myself from Five0motorsports, which I am waiting for now.

So this is where I am at right now....waiting for my new injectors. I would WELCOME any suggestions since I have the injectors out and waiting.

Thanks guys.

[632 Regal]

first thing, rule of thumb: backfire through intake = carburetion (fuel/vacume issues) backfire through exhaust = ignition. Not 100 percent of the time but a rule of thumb.

It's running rough, you should be able to pull the plugs (when engine is cool) and compare them side by side and see if any particular cylinders are dead. If it's one or a few you could have had the plug boots/coils short out from the water they dumped. Try to isolate the cylinders in question, water in plug wells is NOT a good thing.

Let is know what you find out!

[bimmer2u]

It seems the misfire, not really a backfire, is mainly at the exhaust. Coils all checked out good and the car ran fine after the tranny install but I notice a leak in the reseivor hose so I took it back to have them replace it at their cost, which they agreed. My excellent repair shop could not find anything, so they suspect injectors. It could be just a fluke that the problem showed up after the hose replacement, so I can't blame the tranny shop for the misfire, unless I find evidence they did something to it.

I let you know if it goes away after I install the new injectors this week. Just wanted to keep looking while she is in the "down" mode.

[632 Regal]

a short can easily cause the coil packs to fry, and a miss from there can cause the DME to fry. So you might want to really make sure the coils are good.